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Plate XVI 
 
MAIN DRAINAGE WORKS 
 
 OF THE 
 
 CITY OF BOSTON 
 
 {MASSAGEUSETTS, U.S.A.) 
 
 BY 
 
 ELIOT C. CLAEKE ?^ 
 
 Principal Assistant Engineer, in charge 
 
 BOSTON 
 ROCKWELL AND CHUECHILL, CITY PRINTERS 
 
 No. 39 Abch Street 
 
 1885 
 
 BOSTON COLLEGE I|gBAf,J 
 CHEiSTiiUT HILL, MA«9, 
 
Digitized by tine Internet Archive 
 
 in 2010 with funding from 
 
 Boston Library Consortium IVIember Libraries 
 
 A 
 
 http://www.archive.org/details/maindrainageworkclar 
 
PREFACE. 
 
 This brief description of the Main Drainage Works, of Bos- 
 ton, aims to record, for the benefit of engineers, an account of 
 the engineering problems involved and the methods of construc- 
 tion adopted. It also aims to give to the tax-payers and gen- 
 eral public a descriptive account of why the large appropriation 
 for "An Improved System of Sewerage " was needed, and how 
 it has been spent. By attempting to accomplish both of these 
 purposes it fulfils neither of them adequately ; since one class 
 of readers will find it too technical, and the other too deficient 
 in detail. It has been prepared amid pressing engagements, 
 and to save time the writer has not hesitated to borrow freely 
 from previous reports, by himself and others. Traces of such 
 compilation will, doubtless, be noticed by the discerning. It is 
 hoped that a fair idea of the works can be obtained from the 
 illustrations ; and that the description, even by its defects, may 
 encourage other engineers to publish, as they too seldom do, 
 accounts of works with which they have been connected. 
 
 E. C. C. 
 
 Boston, April, 1885. 
 
TABLE OF CONTENTS. 
 
 PAGE 
 
 CHAPTER I. 
 
 Early history of sewerage at Boston ...... 7 
 
 CHAPTER 11. 
 Character and defects of the old sewerage system ... 12 
 
 CHAPTER III. 
 Movements for reform — Commission of 1875 16 
 
 CHAPTER IV. 
 Preliminary investigations 22 
 
 CHAPTER V. 
 Main sewek 31 
 
 CHAPTER VI. 
 Intercepting sewers 37 
 
 CHAPTER VII. 
 
 PUMPING-STATION 53 
 
 CHAPTER VIII. 
 Outfall sewer 62 
 
 CHAPTER IX. 
 Reservoir and outlet .......... 76 
 
 CHAPTER X. 
 Details of engoeerino and construction ..... 83 
 
6 CONTENTS. 
 
 PAGE 
 
 CHAPTER XI. 
 Working of the new system . 93 
 
 APPENDIX A. 
 
 Record op tests of cement made for Boston Main Drainage 
 
 Works 113 
 
 APPENDIX B. 
 
 List of officers connected with Boston Main Drainage Works, 140 
 
MAIN DRAINAGE WORKS. 
 
 CHAPTEE I. 
 
 EAELY HISTOEY OF SEWERAGE AT BOSTON. 
 
 The conditions which necessitated a change in the system of 
 sewage disposal at Boston, and the problems to be solved in 
 making that change, can be better understood after a brief con- 
 sideration of the early history of sewerage at that city and the 
 manner in which the sewers were originally built. 
 
 Boston was first settled in 1630. When the first sewer was 
 built cannot now be determined, but it was earlier than the 
 year 1700, for already, in 1701, the population being about 
 8,000, a nuisance had been created by frequent digging up of 
 streets to lay new sewers and to repair those previously built ; 
 and in town meeting, September 22, 1701, it was ordered, 
 " That no person shall henceforth dig up the Ground in any of 
 the Streets, Lanes or High-way es in this Town, for the laying or 
 repairing any Drain, without the leave or approbation of two 
 or more of the Selectmen." 
 
 The way in which sewers were built at this time was, appar- 
 ently, this. When some energetic householder on any street 
 decided that a sewer was needed there, he persuaded such of 
 his neighbors as he could to join him in building a street drain. 
 Having obtained permission to open the street or perhaps 
 neglected this preliminary, they built such a structure as they 
 thought necessary, on the shortest line to tide-water. The ex- 
 pense was divided between them, and they owned the drain 
 absolutely. Should any new-comer, or any neighbor, who had 
 at first declined to assist in the undertaking, subsequently desire 
 to make use of the drain, he was made to pay for the privilege 
 
b MAIN DEAINAGE WORKS. 
 
 what the proprietors saw fit to charge. When a drain needed 
 repairing all persons using it were expected to pay their share 
 of the cost. 
 
 As might have been expected, under such a system, great 
 difficulty was experienced in distributing fairly the expenses 
 and in collecting the sums due ; so that it became of sufficient 
 importance to engage the attention of the Legislature, and in 
 1709 an act was passed regulating these matters. It is entitled, 
 " An Act — Passed by the Great and General Court or Assem- 
 bly of Her Majesty's^ Province of the Massachusetts-Bay. For 
 regulating of Drains and Common Shores.^ For preventing of 
 Inconveniences and Dammages by frequent breaking up of 
 High-Wayes .... and of Difi'erences arising among 
 Partners in such Drains or common Shores about their Propor- 
 tion of the Charge for making and repairing the same." 
 
 The act recites that no person may presume to break up the 
 ground in any highway within any town for laying, repairing 
 or amending any common shore, without the approbation of the 
 selectmen, on pain of forfeiting 20 shillings to the use of the 
 poor of said town ; that all such structures, for the draining of 
 cellars, shall be " substantially done with brick or stock ;" ^ 
 that it shall be lawful for any inhabitant of any town to lay a 
 common shore or main drain, for the benefit of themselves and 
 others who shall think fit to join therein, and every person who 
 shall afterwards enter his or her particular drain into such main 
 drain, or by any more remote means receives benefit thereby, 
 for the drainage of their cellars or lands, shall be obliged to 
 pay unto the owner or owners a proportionate part of the charge 
 of making or repairing the same, or of that part of it below 
 where their particular drain enters. In case of dispute the 
 selectmen decided how much each person should pay, and there 
 was an appeal from their decision to the courts. 
 
 For one hundred and fifteen years the sewers in Boston were 
 built, repaired, and owned by private individuals under author- 
 ity of this act. 
 
 It may be doubted if most of them were "substantially done 
 with brick or stock," and there certainly was much difficulty 
 
 ^Anne. ^Sewers. ^ Stone. 
 
Plate I. 
 
 MAP OF 
 1775. 
 
 SCALE 
 
 Yzmtt 
 
EARLY HISTORY OF SEWERAGE AT BOSTON. 9 
 
 about payments ; so that in 1763 the act of 1709 was amended, 
 the amendment reciting that " Whereas it frequently happens 
 that the main drains and common shores decay or fill up . 
 
 . and no particular provision is made by said act to com- 
 pel! such persons as dwell below that part where said common 
 shores are repaired, and have not sustained damage, to pay 
 their proportionable share thereof, as shall be adjudged by the 
 selectmen, which has already occasioned many disputes and 
 controversies," therefore it was decreed that in future all per- 
 sons benefited should pay for repairs. 
 
 No further change was made till 1796, and then only to 
 provide that persons who did not pay within ten days of notifi- 
 cation should pay double, and that the sewers, besides being of 
 brick or stone, might be built of such other material (probably 
 wood) as should be approved by the selectmen. 
 
 Under this act the greater part of Boston was sewered by 
 private enterprise. The object for which the sewers were built 
 was, as indicated "for the draining of cellars and lands." The 
 contents of privy-vaults, of which every house had one, and 
 even the leakage from them, were excluded ; but they received 
 the waste from pumps, and kitchen sinks, and also rain-water 
 from roofs and yards. 
 
 That much refuse got into them is proved b}^ their frequently 
 being filled up, and as they had a very insufficient supply of 
 water they were evidently sewers of deposit. That they 
 served their purpose at all is due to the fact that the old town 
 drained by them, as shown in Plate I., consisted of hills with 
 good slopes on all sides to the water. Of this early method of 
 building sewers Josiah Quincy, then Mayor, said, in 1824 : 
 "No system could be more inconvenient to the public, or embar- 
 rassing to private persons. The streets were opened with little 
 care, the drains built according to the opinion of private in- 
 terest or economy, and constant and interminable vexatious 
 occasions of dispute occurred between the owners of the drain 
 and those who entered it, as to the degree of benefit and pro- 
 portion of contribution." 
 
 In 1823 Boston obtained a city charter, and one of the first 
 acts of the city government was to assume control of all exist- 
 
10 MAIN DEAINAGE WORKS. 
 
 ing sewers and of the building and care of new ones. The 
 new sewers were built under the old legislative acts, and 
 the whole expense, as before, was charged to the estates bene- 
 fited, being divided with reference to their assessed valuation. 
 A small, variable portion of the cost was, however, generally 
 assumed by the city, in consideration of its use of the sewers 
 for removing surplus rain-water from the public streets. 
 
 The city ordinances regulating sewers required that, when 
 practicable, they should be of sufficient size to be entered for 
 cleaning. Some supervision was exercised over connecting 
 house-drains, and, if thought necessary, a strainer could be placed 
 on each. Fecal matters were rigidly excluded until 1833, when 
 it was ordered that, while there must be no such connection 
 between privy-vaults and drains as would pass solids, the 
 Mayor and Aldermen, at their discretion, might permit such 
 a passage or connection as would admit fluids to the drain. 
 This action was perhaps due to an advent of cholera during the 
 previous year. To assist in flushing out deposits, it was pro- 
 vided, in 1834, that any person might discharge rain-water from 
 his roof into the sewers, without any charge for a permit. The 
 same year control of the sewers and sewer-assessments was 
 given to the City Marshal. He was especially to devote him- 
 self to the collection of assessments, new and old, which were 
 largely unpaid. The other duties of the marshal probably pre- 
 vented him from devoting sufficient energy to the accomplish- 
 ment of this task ; for it appears that, while there had been 
 expended by the city, for building sewers, from 1823 to 1837, 
 the sum of $121,109.52, there had been collected of this sum 
 but $26,431.31. 
 
 That there might be some one to give his whole time to the 
 financial and administrative duties connected with the sewer- 
 age system, a " Superintendent of Sewers and Drains " was 
 appointed in July, 1837. He was empowered to assess the 
 whole cost of any new sewer upon the real estate, including 
 buildings benefited by it. In 1838 the city decided to assume 
 one-quarter of the gross cost; and in 1840, in obedience to a 
 decision by the Supreme Court, it was ordered that the three- 
 quarters of the cost of sewers which was to be paid by the 
 
EARLY HISTORY OF SEWERAGE AT BOSTON. 11 
 
 abutters, should be assessed with reference to the value of 
 the land only, without taking into consideration the value of 
 buildings or other improvements, and such has been the prac- 
 tice up to the present time. 
 
 It is estimated that there are at the present time (1885) 
 about 226 miles of sewers in Boston. In 1873 there were 
 about 125 miles, and in 1869 about 100 miles. There are at 
 present supposed to be more than 100,000 water-closets in use 
 in the city ; in 1857 there were 6,500. 
 
12 MAIN DRAINAGE WORKS. 
 
 CHAPTER II. 
 
 CHARACTER AND DEFECTS OF THE OLD SEWERAGE SYSTEM. 
 
 Such changes have taken place in the contours of the city, 
 through operations for reclaiming and filling tidal areas border- 
 ing the old limits, that, from being a site easy to sewer, Boston 
 became one presenting many obstacles to the construction of an 
 efficient sewerage system. 
 
 This will be understood from an examination of the plan of 
 the city proper, Plate V. On this plan the shaded portion rep- 
 resents the original area of the city, and very nearly its limits 
 in 1823. The unshaded portion of the plan, indicating present 
 limits, consists entirely of reclaimed land filled to level 
 planes little above mean high water, the streets traversing such 
 districts being seldom more than seven feet above that eleva- 
 tion. A large proportion of the house basements and cellars 
 in these regions are lower than high water, and many of them 
 are but from five to seven feet above low-water mark, the mean 
 rise and fall of the tide being ten feet. This lowness of land 
 surface and of house cellars necessitates the placing of house- 
 drains and sewers at still lower elevations. Most house-drains 
 are under the cellar floors, and fall in- reaching the street sew- 
 ers ; the latter must be still lower, and in their turn fall 
 towards their outlets, which were rarely much, if at all, above 
 low water. 
 
 Moreover, as filling progressed on the borders of the city, it 
 became necessary to extend the old sewers whose outlets would 
 have been cut off. The old outlets being generally at a low 
 elevation, even where the sewers themselves were sufficiently 
 hio-h, the extensions had to be built still lower, and when of 
 considerable length could have bilt little fall towards the new 
 mouths. 
 
 As a consequence, the contents of the sewers were dammed 
 back by the tide during the greater part of each twelve hours. 
 
CHARACTER AND DEFECTS OF THE OLD SEWERAGE SYSTEM. 13 
 
 To prevent the salt water flowing into them many of them 
 were provided with tide-gates, which closed as the sea rose, and 
 excluded it. These tide-gates also shut in the sewage, which 
 accumulated behind them along the whole length of the sewer, 
 as in a cesspool ; and, there being no current, deposits occurred. 
 The seAvers were, in general, inadequately ventilated, and 
 the rise of sewage in them compressed the foul air which 
 they contained and tended to force it into the house connec- 
 tions. To aiford storage room for the accumulated sewage, 
 many of the sewers were built very much larger than would 
 otherwise have been necessary, or than was conducive to a 
 proper flow of the sewage ; and, as there would have been little 
 advantage in curved inverts where there was to be no cur- 
 rent, flat-bottomed and rectangular shapes were frequently 
 adopted. 
 
 Although at about the time of low water the tide-gates 
 opened and the sewage escaped, the latter almost immediately 
 met the incoming tide, and was brought back by it, to form 
 deposits upon the flats and shores about the city. Of the large 
 amount of sewage which flowed into Stony Brook and the Back 
 Bay, and especially that which went into South Bay, between 
 Boston proper and South Boston, hardly any was carried 
 away from the vicinity of a dense population. 
 
 The position of the principal sewer outlets and of the areas 
 on which the sewage which caused most ofl'ence used to accu- 
 mulate, is indicated on Plate V. From these places foul- 
 smelling gases and vapors emanated, which were diftused to a 
 greater or less distance, according to the state of the tempera- 
 ture or of the atmosphere. Under certain conditions of the 
 atmosphere, especially on summer evenings, a well-defined 
 sewage odor would extend over the whole South and West 
 Ends of the city proper. 
 
 This evil was thus described by the City Board of Health in 
 one of their annual reports : — 
 
 Complaints of bad odors have been made moi*e frequently dm'ing the 
 past year than ever before. 
 
 They have come from nearly all jiarts of the city, but es2:)ecial]y and 
 seriously from the South and West Ends, 
 
14 MAIN DRAINAGE WORKS. 
 
 Large territories have been at once, and frequently, enveloped in an 
 atmosphere of stench so strong as to arouse the sleeping, terrify the weak, 
 and nauseate and exasjaerate everybody. 
 
 It has been noticed more in the evening and by night than during the 
 day ; although there is no time in the whole day when it may not come. 
 
 It visits the rich and the poor alike. It fills the sick-chamber and the 
 office. Distance seems to lend but little protection. It travels in a belt 
 half-way across the city, and at that distance seems to have lost none of its 
 potency, and, although its source is miles away, you feel sure it is directly 
 at your feet 
 
 The sewers and sewage flats in and about the city furnish nine-tenths of 
 all the stenches complained of. 
 
 They are much worse each succeeding year ; they will be much worse 
 next 3^ear than this. 
 
 The accumulation of sewage upon the flats and about the city has been, 
 and is, rapidly increasing, until there is not probably a foot of mud in the 
 river, in the basins, in the docks, or elsewhere in close proximity to the city, 
 that is not fouled with sewage. 
 
 Various palliative measures were adopted. The Back Bay, 
 into which the waters of Stony Brook, and with them most of 
 the sewage of Roxbury and Jamaica Plain, used to empty, was 
 lately partly tilled with gravel, forming the present Back-Bay 
 Park. The brook was carried in a covered channel to Charles 
 River, which somewhat lessened the nuisance caused by it, or at 
 least transferred it to another locality. Owing to complaints 
 from the physicians of the City Hospital and other residents in 
 that neighborhood the city purchased and filled the upper por- 
 tion of Old Roxbury Canal at the head of South Bay. The 
 sewers emptying into it were extended, and the position of the 
 nuisance caused by them was thus altered by a few hundred 
 feet. In general terms it may be said that none of the old 
 sewer outlets were in unobjectionable locations. 
 
 There are no plans in detail of the sewers of Boston. Many 
 of the older ones have no man-holes. In some streets several 
 sewers exist side by side. Occasionally a sewer is found built 
 directly above an older one. Probably one-half of the larger 
 main sewers are wholly or partly built of wood and have flat 
 bottoms. An unwise provision was inserted in the charters of 
 some of the private corporations organized for the purpose of 
 reclaiming and filling areas of flats, by which it was stipulated 
 
Plate 11. 
 
 Fig, I Fig. 2 
 
 Fig. 3 Fig. 4 
 
 Fig. 9 
 
 Fig. 15 
 
 Fig. 17 
 
 Fig. 10 
 
 BOSTC 
 
 I O I 2 
 
 HOL 
 
 ng.23 24- 25 
 
 Fi^.l8 
 
 F,6,.2I 
 
Fig. I Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fi^.6 
 
 Fi6.7 
 
 Fi^.8 
 
 Fig. II Fig. 12 
 
 COMMON TYPES 
 
 OF 
 
 BOSTON CITY SEWERS. 
 
 SCALE, 
 
 FigJ3 
 
 HOUSE DRAINS. 
 
 27 
 
 FiS.I6 
 
 Fig. 19 
 
 Fig. 14- 
 
 28 29 
 
 ng.2l 
 
 Fig. 16 
 
 Fig. 20 
 
 Fig- 22. 
 
CHARACTER AND DEFECTS OF THE OLD SEWERAGE SYSTEM. 15 
 
 that the corporations should themselves extend all sewers whose 
 discharge would be obstructed by the filling. Such extensions 
 were made without system, by building flat-bottomed wooden 
 scow sewers, which were laid upon the soft surface of the flats 
 before the filling was done. Cross-sections of various common 
 forms of existing city sewers are shown on Plate II., Figs. 
 1 to 22. Fig. 22 shows Stony-Brook culvert, which consti- 
 tutes the lower mile of Stony Brook, and is that part of it which 
 is covered and used as a sewer. 
 
 One fact which increased the danger arising from the dam- 
 ming up of the sewers, and the consequent compression of their 
 gaseous contents, was that the house-drains connecting with 
 these sewers were ill adapted to resisting this pressure. 
 Most of them were built of brick or of wood, before the rise of 
 modern ideas in regard to sanitary drainage ; and, as they were 
 usually leaky, the gases forced into them found ready egress 
 into the houses. Figs. 23 to 29 on Plate II. show common 
 forms of these house-drains. 
 
 The drains differ greatly in size. Of 113 which were ob- 
 served while building the intercepting sewers in 1878, — 
 
 11 were about 4 inches in diameter. 
 
 4 
 
 
 5 
 
 21 
 
 
 6 
 
 5 
 
 
 7 
 
 27 
 
 
 8 
 
 8 
 
 
 9 
 
 11 
 
 
 10 
 
 26 
 
 
 12 
 
 or more. 
 
 113 
 
 Of these 113 drains, 9 were level and 14 pitched the wrong 
 way ; 45 had flat bottoms and 68 curved ones ; 38 were 
 wholly or partly choked with sludge, and 75 were reasonably 
 clean. At about the same time examinations made with 
 peppermint, by the City Board of Health, of 351 house-drains 
 in various sections of the city, showed that 193 of them, or 55 
 per cent., were defective in regard to tightness. 
 
16 MAIN DRAINAGE WORKS. 
 
 CHAPTEE III. 
 
 MOVEMENTS FOR REFORM-COMMISSION OF 1875. 
 
 For the ten years preceding 1875 the average annual death- 
 rate of Boston was about 25 m 1,000. On April 14, 1870, the 
 Consulting Physicians of the city addressed to the authorities a 
 remonstrance as to the then existing sanitary condition of the 
 city, in which they declared the urgent necessity of a better 
 system of sewerage, stating that it would be a work of time, of 
 great cost, and requiring the highest engineering skill. 
 
 At about the same time, and in each of their Annual Eeports 
 thereafter, the State Board of Health referred to the matter, 
 saying that the question of drainage for Boston and its immediate 
 surroundings was of an importance which there was no danger 
 of overstating. 
 
 Of such great importance was the matter considered by the 
 State Legislature that, in the special session of 1872, an act was 
 passed authorizing the appointment of a commission, to be paid 
 by the City of Boston, to investigate and report upon a compre- 
 hensive plan for a thorough system of drainage for the metro- 
 politan district. This was not accepted by Boston, on the 
 ground that the expense should be shared by the neighboring 
 cities and towns, and no commission was appointed. 
 
 In a communication to the City Council (Dec. 28, 1874), up- 
 on the necessity of improved sewerage, the City Board of 
 Health pointed out clearly the evils of the existing system, and 
 strongly urged that a radical change should be made. March 
 1, 1875, an order passed the City Council authorizing the Mayor 
 to appoint a commission, " consisting of two civil engineers of 
 experience and one competent person skilled in the subject of 
 sanitary science, to report upon the present sewerage of the 
 city .... and to present a plan for outlets and main 
 lines of sewers, for the future wants of the city." The Mayor 
 thereupon appointed as members of the commission Messrs. E. 
 
MOVEMENTS FOR EEFOEM-COMjMISSION OF 1875. 17 
 
 S. Chesbrough, C.E., Moses Lane, C.E., and Charles F. Fol- 
 som, M.D., and in December of the same year their report was 
 submitted. 
 
 As was to be expected from the professional attainments and 
 reputation of these gentlemen, the report contained a compre- 
 hensive and exhaustive statement of the defects in the existino- 
 s^^stem of sewerage, and of the causes which had produced such 
 a condition of affairs, and finally recommended for adoption a 
 well-considered plan for remedying present defects and for pro- 
 viding for future needs. 
 
 The commission stated, as essential conditions of efficient 
 sewerage : first, that the sewage should start from the houses, 
 and flow in a continuous current until it reached its destination, 
 either in deep water or upon the land; and, second, that the 
 sewers should be ventilated so that the atmosphere in them 
 should attain the highest possible degree of purity. To quote 
 from the report ; — 
 
 The point Avliicli must be attended to, if we would get increased com- 
 forts and kixuries in our houses, Avithout doing so at cost of health and life, 
 is to get our refuse out of the way, far beyond any possibility of harm 
 before it becomes dangerous from putrefaction. In the heat of summer 
 this time should not exceed twelve hours. We fail to do this now in three 
 ways : — 
 
 First. We cannot get our refuse always from our house-drains to our 
 sewers, because the latter may not only be full themselves at high tide, but 
 they may even force the sewage up our drains into our houses. 
 
 Second. We do not empty our sewers promptly, because the tide or tide- 
 gates prevent it. In such case the sewage being stagnant, a precipitate 
 falls to the bottom, which the slow and gradual emptying of the sewers, as 
 the tide falls, does not produce scour enough to remove. This deposit re- 
 mains with little change in some places for many months. i 
 
 Third. With our refuse, which is of an especially foul character, once 
 at the outlets of the sewers, it is again delayed, there to decompose and 
 contaminate the air. 
 
 As a result of this failure to carry out the cardinal rule of sewerage, 
 we are obliged to neglect the second rule, which is nearly as important, 
 namely, ventilation of the sewers ; for the gases are often so foul that we 
 cannot allow them to escape without causing a nuisance ; and we compro- 
 mise the matter by closing all the vents that we can, with the certainty of 
 poisoning the air of our houses. 
 
 ' The catch- basins, too, in the course of the sewers, serve only to ag-gravate this evil, 
 and should be filled as early as is practicable. 
 
18 MAIN DRAINAGE WORKS. 
 
 In the opinion of the commission there are only two ways open to us. 
 The first, raising more than one-lialf of the superficial area of the city 
 proper (excluding suburbs) is entirely out of the question, from the enor- 
 mous outlay of money which would be required, — more than four times as 
 much as would be needed for the plan which we propose, and which con- 
 sists in intercepting sewers and pumping. 
 
 There are in use now in various parts of the world three methods of 
 dis^Dosing of the sewage of large cities, where the water-carriage system 
 is in use : — 
 
 First. Precipitation of the solid parts, with a view to utilizing them as 
 manure, and to purifying the streams. 
 
 Second. Irrigation. 
 
 Neither of these processes has proved remunerative, and the former only 
 clarifies the sewage without purifying it ; but if the time comes, when, by 
 the advance in our knowledge of agricultural chemistry, sewage can be 
 profitably used as a fertilizer, or if it should now be deemed best to util- 
 ize it, in spite of a pecuniary loss, it is thought that the point to which we 
 propose carrying it will be as suitable as any which can be found near 
 enough to the city, and at the same time far enough away from it. 
 
 The third way is that adopted the world over by large cities near deep 
 water, and consists in carrying the sewage out so far that its point of 
 discharge will be remote from dwellings, and beyond the possibility of 
 doing harm. It is the plan which your Commission recommend for 
 Boston. 
 
 On Plate III. is reproduced a portion of the plan accompany- 
 ing the report of the commission. The plan shows the routes 
 of the main, intercepting, and outfall sewers recommended, and 
 the proposed locations of the pumping-stations, reservoirs, and 
 outlets. It will be seen that two main drainage systems were 
 proposed, one for each side of the Charles River ; that on the 
 south side having its outlet at Moon Island and that on the 
 north side discharging at Shirley Gut. 
 
 The former system was designed to collect and carry off the 
 sewage from all of Boston south of Charles River and from 
 Brookline ; the latter was to drain the Charlestown and East 
 Boston districts, and also the neighboring cities of Cambridge, 
 Somerville, and Chelsea. The two systems were identical in 
 their general features. These were : intercepting sewers along 
 the margins of the city to receive the flow from the already 
 existing sewers ; main sewers into which the former were to 
 empty and by which the sewage was to be conducted to pump- 
 ing-stations ; pumping machinery to raise the sewage about 35 
 
Plate III. 
 
MOVEMENTS FOR REFORM-COMMISSION OF 1875. 19 
 
 feet ; outfall sewers leading from the pumping-stations to reser- 
 voirs near the points of discharge at the sea-coast, from which 
 reservoirs the sewage, accumulated during the latter part of 
 ebb and the whole of flood tide, was to be let out into the har- 
 bor during the first two hours of ebb-tide. 
 
 The cost of the proposed main drainage works, as estimated 
 by the commission in its report, was : — 
 
 For the territory south of Charles River . . $3,746,500 
 north " . . 2,804,564 
 
 Total $6,551,064 
 
 The commissioners' recommendation met with very general 
 acceptance. But, as was to be expected, a certain amount of 
 opposition to it was encountered. 
 
 One remonstrance against the adoption of the proposed plan, 
 which was presented to the City Council by a number of esti- 
 mable citizens, may be of sufficient interest to cite, because it is a 
 type of the kind of objections which are often urged against 
 plans for municipal improvement, however carefully considered 
 by the most competent experts : — 
 
 The undersigned resj)ectfully remonstrate against the adoption of the 
 system of sewerage proposed in Report No. 3 of this year. We believe if 
 carried into execution it will prove not only ineffectual, but destructive to 
 
 the health and prosperity of the city Of late years the cost 
 
 of many, if not most, of the public works has greatly exceeded the esti- 
 mates ; in some instances, it is said, two or three hundred per cent. 
 
 Shou-ld this new system exceed the estimates to a like extent, the amount 
 would be augmented to between fifteen and twenty millions of dollars. . . 
 
 But we do not believe it (flushing) will, or even can, be made to per- 
 form that end in an effective or satisfactory manner ; because we under- 
 stand, by the report, that the inclinations of the sewers will afford a flow at 
 a minimum rate of only two miles an hour, so that it will be almost impos- 
 sible to i:)revent the glutinous slime and putrefactions from constantly gath- 
 ering and adhering more or less to the sides and bottoms of the sewers 
 and drains, and as constantly exhaling the deadly gases on every side. 
 . . . . It will likewise be borne in mind that the thick mass of liquid 
 corruption within the sewers and drains must be drawn along to their up- 
 hill or final ascent of thirty feet and over, and kept in motion and delivered 
 at the distant outlets on the bay, by means of enormous pumps and ma- 
 chineiy worked by steam-engines, .... for a stoppage in the ojjer- 
 
20 MAIN DRAINAGE WORKS. 
 
 ations of such an extensive system for only a clay or two, along the low 
 lands and other parts of the city, would almost inevitably result in serious 
 
 maladies and other evil consequences Will not the exhalation 
 
 and odor (from the storage reservoirs) blown by every changing wind here 
 and there along the wharves, upon the shipping and back upon the land, 
 create a nuisance so offensive and unhealthful as to become intolerable ? No 
 provision seems to be devised to prevent such emanations or their baleful 
 consequences. In these noisome reservoirs the contents must ever be ex- 
 posed to the sun, the storms, and the inclemency of the weather. 
 
 In the severity of winter they must become as frozen as the water in 
 the bay or along the shores ; and as often as they are converted into ice 
 there must be an entire stoppage of the works. . . . Such reservoirs and 
 outlets might be reduced to ruins in any future day of hostilities — either 
 foreio-n or domestic — should such hostilities ever occur, the effect of which 
 ruins would be the fatalities of the plague 
 
 There is now but a single system before the authorities, although there 
 are not less than five different systems in Europe alone. . . . It is hereby 
 requested that the same be postponed, and that a reward be offered for the 
 best plan for sewerage relief .... and that such plans be referred to 
 a commission of citizens . . ... with power to give the reward for the 
 best plan. 
 
 Other remonstrants thought that city sewage had a great 
 manurial value, and should be so utilized as to be a source of 
 revenue ; still others considered the proposed scheme extrava- 
 gant, and advised temporary palliative measures. 
 
 What prevented these remonstrances from having much 
 weight, was that while criticising the proposed scheme, they 
 either suggested no alternative plan, or else failed to show that 
 the method which they themselves recommended would remedy 
 the existing evils. 
 
 As a compromise the City Council inclined to adopt the 
 recommendations of the commission in so far as they referred 
 to the territory South of Charles River, which included those 
 portions of the city which suffered most from inefiective sewer- 
 age. Application was made to the Legislature for authority to 
 construct works in general accordance with the recommendations 
 of the Commissioners, and an act, approved April 11, 1876, 
 entitled " An Act to empower the City of Boston to lay and 
 maintain a main sewer discharging at Moon Island in Boston 
 Harbor, and for other purposes," was passed. 
 
 The subject had been referred by the City Council to a Joint 
 
MOVEMENTS FOR REFORM COMMISSION OF 1875. 21 
 
 Special Committee on Improved Sewerage, and in June, 1876, 
 this committee reported, recommending the adoption of the 
 system devised by the commission, and that surveys and esti- 
 mates be made for the work, and also that the feasibility of an 
 outlet at Castle Island be considered. 
 
 By an order approved July 17, 1876, the sum of $40,000 was 
 appropriated for the purpose of making surveys and of procur- 
 ing estimates for an improved system of sewerage for the City 
 of Boston, on a line from Tremont Street to Moon Island, and 
 also on a line from said street to deep water east of Castle 
 Island. 
 
 A few days later the City Engineer, Mr. Joseph P. Davis, 
 appointed the writer principal assistant, in immediate charge 
 of the survev and investio-ations, which were at once begun. 
 
22 MAIN DRAINAGE WORKS. 
 
 CHAPTER IV. 
 
 PRELIMINARY INVESTIGATIONS. 
 
 By a liberal interpretation of the order in compliance with 
 which the survey was carried on, it was assumed that any 
 information was desired which might be of use in designing 
 main drainage works, in general accordance with the plan 
 recommended by the commission. 
 
 As the location of the outlet would affect materially the 
 whole scheme its consideration received the earliest attention. 
 It was necessary that the discharge should be into favorable 
 currents, and also near a practicable site for a reservoir which 
 could be reached by the outfall sewer from the city. A party 
 for hydrographic work was organized, consisting of one assist- 
 ant engineer, one additional observer, two sailing-masters, 
 and two boatmen. Their outfit included a small yacht and two 
 tenders. 
 
 A projection of the harbor was first made, and the triangula- 
 tion points given by U.S. Coast Survey were plotted upon it, 
 together with others obtained by ourselves from these, by 
 means of the plane table ; the shore line being taken from a 
 chart belonging to the Harbor Commissioners. A sufiicient num- 
 ber of prominent points having been determined in this way, it 
 was easy at any time to locate the position of a float by the sex- 
 tant. At night, when other objects could not be seen, the har- 
 bor lights furnished points for observation. 
 
 Some difiSculty was experienced in deciding upon the best 
 form of float. That first adopted consisted of four radiating 
 arms, with canvas wings projecting downward from them (Plate 
 IV., Fig. 4). Upon calm days this form indicated very fairly 
 the surface velocit}'' ; but was too easily influenced by winds 
 and waves to be used in windy weather, as it then invariably 
 grounded on a lee shore. 
 
 A "surface and sub-surface " can-float (Plate IV., Fig. 5) was 
 
Plate IV. 
 
 (uiiiM»i.ni//iii/jii//ii,v/(Minmii/iiiiiiiiiiiiiiii Wiiiwiwinwimnii ) NMrniiiiviiiiinnii'iiivV jiiillll/iiiMUMiiimiiiiiiiiiiuiiiiMiiiiniiiiiiiiimiiimi 
 
 niiii'iiivV fir 
 
 ^'Mym*vA.vilviiiiHiiiii«iiiii»iiihiii:Uihiiffli»iiJUii)nimininiin«iWlllli'illW/ii)||\i«,« 
 
 lllllmiiiiiiiiiiiiiiiniiiiiiiiiiiiiiii>iiimiiii|iiiiiiiiiiiiiNiuiiinii|iiii^ (^>. yiiiini>/iiiiiiirii>>''<ii>iiiiiuiliiiUMiiMiiiiniijiiiiiiiiilli{iiiiiiiuiUil 
 
PRELIMINARY INVESTIGATIONS. 23 
 
 used somewhat, and gave better results ; but an ordinary pole- 
 float (Plate IV., Fig. 6), about 14 feet long and 4 inches in 
 diameter, was finally found to be the most satisfactory, indicat- 
 ing the mean current, which often differed both in direction and 
 velocity from the surface current. This float supported a flag, 
 or lantern, and, when there was danger of its grounding, a 
 shorter one was substituted for it. 
 
 In all, about 50 " free-float " experiments were made upon 
 the currents in the vicinity of Moon, Castle, Thompson's, and 
 Spectacle Islands. The trips varied in duration from 6 hours, 
 or one ebb-tide, to 52 hours. Angles to determine the posi- 
 tion of the float were taken each half-hour, and were re- 
 corded together with the direction and force of the wind and 
 other data. During observations a man was stationed at a tide- 
 o-au^e, and all velocities were reduced to a mean rise and fall 
 of ten feet. The results obtained from the float experiments, 
 stated briefly, were as follows : — 
 
 Favorable ebb currents were found to pass both Moon and 
 Castle Islands. 'That passing Spectacle Island was sufficient in 
 strength, but unsuitable, owing to its direction and some other 
 characteristics ; while that skirting Thompson's Island was alto- 
 gether unfavorable. Floats leaving the vicinity of Moon Island 
 with the early ebb would travel seawards with an average 
 velocity of .74 miles an hour, passing between Rainsford and 
 Long Islands, through Black Rock Channel, and at the turn of 
 tide would reach a position between the Brewsters and George's 
 Island about four miles from the point of starting. This course 
 is, for its whole extent, outside of the inner harbor. Floats from 
 Castle Island followed Main Ship Channel and Broad Sound, 
 and travelled about as far as those from Moon Island. Return- 
 ins^ with the flood-tide the floats would travel about two miles 
 towards the city, and with the succeeding ebb would once more 
 move seaward, not again to enter the harbor. 
 
 Sewage, being fresh water, remains for a while at least upon 
 the top of the denser sea-water, and is more affected by surface 
 currents than by deeper ones. An attempt, more interesting 
 than practically instructive, was made to ascertain to what ex- 
 tent sewage put into Boston Harbor would be difi'used within 
 
24 MAIN DRAINAGE WORKS. 
 
 a few days. Fifty bottle's were put into the water at Moon 
 Island, each containing a postal card, which the finder was re- 
 quested to mail, stating when and where it was found. Ten of 
 these bottles were picked up within the next three weeks. One 
 of them was found at Marshfield, about 25 miles south of its 
 starting-point ; another at Salem, about the same distance 
 north ; a third, 30 miles south-east of Cape Ann, and the re- 
 maining seven outside of Cape Cod, near Provincetown, Well- 
 fleet, and Chatham, from 50 to 80 miles distant. 
 
 Castle island would have been much more easily accessible 
 from the city than Moon Island, but its selection involved sev- 
 eral serious disadvantages. It belongs to the United States, 
 and is the site of Fort Independence. Although this old fort 
 is of little practical value, there were no reasonable grounds 
 for hope that the government would permit a storage reservoir 
 to be located on the island. It would have been necessary to 
 place that structure on the main land in South Boston. The 
 area available for the purpose would have been restricted on 
 account of its great cost. Even if the works could have been 
 so constructed as to be wholly inoffensive, the natural prejudice 
 in the community against the proximity of sewage would have 
 caused great opposition to the building of a reservoir so near 
 to a densely populated district. Moon Island, on the contrary, 
 afforded an excellent site for a reservoir. The neighboring 
 country is sparsely settled, and there is no dwelling within a 
 mile of the works. The outlet, therefore, was finally located 
 at this point. 
 
 The next problems considered were the selection of a route 
 for the outfall sewer between the city and Moon Island and the 
 location of the pumping-station. As any route would neces- 
 sarily cross a portion of the harbor near the mouth of Neponset 
 River, it was thought best to explore the nature of the ground 
 underlying the harbor in that vicinity. To this end a number 
 of artesian borings were made from a scow fitted for the pur- 
 pose. Five-inch or smaller gas-pipe was driven to the required 
 depth, varying from 20 to 100 feet, and the earth excavated 
 from within them. In all, 139 such borings were made. 
 Those on the line selected by the commissioners, between Fox 
 
CITY OF BOSTON, 
 
 MAIN DRAINAGE. 
 
 PLAN SHOWING 
 
 AIN, INTERCEPTING &OUTFALL SEWERS///^/ ^^ 
 
 Aisin [[{(' 
 
 9 '^ y-^ yz" %. I MI LE V^-- -_ , , ,.„ ,.„„ , 
 
PRELIMINARY INVESTIGATIONS. 25 
 
 Point and Squantimi Beach, showed deep beds of mud under- 
 laid by sand and gravel ; so that any method of crossing at that 
 point would have been difficult and expensive. Moreover Fox 
 Point Avas thought to be too near to the valuable residence 
 property of Savin Hill to make it a suitable place for a pump- 
 ing-station. Borings at the mouth of the river opposite Com- 
 mercial Point also found deep beds of mud, but the crossing 
 being much shorter, it would have been comparatively easy to 
 have constructed a stable siphon on that line. Commercial 
 Point itself was a fairly good site for a puraping-station, but 
 would have been somewhat difficult of access from the city. 
 Ground suitable for tunnelling was discovered between Old 
 Harbor Point and Squantum Neck. This was the most direct 
 line from the city to Moon Island, and comparative estimates 
 showed it to be also the cheapest line. Its chief merit, however, 
 which caused it to be selected, was that it permitted the use of 
 Old Harbor Point as a site for the pum ping-station. This 
 point comprises over 100 acres of marsh land, valued by 
 the city assessors at only $200 an acre. It is itself destitute 
 of habitations, and sufficiently remote from any to afford assur- 
 ance that operations carried on there will not be a source of 
 offence. 
 
 Before adopting the tunnel line a plan was considered by 
 which the sewage, instead of being raised at Old Harbor Point, 
 was to flow thence by gravitation to a pumping-station at Moon 
 Island, on a nearlj^ direct line between the two points. The 
 sewer was to be built above oround and sunk into a trench dugf 
 to an even grade in the bottom of the harbor. To determine 
 the feasibility of this plan borings were made to test the 
 nature of the ground on the proposed line. The character of 
 the ground developed by these borings was not considered very 
 favorable, and a decision of the Harl)or Commissioners requir- 
 ing the sewer to he placed lower than was considered practi- 
 cable caused the proposed plan to be abandoned. 
 
 Having decided to locate the pumping-station at Old Harbor 
 Point the routes of the main and intercepting sewers were 
 next selected. The peculiar geological formation of the region 
 about Boston, causing frequent elevation of the bed-rock, not 
 
26 MAIN DEAINAGE WORKS. 
 
 always shown by surface indications, and the sometimes un- 
 suspected presence of deep beds of marsh mud, rendered it 
 necessary to test carefully the nature of the ground through 
 which it was proposed to build the sewers, since its character 
 would form such an important element in their cost and sta- 
 bility. The slowness and expense of artesian methods of 
 boring precluded their use. Light auger-rods were therefore 
 constructed, and it was found that by them the character of the 
 ground could be ascertained with approximate accuracy and 
 with little expense or delay. These tools, and the manner of 
 using them, are shown on Plate IV., Figs. 1 to 3. Including 
 work done before and after the beginning of construction, more 
 than 30,000 lineal feet of borings were thus made, at an average 
 cost of about 25 cents per foot. 
 
 There was no trustworthy information extant concerning the 
 position and condition of the city sewers which were to be inter- 
 cepted. Careful surveys were therefore made, of about 50 
 miles in extent, of such sewers as were in the vicinity of the 
 proposed intercepting sewers. Plans and profiles of these 
 were made, with cross-sections and such details of construction 
 as could be ascertained. 
 
 Nearly all buildings in the Back-Bay and South-End districts 
 of the city are supported on piles. By city ordinance the tops 
 of the piles are not to be higher than Grade 5, or mid-tide 
 level ; in fact many of them are a foot or tw^o higher. Fears 
 were expressed that the intercepting system (by doing away 
 with the semi-daily damming up by the tide of the contents 
 of the sewers) might lower considerably the soil-water in such 
 regions, and, by reducing it below the tops of the piles cause 
 them to decay and endanger the stability of the buildings sup- 
 ported by them. 
 
 To see if such danger was to be apprehended, it was decided 
 to produce in one of the Back-Bay sewers the precise condition 
 which would exist if the new system was constructed, and to 
 notice the effect upon the soil-water. To this end a steam 
 pump w^as put into the Berkeley-Street sewer near the outlet 
 and by continual pumping (except at low tide) the sewage 
 was kept but a few inches deep, as it would be if discharging 
 
PRELIMINAEY INVESTIGATIONS. 27 
 
 into an intercepting sewer. Previously 20 pipes had been 
 driven below the surface of soil-water ; some within a few feet 
 of the sewers, others a few hundred feet away, and still others 
 several blocks distant. The height of the soil-water standing 
 in each pipe was measured twice each day during the continu- 
 ance of the pumping. 
 
 The method of making these measurements was ingenious, 
 and perhaps novel. The elevation of the top of each pipe was 
 known, and the distance from the top to the surface of water 
 was taken with a steel tape. To the bottom of the tape was 
 attached a lead weight, with a needle fixed in its top so adjusted 
 that the point of the needle was just opposite to the end of the 
 tape. A small bit of metallic potassium was put on the point 
 of the needle. The instant this touched the water it ignited 
 explosively, and the flash and sound could be easily distin- 
 guished from above. A sketch of the apparatus is shown by 
 Fig. 7, Plate IV. 
 
 It was found that the surface of the soil-water was nearly 
 level over the whole Back-Bay district, averaging 7.7 feet 
 above mean low water, and its height, while slightly affected 
 by local contours of the surface, was independent of the sewers 
 in its vicinity. For instance, the water in the vicinity of the 
 Dartmouth-Street sewer was at the same level as that near the 
 Berkeley-Street sewer, although the latter sewer is two feet 
 lower than the former. Also it was found that the soil-water 
 rose and fell, responding quickly to any rain or melting of 
 snow (the extreme rise due to four inches of surface-water being 
 one foot) , and that the variation was nearly uniform over the 
 entire district. 
 
 Finally it appeared that the pumping, which continued 53 
 days, afiected but slightly, and that only within 100 feet of the 
 sewer, the soil-water in the vicinity of Berkeley Street. At 
 the close of the experiment, the sewer resuming its former 
 conditions, the soil-water in its immediate vicinity rose from 
 an inch to an inch and one-half, and thereafter fluctuated in 
 unison with the water in other localities. 
 
 The experiment was thought to show that no dangerous low- 
 
28 MAIN DRAINAGE WOEKS. 
 
 ering of the ground-water need be apprehended in consequence 
 of the adoption of an intercepting system. 
 
 The following was the general basis of calculations for 
 amounts of sewage and sizes of sewers. It was necessary to 
 assume some limit to the territory which should be tributary 
 to the intercepting system. A natural limit in this case seemed 
 to be afforded by the Charles and Neponset Rivers, which, with 
 Mother Brook connecting them, include an area of about 58 square 
 miles. Of this area about 46 square miles is high land, 40 or 
 more feet above low water, and, as suggested by the com- 
 missioners, drainage from districts above Grade 40 could, if 
 necessary, be intercepted by a "high-level" intercepting sewer 
 and could flow by gravitation to the reservoir at Moon Island. 
 There remain 12 square miles below Grade 40 which must 
 forever drain into the " low-level" system. As, however, it will 
 be long before the high-level sewer is built, and in the mean 
 time sewers from areas above Grade 40 must connect with the 
 low-level system, for purposes of calculation, it was assumed 
 that 20 squkre miles would be tributary to the proposed sys- 
 tem. 
 
 The prospective population was estimated at an average of 
 62|- persons to each acre, or 800,000 in all. This estimate of 
 62^ persons to the acre was used in calculations affecting the 
 main sewer ; but in proportioning branch intercepting sewers 
 greater densities of population were assumed, to provide for 
 possible movements of population. The amount of sewage per 
 individual was estimated at 75 gallons, or 10 cubic feet, in each 
 24 hours. The maximum flow of sewage per second was esti- 
 mated at one and one-half times the average flow due to 10 
 cubic feet per day. 
 
 On this basis the maximum flow of sewage-proper to be 
 
 provided for would be ^?^'^!?a ^ I-a X 1.5 = 138.88 cubic feet 
 ^ 24 X 60 X bO 
 
 per second. 
 
 This amount was nearly doubled by adding to it 100 cubic 
 feet per second as a provision for rain-water. This would rep- 
 resent a little less than one-fourth inch of rainfall in 24 hours, 
 per acre of tributary area ; but it was intended, in practice, to 
 
PRELIMINARY INVESTIGATIONS. 29 
 
 admit little, if any, rain from regions where the cellai-s were 
 not subject to flooding, and reserve the full capacity of the 
 sewers and pumps to relieve certain low districts where the 
 cellars are generally much below high tide, and were often 
 partly filled with water in time of rain. 
 
 For purposes of calculation, therefore, the prospective maxi- 
 mum flow per second in the main sewer was assumed to be 
 138.88 -|- 100 = 238.88 cubic feet per second. The inclination 
 of the sewer was 1 in 2,500, and it was designed (as were all 
 of the sewers) to flow about half full with its calculated maxi- 
 mum amount of sewage. Although this rule required that the 
 sewers should be larger than they would be if designed to flow 
 full, it was adopted because it gave about three feet less depth of 
 excavation for the whole sewer system, saved three feet lift in 
 pumping, provided storage-room for large additional amount* 
 of sewage due to intermission of pumping or to rain, and 
 afibrded more head-room to workmen entering the sewers. 
 
 In designing the smaller intercepting sewers the method em- 
 ployed was somewhat as follows : the districts drained by the 
 several city sewers were ascertained, and their respective areas 
 in acres were calculated. The largest population which by any 
 chance might live on these areas in the future was estimated, 
 i.e., guessed. The future average amount of sewage proper 
 due to such population was doubled for safety, and an addi- 
 tional amount added for rain, usually equalling that from .25- 
 inch rainfall in 24 hours. If an intercepting sewer large enough 
 to carry this total amount when flowing half full would have 
 been too small to be entered conveniently, its size, or sometimes 
 only its height, was increased sufiiciently to aftbrd convenient 
 head-room. 
 
 Velocities of flow were calculated by the formula V = C VRI, 
 with Mr. Kutters coefficients, obtained by using .013 as the 
 coefficient for roughness. 
 
 During the early stages of the work, the City Engineer, Mr. 
 Davis, made a trip to Europe to examine the foreign sewerage 
 works of best repute. Information was thus gained which was 
 used in designing the Boston works. 
 
 In July, 1877, the City Engineer reported the results of his 
 
30 MAIN DRAINAGE WORKS. 
 
 preliminary survey, and on August 9 of the same year orders 
 of the City Council were approved, authorizing, and making an 
 appropriation for, the construction of an improved system of 
 sewerage, in general accordance with the proposed plan, under 
 authority of the Act of Legislature. 
 
 The City Council committed the charge of building the Main 
 Drainage Works to a Joint Special Committee on Improved 
 Sewerage, consisting of three Aldermen, and five mem1)ers of 
 the Common Council. This committee changed its member- 
 ship every year except when one or more of its members were 
 reelected and were again appointed on it. By city ordinance 
 all engineering works are built by the City Engineer. The 
 Main Drainage Works, therefore, were constructed under the 
 direction of Mr. Joseph P. Davis, C.E., City Engineer, until 
 his resignation in 1880, and since that date by his successor in 
 office, Mr. Henry M. Wightman, CE.^ 
 
 ^ Since the above was written the city has sustained a great loss in the death of Mr. 
 Wightman. Mr. WilHam Jackson has been elected City Engineer. 
 
MAIN SEWEB. 31 
 
 CHAPTEE V. 
 
 MAIN SEWER. 
 
 The main sewer is about 3i miles long, and extends from the 
 pumping-station at Old Harbor Point to the junction of Hunt- 
 ington Avenue and Camden Street. Its inclination throughout 
 its whole extent is 1 foot vertical in 2,500 horizontal. At 
 the pumping-station the water-line of the invert, i.e., its bot- 
 tom, is about 14 feet below the elevation of mean low tide. From 
 this point, in its course towards the city, the sewer passes for 
 about a mile across the Calf Pasture Marsh, so called. The 
 surface of this marsh is about six inches above mean high water, 
 and, the mean rise and fall of the tide being ten feet, the aver- 
 age depth of excavation required for this section of work was 24 
 feet. Up to the junction of the South Boston intercepting 
 sewer the main sewer is ten feet six inches in diameter. It was 
 founded sometimes upon clay and sometimes upon sand. 
 Figs. 1 and 2, Plate VI., show the usual methods of construc- 
 tion. Eubble side walls were built for the greater portion of the 
 distance. Fig. 3 shows the bond used in the spandrels. 
 
 On this section occurred the only case during the construction 
 of the entire Main Drainage Works in which a sewer was 
 broken so that a portion of it had to be taken down and rebuilt. 
 At one point, for a distance of 150 feet, the marsh mud, which 
 usually was from five to ten feet deep below the surface of the 
 ground, came down below the spring-line of the sewer. Owing 
 to carelessness, on the part of the contractor, in back-filling 
 around the haunches, or in withdrawing the sheet planks, the 
 sewer spread six inches, and sank correspondingly at the crown. 
 Fig. 4 shows the shape assumed at the point of maximum dis- 
 tortion. Although even this portion was probably stable, it was 
 not considered wise to establish a precedent of accepting any im- 
 perfect work. Accordingly the trench was reopened, the sewer 
 uncovered, and its arch broken down with sledge hammers. 
 
32 MAIN DRAINAGE WORKS. 
 
 It was found that the 12-mch Akron drain-pipe built under 
 the sewer, to facilitate drainag-e of the trench durino- construe- 
 tion, was broken at this point, and the water from it, accumu- 
 lated from 4,000 feet of trench, found an outlet and poured 
 over the side walls into the invert. This water was controlled 
 by pumps, but was found to have washed out a quantity of 
 sand, causing a considerable cavity under the sewer platform. 
 The limits of the cavity having been determined, five holes, 
 ten feet apart on centres, were made through the bottom of the 
 sewer and 3-inch wrought-iron gas-pipes were inserted into 
 them. Two of these pipes were about 30 feet long and three 
 others, for vents, were five feet long. Constant streams of 
 grout, made from 47 casks of neat, quick-setting Portland ce- 
 ment, were forced under a 25-foot head, through the long pipes 
 into the cavity until it was filled, as proved by the cement ris- 
 ing in the short pipes. The grout hardened and furnished a 
 secure foundation. Special ribs were cut to fit the invert, which 
 was again arched over and the trench refilled. 
 
 Figs. 5 and 6, Plate VI., show methods of connecting man- 
 holes with the main sewer. These structures are about 400 
 feet apart, and are placed alternately on one side of and over 
 the centre of the sewer. At man-holes the arch is supported 
 by cut-granite skewback stones. At the top of the man-holes 
 are cast-iron frames supporting circular iron covers. The cov- 
 ers are perforated for purposes of ventilation. The holes are 
 quite large, so that they are not liable to become stopped up. 
 They also taper considerably, being larger below than they are 
 on top. To prevent road detritus and miscellaneous rubbish 
 from falling into the sewers, catch-pails are suspended below 
 the covers to receive whatever may fall through the holes. The 
 pails are of galvanized iron, well coated with tar. They can be 
 lifted out, emptied, and replaced, as occasion demands. 
 Wrought-iron steps were built into the man-holes during 
 construction. These details are shown on Plate VI., Figs. 
 7 and 8. 
 
 Above the point where the South Boston intercepting sew- 
 ers join the main sewer the latter is nine feet in diameter. For 
 about half a mile the ground is high, but a location through 
 
Plate VI. 
 
 SIDE ENTRANCE AND BOAT CHAMBER 
 
 Fi.^. 16 
 
 COVER 
 
MAIN SEWER. 33 
 
 it could not be avoided without making a considerable detour. 
 For 1,900 feet, in Mount Vernon Street, the sewer was built by 
 tunnelling through conglomerate rock and coarse sand. The 
 rock, where it surrounded the tunnel, presented no serious ob- 
 stacle : but the sand tended to run into the excavation, and re- 
 quired close sheeting and heavy bracing to support it. Fig. 
 9, Plate VI., shows the sewer in tunnel on this section. For 
 several hundred feet the sewer grade was near the surface of 
 the ledge and, the latter being very irregular and covered with 
 boulders, tunnelling operations were attended with much diffi- 
 culty, and several caves occurred. For a length of 160 feet 
 the ground was opened from the top and the sewer was built in 
 an open trench about 45 feet deep. 
 
 The sewer in the tunnel was well built, but after completion, 
 on removing the pumps so that the water table in the vicinity 
 was permitted to rise above the sewer, the latter was found to 
 leak a good deal. The leaks, however, could be successfully 
 calked. The process consisted in raking out a joint, where a 
 leak occurred, to the full depth of the brick and driving in 
 sheet lead for half the depth, the remainder being filled with 
 cement. 
 
 Excepting a section in East Chester Park, from Clapp Street 
 to Magazine Street, the main sewer was built by contract. The 
 laying, out as a street of East Chester Park, east of Albany 
 Street, had been contemplated by the authorities for some time, 
 and action to that end was taken in time to permit the sewer 
 being located there. The borings on this line showed that there 
 were beds of mfa'sh mud between Clapp and Magazine Streets 
 which were from 20 to 86 feet deep below the marsh surface. 
 As it would have been difficult to build a stable sewer in such 
 ground, and impossible to prevent one, if built, being destroyed 
 when the street should be filled over and around it, it was de- 
 cided to fill the street to full lines and grades before attempting 
 to build the sewer. 
 
 A contract was accordingly concluded by which the street 
 was filled with gravel brought by the N.Y. and N.E. Eailroad. 
 So great was the settlement of this filling into the mud that 
 over 106,000 cubic yards of gravel were required. The marsh 
 
34 MAIN DRAINAGE. WORKS. 
 
 level for 100, or more, feet on either side of the filled 
 street was pushed up by the filling from 8 to 14 feet high. A 
 surcharge, 20 feet wide on top and eight feet high, was put 
 upon the street, west of the N.Y. & N.E. Eailroad, where the 
 mud was deepest, to insure prompt settlement. 
 
 Building a stable sewer in a street so recently filled being a 
 difficult operation, requiring methods of treatment which can- 
 not be determined upon beforehand, it was thought best to 
 build this section by day's labor. 
 
 As a masonry structure would have been broken when the 
 trench was refilled, a wooden sewer was adopted (Fig. 10, 
 Plate YI. ) . This consisted of an external wooden shell, formed 
 of 4-incli spruce plank, ten inches wide, every fourth plank 
 being wedge-shaped ; the whole securely spiked and treenailed 
 together and finally lined with four inches of brick or concrete 
 masonry. 
 
 The depth of excavation for this sewer was from 32 to 36 
 feet, and the pressures were so great as to require very heavy 
 bracing. As many as 60 braces of 8 inch X 8 inch, or heavier 
 timber, were sometimes used for a length of 18 lineal feet of 
 trench ; and these, when taken out, were all found to be either 
 broken, or so crippled as to be unfit to use again. Frequently 
 the earth on one side of the trench was found to be diiferent 
 from that on the other, which caused very unequal pressures, so 
 that internal bracing was necessary to maintain the sewer in its 
 proper shape until the trench had been back-filled. It was 
 found necessary to build the shell with a vertical diameter 
 four inches greater than was required for the^tnasonry lining, 
 to allow for settlement, change of shape, and compression of 
 the timber. The vertical diameter inside of the lining was also 
 increased, so that, if in places the sewer should settle as a whole, 
 the bottom could be brought to the true grade, and still leave 
 the established sectional area. 
 
 The length of this section was 1,894 feet. Ground was first 
 broken in August, 1879, and the work was completed in Octo- 
 ber, 1880. For excavating and back-filling the trench, machin- 
 ery designed by the Superintendent, Mr. H. A. Carson, was 
 used. The average cost per lineal foot of the completed sewer 
 
MAIN SEWER. 35 
 
 was $56. For severiil hundred feet, where the mud htid been 
 deepest, a continual slight shrinkage and settlement of the 
 gravel tilling under the sewer occurred for a year or more. 
 The sewer itself, also, settled in a long curve, whose greatest 
 depth below the original grade line was about 1(S inches. A 
 masonry sewer would have been broken by such movement, 
 but the wooden one having consideralile tlexibility was appar- 
 ently uninjured. At present (1885) the street seems to have 
 assumed a condition of permanent stability. 
 
 In East Chester Park, from Magazine Street to Albany 
 Street, clay was chiefly encountered, and the sewer generally 
 consisted of a simple ring of brick-work without side walls, and 
 its construction presented few features of special interest. As 
 a precaution in passing within 35 feet of a large gas-holder, 
 tongued and grooved 4-inch sheet planks were driven, and 
 the trench was back-filled with concrete to the crown of the 
 sewer arch (Fig. 11). In passing across the old Roxbury 
 Canal, which had been recently filled by the city, an influx of 
 tide-water alono- the loose walls of the canal and throuoh the 
 filling occasioned some' delay and expense. The water was 
 finally kept out by double rows of tongued and grooved sheet- 
 piling. A side entrance and boat-chamber (Fig. 12), were built 
 on this section, at the corner of Swett Street. The latter 
 structure resembled a very large man-hole, with a rectangular 
 opening from the street, 11X4 feet in dimensions. This was 
 built to allow the lowerino- of boats into the sewer. 
 
 At Albany Street the east-side intercepting sew^er joins the 
 main, and above this point the latter is again reduced in size, to 
 eight feet three inches wide by eight feet five inches high. The 
 extra horizontal course was put in at the spring line because it 
 was supposed to facilitate dropping and moving the centres. 
 In East Chester Park, and Washington Street from Albany to 
 Camden Street, the sewer was built chiefly in clay, and con- 
 sisted of a ring of brick-work. For about 300 feet, however, 
 near Albany Street, mud was found, and a foundation, consisting 
 of a timber platform supported on piles, became necessary 
 (Fig: 13, Plate VI.). 
 
 In Camden Street, from Washington Street to Tremont 
 
36 MAIN DRAINAGE WOEKS. 
 
 Street, a distance of 1,391 feet, the depth of trench required 
 would have been 26 feet. Camden Street is rather narrow, and 
 contains sewer, gas, and water pipes. As good clay was found 
 at a depth five or more feet above the top of the sewer, it was 
 thought that it would be as cheap to the city, and decidedly 
 less annoying to residents on the street, to build the sewer by 
 tunnelling beneath the surface (Fig. 14). Working shafts were 
 sunk about 250 feet apart, and headings in each direction driven 
 from them. At one or two points the miners permitted the 
 roof of the tunnel to settle slightly, by which the common sewer 
 above was cracked, and some trouble caused by the sewage 
 leaking into the tunnel. The main sewer was back-filled above 
 the arch with clay, packed in under the lagging as firmly as 
 possible. On the whole the method of construction was suc- 
 cessful, and a well-built sewer was obtained. Its cost was 
 $22.52 per lineal foot. 
 
 At Tremont Street the Stony-Brook intercepting sewer is 
 taken in. At this point, as at all other places where intercept- 
 ing sewers join the main sewer, the grade of the latter rises 
 abruptly somewhat less than a foot, or enough to maintain the 
 established inclination on the surface of the sewage at the time 
 of maximum How. From Tremont Street to the present end of 
 the main sewer, at Huntington Avenue, the sewer was built in 
 open cut (Fig. 15), and for a large part of the distance needed 
 side walls and piling for its support. Just west of the B. & 
 P. R.R. another boat-chamber and side entrance (Fig. 16) 
 were built, and a third side entrance, reached by a stone stair- 
 way leading from the sidewalk, was constructed at Huntington 
 Avenue. 
 
 The total cost of the 3.2 miles of main sewer was $606,031 
 being an average of $36.09 per lineal foot. 
 
INTERCEPTING SEWERS. 37 
 
 CHAPTER VI. 
 
 INTERCEPTING SEWPiRS. 
 
 As before stated, and as shown by the plan (Plate V.), the 
 South Boston intercepting sewer is the first to- join the main 
 sewer in the latter's course from the pumping-station towards 
 the city proper. This intercepting sewer, by its two branches, 
 is intended finally to encircle the peninsula on which South 
 Boston is situated, and intercept the sewage flowing in the com- 
 mon sewers, which have heretofore discharged their contents at 
 nineteen outlets, in the immediate vicinity of a dense popula- 
 tion. 
 
 At the point of junction the grade of the intercepting sewer 
 is 1.5 feet higher than that of the main sewer, so that the sew- 
 age in the former shall not be dammed back, and the established 
 rate of inclination shall be maintained on the surface of the 
 sewage in both sewers at the time of maximum discharge. In 
 all cases where a main-drainage sewer joins another, the junc- 
 tion is made at a " bell-mouth " connection chamber, in which 
 the axes of the sewers meet by lines or curves tangent to each 
 other, so that the two currents may unite with the least dis- 
 turbance to either. Sections of the " bell-mouth " junction of 
 the two branches of the South Boston sewer, at Hyde Street, 
 are shown by Fig. 14, Plate VII. On each intercepting 
 sewer, just before it reaches the main sew^er, is built a penstock 
 chamber, containing a cast-ii'on penstock gate, by which the 
 flow can be cut ofi", so that the main sewer can be entirely 
 emptied, should it ever be desirable to do so. At such times 
 the city sewage would be discharged at the old outlets, which 
 are all retained and protected by tide-gates. A sketch of the 
 penstock on the South Boston sewer is given by Fig. 6. 
 
 Up to where it divides this sewer is circular, six feet in 
 diameter. The average depth of excavation was 20 feet. Clay 
 or sand was usually found, and the sewer consists of a simple 
 
38 MAIN DRAINAGE WORKS. 
 
 ring of brick-work, 12 inches thick, though for about 350 feet, 
 where the sand was wet and inclined to run, abutment walls of 
 rubble masonry were used. Figs. 12 and 13 show cross- 
 sections of this sewer. The brick invert was laid with Port- 
 land cement mortar, one part cement to two parts sand, and the 
 arch was laid with American (Eosendale) cement mortar, one 
 part cement to 1.5 parts sand. This was the common practice 
 in building the main-drainage sewers, Portland cement being 
 used in the inverts, on account of its greater resistance to abra- 
 sion. When Rosendale cement was used for building inverts, 
 the proportion required was equal parts of cement and sand. 
 
 The inclination of this sewer throughout the greater portion 
 of its extent is 1 in 2,000, which affords a velocity of flow 
 sufficient to prevent deposits of sludge, but not sufficient to 
 keep in suspension sand and road detritus. A sharper inclina- 
 tion would have been desirable had it been practicable to ob- 
 tain one. Few of the main drainage sewers have a greater 
 inclination than 1 in 2,000, and it was expected from the first 
 that flushing would occasionally be required to prevent the 
 accumulation of deposits. To provide for this, iron flushing- 
 gates are built into the sewers at intervals of about half a mile. 
 The first flushing-gate on the South Boston sewer is just below 
 the fork at Hyde Street. A sketch of this gate is given b}^ 
 Fig. 15. Usually the gate stands above the sewer, in the 
 man-hole. It is kept vertical by two small stop-bolts at its top. 
 To flush the sewer the gate is lowered against its seat, built 
 into the bottom of the sewer, and the sewage accumulates be- 
 hind it as deep as the gate is high. The stops are then with- 
 drawn and the gate raised until it clears its lower seat, when it 
 tilts over into a horizontal position and opens a free passage 
 for the dammed-up sewage. 
 
 The greater [)art of South Boston is high land, and there are 
 but few low cellars there which are subject during rain-storms 
 to flooding at high tide. In order that the full capacity of the 
 sewers and pumps might be available to relieve other parts of 
 the city, less favored in this respect, it was necessary to ar- 
 range that no more than a fixed quantity of sewage should 
 ever be relfceived by the main sewer from the South Boston 
 
Plate VII. 
 
 R^.2 
 
 Fi^.3 
 
 n§.4 
 
 LARGE REGULATOR 
 
 PENSTOCK GATE 
 
 n§.6 
 
 CONNECTION WITH %^ vale: ST, SEWER 
 Fig.O 7 
 
 SECTIONAL PLAN 
 
 PLAN 
 
 BOSTON MAIN DRAINAGE 
 INTERCEPTING SEWERS. 
 
 O 2 4 6 8 10 
 l<d bd lid M M M 
 SCALE OF FEET 
 
 BACK. VIEW. FRONT VIEW 
 
 TIDE GATES. 
 
 Fig. 12 
 
 Fig. 13 
 
 FLUSHING GATE 
 
 Fig. 15 
 
INTEECEPTIXG SEWERS. 39 
 
 intercepting seTrer. To accomplish this a " regulator " was 
 built into the intercepting sewer just below its last connection 
 with a common sewer, at Kemp Street. 
 
 A sectional plan and elevation of this machine, and of the 
 chamber containing it, is given by Fig. 9, Plate VII. 
 As will be seen, the apparatus is very simple, and consists of 
 stop-planks, closing the sewer from its top down to about 
 the ordinary dry-weather flow line, the sewer below the planks 
 being lined with a cast-iron gate frame, or seat, curved to fit 
 the invert, and also vertically to correspond with the curve of 
 motion of a cast-iron valve, which plays up and down in front 
 of it. The valve is held by two cast-iron levers, pivoted by a 
 3-inch wrought-iron shaft in two bearings, the other ends 
 of the lever being connected by vertical arms to a 3-inch 
 square bar. To the ends of this bar are fastened two boiler- 
 plate floats, placed in wells on either side of the sewer. To 
 avoid disturbance to the motion of the floats, by waves caused 
 by the rush of sewage under the valve, water is brought to the 
 wells through a 5-inch pipe, as shoAvn, from a point 50 feet 
 below the regulator. 
 
 The connection between the valves and the floats can be so 
 adjusted that the former will begin to close when the surface of 
 sewage in the sewer has reached any desired height. As the 
 floats rise the valve descends until the opening below it is just 
 sufficient to let enough sewage pass to maintain the allowed 
 depth of flow in the sewer. Should the amount of rain-water 
 from low districts, reaching the main sewer through other 
 intercepting sewers, exceed the capacity of the pumps to con- 
 trol it, the main sewer fills, and its sewage backs up into the 
 South Boston sewer, and still further raises the floats. The 
 opening under the stop-planks is thus entirely closed, and all 
 of the common sewers above discharge at their old outlets, and 
 continue to do so until the amount of water reaching the pumps 
 can be controlled by them. 
 
 Above where this sewer divides, at Hyde Street, the branch 
 which turns to the right, and skirts the southerly margin of 
 South Boston, is egg-shaped, four feet six inches high hy three 
 feet wide (Fig. 11, Plate VII.). After passing under the 
 
40 MAIN DRAINAGE WORKS. 
 
 Old Colony Eailroad the shape is changed somewhat (Fig. 
 3). At Vinton, Vale, and other streets, common sewers are 
 intercepted. Fig. 7, Plate VII., shows the connection with the 
 Vale-Street sewer, and may stand as a type of such connec- 
 tions between common and intercepting sewers, wherever no 
 regulation of the amount to be received from the former is 
 required. Nearly every individual case presented special con- 
 ditions, which necessitated some modification of the method of 
 construction ; but the general plan was the same in most cases, 
 and its features are shown in this case. 
 
 A sump hole, two feet deep, into which the sewage falls, is 
 first built in the common sewer. Into the bottom of this sump 
 is built a short section of iron pipe (Fig. 5), from 12 to 24 
 inches in diameter, protected by a cast-iron flap-valve. Ordi- 
 narily this valve stands open, but can be closed if it is desired 
 to break the connection between the two sewers. The bottom 
 of the sump, around the pipe, is rounded ofi" with strong Port- 
 land cement concrete, so that there shall be no corners in which 
 deposits can lodge. The sewage passes to the intercepting 
 sewer through a short branch connecting; with the lower end of 
 the iron pipe. 
 
 Beyond the sump the common sewer is provided with a 
 chamber containing a double set of tide-gates. These gates 
 give a clear opening of from two to four feet diameter. Each 
 set of gates is hinged to a cast-iron ring, or gate seat (Fig. 
 8), which is built into the brick- work. The two wooden gates 
 close against each other. To make tight joints the bearing 
 surfaces of the gates are covered with strips of rubber about 
 three-eighths of an inch thick. The gates are inclined somewhat, 
 so that they are self-closing. 
 
 From the main sewer to the Old Colony Eailroad this inter- 
 cepting sewer was built by contract, at an average cost of $12.68 
 per lineal foot. From the railroad to H Street it was built by 
 day's labor, and cost $13.25 per lineal foot. On Ninth Street, 
 between Old Harbor Street and G Street, for a distance of 
 about 800 feet, the sewer location crossed a beach which was 
 several feet below high-tide level. No cofler dam or other 
 protection was used in this place, but construction was carried 
 
INTERCEPTING SEWERS. 41 
 
 on only when the tide was down. When the sea rose it over- 
 flowed and filled the trench. When it again fell the water in 
 the trench was let off through the sewer already built, to pumps 
 at the pumping-station, and work was resumed. From H 
 Street to N Street, on Ninth Street, the sewer was built by 
 contract. For about 1,000 feet, near K and L Streets, the 
 average depth of the trench was about 27 feet. The sewer was 
 nearly circular, three feet wide and three feet two inches high 
 (Fig. 1, Plate VII.). This section was among the earliest built, 
 and its design is not in accord with later practice. It might have 
 been made much more convenient for workmen to enter, at slight 
 additional expense, by giving it a greater vertical diameter. Its 
 fall is 1 in 1,666|-. 
 
 From the point of division on Hyde Street the sewer which 
 turns to the left, and follows the westerly shore of South Boston, 
 is egg-shaped, five feet six inches by four feet nine inches, up to 
 the Old Colony Eailroad crossing, on Dorchester Avenue. A 
 timber platform and rubble masonry side walls were required for 
 the entire distance, and the usual cross-section of this sewer is 
 shown by Fig. 10, Plate VII. This section was built by con- 
 tract. Its length is 3,350 feet ; the average depth of excavation 
 was about 24 feet, and the average cost per lineal foot was 
 $16.85. 
 
 After taking in the B-Street sewer the intercepting sewer 
 changes its shape (Fig. 3), and continues in Dorchester 
 Avenue, passing under the N.Y. & N.E. Railroad, and turns 
 into Foundry Street, which it follows to its end, at the corner 
 of Dorchester Avenue and First Street. Considerable difiiculty 
 was encountered in passing under the abutments of the bridge 
 on Dorchester Avenue, over the N.Y. & N.E. Railroad. 
 These were underlaid by running sand, and the northerly abut- 
 ment over the sewer, which had been built without mortar, had 
 to be taken down. Under the tracks of the same railroad, 
 head-room being limited, the shape of the sewer was altered 
 (Fig. 2), so that there should be no danger of its interfering 
 with, or being injured by, repairs to the road-bed. This section 
 of sewer is 2,820 feet long, and its average cost per foot was 
 $19.25. 
 
42 MAIN DRAINAGE WORKS. 
 
 The second large intercepting sewer which enters the main 
 sewer, had its point of connection at the intersection of East 
 Chester Park and Albany Street. It is called the East Side 
 intercepting sewer, and is located in streets following the east- 
 erly margin of the city proper for a distance of about 21 miles. 
 In Albany Street, from East Chester Park to Dover Street, a dis- 
 tance of 4,524 feet, the sewer is nearly circular, with a vertical 
 diameter of five feet eight inches, and a horizontal one of five 
 feet six inches. The inclination is 1 in 2,000. The average 
 depth of excavation for this section of work was 24 feet, and, as 
 marsh mud and peat extended from near the surface of the 
 ground to a depth always considerably below the bottom of the^ 
 sewer, piles were required to. furnish a secure foundation. A 
 timber platform was fastened to the tops of the piles, and on 
 the platform the sewer, with its rubble masonry abutment walls, 
 was built. The bottom of the excavation was about 6.5 feet below 
 the elevation of low tide, and considerable trouble was experi- 
 enced from sea-water making its way into the trench, esjoecially 
 in places where old sea-walls and other such obstructions were 
 encountered. The mud on the sides of the trench exerted much 
 lateral pressure, and close sheet-piling and heav}'^ bracing were 
 necessary. Opening so deep a trench in such material drained 
 the water out of the adjacent soil, rendering it spongy and some- 
 what compressible, so that the whole street settled and had to 
 be resurfaced and repaved. This section was built by contract. 
 One firm of contractors gave up the job, and the work was re-let 
 under provisions of the contract. The average cost per lineal 
 foot of the completed sewer was $26.16. 
 
 The first common sewer taken in by the intercepter is that 
 on Concord Street. This sewer drains a district in which the 
 cellars are not subject to flooding from rain-water during high 
 tides. It was not necessary, therefore, to let this sewer dis- 
 charge into the intercepter an amount of sewage in excess of 
 its ordinary maximum dry-weather flow, and temporarily, during 
 rain-storms, the whole dilute contents of the sewer could, with- 
 out injury, be permitted to discharge into the bay at the old 
 outlet. An arrangement to effect this was desirable, because, 
 during very heavy rain-storms, the whole capacity of the inter- 
 
INTERCEPTING SEWERS. 43 
 
 cepting sewer might be needed to aftbrd relief to sewers drain- 
 ing low districts beyond Concord Street. 
 
 Accordingly the connection between this sewer and the 
 intercepting sewer was made through a chamlier containing a 
 small regulating apparatus, designed to control or cut oft' the 
 flow automatically. Figs. 1 and 2, Plate VIII., show sec- 
 tions of this apparatus and its arrangement. Eight similar 
 appliances, with slight modifications in the methods of arrange- 
 ment, were used in connection with the same number of common 
 servers. 
 
 The operation of the apparatus will be understood from an 
 examination of the figures. Under ordinary circumstances the 
 sewage falls into a sump, and thence passes to the regulating 
 chamber, which it enters through a cast-iron nozzle. This nozzle 
 is circular, 12 inches in diameter at its upper end, and rec- 
 tangular 20 X 6 inches at its orifice. In front of the orifice 
 plays a cast-iron valve, moved by afloat in a tank set in the floor 
 of the chamber. The water in the tank stands at the same 
 elevation as that in the intercepting sewer, a 4-inch iron pipe 
 connecting one with the other. The apparatus can be adjusted 
 so that the valve will begin to close and cut off* the flow of 
 sewage when the water in the intercepting sewer reaches any 
 desired dei)th. When not cut off", the sewage flows around the 
 tank and passes on through an opening at its further end. 
 
 The second common sewer taken in is that in Dedham Street. 
 This sewer drains a district which used to sufifer greatly from 
 flooding during rain-storms. In order to afibrd relief this sewer 
 was connected directly with the intercepter by a branch two feet 
 in diameter, the inlet to which is never closed. 
 
 The third sewer taken in is that in Union Park Street. The 
 district drained by it has suflered but slightly from wet cellars, 
 and that only during severe storms and very high tides. The 
 flow from this sewer was regulated in the same manner as that 
 from the Concord-Street sewer, but the apparatus was so 
 adjusted that it cuts oft' the flow later than in the case of most 
 other sewers, and only when the intercepting sewer is nearly 
 full. 
 
 'J'he fourth common sewer met with is that in Dover Street. 
 
44 MAIN DRAINAGE WORKS. 
 
 This drains a low district, and a free connection, two feet in 
 diameter, was made with it. According to the usual practice 
 in such cases this sewer would have been connected with tlie 
 intercepter at or near the point in Albany Street where their 
 two locations intersect. But it was found in examining the 
 city sewers, with reference to connections with them, that the 
 Dover-Street sewer was not in condition to be intercepted at 
 any point east of Harrison Avenue. Between that street and 
 its outlet it is a rectangular wooden structure, 5 x ^ feet in 
 dimensions, placed close to an old stone retaining-wall and 
 surrounded b}^ loose stone ballast. It is considerably broken, 
 so that the tide-water from the bay which ebbs and flows about 
 the wall and in the ballast has free access to the sewer, and 
 would have flowed into the intercepting sewer, and so 
 reached the pumps. From Harrison Avenue westerly, the 
 Dover-Street sewer was built of brick, and was tight so that sea- 
 water could be excluded from it by tide-gates. Accordingly 
 the connection was made west of Harrison Avenue, and a 2 X 3 
 feet oval branch sewer (Fig. 3), 588 feet long, was built from 
 that point to convey the sewage to the intercepting sewer at 
 Albany Street. 
 
 Above Dover Street are few districts which sufi'er from flood- 
 ing. Accordingly a large regulating apparatus, to control the 
 flow from above, was built into the intercepting sev/er at this 
 point. It resembled that on the South Boston sewer, before 
 described, and shown on Plate VII, by Fig. 9. 
 
 From Dover Street to its upper end on Atlantic Avenue the 
 East Side sewer was built by day's labor, under a superintend- 
 ent appointed by the city. This was done because above 
 Dover Street the sewer location was confined to crowded 
 thoroughftires, in which peculiar management was required to 
 prevent serious obstruction to travel and to the business of 
 abutters ; and also because, operations being principally car- 
 ried on in filled land, beds of dock mud, old walls, wharves, 
 and other obstructions were continually encountered, requiring 
 frequent changes in methods of construction which could not be 
 foreseen and provided for in the specifications of a contract. 
 
 From Dover Street the sewer location extends in Albany 
 
-Plate Vlir, 
 
 
 1- 
 
 "^^.^ 
 
 
 _J 
 
 
 
 
 
 
 
 
 , 
 
 
 iNTERGEPJlNCi 
 
 -s- 
 
 
 
 \ 
 
 Ay 
 
 
 \/ 
 
 / 
 
 
 /W 
 
 
 
 // 
 
 REGULA" 
 
 o 
 
 
 
 r 
 
 / 
 
 
 -L 
 
 SUMP 
 
 
 
 
 
 GENERAL PLAN OF 
 CONCORD ST. CONNECTION 
 
 Fig. 14 Fig. 15 
 
 BOSTON MAIN DRAINAGE, 
 
 INTERCEPTING SEWERS. 
 
 10 15 20 FEET 
 
 O 5 10 15 20 
 
 hH-ri-H4n. 4 --i--h-ht-i--Lr- M^ 
 
 SECTIONAL PLAN. 
 
 FALMOUTH ST. SEWER. 
 
> INTERCEPTING SEWERS. 45 
 
 Street to Lehigh Street, at which point it enters private land, and 
 crosses the freight and switch yards of the Boston and Albany, 
 and Old Colony Railroads, to Federal Street near the bridge, 
 a total distance of 2,331.5 feet. In Albany and Lehigh Streets 
 are the tracks of a Freight Railway Company, and in the rail- 
 road yards are about 40 lines of rails in constant use, which 
 it was very important should not be disturbed. The whole 
 section of work is in tilled land, underlaid by beds of mud from 
 5 to 20 feet deep, below the bottom of the sewer, which is 
 itself several feet below the level of low tide. At different 
 points obstruction in the shape of old walls and wharves were 
 encountered, which admitted sea-water freely to the trench, so 
 that, as a rule, work could only progress during low stages of 
 the tide. 
 
 The sewer is oval, five feet high (Fig. 4), and generally 
 required piling for its support. It is built partly of wood, lined 
 with two inches of concrete, and partly of brick-work resting on 
 a solid cradle of wood, six inches thick. Travel upon the streets 
 was not interrupted, and with considerable difiiculty the freight- 
 railway tracks were supported and maintained. As it would 
 have been impossible to have had an open trench through the 
 Albany and Old Colony Railroad yards without interfering with 
 their traflac, operations at that point were carried on entirely 
 below the surface. The tracks were supported by stringers, 
 and the spaces between them floored over. By the use of 
 special machinery all the earth excavated or refilled, as well as 
 materials for constructions, was conveyed by tracks suspended 
 below the floor. The trench was well braced, and its sides pro- 
 tected by lag-sheeting, which, together with the piles driven to 
 support the sewer, were all put in place without encroaching 
 upon the surface. It is believed that not a single train was 
 delayed, nor any inconvenience caused, by these operations. 
 The average cost of this section of sewer was about $31.26 per 
 lineal foot. 
 
 In Federal Street, and Atlantic Avenue to its end at Central 
 Street, the intercepting sewer is oval, four feet six inches high by 
 two feet eight inches wide. Fig. 5, Plate VIII. , shows the usual 
 mode of construction. Federal Street contained double horse- 
 
46 MAIN DRAINAGE WOEKS. 
 
 railroad and single freight-raihvay tracks, and beneath its sur- 
 face were one sewer, two water pipes and two gas pipes. 
 Beds of dock mud extended from 5 to 20 feet below the bottom 
 of the new sewer, and old dock walls and timber structures 
 were frequently encountered. A location on the east side of 
 the street was found to be most practicable, and the sewer was 
 built by methods which left the roadway open for travel. By 
 flooring over the trench at intervals, passages were maiutained 
 through the excavating machine (shown on Plate XXV.) to the 
 yards and wharves bordering Fort Point Channel. 
 
 The freight-railway tracks were shifted towards the centre 
 of the street, and were used during the day for the passage of 
 horse-cars in one direction. Bricks, cement, and other mate- 
 rial were piled on the outer edges of both sidewalks where 
 they would cause least inconvenience, and always so as to leave 
 a clear passage-way four feet wide. Endeavors were made to 
 cause the least possible annoyance to corporations and individu- 
 als ; and in general these efl:brts seemed to be appreciated and 
 reciprocated by the public, so that complaints were rare. 
 This section of work was 5,159 feet long. The average depth 
 of excavation was about 21 feet, and the average cost of com- 
 pleted sewer was $15.06 per lineal foot. The Stony-Brook in- 
 tercepting sewer joins the main sewer at the intersection of 
 Camden and Tremont Streets. This sewer intercepts the sew- 
 age which formerly emptied at seven outlets, into Stony Brook, 
 and thence found its way into the Back Bay. In Tremont and 
 Cabot Streets, from Camden to Euggles Street (Plate V.), a 
 distance of 2,135 feet, the sewer was built by contract. The 
 rate of inclination is 1 in 700, and the average depth of excava- 
 tion required was 21 feet. The sewer is nearly circular, four feet 
 six inches wide by four feet eight inches high, and is chiefly 
 founded on clay, so that side walls were only needed for about 
 300 feet, and the average cost per lineal foot, including inspec- 
 tion, was $11.97. The customary iron penstock gate w^as built 
 into the sewer just above the bell-mouth connection chamber 
 by which it joins the main. 
 
 As the territory drained by the sewers which empty into 
 Stony Brook is high land, a large automatic regulating appara- 
 
INTERCEPTING SEWERS. 47 
 
 tus, similar to the one shown on Phite VII., was ])uilt into the 
 intercepting sewer at Rnggles Street, by means of which the 
 flow is partly or wholly cut off during severe and continuous 
 rain-storms. Above the regulator is a three-way bell-mouth 
 chamber (Fig. 10, Plate VIII.), from which radiate three 
 principal branch sewers. The centre or main branch, al)out 4^ 
 feet in diameter, is 1,700 feet long, and intercepts the sewage 
 formerly discharging into the brook by outlets at Elmwood and 
 Hampshire Streets. This sewer passes twice under the brook, 
 at so low an elevation that it preserves its regular grade and 
 shape. The other two branches are Ijuilt just large enough to 
 enter, being 2x3 feet, egg-shaped, with the smaller end 
 down. These also cross twice under the brook, at Tremont 
 Street and at Ruggles Street. Including the regulating cham- 
 ber, and all sewers above it, this section of work was built by 
 the day, under the City Superintendent, Mr. H. A. Carson. 
 There were built in all 4,229 lineal feet of sewers, includin£>-415 
 feet of 15-inch pipe. The average cost per foot of the whole 
 was $14.30. A considerable portion of the 2X3 feet sewers 
 was built during the winter of 1880-81. The sewers were 
 from 14 to 19 feet below the street surface, and the excavation 
 was done by tunnelling from pits about 10 feet apart. The 
 outlets of the city sewers being below the level of high tide, in 
 order to prevent back-water reaching the intercepting sewer, it 
 was necessary to build gate-chambers just beyond the points 
 of interception, each chamber containing a double set of tide- 
 gates. 
 
 The last of the large intercepting sewers joins the main sewer 
 at its present end at the intersection of Camden Street with 
 Huntington Avenue (Plate V.). It is commonly called the 
 West Side intercepting sewer, and is located in streets border- 
 ing the westerly margin of the city proper, and intercepts the 
 sewage which formerly discharged into Charles River. This 
 sewer is about 3| miles long, and its inclination from end to end 
 is 1 in 2,000. 
 
 From the main sewer to Beacon Street, and in that street to 
 Charles Street, a distance of 9,325 feet, the West Side sewer 
 was built by day's labor, at an average cost of $13.35 per lineal 
 
48 MAIN DRAINAGE WORKS. 
 
 foot. This section of work includes, besides the customary 
 man-holes, six common-sewer connections, five small regulators, 
 one side entrance, one penstock, and three flushing-gates. The 
 usual form of this sewer is shown by Fig. 8, Plate VIII. It is 
 egg-shaped, five feet six inches high by four feet nine inches wide. 
 It will be noticed that the usual position given to an egg-shaped 
 sewer is reversed in this case, the larg-er end of the ess: formino- 
 the invert. This position was adopted because, while affording 
 convenient head-room, it kept the flow line as low down as was 
 practicable. As the flow in this sewer is always a foot or 
 more deep,. the hydraulic mean depth, and consequently the 
 velocity of flow, is greater than it would have been had the 
 smaller end of the sewer been below. 
 
 A case of slight injury to this sewer may be worth noticing. 
 When the sewer was built on the line of Falmouth Street that 
 street had not yet been filled and graded, and the mud and peat, 
 which underlay the marsh surface in that locality, sometimes ex- 
 tended down below the top of the sewer. About a year after- 
 wards the street was graded with gravel about seven feet high 
 above the original surface of the marsh over the sewer. One 
 side of the street was filled before the other, and the unequal 
 pressure which resulted was transmitted to the sewer, and 
 caused its arch to bulge, as shown by Fig. 12. Fortunately the 
 amount of distortion was not sufficient to endanger the sewer's 
 stability, and the crack was pointed with Portland cement. 
 
 In Hereford Street, for a distance of 282 feet, the sewer lo- 
 cation passed under a freight-yard of the Boston & Albany 
 Railroad, in which were about 20 lines of track. Piles were 
 driven and stringers placed to support these tracks, and nearly 
 all of the sewer building operations were carried on beneath 
 the surface of the ground, so that the traffic of the railroad was 
 not interfered with. At this point, and beyond the railroad 
 location for a total length of about 800 feet in Hereford Street, 
 a common sewer was built in the same trench, directly above 
 the intercepting sewer. This was done by an arrangement with 
 the City Sewer Department, which designed and paid for the 
 upper sewer. A cross-section of the two sewers, showing their 
 arrangement, is shown by Fig. 9. 
 
INTERCEPTING SEWERS. 49 
 
 In Beacon Street, for a distance of 590 feet in the vicinity of 
 Exeter Street, 22 old stone walls, from five to twelve feet thick, 
 were encountered and had to ])e cut through. These walls con- 
 stituted the sluiceway of the old mill-dam, and their removal 
 caused considerable delay. The cost of excavation per lineal 
 foot of trench, 20 feet deep in this street, varied from $3.94 to 
 $14.49. The section from Camden to Charles Street was 
 built in 1878. During a portion of the season work was car- 
 ried on day and night at two different points. The largest 
 number of men and boys employed at any one time was 369. 
 The rate of progress varied greatly ; where no special obstacles 
 were met, 108 feet of completed sewer was built each 24 
 hours. 
 
 On Beacon Street the large common sewers in Hereford, 
 Fairfield, Dartmouth, and Berkeley Streets are intercepted. 
 The sewage from each of these sewers passes to the intercept- 
 ing sewer through a chamber in which is a small automatic 
 regulating apparatus, similar to the one shown on Plate VIII., 
 so adjusted as to cut off the flow whenever the water in the 
 intercepting sewer exceeds an established depth. The sewers 
 just mentioned are too low to pass over the intercepting sewer, 
 and a somewhat different method of construction was necessary 
 in connecting them. The arrangement at Berkeley Street is 
 shown by Fig. 13, Plate VIII. 
 
 A secondary intercepting sewer was built in Brimmer Street, 
 which collects all of the sewage flowing westward from Beacon 
 Hill, and conveys it to the principal intercepting sewer in Bea- 
 con Street. For the sake of economy and simplicity, the old 
 outlets of the common sewers in Eevere, Pinckney, Mt. Ver- 
 non, Chestnut, and Beacon Streets were abandoned, and the 
 total flow from these sewers, including rain, is taken by the new 
 Brimmer-Street sewer, a single storm overflow being provided 
 at Back Street. The construction of the Brimmer-Street sys- 
 tem involved the building of 1,456.5 feet of oval brick sewers, 
 varying from 2X3 feet to 3 X 4 feet 6 inches in diameter ; 
 also the rebuilding of about 556 feet of common sewers, which 
 were found to be too low or otherwise defective. The flow 
 from the Brimmer-Street sewer into the intercepting sewer in 
 
50 MAIN DRAINAGE WORKS. 
 
 Beacon Street is regulated in the same manner as that from the 
 ordinary city sewers. 
 
 A little beyond Brimmer Street a large common sewer, which 
 comes from the south across the Public Garden, is intercepted. 
 This drains what is called the Church-Street district, compris- 
 ing low territory, in which are many cellars which used often 
 to be inundated. Sewage from this sewer, therefore, is taken 
 directly into the intercepting sewer without the intervention 
 of any regulating apparatus. 
 
 On Charles Street, from Beacon to Cambridge Street, a dis- 
 tance of 1,832 feet, the sewer was built by contract. It is Qgg- 
 sliaped, 4 X 4.5 feet in diameter (Figs. 6 and 7), and cost 
 $10.10 per lineal foot. This was the only section of the West 
 Side sewer which was built by contract. In excavating the 
 trench many of the hollow-log water-pipes of the old Jamaica 
 Pond Aqueduct Company were found in a perfect state of pres- 
 ervation. A house-drain was found which the drain-layer had 
 connected with one of these water-pipes, although the street 
 sewer was but a few feet distant. The log had but three inches' 
 bore, and, of course, led to no outlet. 
 
 At the intersection of Cambridge and Charles Streets a large 
 automatic regulating apparatus, similar to the one shown on 
 Plate VIL, was built into the sewer, to control the flow from 
 above. The excavation in which the chamber for this appa- 
 ratus was built was 30 feet square ; but, by flooring over the 
 top of the excavation, and supporting the various lines of street- 
 railway tracks at that place, travel was not impeded, all build- 
 ing operations being carried on below the surface of the street. 
 
 From Cambridge to Leverett Street, a distance of 2,150 feet, 
 the intercepting sewer is oval, four feet six inches by three feet 
 in diameter. It is of brick-work, eight inches thick, and usu- 
 ally required a timber cradle support. The work on this section 
 presented the usual difficulties met with in excavating through 
 filled land, in the way of old obstructions and the free access of 
 tide-water. By a rather curious coincidence, for a distance of 
 about 500 feet, the remains of an old wharf or bulkhead were 
 found, with longitudinal rows of piles within the trench in such 
 positions that, by cutting them ofl'at the proper elevation, they 
 
INTERCEPTING SEWERS. 51 
 
 served as a support for the sewer, in the place of new piles which 
 would otherwise have been necessary. Seven hundred and one 
 feet, in all of the Fruit-Street and Livingstone-Street sewers, 
 which were too low to be intercepted, were replaced by 2 X 3 
 feet oval brick sewers. The private sewer from the Massachusetts 
 General Hospital was also too low to be intercepted. This was 
 found to be a rectangular wooden scow, 2.5 X 2.5 feet in diam- 
 eter, Avith its bottom at low-tide level. The Trustees of the 
 hospital themselves replaced it with a 10-inch drain-pipe at a 
 higher elevation. 
 
 From Charles Street to its upper end at Prince Street, a dis- 
 tance of 3,571 feet, the West Side sewer maintained, Avith rare 
 exceptions, an even size, of three feet wide and four feet six 
 inches high. The arch consisted of eight inches of brick, and 
 the invert was generally made with four inches of brick resting 
 on a timber cradle, also four inches thick. The common sewer 
 in Lowell Street, which was a large, flat-bottomed wooden scow, 
 was too low to be intercepted. It was accordingly abandoned, 
 and all branch sewers and house-drains were connected directly 
 with the intercepting sewer. To facilitate making these connec- 
 tions the intercepting sewer w^as located exactly on the line of 
 the old sewer. The top planks of the latter were removed, but 
 its side planks were retained, and the new sewer, with its width 
 reduced to two feet eight inches, was built between them. The 
 flow of sew'ase was maintained durino- construction throuoh 
 channels above the floor of the old sewer and below the bottom 
 of the new one, which was supported on timber saddles (Fig. 
 14, Plate VIII.). 
 
 Causeway Street is one of the most crowded thoroughfares of 
 the city. It contains two lines of track for horse-cars and one 
 for freight-cars. On its north-westerly side are the depots of 
 three railroads, with no outlet for their passengers and freight 
 except into this street. The tracks of another railroad cross 
 the street. The territory traversed by the street is all made 
 land, consisting of loose materials filled upon a mud bottom. 
 
 It was with some apprehension of trouble that work was 
 begun on this section. The most difficult feature of the work 
 was so to conduct it that travel should not be seriously impeded. 
 
52 MAIN DRAINAGE W0EK8. 
 
 Owing to the skill and care of the superintendent and his subor- 
 dinates, and to the appliances used for handling the earth and 
 other material, the sewer in this street was built within four 
 months, without closing any portion of the street to travel, and 
 with the minimum of inconvenience to the public. At street- 
 crossings and entrances to railroad-yards, work was carried on 
 below timber platforms, or bridges, without encroaching upon 
 the street surface. In crossing the Boston and Maine Railroad 
 tracks, the excavating apparatus, with its steam-engine, was so 
 elevated as to leave head-room for the passage of trains. 
 Plate IX. is from a photograph taken at this point. 
 
 As a precaution, where the foundation seemed insecure, the 
 vertical diameter of the sewer was increased by six inches, so 
 that, should slight unequal settlements occur, the invert may be 
 brought to its true grade without lessening the desired size of 
 the sewer. For about 76 feet, to avoid interfering with the 
 street surface, the intercepting sewer was built entirely within 
 an abandoned common sewer (Fig. 15, Plate VIII.). At the 
 upper end of the intercepting sewer, at Prince street, the grade 
 of the invert is about four feet above mean low water, which is 
 the highest elevation of any portion of the Main Drainage Sys- 
 tem. At this point a direct connection with the harbor has 
 been made, which is closed under ordinary circumstances by a 
 three feet square penstock gate. By opening this gate at the 
 time of high tide the sewer can be thoroughly flushed. 
 
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PUMPING-STATION. 53 
 
 CHAPTER VII. 
 
 PUMPING-STATION. 
 
 As before stated, and as shown by the plan (Plate V.), the 
 Main Drainage Pumping-Station is situated at Old Harbor 
 Point, on the sea-coast in Dorchester, about a mile from any 
 dwelling. In flowing by gravitation to this point the sewage 
 has descended, so that it is from 11 to 14 feet below the eleva- 
 tion of low tide. To reach its final destination it must flow 
 about 21 miles further, to Moon Island, and be high enough, 
 after arrivino- at the storao-e reservoir on the Island, to be let 
 out into the harbor at the time of high water. That it may do 
 this it must first be raised by an average lift of 35 feet. 
 
 The essential parts of the pumping-station are : a filth- 
 hoist (so called), where the sewage passes through screens to 
 remove solid matters which might clog the pumps ; pump-wells, 
 into one or more of which the sewage can be turned ; pumping- 
 engines to raise the sewage ; an engine-house to protect the 
 engines ; a boiler-house, containino; boilers to furnish steam 
 power ; a coal-house to store a supply of coal, and a dock and 
 wharf, where vessels bringing coal can be unloaded. The posi- 
 tion and arrangement of these principal structures and apparatus 
 are shown on Plate X. 
 
 The filth-hoist is a solid masonry structure, extending from 
 the surface of the ground down to below the main sewer. Its 
 inside dimensions are 25 X 32 feet, and its exterior walls are from 
 4 to 5 feet thick, founded upon two courses of 10-inch timber. 
 In excavating for building the filth-hoist, the ground, which con- 
 sisted of wet sand, was held by round wooden curbs. The 
 total depth of excavation was 35 feet, and the upper 12 feet 
 were dug without bracing to natural slopes. Below this, three 
 tiers of 4-inch sheet planks, each 10 feet long, were driven, and 
 were braced by circular ribs. The three curbs were 71.61 
 and 57 feet in diameter, respectively, and by this method of 
 
54 MAIN DRAINAGE WORKS. 
 
 bracing an unobstructed space was secured for building the 
 masonry. 
 
 As will be seen by referring to Plates X. and XI., the main 
 sewer passes through the westerly foundation wall of the filth- 
 hoist. At this point the sewer has granite voussoirs cut to 
 form a bell shaped opening. Facing the sewer opening are two 
 gate-openings, protected by iron penstock gates, 7 X 6.5 feet 
 each, throuo^h one or both of which the sewas^e flows. These 
 gates are counterbalanced and are moved by hydraulic pressure 
 derived from a city water-pipe. The pressure is sufficient to 
 move them freely ; but to start them when down, with a head of 
 water against them, a hydraulic force pump is added, by means 
 of which the initial pressure can be increased to any extent re- 
 quired. Beyond the gates the structure is divided longitudinally 
 by a brick partition wall into two parts, in each of which are 
 chambers containing two independent cages, or screens, one 
 before the other. The cages are rectangular in shape 7 feet 8 
 inches high, 7 feet 3|- inches wide, and 3 feet 4^ inches deep. 
 They are shown in detail by Fig. 4 on Plate XIV. Their 
 backs, sides, and tops are formed of |-inch round iron rods, 
 with 1-inch spaces between them. The cages are counterbal- 
 anced, and are raised and lowered by four small steam-engines. 
 The steam for these engines, as well as for heating purposes, 
 is brought underground from the boiler house. The super- 
 structure of the filth-hoist is 30 X 37 feet outside dimensions, 
 and is built of quarry-faced granite dimension-stones, lined 
 inside with brick. A view of the outside of this building is 
 shown at the left side of Plate XVII. Plate XIL is from a 
 photograph taken inside of the filth-hoist when one pair of 
 cages was raised. It gives a general idea of the arrangement 
 of the hoisting machinery. 
 
 After passing through the cages the sewage is conveyed by 
 one or both of two sewers, nine feet in diameter each, to galleries 
 on either side of the engine-house substructure, from which 
 galleries it can be admitted through gate openings to one or 
 more pump-wells, situated between the galleries. The bottom 
 of the pump-wells is 19.5 feet below low-tide level and 36.5 
 
MAIN SEWER 
 
 ^^«Stf,: 
 
 EN^jlNE H(pUS;EJ 
 
 
 
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 C-_-i--:z 
 
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 Z 
 
 
 10. W 
 
 
 -:l^ 
 V ^ 
 
 CITY OF BOSTON 
 
 MAIN DRAINAGE WORKS 
 
 PUMPING STATION. 
 
 #- 
 t^'' 
 
 COAL HOUSE 
 
 DOCK 
 
PUMPING-8TATI0N. 55 
 
 feet below the surface of the ground. From the wells the sew- 
 age is raised by the pumps to its required elevation. 
 
 The complete design of the pumping-station, as indicated on 
 Plate X., consists of an engine-house, two boiler-houses and a 
 coal-house, so arranged as to include a court-yard. The build- 
 ings are to be of dimensions suitable for containing eight pump- 
 ina-enirines with their boilers and other appurtenances. Only 
 the portions of these buildings shown on the plan by full lines 
 are at present constructed or needed. 
 
 The foundation walls of the engine-house aggregate about 
 350 feet in length. They are 37.5 feet in height and nine feet 
 thick at the bottom, where they rest on a timber platform, 24 
 inches thick, which also extends under the whole building, and 
 furnishes a foundation course for the piers which support the 
 engines. To build the exterior walls trenches 16 feet wide 
 were first excavated. A core of earth was left inside these 
 trenches until the walls had been erected, when it was removed 
 to make place for the pump-wells and engine foundations. The 
 exterior retainins^ and foundation walls were built of granite, 
 and, although called rubble masonry, yet, owing to the sizes 
 and shapes of stones used and the care taken in selecting and 
 laying them, the work more nearly resembles a fair quality of 
 roughly coursed block-stone work. 
 
 The pump-wells and engine foundations are built chiefly of 
 brick, but contain in addition about 300 dressed granite stones. 
 These stones are used for copings, as bearings for holding-down 
 bolts, for lining gate and other openings, etc., etc. There are 
 nine iron gates, with suitable attachments and shafting, operated 
 hj two small steam-engines. Eight of these gates, 4 feet 9^ 
 inches bj^ 6 feet 3^ inches each, control the flow of sewage from 
 the side galleries into the four pump-wells. Another gate, 4 X 
 4 feet square, controls the admission of salt water from the salt- 
 water conduit. 
 
 This last-mentioned structure, as shown by the plan (Plate 
 X.), is a solid masonry conduit, with its bottom six feet below 
 the elevation of low tide, and connects tide-water at the dock 
 with one of the engine-house galleries. Its ofiice is to conduct 
 salt water to the engine-house for use in the condensers, and 
 
56 MAIN DRAINAGE WORKS. 
 
 also to furnish an additional supply of water to the pumps for 
 flushing or other purposes, whenever the amount of sewage re- 
 ceived from the main sewer is insufficient for such purposes. 
 
 As has been stated, the sewage is elevated to heights (de- 
 pending at any time upon the depth of sewage in the reservoir) 
 which average about 35 feet. 
 
 As the city sewers receive rain-water, and as it is desired to 
 take as much of this as possible, especially from certain districts, 
 it follows that during short periods of time, when it rains, very 
 much greater pumping capacity is needed than is usually suffi- 
 cient. There must, therefore, be a pump, or pumps, to run 
 continuously, and others to run only when it rains or thaws. 
 
 The chief item of expense in pumping is the cost of fuel. 
 For the sake of economy the pumping engines for continuous 
 service must do their work with as little consumption of fuel as 
 possible, and to accomplish this an expensive machine can be 
 afibrded. For the engines which run onlj^ occasionally cheaper 
 machines are more economical, the saving in interest on the first 
 cost more than compensating for the extra fuel consumed by 
 them. The pumping plant of the Boston Main Drainage Works 
 includes two expensive high-duty engines and two cheaper lower- 
 duty engines. 
 
 The high-duty engines were designed by Mr. E. D. Leavitt, 
 Jr., on general specifications prepared by the City Engineer, 
 Mr. Davis. They were built by the Quintard Iron Works, of 
 New York, and cost about $115,000 each. A plan and elevation 
 of one of them is given on Plate XIII. 
 
 As Avill be seen, it is a compound beam and fly-wheel engine, 
 working two single-acting plunger-pumps. The steam cylin- 
 ders are vertical and inverted, their axes coinciding with those 
 of the pumps below them, the pistons of the engines and 
 plungers of the pumps being connected in the same line with 
 the ends of the beam. 
 
 In designing these engines particular attention was given to 
 the following conditions : — 
 
 First. The distribution of the weight of the engine so as 
 not to produce concentrated pressure on any part of the foun- 
 dations. 
 
Plate XII. 
 
PUMPING-STATION. 57 
 
 Second. Great strength in the details and combinations of 
 the parts, to render the h'ability of breakage a minimum. 
 
 Third. A proportion of the wearing surfaces such as will 
 allow of an uninterrupted running for extended periods, with 
 the least wear. 
 
 Fourth. Easy accessibility of all the parts for examination, 
 repairs, and renewals. 
 
 Fifth. An adaptation of the pumps and their valves to the 
 peculiar duty required of them, i.e., to allow the passage of 
 rags, sticks, and such other small bodies as will not be detained 
 by the filth-hoist ; and, in addition, a construction which will 
 admit of the easy removal of an entire pump or any of its 
 parts, without disturbing any important part of an engine. 
 
 Sixth. A high degree of economy in the consumption of 
 coal. 
 
 The following are a few of the leading dimensions : — 
 
 Diameter of high-pressure cylinder, 2b\ inches. 
 
 Diameter of low-pressure cylinder, 52 inches. 
 
 Diameter of plunger, 48 inches. 
 
 Stroke, 9 feet. 
 
 Distance between centres of cylinders, 15 feet 2 inches. 
 
 Eadius of beam to end centres, 8 feet 3 inches. 
 
 Radius of crank, 4 feet. 
 
 Diameter of fly-wheel, 36 feet. 
 
 Weight of fly-wheel, 36 tons. 
 
 Nominal capacity, 25,000,000 gallons a day. 
 
 Speed for capacity, 11 strokes per minute. 
 
 Steam at a pressure of about 100 pounds is admitted from 
 the supply-pipe, A (see Plate XIII.), through the side-pipe, B, 
 to the steam-chests of the high-pressure cylinder, C. The dis- 
 tribution of steam is efiected by gridiron slide-valves, having a 
 short, horizontal movement imparted by revolving cams, D, 
 fixed on a horizontal shaft, E, running along the bases of the 
 cylinders, and driven by the crank-shaft through suitable gear- 
 ing, F. The steam is cut ofi" by the further revolution of the 
 cam. The cut-off is adjustable, and controlled by the gov- 
 ernor, G. 
 
 After expanding to the end of the stroke the steam passes 
 
58 MAIN DRAINAGE WORKS. 
 
 through the exhaust steam-chests to reheaters, H. These are 
 cast-iron boxes, each contaming about 750 |-inch brass tubes, 
 two feet nme mches loiiir. These tubes are filled with hio-h- 
 pressure steam, and in circulating about them the working 
 steam is thoroughly dried. 
 
 From the reheaters the steam is admitted to the low-pressure 
 cylinder, I, where further expansion takes place. Thence it 
 passes to the condenser, J, where it is condensed by salt water 
 from a rose jet. K is the air-pump, and L the outboard 
 delivery-pipe. 
 
 The pumps, M, are hung to heavy girders supporting the 
 engines by cast-iron hangers, N. A part or the whole of the 
 weight of the pumps can also be supported by the wheels, O, 
 resting on very strong cast-iron beams, P, built into the ma- 
 sonry on either side of the pump-wells. By disconnecting 
 their hangers, the pumps, supported entirely by these wheels, 
 can be run back on the beams (which then serve as tracks), 
 and can be hoisted out of the pump-wells without interfering 
 with the fixed parts of the engine. 
 
 At Q are side galleries, through either of which the sewage 
 reaches the gateways, K, leading into the pump-wells. In front 
 of these gateways are iron gates, not shown on the plate, which 
 admit or exclude the sewage. S S are the plungers. TJ U are 
 man-holes. T is the force-main. The discharo^e from one 
 pump passes through the delivery-chamber of the other. 
 
 The interior construction of the pump is shown by Fig. 1 
 on Plate XIV., which is a vertical section through the pump 
 under the high-pressure cylinder. The plunger is represented 
 as just completing its down stroke. The suction-valves (of 
 which there are 36 to each pump) are closed, and the delivery- 
 valves (27 in number) are wide open, to permit the discharge 
 of the sewage displaced by the plunger. In the other pump, 
 at the same moment, the plunger would be completing its up- 
 ward stroke, and the action of the valves would be reversed. 
 
 The valves are of somewhat novel construction, and are 
 shown by a section of a portion of one of the valve-plates and 
 the whole of one valve (Plate XIV., Fig. 2). As will be seen, 
 they are simply rubber flaps, |-inch thick, with wrought-iron 
 
Plate; XIII. 
 
 rTjTnp mwmrmTTTTrnTia 
 
Plate ZIV 
 
 LEAVITT PUMP 
 
 WORTH INGTON PUMP 
 
 Fig. 3 
 
 FRONT ELEVATION 
 PLAN 
 
 TOP BOTTOM 
 
 FILTH CAGES 
 
 CITY OF BOSTON, 
 MAIN DRAINAGE. 
 
 PUMPS AND FILTH CAGES. 
 
PUMPING-STATION. 59 
 
 backs and washer plates, the rubber faces bearing on cast-iron 
 seats inclined at an angle of 45°. The valves form their own 
 hinges, and open against guards or stops faced with leather. 
 The clear opening is 4^ x 13 2 inches. Pieces of board 10 
 inches wide and 24 inches long have passed through these valves. 
 
 The ordinary working duty of these engines is nearly or 
 quite 100,000,000 foot-pounds to each 100 pounds of coal.^ 
 
 The two pumping-engines for storm service were built at the 
 Hydraulic AVorks, Brooklyn, L.I., by the firm of Henry R. 
 Worth ington, of New York, from their own designs, and cost 
 $45,000 each. 
 
 They are of the Worthington duplex, compound, condensing 
 type. Each machine consists in reality of two distinct com- 
 pound engines coupled together, each engine working a double- 
 acting plunger-pump. The capacity of each double engine is 
 25,000,000 gallons of sewage a day raised against a total head 
 of 43 feet. This requires about twelve double strokes a minute 
 and a piston speed of about 115 feet per minute. 
 
 Steam at from 40 to 50 pounds is carried full pressure 
 through the stroke of each high-pressure cylinder. Thence it 
 passes through reheaters to the adjoining low-pressure or ex- 
 pansion cylinders, and is expanded during the reverse stroke. It 
 is then admitted to the condenser and condensed by a jet of salt 
 water. The steam cylinders are 21 and 36 inches in diameter 
 respectively. They are steam-jacketed all over and suitably 
 coated and lago-ed. The stroke is four feet. 
 
 The steam-valves are moved by a novel and ingenious con- 
 trivance, called by the makers "the hydraulic link." Each 
 engine has two small vertical cylinders, in which are plungers 
 w^orked from the air-pump bell-crank. These plungers force 
 water forward and backward through pipes leading to a 
 cylinder in front of the high-pressure steam-chest. In this 
 
 1 Two duty trials, of 24 hours' duration each, have heen made recently of one of the 
 Leavitt pumping-engines. These tests were very carefully conducted, and all fuel burned 
 under the boiler was charged, no deductions being made for ashes and clinkers. In the 
 first trial steam required for the feed-pump was supplied from a separate boiler. Making 
 no deduction for this, the duty developed was a little over 123,000,000 foot-pounds for 
 each 100 pounds of coal. In the second trial the same boiler supplied steam for the 
 pumping-engine and the feed-pump, and the duty developed was about 122,000,000 foot- 
 pounds. 
 
60 MAIN DRAINAGE WORKS. 
 
 cylinder is a piston connected with the main valve-stem of the 
 engine, and the pressure imparted by the water alternately to 
 opposite sides of the piston, moves the valve-stem and effects 
 the steam distribution. 
 
 There are two pumps to each machine. Fig. 3, Plate XIY., 
 is a section through the pumps of one engine. Each pump is 
 double-acting, being divided transversely in the middle by a 
 ring which packs the plunger. The plunger is hollow, 45 
 inches in diameter, and has a 4-foot stroke. It displaces its 
 bulk of sewage at each stroke in either direction. The positions 
 of the valves, suction and delivery chambers are indicated by 
 the section. The valves, are similar to those of the Leavitt 
 engines. 
 
 The engines and pumps are compact, and very conven- 
 iently arranged for inspection of all their parts. A fair idea of 
 their appearance can be obtained from Plate XV., which is a 
 photograph taken inside the engine-house. The guaranteed 
 duty of these engines is 60,000,000 pounds of sewage raised 1 
 foot high by the consumption of 100 pounds of coal. 
 
 To supply steam for the four engines there are four boilers, 
 of a nominal capacity of 250 horse-power each. They were 
 built by Kendall & Eoberts, of Cambridge, Mass., and cost 
 about $9,500 each. 
 
 The boilers are of the horizontal fire-box, tubular form, and 
 are made of homogeneous steel , having a tensile strength of not 
 less than 60,000 pounds per square inch, an elastic limit of 
 37,000 pounds, and an elongation of 30 per cent. The shell is 
 j5g-inch, and the tube-sheets are ^-inch thick. The length over 
 all is 39 feet 10 inches. There are 132 tubes, 3-inch internal 
 diameter, 15 feet long. 
 
 Each boiler has two fire-boxes, 3^ feet wide, 5 feet high, and 
 11 feet long. At the ends of the fire-boxes is a combustion 
 chamber four feet long. 
 
 The smoke-flues return into chambers containing flue-heaters, 
 composed of 80 seamless brass tubes, 2^ inches in diameter and 
 15 feet lono'. The heaters are on a level with the boiler-house 
 floor, and can be run out from their chambers for cleaning or re- 
 pairs. From the heaters the smoke passes by brick flues under 
 the floor to the chimney. 
 
Plate XV. 
 
 m 
 
 c 
 
 r; 
 
 en 
 
 a 
 
 05 
 
 c 
 
 
 
 03 
 
 
 
 c 
 c 
 
Plate XVfl. 
 
 03 
 
 CO 
 
 r; 
 'cO 
 Q 
 
 
 wm ■ 
 
PUMPING-STATION. 61 
 
 The chimney Las a circular flue, 06 inches internal diameter 
 and 140 feet high. 
 
 Among the minor engines and pumps appertaining to the 
 pumping-station are four engines for raising and lowering the 
 filth cages ; two engines for moving the gates in the engine- 
 house galleries ; two pair of double-acting steam-pumps for 
 feeding the boilers ; two double-acting steam-pumps for supply- 
 ing salt water to the condensers ; one large steam-pump for 
 emptying the pump-wells and galleries in the engine-house. 
 
 The buildings are warmed by a system of steam-pipes and 
 radiators, and are lighted by gas made on the premises from 
 gasoline. 
 
 The coal-house is 129 X 59.5 feet in mternal dimensions. 
 It contains six coal bins, or pockets, with a combined capacity of 
 about 2,500 tons of coal. These bins are 23 feet high, and are 
 built with solid walls formed of 2 X 6 inch spruce lumber, 
 planed to an even thickness, and spiked flatwise on each other, 
 — a method of construction similar to that used in building grain 
 elevators. The coal-house floor is made of Portland cement 
 concrete. Iron cars are used for bringing coal from the bins 
 to the boilers, and suitable tracks, turn-tables, and scales are 
 provided. 
 
 To furnish access to the pumping-station for colliers and 
 other vessels, a channel one-half of a mile lono; was dredsfed out 
 to the ship-channel in Dorchester Bay ; 380 feet of dock- wall 
 and a wharf 280 feet long were constructed. To facilitate the 
 unloading of coal a coal-run, supported on a trestle 27 feet high, 
 connects the wharf with the coal-house, and extends over the 
 tops of the bins within the house. 
 
 Above their foundations all buildings at the pumping-station 
 were designed and built by the City Architect's Department. 
 A front view of the main building is given by Plate XVI 
 (frontispiece) , and a side view by Plate XVII. This building 
 cost about $300,000. 
 
62 MAESr DRAINAGE WORKS. 
 
 CHAPTER yni. 
 
 OUTFALL SEWER. 
 
 The sewage is pumped through 48-inch iron force mains 
 (Plates X. and XI.) into what is called the pipe-chamber. At 
 this point the sewage reaches its greatest elevation, and is high 
 enough to flow into the reservoir at Moon Island. The pipe- 
 chamber is a granite masonry structure, 51 feet long inside, 
 resting; on a foundation bed of concrete, 24 inches thick. 
 The walls are 21 feet high, from 4 to 7.5 feet thick, and contain 
 more than 100 dressed stones. The force mains from the four 
 pumps already provided pass through the westerly wall of the 
 pipe-chamber, and four more short sections of 48-inch pipes 
 are also built into that wall, to connect finally with the four 
 additional pumps, which it is expected may be needed in the 
 future. 
 
 From the pipe-chamber the sewage passes into what are 
 called the deposit sewers, and through them flows nearly a 
 quarter of a mile to the west shaft of the tunnel under Dor- 
 chester Bay. These sewers are supported and protected by a 
 gravel pier, or embankment, built from the original shore line 
 at the engine-house out to, and including, the tunnel shaft. 
 Plate XVIIl. gives a general view of this pier from its outer 
 end. The picture is a reproduction of a photograph taken 
 during the winter when the bay was frozen over. A cross- 
 section of this pier is shown by Fig. 5, Plate XIX. It is 
 built of gravel, which was mostly dredged from the harbor. 
 On its northerly or most exposed side the pier is protected by 
 a rip-rap embankment, ballasted with broken stones and oyster- 
 shells. The southerly slope is ballasted and paved with stone, 
 and the easterly end of the pier is protected by a retaining- 
 wall (Fig. 4) of cut-stone masonry, laid in mortar and 
 backed with concrete, the whole resting on a pile foundation. 
 In all there were used in building this pier about 41,000 tons 
 
Plate XVIII. 
 
 & 
 
 m 
 
 G 
 
 ♦-) 
 CO 
 ♦J 
 
 (/] 
 
 CD 
 C 
 
 a 
 S 
 
 0. 
 
OUTFALL SE"\VER. 63 
 
 of rip-rap, 1G,000 yards of ballast, 120,000 yards of gravel, 
 600 yards of dimension stone, and 650 piles. The pier was 
 built l)y contract, and its total cost, excluding that of the sewer, 
 was $142,064.97. 
 
 The general character of the deposit sewers is shown by 
 Fig. 7. As will be seen they consist of a monolithic struct- 
 ure of concrete, forming two conduits, each 16 feet high and 8 
 feet wide. This height is necessary to accommodate the daily 
 variations in the elevations of the surface of the sewage due to fill- 
 ing and emptying of the reservoir at Moon Island. The sewers 
 are dammed at their lower ends to maintain a depth of from 8 
 to 10 feet, in order that the velocity of flow through them may be 
 very sluggish, so that any suspended matters may be deposited 
 here before reaching the tunnel . They are provided with gates 
 and grooves for stop-planks, so that the sewage can be turned 
 through either or both sewers, and either can be entirely emp- 
 tied if necessary. 
 
 The whole structure contains about 10 cubic yards of con- 
 crete to the lineal foot, or over 12,000 yards in all. The 
 bottom portion up to the straight walls is formed of Eosendale 
 cement, sand, and stone, in the proportion of each, respect- 
 ively, of 1, 2 and 5. Above this elevation, for the outer side 
 walls, the same proportion is maintained ; but the cement used 
 was a mixture of 1 part Portland and 2 parts Rosendale. 
 For the concrete forming the centre wall and top arches only 
 Portland cement was used. The best Rosendale and very fine 
 ground Portland cement were procured for the work. The 
 sand was screened on the spot from the gravel forming the pier, 
 and a portion of the stone was obtained in a like manner. A 
 still larger proportion of the stone came from the tunnel exca- 
 vation, being brought in lighters from the middle shaft and 
 passed through a stone-crusher. Machine concrete mixers 
 were used, into which the cement, sand, and stones, in proper 
 proportions, were continuously shovelled. 
 
 The concrete was rammed thoroughly in 6-inch courses. 
 Long sticks of timber were embedded in each layer of concrete 
 while it was being rammed into place, and were removed after 
 it had set, and before the next layer was added. The spaces 
 
64 MAIN DRAINAGE WORKS. 
 
 occupied by the sticks formed grooves, into which the succeeding 
 layers bonded. In cutting through one side of this structure six 
 months after its completion the whole mass was found to be 
 perfectly homogeneous, and lines of demarcation between the 
 different layers could not be detected. 
 
 The bottoms of the sewers are lined with one layer of hard- 
 burned bricks to resist erosion when the sewers are cleaned. 
 The sides are plastered with a |^-inch coat of Portland cement 
 mortar. The arches are of long radius and but 13 inches thick. 
 As they were to be loaded at once, they were tied, as shown, by 
 l|^-inch wrought-iron rods, spaced five feet apart. Brick man- 
 holes were built at intervals of 300 feet. 
 
 Comparatively heavy matters, such as gravel and sand, settle 
 almost at once at the west end of the deposit sewers. Lighter 
 matters travel a little further ; but only a very light semi-fluid 
 precipitate is ever found at the easterly end of the sewers, near 
 the shaft. 
 
 The best way to clean out this deposit was long considered, 
 and the following plan was finally adopted. A large wooden 
 tank was built near the end of the pier, just outside of its 
 southerly slope, about 120 feet distant from the sewers (Figs. 
 3, 5, and 6, Plate XIX.). It is supported on piles, its floor 
 beino- three feet above high water and one foot lower than the bot- 
 toms of the sewers. One end of this tank is connected with the 
 deposit sewers by two 6-inch iron pipes, the other end is con- 
 nected with the chamber about the tunnel-shaft by a 12-inch 
 pipe. By means of stop-planks the surface of water is made to 
 stand about three feet higher in the deposit sewers than it does 
 in the shaft-chamber. Circulation is thus established from the 
 deposit sewers through the 6-inch pipes into the tank, and 
 thence through the 12-inch pipe to the shaft, and a part of the 
 sewage goes to the tunnel through this by-pass. 
 
 The 6-inch pipes leave the deposit sewers near their bot- 
 toms, and the sewage which enters the pipes draws sludge along 
 with it and again deposits it in the still water of the tank. The 
 tank is 10 feet wide, 15 feet high, and 50 feet long, and will 
 hold about 150 yards of sludge. It has on its seaward side 
 three gate-openings, terminating in cast-iron nozzles, 12 inches 
 
SECTIONAL PLAN ON LINES E.F.G.H.K.L. 
 FIG. I 
 
 CITY or BOSTON 
 
 MAIN drainage: 
 
 OUTFALL SEWER 
 
 CHAMBER CONNECTING DEPOSIT SEWERS 
 WITH WEST SHAFT Of TUNNEL 
 
 SECTIONAL ELEVATION ON LINES A.B.C.D. 
 riG. 2 
 
 OLD HARBOR PIER PLAN AT END. 
 FIG. 3 
 
 OLD HARBOR PIER CROSS SECTION. 
 FIG. 5 
 
 
 TRANSVERSE SECTION OF DEPOSIT SEWERS LONG. SECTION OF DEPOSIT SEWER 
 AND END VIEW OF SCRAPER. SHOWING SCRAPER. 
 
 FIG. 7 FIG. 8 
 
OUTFALL SEWER. 65 
 
 in diameter. When the tank is full of sludge a scoav is laid 
 alongside it, and the nozzles are connected with the interior of 
 the scow by means of canvas tubes. The gates are then opened, 
 and the sludge flows from the tank into the scow. 
 
 In order to draw down to the 6-inch pipes the sludge which 
 has been deposited at the upper ends of the deposit sewers 
 scrapers are used. These consist of floating rafts (Figs. 7 and 
 8, Plate XIX.), made of 12-inch hollow iron tubes, to the bot- 
 toms of which are hung wooden aprons, a little less wide than 
 the sewers. The aprons are weighted so that their lower edges, 
 which are provided with broad iron teeth, sink somewhat into 
 the sludge. The current in the sewers carries the whole 
 apparatus down stream, and the sludge is scraped and flushed 
 before it. 
 
 The deposit sewers connect with the tunnel shaft at a masonry 
 chamber built about the latter (Figs. 1 and 2, Plate XIX.). 
 At the ends of the sewers are placed gates 7X8 feet in size. 
 These gates maintain a depth of eight or more feet in the sewers. 
 They are so arranged that on tripping a latch they can swing 
 open and empty suddenly the liquid contents of the sewers into 
 the tunnel, producing temporarily a strong flushing velocity. 
 Immediately about the shaft is a wrought-iron cage , to prevent 
 any bulky object w^hich may fall into the sewers from reaching 
 the tunnel. 
 
 The shaft chamber is encircled by two 6|-feet " waste sewers," 
 into which the deposit sewers can overflow above waste weirs, 
 or with which they can directly connect instead of discharging 
 into the tunnel. The waste sewers unite just east of the shaft- 
 chamber and pass to an outlet built through the sea-wall at the 
 end of the pier. Should the tunnel ever be emptied for inspec- 
 tion sewage can temporarily be pumped into Dorchester Bay 
 throuirh this outlet. Above the shaft chamber is a brick o-ate- 
 house of ornamental design, built by the City Architect. 
 
 The second section of outfall sewer comprises the tunnel 
 under Dorchester Bay. Exploratory borings made on the 
 tunnel line during the preliminary survey showed that the sur- 
 face of bed rock was but little below the bottom of the harbor, 
 fi'om Squantum to aljout the middle of the bay. From that 
 
6Q MAIN DRAINAGE WORKS. 
 
 point westwardly towards Old Harbor Point the rock dipped 
 rapidly, so that under the pumping-station its surface is 214 
 feet below the surface of the ground. The surface of the rock 
 is somewhat shaken, and immediately above it is a water-bearing 
 stratum of sand, gravel, and boulders. Above this, clay extends 
 nearly to the harbor bottom, which is composed of a bed of mud 
 of varying thickness. 
 
 The clay is of uniform character, and contains occasional 
 veins and pockets of sand. Using reasonable precautions a 
 tunnel could be safely and expeditiously built in it. The per- 
 vious stratum over the rock and the demoralized upper portion 
 of the rock itself were not at all favoral)le for tunnelling opera- 
 tions, and could only have been penetrated with extreme pre- 
 caution and a considerable chance of ftiilure. The rock itself 
 was well adapted for tunnelling. It consists of a succession of 
 clay-slates and conglomerates, and belongs to the series known 
 as the Roxbury "pudding-stone" beds. 
 
 When the trough in which these beds lie was formed they 
 were subjected to great pressures, which crumpled and tilted 
 them, and produced many faults, fissures, and joint planes. 
 The fissures were filled solidly from below, and few shrinkage 
 seams were found sufficiently open for the passage of water 
 from above. The existence of the joint planes, especially in 
 the clay-slates, greatly fiicilitated the breaking and removal of 
 the rock. 
 
 As at first designed, the tunnel was to start from a shaft 100 
 feet deep at Old Harbor Point and be built in the clay for about 
 2,100 feet, when it would enter the rock and continue in it to 
 its end, at Squantum. Further consideration of the difficulty 
 and possible danger of passing gradually from soft ground into 
 rock, and of tunnelling for several hundred feet wholly or 
 partly through very wet and loose material, led to locating the 
 west shaft at such a distance from the shore that rock could be 
 reached at a practicable depth and the tunnel could be safely 
 built wholly within it. 
 
 The average elevation of the tunnel is 142 feet below low 
 water (Plate XX., Fig. 1). The total length through which 
 the sewage flows is 7,160 feet. Of this distance 149 feet is in 
 
OUTFALL SEWER. 67 
 
 the west shaft, 6,088 feet is nearly horizontal between the west 
 and cast shafts, and 923 feet is in the inclined portion leading 
 from the bottom of the east shaft to the end of the tunnel, on 
 Squantum Xeck. 
 
 To facilitate construction there were three working shafts 
 about 3,000 feet apart. 
 
 The tunnel was built under a contract which was drawn with 
 great care. The contractor was first to build, in accordance with 
 plans furnished, three timber bulkheads, or piers, to protect 
 the shafts. Inside of these bulkheads he was to sink iron 
 cylinders, constituting the upper portions of the shafts. These 
 c^dinders were paid for by the lineal foot, and the contractor 
 was permitted and required to build as much of the shafts as 
 possible in this way, loading and forcing the iron to the greatest 
 ■attainable depth. Below the cylinders the shafts could be ex- 
 cavated of any desired size and shape. The tunnel, also, could 
 be excavated of any size, provided that both it and the shafts 
 were finally lined with a 7^- feet diameter circular shell of brick 
 work, 12 inches thick, backed with brick or concrete masonry 
 to the sides of the excavation. Bricks and cement were to be 
 purchased from the city at stipulated prices. The completed 
 tunnel was to be paid for at the proposed price per lineal 
 foot. 
 
 Great stress was laid upon the precautions to be adopted to 
 prevent delay and damage arising from an influx of water into 
 the shafts. Appliances to control any such influx were to be 
 kept in readiness, and, should these prove insufficient, the ple- 
 num process, or use of compressed air within the shafts, was to 
 be resorted to. 
 
 The work was let Oct. 29, 1879, and the contractor at once 
 proceeded with the building of the bulkheads. These were alike, 
 and consisted (Fig. 2, Plate XX.) of wooden boxes 20 feet 
 square inside, formed of large oak piles, driven two feet on 
 centres, capped and braced with hard-pine sticks, and tied 
 diagonally at the corners with 2-inch iron bolts. The boxes 
 were lined inside with 4-inch tongued and grooved sheet-piling, 
 and the spaces between the sheet planks and cylinders were 
 filled with puddled clay. The tops of the bulkheads were eight 
 
68 MAIN DRAINAGE WORKS. 
 
 feet above mean high water, and the contract price for them 
 was $2,500 apiece. 
 
 Having completed the bulkheads the cylinders were sunk 
 inside of them. Each cylinder (Plate XX., Fig. 3) consisted 
 of a circular shell of cast iron, 9.5 feet inside diameter, with 1| 
 inches thickness of metal. They were cast in sections, five 
 feet long, and united by l^-inch bolts passing through inside 
 flanges. The abutting ends of the sections were faced, and the 
 bolt-holes, of which there were 30 in each flange, were drilled 
 to a templet, so that the sections were interchangeable. The 
 bottom section of each cylinder had its lower 10 inches cham- 
 fered off to a cutting edge. The contract price for furnishing 
 the cylinders, which weighed a ton to the foot, was $88 per 
 lineal foot. 
 
 At the east and middle shafts the cylinders were easily 
 forced down to the rock, at depths below the surface of the 
 ground of 21 and 38 feet respectively. It was known that it 
 would be impossible to drive the cylinder at the west shaft down 
 to the rock. By weighting it with about 180 tons of iron dross 
 it was finally forced into the clay to a depth of about 60 feet 
 below the harbor bottom. Below this point a square shaft, 10 
 feet across, was excavated with great ease in plastic clay, pene- 
 trated with occasional veins of fine sand, but yielding little 
 water (Plate XXI., Fig. 1). 
 
 The timbering of this shaft was hastily and, as it seemed to 
 the engineers, carelessly done, the timbers being insecurely 
 braced, and cavities being continually left outside of them. 
 The engineer in charge consulted the City Engineer as to the 
 possibility of requiring greater caution in doing this work. It 
 was decided, however, that the spirit of the contract would not 
 permit interference with the contractor's method of building this 
 portion of the shaft. 
 
 No difficulty was encountered until the rock was neared, when 
 water, to the amount of 10,000 gallons an hour, broke in from 
 below, and, no provision having been made for its removal, filled 
 the shaft. Pumps were obtained and the shaft emptied, when 
 it was found that the water, following the cavities behind the 
 lining, had softened the clay and loosened the timbering, so that 
 
CITY OF BOSTON - MAIN DRAINAGE. 
 OUTFALL SEWER. DORCHESTER BAY TUNNEL. 
 
 LONGITUDINAL SECTION OF TUNNEL 
 
 FIG. I. 
 
 'T^° 
 
 SIDE ELEVATION 
 
 HALF SECTION HALF PLAN 
 
 BULKHEADS ABOUT SHAFTS 
 
 FIG, a. 
 
 IRON CYLINDERS 
 FIG. 3. 
 
OUTFALL SEWER. 69 
 
 it was in very bad shape. About 40 feet in length of the shaft 
 had to be retinibered, the ohl sticks being cut out with chisels. 
 
 This work was not accomplished without great difficulty. 
 Although the quantity of water to be dealt with was not great, 
 the cramped dimensions of the shaft afforded little room for 
 the pumps, or opportunity for supporting them. When these 
 gave out, as they occasionally did, the shaft filled w^ith water, 
 causing considerable delay and damage. To counteract a 
 downward pressure exerted by the clay upon the timber lining, 
 a portion of it was suspended by heavy wire cables from the 
 cylinder above. During all these operations the whole shaft, 
 including timbered portion and cylinder, also the surrounding 
 clay and the bulkhead above, were in motion, settling slowly. 
 By the time the shaft had l)een iirmly founded on the rock the 
 pile bulkhead had settled nearly five feet. 
 
 After the shafts had been sunk and secured the excavation 
 for the tunnel proper encountered no serious obstacles. The 
 work was carried on at six diiferent headings. From the mid- 
 dle and east shafts work progressed in both directions, and 
 from the west shaft and the upper end of the incline at Squan- 
 tum single headings w-ere driven. 
 
 The incline descends one foot vertical in six feet horizontal. 
 At this ponit a heading was driven downwards for about 400 
 feet and then stopped, owing to the difficulty and expense of 
 removing the water which accumulated at its face. At the 
 middle shaft power drills, driven by compressed air, were used, 
 and at other points hand drilling was employed. 
 
 There was not much difi^erence as to either expense or rapid- 
 ity in the two methods. By either an advance of four feet was 
 considered a fair day's work. The chief merit of the air drills 
 seemed to be that they were not demoralized by pay-days, and* 
 never struck for higher wages. 
 
 Various forms of nitro-glycerine were employed as explo- 
 sives, and no casuality occurred through its use. The average 
 diameter of the excavation (Plate XXL, Fig. 2) was about 10.2 
 • feet, approximating very well to the 9.5 feet required to receive 
 the final In-ick lining. The excavated material, amounting to 
 about 25,000 yards in all, was deposited around the shafts, 
 
70 MAIN DRAINAGE WORKS. 
 
 formino^ small islands. The maximum amount of water leaking^ 
 into the tunnel at any time was 64,000 gallons an hour. 
 
 The headings between the east and middle shafts met Jan. 
 24, 1882, and those between the middle and west shafts met 
 June 22, 1882. Lining the excavation with brick-work began 
 March 10, of the same year. Projecting portions of rock were 
 first trimmed off, so that room for a solid brick lining, 12 inches 
 thick, laid in courses, could always be obtained. Kosendale 
 cement mortar was used, composed of equal parts of cement and . 
 sand. All spaces between the coursed lining and the sides of 
 the rock excavation were solidly filled with masonry, principally 
 brick-work. The amount of backing thus required to make solid 
 work averaged about three-fourths of a yard per lineal foot. Fig. 
 5, Plate XXI. is a section of the tunnel at the point of maximum 
 size where the largest amount of backing was needed. In all, 
 7,416,000 bricks and 23,377 barrels of cement were used in 
 building the tunnel. About 12 lineal feet of tunnel could be 
 completely lined in 24 hours, at any one point. 
 
 In putting in the lining, iron pipes were built into the brick- 
 work (Plate XXI., Fig. 3) wherever necessary to furnish out- 
 lets for the water, which would otherwise have washed out the 
 mortar. Some of these pipes were afterwards plugged, but 
 most of them were left open. The pressure of the water when 
 kept from entering the tunnel was about 64 pounds per square 
 inch, and it was not practicable to build brick masonry which 
 should be water-tight under such a pressure. When the tunnel 
 is in use the pressure of the sewage within it is somewhat 
 greater than that of the water outside the lining, so that leak- 
 age would be outwards, except that the particles in the sewage 
 will quickly clog any fine holes in the masonry. 
 
 Some experiments were made to determine to what extent 
 the porosity of the brick lining could be destroyed by silting 
 from without. An iron pipe extending up the east shaft was 
 connected at its lower end with the pipes built through the 
 brick-work, and water containing clay, cement, and fine sawdust 
 was forced outside the lining. 
 
 The finer portions of these materials came through holes and 
 cracks in the joints of the masonry. Fine holes were thus filled 
 
Plate XXI. 
 
 BOSTON MAIN DRAINAGE. 
 DORCHESTER BAY TUNNEL. 
 
 EAN HIGH WATER 
 
 
 AVERAGE SECTION OF TUNNEL 
 
 TUNNEL bECTION 
 AT POINT OF MAXIMUM EXCAVATION 
 
OUTFALL SEWER. 71 
 
 and leaknije throuo^h them prevented. Holes of apparent size 
 were calked with lead. By these means the leakage into the 
 inclined portion of the tunnel was reduced from 2,200 to 500 
 gallons an hour. It was not, however, considered practicable, 
 except at considerable expense, thus materially to reduce the 
 leakage ; and, in view of its slight importance in respect to the 
 use of the tunnel, the attempt was given up. 
 
 The west shaft was lined with brick-work. The middle shaft 
 was abandoned, its only purpose having been to facilitate con- 
 struction. The arch of the tunnel where it passes under this 
 shaft Avas made three feet thick, and a counter arch, two feet 
 thick, was built over it to resist upward pressure, in case the 
 tunnel should ever l)e filled suddenly after having been pumped 
 out for any purpose. The shaft itself was not filled up, but 
 near its top an arch was built to prevent any heavy substance 
 ever falling down it (Plate XXI., Fig. 4). 
 
 The east shaft was lined throughout. A large Cornish min- 
 ing pump has been purchased, and is to be set up at this shaft 
 as soon as certain legal complications affecting the city's right 
 to the location shall have been settled. This pump will have 
 sufficient capacity to empty the tunnel, including the leakage 
 into it, within 48 hours. It is to be set up as a precaution, as 
 it did not seem wise to leave any portion of the work entirely 
 inaccessible. Should the tunnel ever be pumped out at this 
 point it would first be filled with salt water, so that no possible 
 nuisance could be created by the operation. 
 
 A sump, or well-hole, seven feet deep, from which to pump, was 
 built under the east shaft (Plate XXL, Figs. 6 and 7). Pairs 
 of cast-iron beams were built into the lining from the bottom of 
 the shaft to its top. To these are bolted two sets of upright 
 iron guides. One set of these will hold in place the rising col- 
 umn of the pump, and the other set will serve for an elevator, 
 to be used in visiting the pump and tunnel. 
 
 It Avas thought that should deposits occur in the tunnel, they 
 might be removed by passing a ball, somewhat smaller in diame- 
 ter than the tunnel, through it. To guide this ball past the east 
 shaft, four wooden guides, suitably shaped, were built in place 
 
72 MAIN DRAINAGE WORKS. 
 
 at that point. Appliances for handling such a ball were pro- 
 vided at the two ends of the tunnel. 
 
 The tunnel was practically finished July 25, 1883. Its com- 
 pletion required the removal of all elevators, pumps, pipes, etc., 
 used in constructing it and the closing up with masonry of all 
 pump-wells, except the one before referred to, at the east shaft. 
 This work was attended with considerable anxiety, as the pump- 
 ino" capacity of the three shafts was but little more than was 
 necessary to control the leakage of water. 
 
 The finishing and removals were successfully accomplished 
 by systematic and careful management. The last shaft to be 
 cleared was the east shaft, and it was necessary to isolate it from 
 the rest of the tunnel by a timber bulkhead, behind which the 
 water entering the tunnel accumulated while the pumps and 
 their appurtenances were being removed. By the time the shaft 
 was clear the tunnel was two-thirds full of water. The bulk- 
 head was so made and fastened in place that on tripping a catch 
 it fell apart into three pieces, which were hauled out by ropes 
 attached to them. 
 
 The contract price for the shafts, exclusive of iron, was $86, 
 and for the tunnel $48, per lineal foot. The contractor lost 
 money, and after about two years abandoned his contract, 
 alleo;ing his inability to complete it for the prices therein stipu- 
 lated. He ofiered to complete the tunnel for prices about one- 
 half greater than those before agreed upon. Considering that 
 he had the requisite plant on hand, and had acquired valuable 
 experience concerning the character of the work and the best 
 methods of conducting it ; and also considering that the bad 
 reputation which the tunnel would have, if abandoned, would 
 probably deter other bidders from making reasonable offers, — 
 it was thought for the best interests of the city to make a second 
 ao:reement with the same contractor, which was accordingly 
 done. The final total cost of this section of work, including 
 inspection and all incidental expenses, was$658,489.97, amount- 
 ing to about $92 per lineal foot of tunnel. 
 
 The methods of alignment employed by the engineers in 
 immediate charge of the tunnel, while not entirely novel, may 
 be of sufficient interest to be mentioned. The west shaft was 
 
OUTFALL SEWER. 73 
 
 out of plumb, so that by droppinj::^ plumb-linos a base only 5.7 
 feet long could be obtained. This by itself would have made accu- 
 rate alio-nments tedious. Moreover, each shaft contained about 
 six lines of steam, water, and exhaust pipes, besides guides for 
 its cage. As the shafts were 160 feet deep, were dripping with 
 water, and had currents of air produced by hot pipes and leak- 
 ages of steam, it would have been necessary to protect plumb- 
 lines by tubes for the whole depth of the shafts. At the west 
 shaft it would have been impracticable to use such tubes, as 
 they would have been directly in the way of the cage. 
 
 On account of the difficulty attending the use of plumb-bobs, 
 the line was transferred below by means of a large transit 
 instrument set up at the top of the shaft. The telescope, 
 having been set on line, was directed down the shaft, and a fine 
 string, extending about 100 feet into the tunnel, was ranged in 
 line. The string was illuminated by light reflected from a 
 mirror placed beneath it. Communication between the engi- 
 neers at the top and at the bottom of the shaft was maintained 
 by the use of hand telephones. 
 
 At first the line within the tunnel was produced by means of 
 instruments ; but, as the headings advanced, the ventilation be- 
 came so bad that at times a light distant only 75 feet could not 
 be seen. The line was then produced by stretching a stout 
 linen thread, about 600 feet lono;, and takino; ofi*sets to it. The 
 success attending these methods of alignment was very gratify- 
 ing, as the headings met without appreciable error. 
 
 Should a "high-level" intercepting sewer ever be built to 
 conduct a part of the city's sewage, by gravitation, to Moon 
 Island, it is expected that it will join the present system, on 
 Squantum Neck, at the further end of the tunnel. To provide 
 for such a contingency the present outfall sewer is much 
 increased in size beyond this point, being 11 X 12 feet in dimen- 
 sions. 
 
 The connection between the tunnel and the outfall sewer 
 beyond is made in an underground chamber (Fig. 1, Plate 
 XXII.). From this chamber, also, branches a short section of 
 sewer with which to connect the future "high-level " system, 
 should it ever be built. The chamber is covered by a substan- 
 
74 MAIN DRAINAGE WORKS. 
 
 tial brick building, and a flight of stone steps leads to a land- 
 ing in the sewer below. The floor of the building is supported 
 on iron beams, and can be taken up so that boats can be low- 
 ered into the sewer, and a flushing-ball can be taken out. To 
 facilitate these operations the roof was made exceptionally 
 strong, and from it was hung an iron track supporting a traveller 
 and blocks capable of lifting five tons. 
 
 As far as the easterly shore of Squantum Neck the outfall 
 sewer (Figs. 4, 6 and 7, Plate XXII.) was built partly in rock 
 excavation and partly in embankment. In the latter case the 
 sewer is tied through its arch by l|-inch iron rods, 8 feet apart. 
 These are designed to prevent the possibility of distortion, due 
 to movements of the bank below the sewer, or on the side of 
 it. The ties will, doubtless, rust out in time, but not before 
 the need of them is over. 
 
 From Squantum to Moon Island an embankment (Plate 
 XXII., Fig. 5) was built. It is a mile long, from 20 to 30 
 feet high, 20 feet wide on top, and about 120 feet at its base. 
 Up to the established sewer grade the embankment was chiefly 
 built of dr^ds^ed o-ravel, and, above that heio-ht, of material ob- 
 tained in excavating for the reservoir on Moon Island. Up to 
 six feet above high water the slopes are protected by ballast 
 and rip-rap. In all, about 141,000 yards of dredged gravel, 
 260,000 yards of other earth, 20,000 yards of ballast, and 
 54,000 tons of rip-rap were used in building the embankment. 
 
 About 4,100 feet in length of the site of the embankment 
 consisted of beds of mud, from 10 to 40 feet deep. It was 
 hoped that the filling would displace this mud and reach hard 
 bottom. It did so at a few points, but not as a rule. As an 
 Experiment an attempt was made to assist this action by explod- 
 ing dynamite cartridges under the embankment. No results of 
 importance were thus obtained ; but the experiment demon- 
 strated the resistance of the mud to displacement and the prob- 
 able future stability of the embankment. 
 
 Broad plates, with vertical iron rods fastened to them, were 
 placed near the bottom of the bank on its centre line, and the 
 amount of settlement as filling progressed was noted. After 
 the bank was completed slight settlements still continued. It 
 
Plate XXII. 
 
 CONNECTION- CHAMBER. 
 
 EMBANKMENT BETWEEN SQUANTUM AND MOON ISLAND 
 
 rig.5 
 
 ^ m 
 
 J 
 
 Fig. 6 
 SECTION IN EMBANKMENT. 
 
 SECTION IN EXCAVATION. 
 
 BOSTON MAIN DRAINAGE 
 OUTFALL SEWER 
 
 %. 
 
 
 Fig. 7 
 
OUTFALL SEWER. 75 
 
 was, therefore, thought more prudent to postpone huilding a 
 masonry structure for some years, or until there was assurance 
 that the bank had assumed a condition of permanent stability. 
 
 For temporary use therefore, a wooden flume (Fig. 2, Plate 
 XXII.) was sul)stituted for the masonry sewer at this point. 
 The flume is located outside of the emljankraent, and 200 feet 
 south of it. It is supported on piles, in bents ten feet apart, 
 generally with three piles to the bent. In all, al)Out 1,300 piles 
 were driven, some of them to a depth of 40 feet. 
 
 The flume proper consists of a square wooden l)ox, six feet in 
 diameter. Its sides, top, and bottom are formed of Canadian 
 Avhite pine, three inches thick, planed all over. The planks, 
 except a single filling in course on each side, are all of even 
 width, so as to allow breaking joint. They are grooved on 
 each edge, and also on their ends (Fig. 3), for 1^ X |-inch 
 tongues. The box is surrounded, at intervals of three feet four 
 inches, by square frames of spruce timber, mortised together and 
 tightened Avith bolts and wedo-es. 
 
 The pine and spruce were fitted at the mills, so as to go to- 
 gether with the least possible further fitting. As much as 250 
 feet in length was assembled and spiked in a single day. After 
 completion the whole was given two coats of cheap paint. The 
 total cost of the flume was a little under $10 per lineal foot. 
 
 From the further end of the flume the outfall sewer (Fig. 
 6) extends up to and m front of the storage reservoir. 
 
76 MAIN DRAINAGE WORKS. 
 
 CHAPTER IX. 
 
 RESERVOIR AND OUTLET. 
 
 Moon Island is distant about a mile from' the main land. It 
 comprises about 36 acres of upland, surrounded by about 145 
 acres of beaches and flats. The easterly end of the island rises 
 to an elevation about 100 feet above tide-water. On the west- 
 ern or landward side is another smaller area of risino; a:round, 
 about 45 feet high. Between these two portions of high land 
 was a valley, crossing the island from north to south, whose 
 central portion was but a few feet above the level of high water. 
 In this comparatively low land the reservoir is situated. 
 
 Plates XXIII. and XXIV. give views of the reservoir and 
 its surroundings, reproduced from photographs. The former 
 was taken from the high part of the island just east of the res- 
 ervoir. It shows the embankment between Moon Island and 
 Squantum, and also the flume, parallel to and south of the 
 embankment. Near the centre of the plate the pumping-station 
 can be dimly discerned, although partly hidden by a clump of 
 trees on Thompson's Island. Plate XXIV. gives a nearer 
 view of the reservoir, looking eastward. It shows one basin 
 partly filled with sewage. 
 
 The reservoir, as at present built, covers an area of about 
 five acres. It is expected that in the future, when the amount of 
 sewage to be stored shall have increased, it will be necessary to 
 extend and enlarge the reservoir to about double its present 
 capacity. The portion already built is so located and arranged 
 that the contemplated extension can readily be made on the 
 south side of the present structure. 
 
 The site for the reservoir was prepared wholly b}^ excavating. 
 On the centre line of the valley this excavation was about ten 
 feet deep, while on the east and west sides the cutting in places 
 was forty feet deep. A drive-way surrounds the reservoir, and 
 the banks are sloped back from it. The excavated material 
 
Plate XXIII. 
 
 t35 
 
Plate XX I V. 
 
 r 
 
 L 
 
 
 
 > 
 
 If) 
 (U 
 
 a: 
 
 Q) 
 05 
 CO 
 S- 
 
 
 m 
 
RESERVOIR AND OUTLET. 77 
 
 was chiefl}' hard clay ; but a bed of gravel and sand was found 
 near the centre of the valley, which, in places, went 20 feet 
 below the reservoir bottom. Part of the reservoir, therefore, 
 is founded on clay, and another, smaller part on sand and gravel. 
 
 The earth was dug by steam excavators, and was carried 
 away in cars by locomotives. It was used for building the up- 
 per portion of the embankment between the island and main 
 land. As more earth was needed for this purpose than could 
 be supplied from the reservoir excavation a further quantity 
 was l)orrowed from the island in such places and to such lines 
 and grades as partly to prepare the site for the proposed future 
 extension of the reservoir. In all, about 283,000 cubic yards 
 of material were taken from the island, and the contractor's 
 price for digging and disposing of it averaged about 59 cents 
 per yard. 
 
 The retaining- walls of the reservoir (Fig; 2, PL XXVI.) are 
 17.5 feet high, and from 6 feet 10 inches to 7 feet 10 inches 
 thick at the base. They are classed as rubble-stone masonry 
 laid in mortar, and are built of split and quarry stone mostly 
 brought from granite quarries in Maine. On top of the w^alls 
 are large coping-stones with pointed surfaces. The rubble 
 stones were laid in somewhat uneven courses. The reservoir is 
 divided into four basins, of nearly equal area by three division 
 walls (Fig. 3) , built of the same class of masonry as that 
 forming the retaining- walls, liosendale cement mortar, made 
 with one part of cement to two of sand, was use.d in building 
 rubble-stone masonry. The contractor's price for this class of 
 masonry was $7.47 per cubic yard. 
 
 The floor of the reservoir consists of a bed of concrete, nine 
 inches thick (Fig. 6, Plate XXV.). The lower five inches was 
 made with Kosendale cement, sand, and pebbles, in the propor- 
 tion of one, two, and five parts of each respectively. In the 
 upper four inches of concrete, Portland cement was substituted 
 for Eosendale. The floor of each basin was shaped into alter- 
 nate ridges and gutters. The gutters are paved with bricks set 
 on edge. 
 
 Considering the distance of Moon Island from habitations, 
 it did not seem that any just cause for complaint would be 
 
78 MAIN DRAINAGE WORKS. 
 
 occasioned if the reservoir were left uncovered, and, therefore, 
 no roof was built over it. But, to provide for any future contin- 
 gency which might require it to be covered, foundation blocks 
 were built into the floor, on which piers to support a roof can 
 hereafter be built, if needed. These foundation blocks are 
 spaced 20 feet apart in one direction, and 30 feet in the other, 
 and consist of granite stones 3 feet square and 18 inches thick. 
 They are rough-pointed on top and are bedded in concrete. 
 They cost, laid, $7.25 each. 
 
 The reservoir was divided into four distinct basins, in order 
 that one or more of them might be kept empty for cleaning, or 
 some similar purpose, while the others were in use. Under 
 such conditions, however, there might be danger that water 
 from a full basin would find its wav down throuo;h the thin 
 sheet of concrete under it, and, passing below the division wall, 
 would blow up the floor of an adjacent empty basin. This 
 would be especially apt to occur where the basins and walls are 
 underlaid by the pervious bed of gravel before referred to. 
 
 To diminish the liability to such a catastrophe, beneath all 
 walls, not founded on clay, was driven a solid wall of tongued 
 and grooved 4-inch sheet-piling. This protection penetrated 
 the gravel stratum and entered the clay below it. As an addi- 
 tional precaution at such places a line of 10-inch drain-pipe 
 was laid just below the floor on each side of the division wall. 
 These drains were connected with others surrounding the 
 reservoir outride of the retaining-walls. The drains within 
 the reservoir also have 10-inch safety-valves opening into the 
 basins. The drain-pipes were laid with open joints, and were 
 surrounded, below the concrete, with dry-laid ballast and peb- 
 bles. Water accumulating beneath the floor of any basin has 
 free access to the drain under that basin. Should any water 
 find its way under a division wall it is immediately intercepted 
 by the line of pipe just beyond the wall. Should a drain under 
 an empty basin become gorged for any reason, the water is 
 discharged into the basin, through the safety-valve, before sufii- 
 cient head has accumulated to endanger the concrete. 
 
 The northerly 100 feet of each division wall, being the end 
 nearest to the discharge sewers, is made hollow, and 1.75 feet 
 
Plate XXV. 
 
EESERVOIE AND OUTLET. 79 
 
 lower than the rest of the reservoir walls (Plate XXV., Fig. 
 4). Long chambers are thus formed, open on top, but other- 
 wise enclosed within the walls. These chambers connect di- 
 rectly w4th the discharge sewers, and through them with the 
 harbor. These portions of the division walls serve as waste 
 weirs, by which the sewage in the basins can overflow, if, owing 
 to negligence on the part of the employees, the gates which 
 empty any basin should not be opened before the basin be- 
 comes too full. 
 
 The arrangements by which the sewage is turned from the 
 outfall sewer into the reservoir and is again permitted to empty, 
 throuo'h the discharo-e sewers, into the harbor, will be under- 
 stood from an examination of Fig. 1, Plate XXV., which is a 
 transverse section of said sewers. The upper sewer in the fig- 
 ure is a continuation of the outfall sewer, and extends along the 
 whole front of the reservoir. Immediately below it are the 
 discharge sewers, which also extend along the front of the 
 reservoir, and, also, about 600 feet beyond it out into the sea. 
 
 In the side of the outfall sewer are 20 3 X 4 feet, cut-stone 
 gate openings. Only eight of these are at present provided with 
 gates, the others being bricked up until an increased amount of 
 sewage and an extension of the reservoir shall require their use. 
 In the side of the discharge sewer nearest the reservoir are also 
 20 gate openings, of which 12 are provided with gates. The 
 two discharge sewers are connected directly by 11 large trans- 
 verse passages. The amount of masonry contained in and 
 surrounding the sewers equals that contained in all of the res- 
 ervoir walls. 
 
 Between the sewers and the reservoirs is what is called the 
 six-foot gallery. This serves as a protection for the gates 
 against frost and as a foundation for a gate-house above. The 
 hollow division walls between the basins extend across the gal- 
 lery and divide it into four sections, corresponding with the 
 four basins of the reservoir. Brick brace- walls, about 10.5 
 feet apart, are thrown across from the sewers to the reservoir 
 ■wall. 
 
 The 20 gates, with their frames and seats, are made of cast- 
 iron. The frames were cast in one piece and closely fitted to 
 
80 MAIN DRAINAGE WORKS. 
 
 the openings prepared in the masonry. They are secured to the 
 stone by |-inch anchor-bolts, let in 4|^ inches and fastened with 
 brimstone. The seat of each gate is a separate piece of cast- 
 iron, planed |-inch thick, fastened to its frame with screw 
 rivets, and scraped true and straight. Fastened to each side of 
 the frame is a guide, which holds the valve in its proper posi- 
 tion while moving. The face of the valve is planed and scraped 
 to fit the facing of the frames, so that there shall be no leak- 
 age. The valve is pressed tight to its seat by means of adjust- 
 able gibs, which bear against inclined planes, cast on the 
 guides. 
 
 The gates are moved by lifting-rods and screws, connected 
 with suitable brackets, gearing, and clutches, above the floor 
 of the gate-house (Plate XXV. Fig. 2). A main line of shaft- 
 ing, from 2^ to 3^ inches in diameter, extends the whole length 
 of the gate-house, or about 575 feet. The clutches for each 
 gate are thrown in and out by a hand lever, and also by the 
 gate itself when it reaches either end of its course. The 20 
 gates, with all their appurtenances and the gearing and shafting 
 for operating them, cost, in place, about $12,000. 
 
 To furnish power both a steam-engine and a turbine wheel 
 are provided. The latter, which is most commonly used, is 
 21 inches in diameter, and is placed in a well near the north- 
 easterly corner of the reservoir. It takes water either from 
 the reservoir or from the outfall sewer, and drains into the dis- 
 charge sewers. Under ordinary circumstances it furnishes 
 without expense ample power for moving the gates, running 
 pumps, and other necessary operations, and requires no atten- 
 tion beyond opening and shutting the gates leading to it. 
 
 The engine, which is seldom used, is of 30 horse-power. To 
 furnish steam for it and also for heating in wintei", there are two 
 upright tubular boilers. The machinery and gates are pro- 
 tected by suitable brick buildings, designed and built by the 
 engineers. The principal one of these, called the Long Gate- 
 House, extends for 575 feet along the front of the reservoir. 
 Connecting with it, at the north-easterly corner of the reservoir, 
 is another larger building, containing engine, boiler, and coal 
 rooms. A chimney, 40 feet high, is also built. 
 
SHOW/NG 
 P/ER AND COrrEH DAM. 
 
 Plate XXVI. 
 
 C/TY or BOSTON MA/N DRA/NA G^. 
 
 D/SCHAHQi: S£IV£/fS BEYOND RESEBVOm 
 
 RETAINING WALL OF BESERVOIR 
 GENERAL SECTION. 
 
 DIVISION WALL 
 ON PER VIOUS MA TERIAL . 
 
 HOLLOW DIVISION WALL 
 SECTION M. N. PL. XXV. 
 
RESERVOIR AND OUTLET. 81 
 
 The sewage flows throus;!! the spates in the outfall sewer 
 into the six-feet gallery, whence it passes through openings in 
 the reservoir wall into the reservoir. There it accumulates 
 during the latter part of ebb-tide and the whole of the flood- 
 tide. Shortly after the turn of the tide the lower gates are 
 opened, and the sewage flows from the reservoir, through the 
 gallery, into the discharge sewers, which conduct it to the out- 
 let. 
 
 That portion of the discharge sewers beyond the reservoir 
 was called the Outlet-Sewer Section, and was built under a 
 separate contract. There are two sewers of brick and concrete 
 masonry (Fig. 1, Plate XXVI.), each 10 feet 10 inches high, 
 by 12 feet wide inside. They extend from the reservoir about 
 600 feet out into the sea, where there is five feet depth of water 
 at low tide. The bottoms of the sewers are 1.5 feet above the 
 elevation of low water. The arches, 12 inches thick, were laid 
 with Rosendale cement mortar, and the inverts and sides with 
 Portland cement mortar. In the top of each sewer are built 
 three large vent-holes, to relieve the arch from any pressure of 
 air due to a succession of waves entering the sewers. 
 
 The immediate outlet consists of a cut granite pier-head laid 
 in mortar. In this are chambers containing grooves for gates 
 and stop-planks. The stones forming the pier-head are quite 
 large, in order to withstand waves and ice. Several of them 
 weighed about eight tons each. Most of the horizontal joints 
 are do welled, and the vertical joints of the coping-stones are 
 secured by gun-metal cramps. 
 
 The sewers are covered by an earth embankment, with its side 
 slopes protected by ballast and rip-rap. This embankment 
 constitutes a pier extending into the harbor, and its top is 
 ballasted and surfaced for a roadway. Xear the end of the pier 
 is a strong wharf, about 40 feet square, supported by oak piles. 
 This is used for landing coal and other supplies. 
 
 To facilitate construction on this section the site of the work 
 was enclosed by building about 1,100 feet of cofl'er-dam around 
 it. The dam consisted of two rows of spruce piles, ten feet apart, 
 the piles in each row being spaced six feet on centres. Inside 
 the piles were rows of 4-inch tongued and grooved sheet-piling. 
 
82 MAIN DRAINAGE AVORKS. 
 
 The dam was tied across with iron bolts and was filled with 
 earth. When pumped out it proved to be very tight, and 
 enabled the work inside it to proceed without interruption. After 
 the sewers were built and covered, the dam was cut down below 
 the surface of the embankment slopes. The total cost of this 
 outlet section was $96,250. 
 
 The top of the I'eservoir floor is about one foot below the eleva- 
 tion of high water. The paved gutters are a little lower, and in- 
 cline nearly a foot from the back of the reservoir to its front. This 
 insures there being a good current in them when the reservoirs 
 are nearly emptied, so that the light deposit of sludge which has 
 been precipitated upon the bottom of the reservoir is mostly 
 washed into the discharge-sewers. 
 
 To assist in cleansing the basins, a system of pipes and 
 hydrants furnishing salt water under pressure is provided. The 
 water is drawn from the sea to a pump in the engine-house, 
 which forces it about the reservoir. A 4-inch pipe, with 
 double hydrants, about 75 feet apart, is laid through the middle 
 of each basin. A line of hose can be connected with any 
 hydrant, and a fire-stream directed against any part of the floor 
 or side walls. The pump can also be used to pump sewage with 
 which to irrigate the banks and grounds surrounding the reser- 
 voir. 
 
 To obtain fresh water for domestic purposes and for the 
 boilers, the high portion of the island has been encircled with 
 ditches, which collect rain-water and conduct it to a cistern hold- 
 ing 75,000 gallons. 
 
 Within the gate-house is provided an automatic recording 
 gauge, moved by clock-work and connected with floats in the 
 sewers. The records traced by this machine furnish a per- 
 fect check on the vigilance of the employees. Each day's record 
 shows, by inspection, the hours at which the gates were opened 
 and closed and the height of tide. 
 
 The total expenditure by the city on account of Main Drain- 
 age Works, from the beginning of the preliminary survey, 1876, 
 to the present time, is about $5,213,000. 
 
DETAILS OF ENGINEERING AND CONSTRUCTION. 83 
 
 CHAPTER X. 
 
 DETAILS OF ENGINEERING AND CONSTRUCTION. 
 
 About one-half of the work required to complete the Main 
 Drainage System was done by contract, and the rest by day's 
 labor, under superintendents appointed by the city. The general 
 rule by which it was decided- whether any given section of work 
 should be built by contract, or not, was this : if the work was of 
 such a nature that its extent and character could be determined 
 in advance, so that full and explicit specifications for it could be 
 drawn, it Avas let out by contract to the lowest responsible 
 bidder. If, on the other hand, all of the conditions liable to 
 affect the work could not be ascertained, so that it was antici- 
 pated that modifications in the proposed methods of construction 
 might prove necessary or desirable, the work was done by day's 
 labor. 
 
 Thus, wherever in suburban or thinly populated districts the 
 character of the earth to be excavated was supposed to be of 
 uniform quality, most of the sewers there located were built by 
 contract. Those located in crowded thoroughfares, where it 
 was necessary to interfere as little as possible with the use of 
 the street, and those in places where there was liability of en- 
 countering deep beds of mud, old walls, wharves, and other ob- 
 stacles, were built by day's labor. 
 
 There was little difference in the quality of the work obtained 
 by these different methods of construction. The contract work 
 was built under more favorable conditions, and as a whole is 
 somewhat superior to the other. It also, as a rule, cost much 
 less. Several reasons can be given for this fact. The physical 
 conditions were generally more favorable. Low prices were 
 obtained through competitive bids. Most of the contractors 
 made no profit ; some even lost money. The contract work 
 was largely done during the first few years of construction, 
 when all prices were lower ; while the bulk of the work 
 done by day's labor was built later, when prices for labor and 
 
84 MAIN DEATNAGE WORKS. 
 
 materials had risen. The wages paid city laborers were fixed 
 by the City Council, and were always higher than the market 
 rates. At times the city superintendents were not untrammelled 
 m respect to hiring and discharging their employees. 
 
 Sixteen sections of sewer were let by contract. In two 
 cases the contractors failed, and the sections were relet. In 
 four other cases the contractors abandoned their work, which 
 was completed by the city, by day's labor. In connection with 
 the Main Drainage System about 50 more contracts were made 
 for materials and machinery, and for construction and work 
 other than sewer building. These contracts were drawn by the 
 engineers. 
 
 In preparmg a contract for building a sewer the object kept 
 in view was to describe only the general character of the work, 
 and to leave for further decisions, as construction progressed, 
 the exact shape, methods of construction, and amounts and 
 kinds of materials to be used. That this might be done with- 
 out unfairness to the contractor the precise character (but not 
 the amount) of every kind of work and material, which miglit 
 be called for, was specified, and a price was agreed on for each. 
 Should anything not specified be called for, the contractor 
 agreed to furnish it at its actual cost to him, plus 15 per cent, 
 of said cost. 
 
 This is a convenient form of contract, because it permits the 
 engineer to modify his methods of construction whenever ex- 
 perience shows that a change is desirable. One kind of mate- 
 rial can be substituted for another; cradles, side walls, and 
 piling can be added or discarded. Rather more opportunities 
 for contention are afforded by this form of contract than by a 
 simpler one ; but, on the whole, it was considered the best for 
 our purposes. 
 
 Contract work was carefully watched, an inspector being 
 continually on the ground. Great care was taken to select 
 suitable men for such positions. They were all experienced 
 masons, and were paid $4.00 or more a day. 
 
 A daily force account was always kept, both of work done 
 by the city and that built by contract. This recorded the number 
 of hours' labor of every class and the amount of material which 
 
DETAILS OF ENGINEERING AND CONSTRUCTION. 85 
 
 entered into each part of the work, so that its cost could be 
 ascertained. On contract work this record proved very useful, 
 because it furnished conclusive evidence in any case of disa- 
 greement as to quantities or cost. 
 
 All materials were carefully inspected for quality. Especial 
 care was exercised in inspecting bricks and cement. About 
 50,000,000 of the former and"l80,000 casks of the latter 
 material were used in building the works. It was required 
 that the bricks should be uniform in size, regular in shape, 
 tough, and burned very hard entirely through. Bricks with 
 black ends were not excluded if otherwise suitable. No machine- 
 made bricks were accepted, as they were usually found to have 
 a laminated structure. A moderate proportion of bats was 
 allowed, but only in the outer ring of the covering arch. From 
 the accepted bricks the most regular were culled out for inside 
 work. Bricks from diflferent localities varied considerably in 
 size, and this fact, so often disregarded, was taken into account 
 in making purchases for the city. For instance, 1,175 Bangor 
 bricks were required to build as much masonry as could be 
 built with 1,000 Somerville bricks. 
 
 A requirement that no bricks should be used which would 
 absorb more than 16 per cent., in volume, of water, although 
 not always enforced, was occasionally found useful, because it 
 permitted the rejection of bricks made of light, sandy stock, 
 which were, however, perfectly hard and shapely. The fol- 
 lowing was the method employed in testing for porosity. The 
 brick to be tested was first dried thoroughly by artificial heat, 
 and then weighed. Next it was put in a pan containing one- 
 half inch of water and allowed to soak for 24 hours, the pan 
 being gradually filled, by adding water from time to time until 
 the brick was covered. When thoroughly soaked it was again 
 weighed, both in water and in air. The difiference between 
 the weights dry and soaked, in air, was the weight of water 
 absorbed, and the difierence between the weights of the soaked 
 brick, in air and in water, was the loss of weight in water, 
 i.e., the weight of a bulk of water equal to that of the 
 
 1 • 1 J.1 The weight of water alDsorbed j_v ,• • i 
 
 brick ; then The iosb of weight m water was the proportion, m volume, 
 of water absorbed by the brick. 
 
86 MAIN DRAINAGE WORKS. 
 
 Natural " E,osendale " cement was chiefly used on the work, 
 but about 26,000 barrels of Portland cement and a little Roman 
 cement were also used. Portland cement mortar was often 
 used in building the inverts of sewers and, in general, where 
 there was liability to abrasion or where especial strength was 
 needed. It was often mixed with Rosendale cement in order to 
 make a somewhat stronger mortar. Very quick-setting Roman 
 cement was used for stopping leaks, and was also mixed with 
 other cements for wet work, because it would set at once and 
 keep the mortar from being washed down before the stronger 
 cements had hardened. 
 
 In Appendix A is given a full account of the methods em- 
 ployed for testing cement, and also the results derived from 
 the tests made for experimental purposes. One advantage 
 resulting from the careful and systematic testing was that manu- 
 facturers and dealers were themselves careful to offer or send 
 no cement but that which they felt confident would be accepted. 
 During the first year or two much of the cement offered was 
 rejected, but later very little of it proved unacceptable. In 
 makino; contracts for cement a standard of streno;th and fine- 
 ness was seldom given. It was simply stipulated that the 
 cement should be, in every respect, satisfactory to the engineer, 
 and, if not satisfactory, should be rejected. 
 
 In one contract, how^ever, for 5,000 barrels of Portland ce- 
 ment, a certain fineness and strength were required. As some 
 of the specifications of this contract are believed to be novel 
 and practically useful, they are here cited : — ; 
 
 Fineness. The cement to be very fine ground, so that not over fifteen 
 (15) per cent, of it will be retained by a certain sieve deposited in the ofiice 
 of the City Engineer of Boston, said sieve having 14,400 meshes to the 
 square inch. 
 
 Strength. The cement, when gauged with three pai'ts by measure of 
 sand, to one part of cement ; formed into briquettes having a breaking area 
 of '2\ square inches ; kept 28 days in water and broken from the water, to 
 have a tensile strength of 150 lbs. per square inch. 
 
 Price. We agree to receive as full payment for the satisfactory delivery 
 of said cement, subject to its fulfilment of the foregoing requirements, as 
 determined by the City Engineer of Boston, the smn of three dollars ($3.00) 
 per cask delivered and accepted. 
 
 We further agree, that, shall the cement, or any portion thereof, fail to 
 
■ DETAILS OF ENGINEERING AND CONSTEUCTION. 8< 
 
 fulfil the above-mentioned requirement as to fineness, but shall nevertheless 
 be accepted by the city, we will receive as full payment for said cement, or 
 said portion thereof, a sum to be determined by the City Engineer, by 
 deducting from the full price, of three dollars ($3.00) per cask, the sum 
 of two cents ($0.02) per cask for each per cent, greater than 15 per cent, 
 that is retained by the sieve before mentioned. 
 
 Contractors were required to use only clean, sharp, coarse 
 sand for making mortar. On city work, if clean sand was not 
 conveniently accessible, a moderately dusty or dirty sand was 
 considered almost as good, and quite good enough. So, also, 
 in making concrete, contractors were obliged to use screened 
 sand and stone ; but a city superintendent might mix his cement 
 directly with the gravel dug from the bank, if it was more con- 
 venient and cheaper to do so. Comparative tests of concrete 
 made by these diJfferent methods failed to distinguish any supe- 
 riority in one over the other. 
 
 The city sewers were so low that the intercepting sewers, 
 which had to be lower still, required unusually deep trenches. 
 The average depth of cut for the whole system was more than 
 21 feet. The bottom of these trenches was generally several 
 feet below the elevation of low tide. As the new sewers fol- 
 lowed the margins of the city near the sea, tide-water frequently 
 found access to the trenches, so that construction could only 
 proceed during a few hours at about the time of low tide, when 
 the leakage of water could be controlled. Sometimes the trench 
 could not be kept entirely free from water. Many of the streets 
 traversed by the sewers were underlaid by beds of mud. Gen- 
 erally the mud was not so deep but that an un3delding founda- 
 tion could be secured by driving piles through the mud down 
 into the hard ground beneath. Sometimes, however, the mud 
 was so deep that hard bottom could not be reached by piling. 
 
 It was under such conditions that the use of wood to form 
 the whole, or the lower part, of the sewer was resorted to. 
 Wood was no cheaper in itself than masonry ; but a wooden 
 sewer could be built very much more rapidly than a brick one, 
 and could be built by unskilled laborers. Also, a wooden 
 invert could be fastened in place, if necessary, under a foot or 
 two of water. Moreover, a wooden sewer, fastened by spikes 
 
0« MAESr DRAINAGE WORKS. 
 
 and oak treenails, possessed considerable elasticity, and could 
 settle slightly in places, or assume an undulating form, without 
 breaking. 
 
 Therefore, under conditions such as those just mentioned, 
 the use of wood to form the shell of a sewer was often resorted 
 to. There were disadvantages attending this mode of con- 
 struction. The elasticity which permitted the sewer to bend 
 longitudinally without breaking, also made it tend to yield trans- 
 versely, sinking at the crown and bulging at the sides, when- 
 ever the earth outside was at all compressible. It was not easy 
 to prevent the wooden shell from leaking badly, especially at 
 the end joints. All wooden sewers had to be lined with brick- 
 work, or concrete, to make them smooth and tight ; but putting 
 such lining inside of a leaky sewer is a somewhat tedious and 
 difficult operation. 
 
 The tops of most of the intercepting sewers are several feet 
 below the level at which ground water stands in the earth about 
 them. Great pains were taken to insure every joint being 
 thoroughly filled with mortar, and the arches were always plas- 
 tered outside with a half-inch coating of cement mortar. By 
 such means the greater part of the system was made perfectly 
 tight and dry. In places, however, especially where there were 
 slight settlements and cracks, a considerable amount of leakage 
 occurred. All leaky joints were calked as well as possible. 
 Various materials were used for this purpose. Among them 
 were neat cement ; cement mixed with grease or with clay ; 
 oakum ; dry pine wedges, and sheet lead. Bj^ one or several of 
 these methods the leakage could either be entirely stopped or 
 reduced to an insignificant amount. 
 
 A considerable item in the total cost of building the inter- 
 cepting system was the expense incurred in repairs to street 
 surfaces and paving, over the sewers. The trenches were so 
 large and deep that the backfilling, often of a peaty consist- 
 ency, could not be sufficiently compacted by ramming or pud- 
 dlino- but continued to settle for a vear or more after the 
 sewer was built. As it was necessary to keep the surface in a 
 safe and reasonably smooth condition the portion over the 
 trench was sometimes repaved three, or even more, times before 
 
DETAILS OF ENGINEERING AND CONSTRUCTION. 89 
 
 it would remain permanently in place. Where the earth un- 
 derlying the street was of a peaty nature, it would be rendered 
 spongy and compressible by its water draining out into the open 
 trench during construction. Then the whole street surface, 
 including sidewalks and sometimes even adjacent yards, would 
 settle out of shape and need repairing. 
 
 Another source of expense and trouble was the breaking of 
 house-drains where they passed across the sewer trench, due to 
 the settlement of the backfilling. The intercepting sew^ers 
 were frequently, indeed generally, built in streets which 
 already contained a common sewer. The house-drains from 
 one side of the street crossed the trench of the hitercepting 
 sewer. These drains were maintained, or replaced, as securely 
 as possible, but many of them were afterwards broken. 
 These were generally found to be sheared off on the line of the 
 sides of the excavation, and the portion within the trench sunk 
 bodily, half a foot or so, below the rest. 
 
 As a rule the streets in which sewers were built were kept 
 open for traffic. When the trench was in the middle of the 
 street, passage-ways for vehicles were maintained on both sides 
 of it, even when the width between sidewalk curbs was only 26 
 feet. This was accomplished by the use of an apparatus for ex- 
 cavating and backfilling, invented by the superintendent, Mr. H. 
 A. Carson, and afterwards patented by him. Various merits 
 are claimed for it, but the chief advantage in its use at Boston 
 was, that by it sewers could be built with very little encroach- 
 ment on the surface of the street. Views of the apparatus are 
 given on Plate XXVII. Although a patented article, a brief 
 description of it seems proper, since it was used in building 
 more than one-half of the intercepting sewers. 
 
 In its general features the apparatus consisted of a light 
 frame structure, extending longitudinally over the sewer trench 
 from a point in advance of where excavation had begun, to 
 another behind where the trench was completely backfilled. 
 All operations, therefore, were carried on beneath the machine. 
 Excavation proceeded under the forward portion of the 
 frame, the sewer was built under the central portion, and 
 backfilling progressed near the rear. A double-drum hoisting 
 
00 MAIN DRAINAGE WORKS. 
 
 engine was carried on a platform at the front end of the frame. 
 From the top of the frame were suspended iron tracks, on which 
 were travellers, moved backwards and forwards by wire ropes 
 leading to the engine. A number of tubs, loaded by the dig- 
 gers in front, were hoisted simultaneously by the engine, and 
 run back to be dumped over the completed sewer. They were 
 then returned and lowered to the points whence they had been 
 taken, by which time a second set of tubs had been filled ready 
 for hoistino;. 
 
 Any surplus earth was dumped through a hopper into carts 
 which were backed mider the machine. When it was neces- 
 sary to furnish a passage across the work the trench was 
 bridged, and the frame trussed. When one section of excava- 
 tion was completed, the whole apparatus, which rested on 
 wheels, was pulled forward 30 or more feet by its own engine. 
 The average total length of one apparatus was 200 feet, and its 
 total weight about 10 tons. 
 
 Sewer building, done by the city, was frequently carried on 
 through the winter months. Contractors, on the other hand, 
 were not allowed to lay masonry between November 15 and 
 April 15. The temperature at the bottom of a deep trench was 
 always considerably higher than that at the surface of the ground ; 
 so that it was only when the mercury was at ten or more de- 
 grees (F.) below the freezing-point that work was suspended. 
 Much extra precautionary work was needed. Bricks were 
 steamed in a close box before using ; sand and water were 
 warmed, and completed work was protected by coverings of 
 straw or sea-weed. Winter work was not economical, and was 
 resorted to chiefly for the purpose of employing laborers, who 
 otherwise might have been idle. 
 
 Experience is probably a better guide to designing stable 
 sewers than are theories concerning lines of pressures and geo- 
 static arches. The physical conditions which determine the 
 direction and amount of the earth pressures are seldom the same 
 in the case of any two sewers. They differ at different points 
 about the same sewer, and often are not alike on both sides of 
 one sewer. The best that can be done is to judge as well as 
 possible of the character of the ground to be penetrated, and 
 
Plate XXVII 
 
 TRENCH MACHINE 
 
 MT. VERNON ST. 1883. 
 
 Fig. I 
 
 CITY OF BOSTON 
 MAIN DRAINAGE 
 
 DIAGRAM machine: 
 
 STOP PLANKS 
 
 3, •^■'^•3 
 
 i 
 
 Fig. 2 
 
 Fig. 4- 
 
DETAILS OF ENGINEERING AND CONSTEUCTION. 91 
 
 befjin to build such a sewer as has proved stable under similar 
 conditions. The sewer should then be examined carefully, 
 during and after loading, for signs of weakness. 
 
 In the case of the main drainage sewers such examinations 
 were made graphically, by taking diagrams of their inside 
 shape. These diagrams were taken by the aid of a machine 
 shown on Plate XXVII. It consisted of a light frame, which 
 could be so fixed against the masonry that its centre should 
 be in the axis of the sewer. A movable arm was then rotated 
 radially from the centre, with its outer end bearing lightly 
 against the inside perimeter of the sewer. At the centre of the 
 machine was a disk, on which was placed a sheet of paper. A 
 pencil point, attached to the rotating arm, traced upon the 
 paper a diagram, showing the shape of the sewer and its varia- 
 tion, if any, from the established form. 
 
 The shape and amount of any distortion suggested the cause 
 which produced it, and the remedy to be applied. The most 
 common causes were too early removal of centres ; too rapid 
 or unequal loading ; the use of improper material for backfilling 
 about the sewer ; insufficient rammino; of backfillina: ao-ainst the 
 haunches ; withdrawing sheet planks after backfilling ; inherent 
 weakness in the design of the sewer. Such errors could be 
 corrected and the design of the structure could be modified 
 until the diagrams taken from the sewer were found to corre- 
 spond with its proper shape. 
 
 The Main Drainage System is so arranged that any principal 
 portion of it cafi be isolated and emptied for inspection and re- 
 pair. Any intercepting sewer can be thus isolated by closing 
 the penstock gate at its lower end, and also the inlet valves 
 connecting it with the common sewers, the latter then discharg- 
 ing at their old outlets. By closing the gates at the ends of all 
 intercepting sewers the main sewer can be emptied. Wher- 
 ever an opportunity for isolating a small portion of the works 
 might prove desirable, but the use of iron gates for such pur- 
 pose would have entailed unwarranted expense, as a cheaper 
 substitute, grooves of iron or stone were built into the masonry 
 for stop-planks. Such grooves for stop-planks were always 
 built above any iron gates, to afford a means of access in case 
 
92 MAIN DRAINAGE WORKS. 
 
 of needed repairs. Where slight leakage could be afforded, a 
 sino-le pair of grooves were considered sufficient. Where a 
 tio-ht dam was desirable, a double set of grooves was provided, 
 so that a double set of stop-planks, with an inside packing of 
 clay, could be used. Some hundreds of stop-planks, of differ- 
 ent lengths, are kept in readiness. Their form is shown on 
 Plate XXVII. They are made of hard-pine planks, from three 
 to five inches thick, jjlaned and oiled. 
 
 The connections between the common sewers and the inter- 
 ceptino- sewers were usually made during the construction of 
 the latter. The valves of the inlet-pipes, built into the common 
 sewers, were closed and made tight by a little cement around 
 their edo'es. By raising these valves the connection between 
 the old and new system could at any time be established. 
 
WOEKING OF THE NEW SYSTEM. 93 
 
 CHAPTER XI. 
 
 WORKING OF THE NEW SYSTEM. 
 
 January 1, 1884, the connections between the common and 
 interceptmg sewers were first opened. Pumping began at the 
 same time, and tlie sewage was sent to the reservoir at Moon 
 Island, and thence discharged into the Outer Harbor. Connec- 
 tion with about one-half of the common sewers was made on 
 that day, and most of the others were connected within a month 
 thereafter ; so that by February, 1884, nearly all of the city 
 sewage was diverted from the old outlets. The upper portion of 
 the West Side intercepting sewer, in Lowell and Causeway 
 Streets, was built in 1884. The common sewers, tributary to 
 it, were intercepted as construction progressed. A common 
 sewer draining a portion of Dorchester, intercepted by the main 
 sewer at East Chester Park just east of the N.Y. & N.E. 
 Eailroad, was not connected until early in 1885. 
 
 Although the whole intercepting system, therefore, was not 
 entirely completed until the present year, yet the greater part 
 of it has been in operation for fifteen months, — a long enough 
 period to afibrd a fair indication of its practical working, and of 
 the results which will be derived from it. 
 
 As elsewhere stated, the Main Drainage Works were designed 
 and built to correct two principal evils inherent in the old sys- 
 tem of sewerage. These were : — 
 
 First. The damming up of the common sewers by the tide, 
 by which, for much of the time, they were converted into stag- 
 nant cesspools, and the air in them was compressed, and to find 
 outlets was driven into house-drains and other openings. 
 
 Second. The discharge of the sewage on the shores of the city 
 in the immediate vicinity of population, thereby causing nui- 
 sances at many points. 
 
 The first of these evils has been entirely corrected by the new 
 system. The old sewers now have a continual flow in them, 
 
94 MAIN DRAINAGE WORKS. 
 
 independent of the stage of the tide, as has been ascertained by 
 frequent observations, and also from the testimony of drain-lay- 
 ers, who formerly were only able to enter house-pipes into the 
 the sewers when the latter were empty at low tide, but now can 
 make such connections at any time. 
 
 The new system has also substantially remedied the second 
 evil. From the moment that any of the city sewers was con- 
 nected with an intercepting sewer, the sewage which had before 
 discharged on the shore of the city was diverted, and has since 
 been conveyed to Moon Island and emptied into the Outer Har- 
 bor at that point. 
 
 It is true that about twenty-four times during the past year, 
 or an average of twice a month, during rain-storms and freshets, 
 the amount of water flowing in the sewers has exceeded the 
 capacity of the pumps. At such times the excess has been dis- 
 charged at the old sewer outlets. But this occasional and tem- 
 porary discharge of very dilute sewage does not seem to have 
 occasioned any nuisance. Examinations and inquiries concern- 
 
 ino- the condition of the shores and docks at the sewer outlets 
 
 o 
 
 have shown that water, once continually foul, has become pure, 
 bad odors have ceased, and fish have returned to places where 
 none had been seen for years. The stenches, referred to by the 
 City Board of Health (p. 13), which formerly, at times, were 
 prevalent over the city, were not noticed during the past year. 
 
 The attempt to relieve certain low districts, subject to flooding 
 of cellars during rain-storms at high tide, b}^ discriminating in 
 favor of such districts in respect to the interception of storm- 
 water, has met with marked success. No case of flooding in such 
 districts has been reported since the sewers draining them have 
 been connected with the intercepters ; and many cellars, which 
 used often to be filled several feet deep with water, are known 
 to have been perfectly dry during the past year. 
 
 Building the intercepting sewers has also dried cellars in other 
 parts of the city in a way which was not at first anticipated. 
 When land on the shores of the city was reclaimed for building 
 purposes, most of the old walls and wharves were covered up 
 by the new filling. Tide-water followed along any such struct- 
 ures through the ground, and entered cellars lower than high-tide 
 
WORKING OF THE NEW SYSTEM. 95 
 
 level. The new sewers were generally built along the present 
 margins of the city, and in digging deep trenches for them the 
 old structures found were cut off and removed. The backfilled 
 earth in the trenches forms an impervious dam surrounding the 
 city, beyond which tide-water cannot pass. 
 
 The sewers have been examined frequently since they went into 
 operation. The average depth of dry-weather flow in the inter- 
 cepting sewers is from ten to twenty inches, so that they can be 
 entered on foot. So, also, can the main sewer above Tremont 
 Street, and, sometimes, above Albany Street. Below that point 
 the dry-weather flow is from two to three feet deep, necessitating 
 the use of a boat. 
 
 The velocity of flow in the sewers varies from about two feet a 
 second upwards. An attempt w^as made to measure the velocity 
 at several ]3oints with a current meter. While integrating, the 
 meter rarely could be kept under water longer than ten seconds 
 at a time without danger of its being clogged by paper, hair, 
 and similar substances. By the use of a stop-watch the instru- 
 ment could be removed for cleaning and again immersed without 
 interfering with the experiment. The inclination of the surface 
 of the sewage, though approximately the same as that of the 
 sewer, was seldom precisely the same, and the observations 
 were not sufiiciently exact, in any case, to determine just what 
 inclination then existed. The mean velocity at the points of 
 measurement were, however, accurately ascertained, and the 
 results may be of sufficient interest to cite. 
 
 In the case of a 4 X 4.5 feet sewer (Fig. 7, Plate YIII.), with 
 an inclination of 1 in 2,000, flowing 1.23 feet deep, the mean 
 velocity was 1.9 feet per second. This sewer had some graA^el 
 on its bottom. In the case of a 4.75 X 5.5 feet sewer (Fig. 8, 
 Plate VIIL), with an inclination of 1 in 2,000, the depth was 
 1.45 feet, and the mean velocity was 2.45 feet per second. In 
 a 4.5 feet circular sewer, with an inclination of 1 in 700, and 
 a depth of 1.15 feet, the mean velocity of flow was 2.56 feet per 
 second. In the case of an 8.25 feet circular sewer (Fig. 14, 
 Plate VI.), the inclination being 1 in 2,500 and the depth 1.76 
 feet, the mean velocity was 2.59 feet per second, sufficient to 
 keep in suspension and carry along all sewage sludge. Most of 
 
96 MAIN DRAINAGE WORKS. 
 
 the city sewers, when first intercepted, were found to contain 
 deposits of sludge varying from a few inches to several feet in 
 depth. All these deposits were carried into the intercepting 
 sewers, and the sludge reached the pumping-station and was 
 pumped up into the deposit-sewers. Gravel, stones, and brick- 
 bats also were swept along and taken out at the filth-hoist. 
 Fine sand, however, did not move so freely, but settled in 
 ridges here and there, and had to be removed by hand. 
 
 The bottoms of the sewers are, as a rule, perfectly clean. No 
 slime accumulates there, or, if it ever begins to grow, it is at 
 once scoured off by the attrition of moving particles. The sides 
 of the invert below the surface of the water have a thin coating 
 of slime, making them very slippery. The arch and the portion 
 of the invert above the water exposed to the air are clean, and 
 often quite dry. In some portions of the sewers earthy accre- 
 tions form on the arch. Where the sewer is surrounded by 
 marsh mud these are turned black by sulphuretted hydrogen, 
 sometimes they are colored yellow by iron, often they appear 
 as white stalactites. In clayey soil the arch seems to be about 
 as clean as when laid. 
 
 The atmosphere in the sewers is not offensive, although a 
 faint sewage smell can be detected on first entering theru. For 
 the first eight months after the sewers went into operation they 
 were not ventilated at the man-holes. This was because it was 
 known that much sludge would be turned into them from the 
 common sewers, and it was feared the smell from it might be 
 noticed. Finally the ventilating covers, shown on Plate VI., 
 were put in place. No smell has ever been noticed from them, 
 and they considerably improved the condition of the atmosphere 
 in the sewers, which is now quite fresh and hardly at all dis- 
 agreeable ; not so much so, for instance, as is that in most railway 
 carriages after an hour's use. The temperature of the sewage 
 varies from 50° to 65° F., and that of the air in the sewers from 
 40° to 60° F., depending upon the outside temperature. 
 
 A small force of men has been constantly employed during 
 the past year, in caring for the main and intercepting sewers. 
 This force has consisted of a foreman, one carpenter, and four 
 laborers. They have also done minor items of work and repairs 
 
WOEKING OF THE NEW SYSTEM. 97 
 
 which might properly be charged to construction. After every 
 rain, whenever there was any likelihood that water might have 
 overflowed at the old outlets, all of the tide-gates have been 
 visited. As a rule they are found to be quite tight. Occa- 
 sionally one pair of a set (but never both pairs) are found to be 
 leaking somewhat at high tide. This is caused by rags, corks, 
 pieces of wood, or other such matters, catching near the hinges. 
 At such visits the gates are washed clean, the hinges greased, 
 and the iron-work examined for traces of incipient rust. 
 
 Some of the tide-gates were made of white pine and some of 
 spruce. A few of the latter, which have been in place for three 
 years, already show signs of deca3^ These are inside gates 
 situated above the elevation of mean tide, so that they are com- 
 paratively seldom Avet. To replace them creosoted lumber 
 will probably be used. The rubber gaskets, fastened to the 
 gates, are in perfectly good condition after about three 
 years' use. They were made of what was called by the manu- 
 facturer " pure rubber ; " but as they cost 75 cents a pound, 
 when crude rubber was selling at more than $1.00 a pound, 
 they probably merely contained a larger percentage of that 
 material than is usual in rubber goods. They were made with 
 special reference to resisting the effects of sewage and grease. 
 
 The penstocks, flushing-gates, and regulators are also in- 
 spected periodically. Moving parts are cleaned, slushed, and 
 moved, so as to insure their being in good working condition. 
 The iron, when carefully painted, does not appear to suffer 
 from rust. About once in eight months it receives a coat of 
 asphaltum paint. Duplicates ar.e provided of all pins and other 
 small parts, so that these can be taken to the yard to be warmed 
 and recoated. The chains attached to the inlet valves, by which 
 they are lifted, are most subject to rust. These are frequently 
 changed and taken to the yard, where, after being cleaned and 
 scraped, they are warmed in a furnace and coated with hot pitch. 
 
 The catch-pails under the ventilating man-hole covers are 
 emptied as occasion demands. In some localities, and at some 
 seasons, pails will be filled in less than a month. Others will 
 not require attention for three months. Men drive along the 
 sewer line with a cart, remove a man-hole cover, lift out the 
 
98 MAIN DRAINAGE WORKS. 
 
 pail, empty its contents into the cart, and again replace the pail 
 and cover. A few extra pails are carried in the cart, so that 
 if any of those in use shows signs of rust it can be replaced by 
 another, and be taken to the yard for cleaning and recoating. 
 
 The filth-hoist at the pumping-station seems satisfactorily to 
 answer the purpose for which it was designed. In dry weather 
 the cages are raised three times a day, and the average daily 
 yield from them is about 16 cubic feet. The matters inter- 
 cepted are, rags, paper, corks, half lemons, lumps of fat, dead 
 animals, pieces of wood, bottles, children's toys, pocket-books, 
 and such-like miscellaneous articles, which by accident or design 
 are thrown into house-pipes . Comparatively little solid fecal mat- 
 ter is caught, as most of it dissolves before reaching this point. 
 
 When it rains, and deposits are scoured out of the old sewers, 
 very much more filth is caught in the cages. The amount some- 
 times equals three or four cubic yards in 24 hours. At such 
 times it is necessary to raise and clean the cages every half-hour, 
 during the night as well as in the day, in order to prevent their 
 becoming clogged and backing up the sewage in front of them. 
 
 At first what was removed from the cages was buried in pits 
 near the pumping-station. This not being considered a satis- 
 factory method of disposal an attempt was made to burn the 
 filth in the furnaces under the boilers. It was found that the 
 filth, as taken from the cages, contained so much water that the 
 fires were injured. Accordingly a simple press, like a cider 
 press, was procured, by which most of the water was pressed 
 out. The comparatively dry cakes remaining after pressing 
 are now burned without injuriously affecting the furnace fires. 
 
 The two high-duty " Leavitt " pumping-engines and the two 
 storm-duty " Worthington " pumping-engines have all been run 
 more or less during the past j^ear. Any one of them is able to 
 pump the ordinary dry-weather flow of sewage. As a rule one 
 of the Leavitt engines is kept running ; should it rain, and addi- 
 tional pumping capacity be needed, the second Leavitt engine 
 is, by preference, started ; if still more capacity is needed, the 
 Worthino-ton engines are started. When the amount of water 
 arriving by the sewer decreases, the Worthington engines are 
 first stopped. 
 
WORKING OF THE NEW SYSTEM. 
 
 99 
 
 The average daily quantity of sewage pumped in dry weather 
 is about 24,000,000 gallons, and the average number of tons of 
 coal consumed in doing the work is about 3^. This, with 
 some steam used for other purposes, gives a working duty in 
 the case of the Leavitt engine, of about 95,000,000 pounds" 
 raised 1 foot high by the consumption of 100 pounds of coal. 
 The Worthington engines, under similar conditions, show a 
 working duty of somewhat more than 50,000,000 foot-pounds. 
 
 The following table gives the results of the first year's pump- 
 ing, beginning with February, 1884, when the works had got 
 fairly into operation : — 
 
 
 Daily 
 Average 
 Gallons 
 Pumped. 
 
 Daily 
 Average 
 
 Pounds 
 op Coal. 
 
 Per 
 Cent. 
 
 op 
 Ashes. 
 
 Gallons 
 
 Pumped 
 
 PER Pound 
 
 op Coal. 
 
 Rainfall. 
 
 Month. 
 1884. 
 
 Inches. 
 
 Number 
 of Days 
 it Rained. 
 
 February . . 
 
 25,777,360 
 
 14,028 
 
 15.8 
 
 1,836 
 
 5.74 
 
 20 
 
 March . . . 
 
 32,437,379 
 
 18,880 
 
 14.8 
 
 1,709 
 
 4.86 
 
 19 
 
 April . . . 
 
 29,949,356 
 
 15,671 
 
 16.2 
 
 1,913 
 
 4.76 
 
 17 
 
 May. . . . 
 
 25,121,056 
 
 13,127 
 
 15.6 
 
 1,915 
 
 3.31 
 
 11 
 
 June . . . 
 
 26,712,298 
 
 13,265 
 
 16.5 
 
 2,015 
 
 4.01 
 
 7 
 
 July. . . . 
 
 25,900,400 
 
 13,529 
 
 19.2 
 
 1.912 
 
 4.25 
 
 17 
 
 August . . . 
 
 31,674,621 
 
 14,704 
 
 16.0 
 
 2,174 
 
 5.01 
 
 14 
 
 September 
 
 28,412,431 
 
 11,099 
 
 12.1 
 
 2,568 
 
 .31 
 
 8 
 
 October . . 
 
 27,601,557 
 
 10,206 
 
 13.3 
 
 2,698 
 
 3.17 
 
 13 
 
 November . . 
 
 27,501,283 
 
 8,985 
 
 8.0 
 
 3,073 
 
 3.03 
 
 9 
 
 December . . 
 
 30,883,501 
 
 10,181 
 
 7.2 
 
 2,885 
 
 4.46 
 
 15 
 
 1885. 
 
 
 
 
 
 
 
 January . . 
 
 38,498,668 
 
 11,448 
 
 7.2 
 
 3,265 
 
 5.33 
 
 9 
 
 It will be seen that the daily average, as given, is larger than 
 the dry-weather flow, because it includes the extra quantities 
 pumped during rains. The largest day's work thus far has 
 been 81,280,883 gallons, but for a few hours this rate has 
 been much exceeded. Until August, 1884, the pumping was 
 not done economically. At that time a change was made in 
 
100 MAIN DEAINAGE WORKS. 
 
 the nianaofement of the station, with a considerable increase in 
 economy. A further gain was made in November, 1884, by 
 substituting bituminous coal for anthracite, which had pre- 
 viously been used. The former coal makes more steam, and 
 costs about $1 less a ton. The comparatively lovv duty shown 
 by the table for December was due to the fact that the Worth- 
 ington engines were largely used during that month, while a 
 temporary building over the Leavitt engines was being taken 
 down. 
 
 There are no means for determining accurately the actual 
 amount of the city water supply in the district whose sewers 
 are tributary to the Main Drainage System. But it is evident 
 that even in dry weather the amount of sewage reaching the 
 pumpin£::-station by the main sewer is greater than the water- 
 supply of the districts drained by it. The excess is not con- 
 stant ; sometimes it is estimated to be 10 per cent, of the 
 whole, and at other times it is probably 25 per cent., or 
 even more. This excess comes from several sources. Many 
 dwellings and factories in sewered districts have private water 
 supplies. Breweries, and other similar large establishments, con- 
 tribute largely in this way. A single sugar refinery was found 
 to pump and use, daily, about 1,000,000 gallons of salt water, 
 all of which properly might have gone back into the harbor, 
 but was, instead, turned into the sewers. In the spring, when 
 the ground is full of water, much of it leaks into the common 
 sewers, and is by them carried to the intercepters. Sea-water 
 also, at high tide, finds its way along some of the old box-sew- 
 ers, and leaks into them back of the tide-gates. It will prob- 
 ably prove to be true economy to rebuild many of the old 
 sewers, in whole or in part. 
 
 The permanent working force employed at the pumping- 
 station at present is as follows : — 
 
 1 Chief Engineer, 
 
 3 Assistant Engineers, 
 
 9 Oilers, 
 
 3 Firemen, 
 
 3 Coal-passers, 
 
 1 Clerk. 
 
WORKING OF THE NEW SYSTEM. 101 
 
 The men employed in the filth-hoist, included in the above, 
 rank as oilers. The administration at this point is, of course, 
 not as economical as it would be if there were a uniform, 
 constant amount of work to be done. 
 
 The deposit-sewers have perfectly answered their purposes 
 in arresting all heavy matters contained in the sewage. The 
 cross-sectional area of these sewers is so large, and the result- 
 ing velocity of flow is so sluggish, even when four pumps are run- 
 ning, that all suspended matters subside before reaching the 
 tunnel. Sand and gravel are deposited at once, as soon as they 
 enter the sewers ; lighter substances are carried a little farther ; 
 but only floating matters or those having about the same spe- 
 cific gravity as water, remain in suspension long enough to reach 
 the further end of the sewers. 
 
 As elsewhere stated, the sludge, contained by the common 
 sewers at the time connection was made between them and 
 the intercepting sewer, passed to the pumping-station and was 
 pumped -into the deposit- sewers. The amount of this was 
 12,000 cubic yards, or more. The best way of removino- it was 
 long considered, and it was only in the autumn of 1884 that 
 the appliances described in Chapter VIII. were adopted and 
 constructed. When the six-inch pipe connecting one deposit- 
 sewer with the sludge-tank was first opened, the deposits near 
 where the pipe entered the sewer were drawn into the tank, 
 which in the space of two days was filled with about 100 yards 
 of sludge. 
 
 The floating scrapers (Plate XIX.) were not completed un- 
 til the winter. They work very well, with a combined scrap- 
 ing and flushing action, and by their use the sand and gravel 
 deposits can be moved from one end of the sewer to the other. 
 The sludge-tank was filled a second time, principally w^ith clear 
 sand, when operations were stopped by the harbor's freezing * 
 over. The bay remained closed by ice until early in March, 
 when the removal of the deposits was again resumed. It seems 
 probable that this method of removal will prove as satisfactory 
 as any which could be adopted. 
 
 As the tunnel is 142 feet below the harbor, and has been con- 
 stantly full of sewage since pumping began, there has been no 
 
102 MAIN DRAINAGE WORKS. 
 
 opportunity for inspecting it. For the first few months of 1884, 
 before all of the city sewers had been intercepted, a compara- 
 tively small amount of sewage was pumped, especially at night. 
 At such times the velocity of flow through the tunnel was very 
 slight, often less than one-half of a foot a second. Occasionally 
 pumping would be stopped for a few hours at night, to allow 
 the sewage to accumulate. At present the ordinary flow in the 
 tunnel is seldom faster than 1 foot a second. As J;he sewage takes 
 from two to four hours to pass through the tunnel, at these slow 
 velocities, it was to be expected that deposits would occur there. 
 
 To ascertain the extent of such deposits, and whether they 
 were likely to become permanent, some experiments were made. 
 These were based upon the following laws : 
 
 That the flow through the tunnel is produced by the differ- 
 ence in elevation of the water at its two ends ; 
 
 That the amount of this difierence is a measure of the fric- 
 tional resistance which the tunnel opposes to the flow of the 
 sewage ; 
 
 That, in proportion as the water-way of the tunnel is ob- 
 structed by deposits, the resistance, and therefore the difference 
 in elevation of the water at its two ends, will be greater than 
 they would be if the tunnel was clean. 
 
 The method of making the experiments was as follows : — 
 
 The quantity of water passing through the tunnel was ascer- 
 tained by pump measurement, with allowance for slip. The 
 diflference in elevation at the two ends of the tunnel was deter- 
 mined by means of sliding gauges, with knife edges where they 
 came in contact with the surface of the water. 
 
 The coeflicient was then calculated for the formula 
 
 V :=: C l/El or C = r^ 
 
 in which 
 
 Y — Velocity in feet per second 
 
 area 
 
 R =r Hvdraulic mean radius 
 
 wet perimeter 
 
 I = Sine of inclination = -j — '^--r- 
 
 length 
 
 C =3 A coe6&cient ascertained by experiment. 
 
WORKING OF THE NEW SYSTEM. 103 
 
 As the tunnel is circular, 7.5 feet in internal diameter, the 
 value of R, corresponding to the full cross-sectional area, is 1.875 
 feet. Experiments on the flow of water in the Sudbury-River 
 Conduit,' which was a brick structure like the tunnel, gave a 
 coefficient corresponding to R = 1.875, of about 137. It was 
 not anticipated that the coefficient found for the tunnel, even 
 when it was clean, would be quite so large as that of the con- 
 duit ; since the surface of the former is somewhat rougher, and 
 some loss of head would be occasioned by changes in direction 
 at bends and by obstructions at the east shaft. 
 
 It was also expected that the coefficient would vary somewhat 
 with the velocity and with the dilution of the sewage. Under 
 the most favorable circumstances, with the tunnel free from 
 depo.sits, the coefficient would approximate 137, being that 
 found by the experiments above mentioned. 
 
 The full area of the tunnel was used in determining the values 
 ofVandR. This assumed that the tunnel was clean. Should 
 the coefficient be found to be nmch lower than that anticipated, 
 it would show that the foregoing assumption was incorrect, and 
 that the area of the tunnel was partly obstructed. 
 
 Whatever was the true value of the coefficient, its increase or 
 decrease, as determined by successive experiments under the 
 same conditions, would show whether the amount of deposit in 
 the tunnel was becoming less or greater. 
 
 Arrangements are provided for flushing the tunnel by running 
 four pumps simultaneously, salt water being admitted to the 
 pump-wells to supply any deficiency of sewage. The volume 
 pumped is generally at the rate of about 114,000,000 gallons per 
 day, which gives a velocity of about four feet per second through 
 the tunnel. 
 
 The first flushing with four pumps was done June 12, 1884. 
 Just previous to this time, by two measurements on different 
 days, the loss of head through the tunnel was ascertained to be 
 about .54 of a foot, and the values of C were found to be CO and 
 82. On June 13, the day after flushing, an experiment, with 
 
 1 Traasactions of the American Society of Civil Engineers, Vol. XII., No, CCLIII. 
 
104 MAIN DRAINAGE WORKS. 
 
 the same conditions as those previously made, gave a loss of 
 head of .30 of a foot, and a value of C = 110. 
 
 This value was still too low to indicate an entirely clean tun- 
 nel, but showed that the water-way had been increased by a 
 removal of a portion of the deposit by the flushing. This was 
 known to be a fact, since the sludge scoured out by the flushing 
 had been observed in the reservoir. Inspection showed that 
 the deposit carried into the reservoir was of a very light nature, 
 containing soft mud, horse-manure, water-logged match ends, 
 bits of lemon-peel, paper, and similar substances. 
 
 Beginning in June, 1884, flushing with four pumps has been 
 done regularly about once a fortnight. At four different times 
 measurements to determine the value of G have been made 
 during the flushing. At such times the velocity of flow is high, 
 and from 75 to 80 per cent, of the volume pumped is clean salt 
 water, aflbrdins^ conditions favorable for obtaininsf a hio;h co- 
 efficient. The values of C, derived from these several experi- 
 ments, were as follows : — 
 
 June 12, 1884. C = 129. 
 
 Oct. 20, 1884. C = 120.7. 
 
 Jan. 15, 1885. C = 146.3. 
 
 Feb. 16, 1885. C = 146.6. 
 
 The last two experiments were made on days following periods 
 when the quantity of sewage pumped had been unusually large, 
 on account of rain and melting snow, which may account for the 
 laro^eness of the coefficients. There mav, also, have been some 
 unusual slip in the valves. There can be little doubt, however, 
 that at this time the water-way of the tunnel was not appreci- 
 ably obstructed. 
 
 Since these were experiments on the flow through a large pipe 
 they may have some general interest for engineers, and their 
 details are given in the following table : — 
 
WORKING OF THE NEW SYSTEM. 
 
 105 
 
 I 
 
 
 
 
 
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 ti aj 
 
 
 
 
 
 
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 ^ 
 
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 0^ 9 "S 
 
 
 
 
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 ^ 
 
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 20 to 25 
 ewage ; 7 
 ent. salt 
 
 CO 
 
 20 to 25 
 ewage ; 7 
 ent. salt 
 
 3 
 
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 CO c; 
 
 
 
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 m/^0 = A 
 
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106 MAIN DRAINAGE WORKS. 
 
 The wooden flume between Squantum and Moon Island has 
 been watched carefully durmg the past year. It was at first 
 tight, but the efiect of the summer's sun lying on one side of it 
 tended to make the planks shrink and warp somewhat, so that 
 leakage occurred in some places. These were stopped by 
 tightening the bolts and wedges, and by fastening the corner 
 bottom planks to the sides with lag screws. To guard against 
 the sun the flume was given a second coat of paint. Putting a 
 cheap roof over it would, doubtless, prolong the duration of its 
 efiective service. 
 
 When the sewage in the reservoir is low, the flume runs 
 about half-full. As the basins fill, the depth of flow increases 
 until finally it runs entirely full, acting as a pipe. The ordi- 
 nary velocity of flow is about three feet a second, or less as the 
 depth increases. Twice a day, when the reservoir is flushed, as 
 described later on, the current through the lower end of the 
 flume attains the remarkable velocity of about seven feet a second. 
 This velocity is sufiicient to move stones and brickbats. 
 
 Nevertheless the flume is not clean. From its bottom up to 
 the ordinary flow line the sides are covered with a slimy deposit 
 from one-eighth to one-quarter of an inch in thickness. Above 
 the middle and on the top there is also some slime, but not so 
 much as below. The condition of this sewer is commended to 
 the attention of those sanitarians who are accustomed to repre- 
 sent flushing as a certain remedy for the accumulation of slime 
 in pipes. 
 
 Some experiments were made to determine the value of C in 
 the formula V =; C a/RI as applied to the flume. In one trial? 
 the flume flowing about half-full with sewage, the value of E, 
 was 1.45 feet, the velocity was 2.94 feet a second, and the value 
 of C was found to be 116.9. In a second trial, under similar 
 conditions, the following values were obtained : E, = 1.41 ; V = 
 2.87; C=116.6. In a third trial, when four pumps were running 
 and the flume was flowing full, 75 to 80 per cent, of the water 
 pumped being clean salt water, the values of R, V, and C respect- 
 ively, were 1.5, 4.80, and 134.8. It will be noticed that the 
 value of R was about the same in the last trial as in the first two, 
 but that the value of C was very much greater. It is thought that 
 
WORKING OF THE NEW SYSTEM. 107 
 
 this may be due to the fact that the first trials were made with 
 clear sewage, whereas, in the case of the last trial, the water was 
 comparatively clean. It seems reasonable to suppose that some 
 head would be expended in maintaining in suspension the solid 
 particles contained by the sewage. The subject is worthy of fur- 
 ther investigation, because it concerns the applicability to the 
 flow of sewage of hydraulic formulae derived from experiments 
 on the flow of clean water. 
 
 The reservoir has a capacity of 25,000,000 gallons. As sew- 
 age is stored in it for about ten hours at a time, between the 
 end of one period of discharge and the beginning of another, the 
 basins, as a rule, have been filled only about half-full during 
 the past year. The process of discharging is begun about one 
 hour after the begimiing of ebb tide. By this time the surface 
 of the sea is as low as the bottom of the reservoir, and a good 
 harbor current is setting outwards past the outlet. Water is 
 admitted to the turbine, and by the power transmitted from it 
 the upper gates in the outfall sewer are first closed. The sew- 
 age then arriving is thus stored in the sewer, and its surface 
 rises several feet. Meantime the lower gates in the discharge 
 sewer are opened, and the sewage in the reservoir flows through 
 them to the outlet. Under ordinary circumstances the basins 
 are emptied in about 30 minutes. 
 
 There is left in the basins a thin deposit of semi-fluid mud, 
 generally about one-quarter of an inch thick, but in greater quan- 
 tity after storms. To remove this, flushing is first resorted to. 
 During the past year four brick pai'tition-walls were built across 
 the gallery between the sewers and the reservoir. One of these 
 was built opposite the middle of each basin. As soon as a basin 
 is empty an upper gate is opened on one side of the divid- 
 ing wall just mentioned, and the lower gates on the other side 
 of it. The sewage, which has by this time accumulated to 
 a considerable depth in the outfall sewer, passes through the 
 openings into one side of the basin, and flows with moderate 
 force up the gutters to the back retaining-wall . As the gutters 
 fill the sewage overflows across the ridges and down the gutters 
 on the other side of the basin. Much of the sludge is in this 
 wav washed ofi" into the o-utters and carried into the discharge 
 
108 MAIN DRAINAGE WORKS. 
 
 sewers. The flushing is done alternately from one and the 
 other side of the basin. 
 
 If a basin cannot thus be entirely cleaned, men descend into 
 it with broad wooden scrapers, convex on one side, to fit the 
 gutters, and flat on the other. With these the mud is scraped 
 into the gutters and pushed down into the gallery, whence it 
 is washed out into the sea at the next time of discharge. Such 
 cleansing operations occupy about one-half hour for each basin, 
 and are not especially disagreeable for the men.^ 
 
 When the sides of a basin need cleaning the pump in the 
 engine-house is started, and one or more lines of hose are 
 coupled to the hydrants on the 4-inch pipe fastened to the floor 
 in the middle of each basin. The pump will give two strong 
 fire streams with sufficient force to wash ofi" any crust which has 
 hardened on the walls. The streams can also be used in con- 
 nection with scraping and washing the floors of the basins. 
 
 The first sewao;e which discharo;es at the outlet contains a 
 considerable amount of sludge which has settled in the 
 gallery and discharge sewers, and gives to the effluent a dark, 
 muddy appearance. After a few minutes the color is somewhat 
 lost, and the effluent looks like moderately dirty water. 
 
 Its efiect in discolorino^ the salt water, and its course as it 
 joins the current out of the harbor, can be plainly noticed. 
 Being fresh water it rises to the surface, and when a half-mile 
 from the outlet seems to lie on top of the salt water in a 
 stratum but a few inches thick. The greasy nature of the sew- 
 age tends to quiet the ripples commonly seen on the surface of 
 the harbor, so that the area affected by the discharge is plainly 
 determined. From experiments with floats it is known that 
 the sewage travels nearly five miles, following the Western Way 
 and Black-Rock Channel out to the vicinity of the Brewster 
 Islands. By the time it has travelled a mile from the outlet 
 most of the color is lost, and by the time it has gone two miles 
 (before passing Rainsford Island) not the slightest trace of it 
 can be distino-uished. 
 
 ^ Since this was written slight changes have been made in the method of flushing the 
 floors and gutters, which render the operation so efiective that it is no longer necessaiy 
 to send men into the basins to clean them. 
 
WORKING OF THE NEW SYSTEM. 109 
 
 When the works went into operation, and for the first nine 
 months thereafter, there were no gates near thfe outlet at the 
 end of the discharge sewers. As a consequence the last por- 
 tion of sewage from the reservoir, filling the discharge sewers, 
 flowed out into the harbor slowly as the tide fell. This was 
 the dirtiest part of the sewage, because it contained scourings 
 from the basins. By referring to the plan (Plate Y.) it will be 
 seen that a cove was formed between the island and the pier 
 containing the discharge sewers. In this cove a foot or more 
 of sludge accumulated. A thin layer of sludge also formed on 
 the beach between the outlet and the extreme point of the 
 island. This last-named deposit was only found between the 
 levels of mid-tide and low water. 
 
 In winter no smell comes from these deposits, and in sum- 
 mer none is noticed except during low tide. On three occa- 
 sions last summer, when the wind was from the east, the 
 smell was so strong as to be noticed at Squantum, a mile 
 away. 
 
 In hopes of preventing, or at least lessening, the formation 
 of such deposits, a set of gates have been placed in the cham- 
 ber at the outlet. By these the sewage filling the discharge 
 sewers is held back until the beo-innino; of the succeedino- dis- 
 charge, when it is forced out into a good current. These gates 
 have not been in place long enough to show how much they 
 will accomplish ; but, should objectionable deposits still continue 
 to form on the island, it is thought that an efifectual remedy 
 can be provided. This will consist in building a solid bulk- 
 head wall near the line of low water, from the outlet to the ex- 
 treme easterly point of the island. Such a structure could be 
 built for $30,000. 
 
 No trace of the sludge has been found on the shores in any 
 other part of the harbor. Very little smell emanates from the 
 reservoir in cool weather ; not enough to be perceptible at a 
 contractor's boarding-house, about 200 feet distant. In sum- 
 mer the smell is more noticeable ; but not nearly so much so as 
 is that arising from the deposits of sludge on the beach . 
 
 As a whole, the Main Drainage System works well, and no 
 radical defect has been detected in any portion of it. It is not 
 
110 MAIN DRAINAGE WORKS. 
 
 claimed that, by itself, it furnishes a perfect system of sewer- 
 age for the city. Many defective house-drains and common 
 sewers still exist, and must in time be replaced ; but the new 
 system provides an outlet for the rest, without which other re- 
 forms would be comparatively useless. 
 
 By building the Main Drainage Works, Boston has taken 
 the first, most essential step in the direction of efficient sewer- 
 age. 
 
APPENDIX. 
 
APPENDIX A. 
 
 RECORD OF TESTS OF CEMENT MADE FOR BOSTON 
 MAIN DRAINAGE WORKS. 
 
 1878-1884.1 
 
 The Main Drainage Works chiefly consist of brick, stone, and con- 
 crete masonry. About 180,000 barrels of cement were required to 
 build this masonry ; and to insure its stability and durability it was 
 necessary that the cement should be of good quality. From the start, 
 therefore, means for determining the qualities of all cements used or 
 offered for use were provided. A room was set apart for these oper- 
 ations and an inspector appointed to conduct them. 
 
 The tests were devised, principally, in order to determine three 
 points, namely : — 
 
 1. The relative strength and value of any cement as compared 
 with the average strength and value of the best quality of similar 
 kinds of cements. 
 
 2. The absolute and comparative strength and value of mortars of 
 different kinds made from the same cement. 
 
 3. The effect produced upon the strength of any cement mortar by 
 different conditions and methods of treatment. 
 
 This knowledge was chiefly sought by observations of the tensile 
 strength of the cements and mortars tested. Reasons for adopting 
 the tensile test were, that it required comparatively light strains to 
 produce rupture ; that, as it was universally used, it afforded results 
 which could be compared with those of other observers ; and, finally, 
 because the tensile stress is precisely that by which the mortar of 
 masonry, in most cases of failure, actually is broken. 
 
 All the particles of any cement are of appreciable size, and its 
 strength as a mortar depends on the extent to which the particles ad- 
 here, at their points of contact, to each other or to some inert substance. 
 This adherence may be overcome and the mortar broken, either by 
 pulling the particles apart by tension, or by pushing them past each 
 
 ' A paper presented to the American Society of Civil Engineers, 
 
114 MAIN DRAINAGE WORKS. 
 
 other by compression. The effect upon the adhering quality of the 
 particles is not very different in the two operations ; but in the latter 
 the friction of the particles against each other must also be overcome, 
 which requires the application of very much more force. Transverse 
 tests are only tensile tests differently applied, and shearing produces 
 a stress intermediate to tension and compression. When masonry is 
 strained, one part of it is in tension, another in compression, and, as 
 mortar yields more readily to tensile stress, failure generally occurs 
 by rupture of the joints in tension. 
 
 Briquettes for testing, with a breaking section of one square inch, 
 were first used ; but it was thought that these, from their small size, 
 were liable to be strained and injured by handling in taking them 
 from the moulds and transferring them to the water. A larger pat- 
 tern, with a breaking section one and one-half inches square, or two 
 and one-quarter square inches, was finally adopted. Comparative 
 tests with briquettes of one inch and two and one-quarter inches sec- 
 tion respectively indicated that there was little, if any, difference in 
 their strength per square inch. 
 
 The shape of the briquette adopted is shown by Fig. 2, Plate XXVIII. 
 Fig. 1 of the same plate shows the brass moulds in which the mortar 
 was packed to form the briquettes. These moulds proved very sat- 
 isfactory. They were strong, and easily clamped and opened. The 
 clamp consisted of a piece of brass wire riveted loose in the project- 
 ing lug of one branch of the mould, and binding by friction when 
 turned against the wedge-shaped lug on the other branch. If a fast- 
 ening worked loose a single tap of the hammer would tighten it. All 
 breaking loads were reduced to pounds per square inch of breaking 
 section by multiplying by four and dividing by nine. 
 
 Before testing a cement its color was first observed. The absolute 
 color of a natural cement indicates little, since it varies so much in 
 this particular. But, for any given kind, variations in shade may indi- 
 cate differences in the character of the rock or in the degree of burn- 
 ing. With Rosendale cements a light color generally indicated an 
 inferior or underburned rock. An undue proportion of underburned 
 material was indicated in the case of Portland cement by a yellowish 
 shade, and a marked difference between the color of the hard-burned, 
 unground particles retained by a fine sieve and the finer cement which 
 passed through the sieve. 
 
 The weight per cubic foot was also sometimes ascertained. As this 
 would vary with the density of packing, a standard for comparison 
 was adopted, which was the density with which the cement would 
 pack itself by an average free fall of three feet. The apparatus used 
 
Plate XXVIII. 
 
 B Ff A S S MOULD 
 
 F/o. /. 
 
 BH/QUETTE. 
 
 PAT OF CEMENT 
 TES TED FOR CHECK CRA CKS. 
 
 TUBE AND BOX 
 FOBWEtGH/NG CEMENT. 
 
 Fig. a. 
 
 Fig. 4. 
 
 PAN FOR KEEPING BR/QUETTES. 
 
 Fig. 3. 
 
 Fig. 7. 
 
 UGHT & HE A VY WIRES. 
 Fig. 5. 
 
 Fig. e. 
 
 SCOOP 
 
 m iif Mlin'iiiaiaiiiBll^fcp FiG. 8. 
 
 FOP TAKING SAMPLES FROM BARRELS. 
 
 BARREL OF CEMENT 
 60PER CENT FINE 
 
 
 Fig. 9. 
 
 40 PER CENT 
 
 eOPEP CENT 
 
 BARREL OF CEMENT 
 SUPER CENT FINE 
 
 sandM^^^^^ ioper cent 
 
 90PER CENT 
 
APPENDIX A. 115 
 
 is shown by Fig. 3, Plate XXVIII. Tlie cement was placed in a 
 coarse sieve on the top of a galvanized iron tube, and, the sieve being 
 shaken, the cement sifted through the tube into the box below. This 
 box held exactly one-tenth of a cubic foot when struck level with its 
 top. 
 
 The weights per cubic foot as determined by this method varied 
 considerably with different kinds and brands of cement, and some- 
 what with different samples of the same brand. The averages were 
 as follows : — 
 
 Table No. 1. 
 
 Rosendale i9 to 56 pounds. 
 
 Lime of Tell 50 
 
 Roman 54 
 
 A fine-ground French Portland 60 
 
 English and German Portlands 77.5 to 87 
 
 An American Portland 95 
 
 The following table shows the effect of fine grinding upon the 
 weight of cement. It gives the weight per cubic foot of the same 
 German Portland cement, containing different percentages of coarse 
 particles, as determined by sifting through the No. 120 sieve : — 
 
 Table No. 2. 
 
 per cent, retained by No. 120 sieve — W't per cubic foot 
 10 " " " " " " 
 
 20 " " " «' " '< 
 
 30 " " " " " " 
 
 4Q (< a a a ii (< 
 
 It was soon discovered that there was no direct ratio between: 
 weight and strength. As a general rule, subject to exceptions, 
 heavy cement, if thoroughly burned and fine-ground, was preferred 
 to light cement. Fine-ground cements were lighter than coarse- 
 ground and underburned rock lighter than well-burned. While color- 
 and weight by themselves indicated little, yet, considered together- 
 and also in connection with fineness, they enabled the inspector to 
 guess at the character of a cement, and suggested reasons for high 
 or low breaking. A cement which was light in color and weighty, 
 and also coarse-ground, would be viewed with suspicion. 
 
 The test of fineness, which followed, was considered of great 
 importance, as showing the quantity of actual cement contained in a 
 barrel, and its consequent value. Small scales were used, made 
 
 . . 75 
 
 pounds. 
 
 . . 79 
 
 (< 
 
 . . 82 
 
 (1 
 
 . . 86 
 
 (( 
 
 . . 90 
 
 (C 
 
116 MAIN DRAINAGE WORKS. 
 
 for this purpose by Fairbanks & Co. One-quarter of a pound of 
 the sample was weighed out and passed through the sieve. The 
 coarse particles retained by the sieve were returned to the scales, 
 whose balance-beam carried a movable weight, and was graduated 
 in percentages of one-quarter pound. The percentage of coarse 
 particles retained by the sieve could thus be read directly from the 
 beam. 
 
 Standard sieves, varying from No. 50 to No. 120, were used. The 
 number of meshes to the lineal inch in any sieve is commonly sup- 
 posed to correspond with its trade number. As sold, however, they 
 vary somewhat, and the number of wires is generally less, by about 
 ten per cent., than the number of the sieve. A No. 50 sieve com- 
 monly has about 45 meshes to the inch, and a No. 1'20 about 100, or 
 a few more. In important contracts, where a certain degree of fine- 
 ness was called for, it was customary carefully to compare two sieves 
 and retain one, which was specified as the standard, while the other 
 was delivered to the manufacturer for his guidance. 
 
 In accordance with common practice the No. 50 sieve was first 
 used. It was soon discovered, however, that so coarse a sieve did 
 not always give a correct indication of the fineness of the cement. 
 This was especially true of Portland cements. Some brands, chiefly 
 German, were evidently bolted by the manufacturers with special 
 reference to tests by this sieve, in which they would leave no re- 
 siduum. Yet the bulk of such cements, while containing no very 
 coarse particles, might prove quite coarse when tested by the No. 
 120 sieve. 
 
 It is obvious that pieces of burned cement slag one-fourth of an 
 inch in diameter would have no cementing quality, and the same is 
 true of particles one one-hundredth of an inch in diameter. At 
 precisely what smaller size the particles begin to act as cement it was 
 impossible to determine. Those retained by a No. 120 sieve, in 
 which the open meshes are approximately one two-hundredth of an 
 inch square, were found to have some slight coherence, even after 
 washing to remove the finer floury cement which was sticking to them. 
 It was also found that the No. 120 sieve was about as fine a one as it 
 was practicable to use, on account of the time required to sift the 
 cemeiit through it. It was, therefore, adopted as a standard. 
 
 Assuming (what was only approximately verified by experiments 
 on tensile strength) that only what passed through this sieve had real 
 value as cement, and that the rest was not very different from good, 
 sharp sand, the difference in the quantity of actual cement obtained 
 in purchasing barrels 60 and 90 per cent, fine, respectively, is shown 
 
APPENDIX A. 117 
 
 by Figs. 9 and 10, Plate XXVIII. This has an important bearing 
 on the proportion of sand to be added in practical use ; for when 
 mortar is mixed for use in the proportion of one barrel of cement 
 to two of sand, if there be nine parts of cement and one of sand in 
 the barrel of cement itself, the actual proportion in the mortar will 
 be .9 to 2.1 or 1 to 2.33. If there be only six parts of cement and 
 four of sand in the barrel of cement the resulting proportion in the 
 mixture will be ,6 to 2.4 or 1 to 4. 
 
 Fine cement can be produced by the manufacturers in three ways : 
 by supplying the mill-stones with comparatively soft, underburnt 
 rock, which is easily reduced to powder ; by running the stones more 
 slowly, so that the rock remains longer between them ; or by bolting 
 through a sieve and returning the unground particles to the stones. 
 The first process produces an inferior quality of cement, while the 
 second and third add to the cost of manufacturing. 
 
 The extra cost, as estimated by a firm of English manufacturers, of 
 reducing a Portland cement from an average of 70 per cent, fine, 
 tested by No. 120 sieve, to 90 per cent, fine, was 18 cents per barrel. 
 The price at which 5,000 barrels of their ordinary make, 70 per cent, 
 fine, were offered, delivered on our work, was S2.82 per barrel. The 
 same cement, ground 88 per cent, fine, was delivered for S3 a barrel. 
 On the foregoing assumption of the value of fine and coarse particles, 
 the city, by accepting the first offer, would have obtained in bulk 
 3,500 barrels of actual cement and 1,500 barrels of sand for $14,100. 
 By accepting the second off'er it obtained in bulk 4,400 barrels of 
 cement and 600 of sand for $15,000; that is, the 900 additional 
 barrels of cement cost $1 a barrel. Experiments illustrating the value 
 of fine grinding, and further comments, will be given later. 
 
 Tests were made both of neat cement and of cement mixed with 
 sand in different proportions. The latter were preferred, because they 
 showed the strength and value of the mortars used in actual work. It 
 was found also that the strength of briquettes made of neat cements 
 did not always indicate the capacity of these cements to bind sand, 
 or the strength of the mortars made with them. This is illustrated 
 by experiment No. 10, on page 127. 
 
 The greater the proportion of sand in the mortar tested the more 
 accurately was the actual cementing quality of the cement indicated. 
 As, however, very weak mixtures took a long time to harden, and were 
 liable to injury from handling, one part cement to three parts sand 
 was adopted as the usual mixture for testing Portland cements, and 
 one to one and one-half or two for American cements. Occasionally 
 when testing large quantities of some well-known brand, the object 
 
118 MAIN DRAINAGE WORKS. 
 
 being to see that a UDiform strengtli was maintained, it was found 
 sufficient, and simpler, to omit the sand and make the briquettes 
 of cement only. 
 
 In making mortars for testing, rather coarse, clean, sea-beach sand 
 was used. 
 
 The subsequent strength of the briquettes depended largely upon 
 the amount of water with which they were gauged. The highest re- 
 sults were obtained by using just enough water thoroughly to dampen 
 the cement, giving the mass the consistency of fresh loam, which be- 
 came pasty b}' working with a trowel. For ordinary testing, sufficient 
 water was added to make a plastic mortar, somewhat stiff er than 
 is commonly used by masons. Different ■ cements varied in the 
 amounts of water needed to produce this result. As a rule American 
 cements needed more water than Portland, fine ground more than 
 coarse, and quick-setting more than more slow-setting cements. 
 Experiment No. 9, page 127, shows the comparative strength of mor- 
 tars gauged with different percentages (in weight of the cement) of 
 water. The standard adopted was 25 per cent, for Portland cement 
 and 33 per cent, for Rosendale ; but these amounts were increased or 
 diminished by the operator to suit the circumstances, his aim being to 
 obtain mortars of unvarying consistency. 
 
 The way in which the test briquettes were made was as follows : 
 the moulds, having been slightly greased inside to prevent the mor- 
 tar sticking to them, were placed on a polished marble slab. This 
 support for them was used because it was easily cleaned and the mor- 
 tar did not stick to it. Experiment No. 6, page 124, shows that the 
 use of porous or of non-porous beds to support the moulds does not 
 materially affect the strength of the mortars. The requisite amounts of 
 cement and sand for one briquette were weighed out and incorporated 
 dry in a mixing-pan. The proper amount of water was also weighed 
 out and added, and the mass worked briskly with a small trowel until 
 of uniform consistency. A brass mould was half filled with the mor- 
 tar, which was rammed into place by the operator with a small wooden 
 rammer, in order to displace any bubbles of air which might be con- 
 fined in it. The mould was then filled to its top with the remaining 
 mortar, which was in turn rammed down. Finally the mortar was 
 struck even with the top of the mould and given a smooth surface 
 by the trowel. 
 
 The amount of mortar packed in the mould, and the consequent 
 density of the briquette, would vary with any variation in the degree 
 of force exerted by the operator in ramming. This variation was re- 
 duced to a minimum by always mixing a fixed amount of mortar, 
 
APPENDIX A. 119 
 
 which was barely more than sufficient to fill one mould. Irregularities 
 in ramming would thus be detected by variations in the amount of 
 surplus mortar, and could be checked. An attempt was made to do 
 away wholly with this element of uncertaint}^ by pressing the mortar 
 into the moulds with certain fixed pressures. Apparatus was devised 
 and used for this purpose, but was finally abandoned on account of 
 the length of time required for its use. 
 
 The initial energy of the cement — that is, the length of time after 
 mixing before it " set " — was determined by noting the length of 
 time before it would bear "the light wire" of -^-^ inch in diameter 
 loaded with J-pound weight, and also "the heavy wire" 2'^ inch in 
 diameter loaded with 1-pound weight. At the former time tlie cement 
 was said to have begun to set, and at the latter it was entirely set. 
 DilJerent kinds and brands of cement varied greatly in the time after 
 mixing when they would bear the wires. Some brands of English 
 Roman cement would set in two minutes, and some of Portland re- 
 quired over 12 hours. Cold retarded the setting, and fresh-ground 
 cements set quicker than older ones. No direct relation was estab- 
 lished between initial energy and subsequent strength. Bj^ judicious 
 mixing of quick and slow setting cements a mixture could be ob- 
 tained which would set within any desired period. 
 
 As soon as the briquettes were hard enough to handle without injury, 
 which with different cements and mixtures varied from five minutes to 
 twelve or more hours, they were removed from the moulds and placed 
 in numbered pans filled with water. Before removal each briquette 
 had marked upon it,, with steel stamps, the name of the cement, date 
 of mixing, and a number by which it could be further identified. The 
 inscription might read thus : — 
 
 "Alsenl-3. May 17, 1880. 47." 
 
 Records were also kept in books and on blanks provided for the 
 purpose. The briquettes were kept in the pans, covered with water, 
 until they were broken. Their age when broken varied from 24 hours 
 to five years. 
 
 In testing a well-known American cement, of generally uniform 
 quality, if it were an object to save time, the comparative excellence 
 of the samples could be sufBciently determined by a 24 hours' test of 
 briquettes made of neat cement. Under similar conditions neat Port- 
 land cement could be tested in seven days. To test mortar of either 
 kind of cement took a week, or, better, a month ; especially if there 
 was a liberal proportion of sand. 
 
 The probable value of an untried brand of cement could hardly 
 
120 MAIN DRAINAGE WORKS. 
 
 be ascertained with certainty in less than a month, and not always 
 then. To illustrate the occasional need of long-time tests a case may 
 be cited. 
 
 A new brand of cement, made by some patent process, was offered 
 for use on the work. When tested it set up well, and at the end 
 of a week the neat cement had a tensile strength of 184 pounds per 
 square inch. In a month this had increased to 267 pounds, indicating 
 a strength equal to that of a low-grade Portland cement. At this 
 time there was nothing in the appearance of the briquettes to indicate 
 any weakness. Yet after about six months they fell to pieces, and had 
 entirely lost their cohesive quality. 
 
 The briquettes were broken by a machine made for the Department 
 by Fairbanks & Co. It worked with levers, acting on a spring bal- 
 ance, which was tested from time to time, and found to maintain its 
 accuracy. 
 
 During the progress of the work the following brands of cement 
 were submitted for approval, and were tested with more or less thor- 
 oughness : — 
 
 Old Newark, Newark and Rosendale, Norton, Hoffman, OldEosen- 
 dale, New York and Rosendale, Lawrenceville, Rosendale, Arrow, 
 Keator, Howe's Cave, Rock Lock, Buffalo, Cumberland, Round Top, 
 Selenitic, Vorwholer, Star, Dyckerhoff, Alsen, Hemmor, Bonnar, 
 Onward, Burham, J. B. White, Knight, Bevan & Sturge, Brooks, 
 Shoobridge & Co., Leavitt, Grand Float, Diamond, Spanish, Red 
 Cross, La Farge, Lime of Teil, S.aylor, Coolidge, Walkill, Cobb, 
 Abbott. 
 
 The following is a record of the more instructive tests, made for 
 experimental purposes. Nearly all of them were made with special 
 reference to the work then in hand, to elucidate some practical ques- 
 tions affecting the purchase, testing, or use of the cements needed for 
 building purposes. The names of the brands of cement tested in the 
 several experiments are generally omitted. This is in order to avoid 
 any unwarranted use of the results as recorded. 
 
 The figures given in the tables always represent average breaking 
 loads in pounds per square inch of breaking section. 
 
 Experiment No. 1. 
 
 Of natural American cements the Rosendale brands (so called) are 
 the only ones which find a sale in the Boston market, and they were 
 chiefly used on the work. Imported Portland cements were also 
 largely used. It was important, therefore, to ascertain the actuai and 
 
APPENDIX A. 
 
 121 
 
 comparative strengths of these cements. The following table gives 
 results compiled from about 25,000 breakings, of 20 different brands, 
 and fairly represents the average strength of ordinary good cements 
 of the two kinds. Some caution, however, is necessary in using the 
 table as a standard with which to compare other cements. Quick- 
 setting cements might be stronger in a day or week, and show less 
 increase in strength with time. Fine-ground cements would probably 
 give lower results tested neat, and higher ones with liberal propor- 
 tions of sand. 
 
 Table No. 3. 
 
 EOSENDALE CEMENT. 
 
 Neat Cement. 
 
 Cement, 1; 
 Sand, 1, 
 
 Cement, 1 ; 
 Sand, 1.5. 
 
 Cement, 1 ; 
 Sand, 2. 
 
 Cement, 1; 
 Sand, 3. 
 
 Cement, 1 ; 
 Sand, 5. 
 
 c 
 
 71 
 
 92 
 
 6 
 145 
 
 o 
 to 
 
 282 
 
 o 
 
 :^ 
 
 290 
 
 56 
 
 6 
 116 
 
 o 
 to 
 
 190 
 
 o 
 256 
 
 41 
 
 
 o 
 
 to 
 
 155 
 
 o 
 
 :^ 
 
 230 
 
 24 
 
 d 
 60 
 
 o 
 to 
 
 125 
 
 o 
 180 
 
 
 6 
 35 
 
 o 
 
 a 
 
 to 
 80 
 
 o 
 121 
 
 5 
 
 d 
 
 I-t 
 
 16 
 
 o 
 to 
 
 46 
 
 o 
 
 a 
 
 SO 
 
 Neat Cement. 
 
 Cement, 1; 
 Sand, 1. 
 
 Cement, 1; 
 Sand, 1.5. 
 
 Cement, 1; 
 Band, 2. 
 
 Cement, 1 ; 
 Sand, 3. 
 
 Cement, 1; 
 Sand, 5. 
 
 ft 
 
 303 
 
 d 
 412 
 
 o 
 to 
 
 468 
 
 o 
 494 
 
 160 
 
 1 
 225 
 
 o 
 to 
 
 347 
 
 o 
 
 1— i 
 
 387 
 
 ^ 
 ^ 
 
 6 
 
 o 
 
 o 
 
 126 
 
 d 
 
 rH 
 
 163 
 
 o 
 to 
 
 279 
 
 o 
 e-i 
 
 323 
 
 95 
 
 d 
 140 
 
 o 
 198 
 
 o 
 
 rH 
 
 257 
 
 55 
 
 d 
 88 
 
 o 
 
 to 
 
 136 
 
 o 
 155 
 
 
 
 
 
 
 
 The table is instructive in several ways. It shows that Portland 
 cement acquires its strength more quickly than Rosendale ; that both 
 cements (but especially Rosendale) harden more and more slowly as 
 the proportion of sand mixed with them is increased ; that, whereas 
 neat cements and rich mortars attain nearly their ultimate strength in 
 six months or less, weak mortars continue to harden for a year or more. 
 The table shows the advantage of waiting as long as possible before 
 loading masonry structures, and the possibility of saving cost by using 
 less cement when it can have ample time to harden. It also shows 
 that Portland cement is especiallj' useful when heavj^ strains must be 
 withstood within a week. 
 
122 
 
 MAIN DRAINAGE WORKS. 
 
 Experiment No. 2. " 
 
 These series of tests are like the preceding ones, except that a 
 single brand of cement was used in making each. The average 
 breaking loads per square inch were obtained from a less number of 
 briquettes (about 500 in all), mortars with larger proportions of sand 
 were included in the series, and the tests were extended for two years. 
 
 Table No. 4. 
 
 PORTLAND CEMENT MORTAR. 
 
 Age when 
 
 Neat 
 
 Cement, 1 ; 
 
 Cement, ] ; 
 
 Cement,! ; 
 
 Cement,!; 
 
 Cement,!; 
 
 Cement,!; 
 
 Broken. 
 
 Cement. 
 
 Sand, 2. 
 
 Sand, 4. 
 
 Sand, 6. 
 
 Sand, 8. 
 
 Sand, 10. 
 
 Sand, 12. 
 
 One week 
 
 295 
 
 166 
 
 89 
 
 50 
 
 33 
 
 23 
 
 17 
 
 One month . 
 
 341 
 
 243 
 
 132 
 
 88 
 
 67 
 
 50 
 
 41 
 
 Six months . 
 
 374 
 
 343 
 
 213 
 
 149 
 
 98 
 
 76 
 
 51 
 
 Two years . 
 
 472 
 
 389 
 
 226 
 
 159 
 
 98 
 
 49 
 
 31 
 
 KOSENDALE CEMENT MORTAR. 
 
 Age when 
 Broken. 
 
 Neat 
 Cement. 
 
 Cement,!; 
 Sand, 2. 
 
 Cement,!; 
 Sand, 4. 
 
 Cement, 1 ; 
 Sand, 6. 
 
 Cement,!; 
 Sand, 8. 
 
 Cement, 1 ; 
 Sand, 10. 
 
 Cement, ! ; 
 Sand, 12. 
 
 
 . . . 
 
 24 
 
 83 
 
 172 
 
 211 
 
 7 
 33 
 93 
 90 
 
 5 
 
 
 
 
 One month . 
 Six months . 
 Two years . 
 
 17 
 
 62 
 56 
 
 8 
 50 
 33 
 
 5 
 33 
 
 22 
 
 21 
 20 
 
 The tables show that considerable strength is acquired in time, even 
 when a very large proportion of sand is used ; also, that most mortars 
 increase very little, if any, in tensile strength after six months or a 
 year. They become harder with time, but also become more brittle 
 and probably less tough. Specimens of mortar two years old, or more, 
 break very irregularly. 
 
 Experiment No. 3. 
 
 The rate at which Rosendale and Portland cements, respectively, 
 increase in strength during the first two months after mixing is very 
 different, and has some bearing on their use, and more on the inter- 
 pretation of tests of them made within that period. The curves (Fig. 
 
Plate XXIX. 
 
 500 
 
 400 
 
 300 
 
 pORTLAmSmMKL 
 
 200 
 
 KX) 
 
 4O0 
 
 300 
 
 20O 
 
 100 
 
 CO 
 
 14 SO 
 
 AGE IN DAYS WHEN BROKEN. 
 FfGJ. 
 
 F/G.2. 
 
 K/ND or SAND USED. 
 
 
 sandTsT^ 
 
 
APPENDIX A. 123 
 
 1, Plate XXIX), which indicate this rate of increase, were compiled 
 from tests with neat cement. It is probable that tests with mortar 
 would give somewhat similar results. By comparing the two curves it 
 appeai-s that after 24 hours Rosendale cement has about three-fourths 
 of the strength of Portland. While the latter increases greatly in 
 hardness during the next few days, the energy of the former becomes 
 dormant, so that at the end of a week the Portland cement is more 
 than three times as strong as the Kosendale. During the second 
 week the Portland cement increases more slowl3-, and the Rosen- 
 dale continues nearly quiescent. At about this period, and for the 
 next six weeks, the Rosendale cement gains strength, not only rela-, 
 tively, but actually faster than the Portland, so that when two months 
 old the former has one-half the strength of the latter. After two 
 months the relative rate of increase and the comparative strength 
 of the two cements remain nearly unchanged. A series of tests with 
 a Buffalo cement, and one with a Cumberland cement, gave results 
 similar to those with Roseudale cement. 
 
 EXPERIMEKT No. 4. 
 
 For making tests it is not always convenient to obtain sand of uni- 
 form size, and still less so to obtain such sand in sufllcieut quantities 
 for use in work. The curves. Fig. 2, Plate XXIX, record some tests 
 made to determine the effect of fineness and of uniformity of size 
 in sand upon the strength of mortars made with it. 
 
 The curves show that for comparative tests it is advisable to have 
 sifted sand of nearly uniform size ; that mortars made with coarse 
 sand are the strongest, and that the finer the sand the less the 
 strength. It also appears that mixed sand, i.e., unsifted sand con- 
 taining a mixture of particles from coarse to fine, makes nearly as 
 strong a mortar as coarse or medium coarse sand. For use in work, 
 therefore, it is well to avoid fine sands ; but it is not necessary to 
 have sand of uniform size, or to sift out a moderate proportion of 
 fine particles. ,, 
 
 Experiment No. 5. 
 
 As some experimenters on cement use a test briquette with a break- 
 ing section of 1 square inch, and others one with a section of 2J 
 square inches, the following experiment was made to determine the 
 difference, if any, in the strength acquired by the same mortars 
 moulded into briquettes of these different sizes. Two series of tests 
 were made, in the same way, with the same mortars. In one series 
 the briquettes had a breaking section of 1 square inch, and in the 
 
124 
 
 MAIN DRAINAGE WORKS. 
 
 other the section was 2^ square inches. The results are given in the 
 following table, in which the iigures represent breaking loads in 
 pounds per square inch, and are averages from five breakings : — 
 
 Table No. 5. 
 
 
 ROSENDALB CeMENT. 
 
 Portland 
 
 Cement. 
 
 
 
 Cement, 1 ; 
 
 Neat 
 
 Cement, ] ; 
 
 
 Neat Cement. 
 
 
 
 
 
 
 Sand, 1.5. 
 
 Cement. 
 
 Sand, 1.5. 
 
 
 
 ^ 
 
 .a 
 
 J2 
 
 ^ 
 
 _^ 
 
 1 
 1 
 
 M 
 
 ^ 
 
 J 
 
 M 
 
 ^ 
 
 •3 
 
 
 >> 
 
 ^ 
 
 a 
 o 
 
 o 
 
 
 o 
 
 d 
 o 
 
 
 ri 
 o 
 
 o 
 
 1 
 
 o 
 
 o 
 
 3 
 
 
 !H 
 
 iH 
 
 '"' 
 
 CD 
 
 1-1 
 
 '"' 
 
 «■ 
 
 i-i 
 
 r-l 
 
 o 
 
 iH 
 
 tH 
 
 to 
 
 1-inch Section . . . 
 
 49 
 
 73 
 
 156 
 
 286 
 
 27 
 
 53 
 
 236 
 
 309 
 
 460 
 
 657 
 
 60 
 
 96 
 
 175 
 
 2^-inch Section . . . 
 
 49 
 
 78 
 
 173 
 
 258 
 
 27 
 
 62 
 
 311 
 
 347 
 
 391 
 
 578 
 
 67 
 
 108 
 
 230 
 
 As is usual, the breaking loads are somewhat irregular, the inch 
 section excelling at some points, and the larger section at others. 
 The experiment, however, seems to indicate that neither size will, as 
 a rule, give higher results than the other. 
 
 Expp:riment No. 6. 
 
 Some experimenters have thought it important to place the moulds 
 ill which the mortar is packed for testing upon a porous bed, such as 
 blotting-paper or plaster. Others use a non-porous bed of glass, slate, 
 or marble. The following series of tests were made to discover the 
 effect of these different modes of treatment. The figures in the 
 tables represent breaking loads, in pounds per square inch, and are 
 averages of about ten breakino-s. 
 
 
 
 Table No. 6. 
 
 KOSENDALE CEMENT. 
 
 
 
 Mixture. 
 
 Kind of Bed. 
 
 One Week. 
 
 One Month. 
 
 Six Months. 
 
 One Year. 
 
 Neat . 1 
 
 Marble . . 
 Plaster . . 
 
 95 
 106 
 
 151 
 
 178 
 
 288 
 303 
 
 825 
 316 
 
 Cement, 1, 
 Sand, 1.6. 
 
 Marble . . 
 Plaster . . 
 
 44 
 62 
 
 107 
 120 
 
 210 
 219 
 
 251 
 265 
 
APPENDIX A. 
 
 125 
 
 A CTJBIBERLAND CEMENT. 
 
 Mixture. 
 
 Kind of Bed. 
 
 One 
 Day. 
 
 One 
 Week. 
 
 One 
 Month. 
 
 Six 
 Months. 
 
 One 
 Tear. 
 
 Neat . . < 
 
 Marble . ' . . 
 Plaster . . . 
 
 128 
 147 
 
 133 
 165 
 
 142 
 176 
 
 231 
 244 
 
 241 
 257 
 
 
 Marble . 
 
 
 107 
 128 
 
 161 
 166 
 
 275 
 299 
 
 339 
 
 Sand 1.5 . . 
 
 Plaster . . . 
 
 
 345 
 
 
 
 
 
 Cement, 1 
 
 Marble . 
 
 
 85 
 111 
 
 134 
 148 
 
 201 
 241 
 
 292 
 
 Sand, 2 . . . 
 
 Plaster . 
 
 
 294 
 
 
 
 
 
 Cement, 1 
 
 Marble . 
 
 
 40 
 46 
 
 94 
 91 
 
 162 
 164 
 
 163 
 
 
 
 
 170 
 
 
 
 
 
 GERMAN PORTLAND CEMENT. 
 
 Mixture. 
 
 Kind of Bed. 
 
 One Weels. 
 
 One Month. 
 
 Six Months. 
 
 One Tear. 
 
 Cement, 1, 
 Sand, 1 . 
 
 Marble . . 
 Plaster . . 
 
 259 
 213 
 
 367 
 376 
 
 390 
 411 
 
 . . 
 
 Cement, 1, 
 Sand, 2 . 
 
 Marble . . 
 Plaster . . 
 
 176 
 196 
 
 256 
 
 258 
 
 346 
 326 
 
 345 
 357 
 
 Cement, 1, 
 Sand, 3 . 
 
 Marble . . 
 Plaster . . 
 
 141 
 147 
 
 225 
 220 
 
 250 
 258 
 
 313 
 312 
 
 Cement, 1, 
 Sand, 4 . 
 
 Marble . . 
 Plaster . . 
 
 103 
 120 
 
 157 
 150 
 
 240 
 233 
 
 274 
 264 
 
 Cement, 1, 
 Sand, 5 . 
 
 Marble . . 
 Plaster . 
 
 82 
 103 
 
 108 
 140 
 
 182 
 193 
 
 213 
 197 
 
 Making allowance for a few irregularities, it appears, from the fore- 
 going tables, that the use of a porous bed gives slightly higher 
 results for the first one or two mouths, but that the difference disap- 
 pears or becomes insignificant with age. 
 
126 
 
 MAIN DRAINAGE WORKS. 
 
 Experiment No. 7. 
 
 It is a well-recognized fact that iu experimenting with cements, even 
 when great care is exercised, individual specimens break very irregu- 
 larl}', and that results even approximately conforming to theory can 
 only be obtained from averages from a large number of breakings. 
 The personal equation of the operator, and the degree of force with 
 which he presses the mortar into the moulds, is one factor in pro- 
 ducing irregular results. To do away with this a machine for i)acking 
 the moulds was devised and used for a time. By this the mortar was 
 pressed into the moulds by a metallic plunger, acting with definite 
 pressures, varying from 50 to 400 pounds. 
 
 The macliine-raade briquettes broke with somewhat greater uni- 
 formity than hand-made ones. So much more time was required to 
 make briquettes with this machine that it was found to be impracti- 
 cable to employ it for general use. 
 
 Experiment No. 8. 
 
 By the sea it is frequently convenient to mix mortar with salt water. 
 Brine is also used in winter as a precaution against frost. This 
 experiment was made to obtain the comparative effect of mixing 
 with, and immersing in, fresh and sea water respectively. The tests 
 were made upon a Rosendale mortar, mixed one part cement to one 
 part sand, and an English Portland mortar, one part cement to two 
 parts sand. The figures are averages of about ten breakings, and 
 give the tensile strength in pound per square inch with the different 
 methods of treatment and at different ages. 
 
 Except for some irregularity in the breakings for one year (which 
 may have been due to the manipulation) the table indicates that 
 salt, either in the water used for mixing or that of immersion, has no 
 important effect upon the strength of cement. Salt water retards the 
 first set of cement somewhat. 
 
 Table No. 7. 
 
 ROSBNDALB CBMENT MoBTAE. 
 1 TO 1. 
 
 
 Portland Cement Mortar, 
 
 1 TO 2. 
 
 Fresh Water. 
 
 Fresh. 
 
 Salt. 
 
 Salt. 
 
 Mixed with 
 
 Fresh. 
 
 Fresh. 
 
 Salt. 
 
 Salt. 
 
 Fresh Water. 
 
 Salt. 
 
 Fresh. 
 
 Salt. 
 
 Immersed in 
 
 Fresh. 
 
 Salt. 
 
 Fresh. 
 
 Salt. 
 
 40 
 126 
 247 
 310 
 
 48 
 185 
 250 
 263 
 
 60 
 114 
 243 
 224 
 
 61 
 126 
 224 
 217 
 
 One week. . 
 One month. 
 Six months. 
 One year. . 
 
 151 
 213 
 314 
 342 
 
 122 
 191 
 245 
 231 
 
 152 
 203 
 
 277 
 346 
 
 149 
 200 
 264 
 295 
 
Plate XXX. 
 
 15 .20 25 30 35 40 45 50 
 
 PER CENT or WA TER Or MfXTURE fN WC/GHT OF CEMENT. 
 
APPENDIX A. 
 
 127 
 
 Experiment No. 9. 
 
 This was an experiment to determine the relation existing between 
 the stiffness of cement mortar when first mixed and its subsequent 
 strength. The stiffness depends on the proportion of water used in 
 mixing, and varies somewhat with different cements. Natural Ameri- 
 can cements take up more water than Portland cements and fine- 
 ground more than coarse cements. Many series of tests bearing on 
 this point were made. The results obtained from two of the more 
 complete series are shown b}' the curves on Plate XXX. The cements 
 used in these tests were a rather coarse English Portland and a fair 
 Rosendale. Each of the points in the curves represents an average 
 from about ten briquettes. The cements were tested neat, and the 
 amounts of water used were different percentages, by weight, of the 
 amounts of cement. The resulting stift"ness of mortar is indicated on 
 the curves. This varied from the consistency of fresh loam to a fluid 
 grout. The time of setting is greatly retarded by the addition of water. 
 
 The curves show that from 20 to 25 per cent, of water gives the 
 best results with Portland cement, and from 30 to 35 per cent, with 
 Rosendale ; that the differences in strength due to the amount of water 
 are considerable at first, but diminish greatly with age ; that the soft 
 mortars, even when semi-fluid, like grout, attain considerable strength 
 in time. 
 
 Experiment No. 10. 
 From the first it was observed that, fine-ground cements were less 
 strong when tested neat, and stronger when mixed with sand, than were 
 coarse cements. A few examples of this are given below. In the first 
 table a coarse English Portland cement is compared with a fine-ground 
 French Portland. The per cent, of each retained by the fine No. 120 
 sieve is given, and the tensile strength, in pounds, per square inch at 
 the end of seven days. 
 
 Table No. 8. 
 
 Kind of Cement. 
 
 Per Cent. 
 
 retained by 
 
 No. 120 Sieve. 
 
 Parts of Sand to 1 part of 
 Cement. 
 
 
 
 
 2 
 
 3 
 
 4 
 
 5 
 
 English Portland .... 
 
 37 
 
 319 
 
 125 
 
 89 
 
 59 
 
 43 
 
 French Portland .... 
 
 13 
 
 318 
 
 205 
 
 130 
 
 114 
 
 86 
 
128 
 
 MAIN DRAINAGE WOBKS. 
 
 Such examples could be multiplied. German Portland cements 
 were commonly finer ground than English, and, as a rule, were no 
 stronger, or less strong, tested neat, but were much stronger with lib- 
 eral proportions of sand. In the following table two lots of the same 
 brand of English Portland cement are compared. The coarse cement 
 was the ordinary make of the manufacturers ; the fine cement differed 
 in no particular from the other except that it was ground more slowly 
 and finer to meet the requirements of a special agreement. The age of 
 the samples wheu broken was 28 days. 
 
 Table No. 9. 
 
 Kind of Cement. 
 
 Per Cent. 
 
 retained by 
 
 No. 120 Sieve. 
 
 Parts of Sand to 1 part of 
 Cement. 
 
 
 
 
 3 
 
 5 
 
 Ordinary Cement .... 
 
 35 
 
 403 
 
 105 
 
 68 
 
 Pine-ground Cement . . . 
 
 12 
 
 30i 
 
 180 
 
 96 
 
 Different brands of Rosendale cement varied considerably in their 
 fineness. Those of the best reputation would leave from 4 to 10 per 
 cent, residuum in the No. 50 sieve ; other brands would leave in the 
 same sieve from 10 to 23 per cent. In the following table is com- 
 pared the average tensile strength obtained from experiments with 
 three of the finer-ground brands, and also with three other brands of 
 good reputation, but more coarsely ground. The age of the speci- 
 mens was one week. 
 
 Table No. 10. 
 
 Kind of Cement. 
 
 Per Cent, 
 retained by 
 
 No. 50 Sieve. 
 
 Parts of Sand to 1 
 Cement. 
 
 part of 
 
 
 
 
 1.5 
 
 2 
 
 Fine Rosendale 
 
 6 
 
 92 
 
 41 
 
 25 
 
 Coarse Rosendale .... 
 
 17 
 
 98 
 
 29 
 
 16 
 
 The foregoing experiments show that it is impossible, by tests on 
 the tensile strength of neat cements alone, to judge of their value 
 
APPENDIX A. 
 
 129 
 
 in making mortars, for practical use ; also, that iiue-grouud cements 
 make stronger mortars than do coarser ones. 
 
 A number of series of tests were made of cements which had been 
 sifted through sieves of different degrees of fineness, and had thereby 
 had different percentages of coarse particles removed from them. 
 The results from these experiments were quite uniform, and showed 
 that, in proportion as its coarse particles were removed, a cement 
 became more efficient for making mortars with sand. The following 
 table gives the results obtained from one such series of tests made 
 with an English Portland cement. In the experiment comparison is 
 made between the strength of mortars made with the ordinary cement, 
 unsifted as it came from the barrel, and those made with the same 
 cement after having been sifted through Nos. 50, 70, 100, and 120 
 sieves, which, respectively, eliminated more and more of the coarse 
 particles. The per cent, of particles which would still be retained by 
 the tine No. 100 sieve, after sifting through the coarser sieves, is 
 given in the second column of the table. There is included in the 
 table an extra coarse cement, which was made so by adding to unsifted 
 cement a certain amount of the coarse particles taken from the sifted 
 cements. The tensile strength is given in pounds per square inch. 
 
 Table No. 11. 
 
 
 Ph 
 
 Kind of Cement 
 used in making 
 
 MOBTARS. 
 
 Cement -with coarse 
 particles added . . 
 
 55 
 
 Ordinary Cement, un- 
 sifted 
 
 33 
 
 Cement which passed 
 No. 50 Sieve . . . 
 
 28 
 
 Cement which passed 
 No. 70 Sieve . . . 
 
 18 
 
 Cement which passed 
 No. 100 Sieve , . . 
 
 8 
 
 Cement which passed 
 No. 120 Sieve . . . 
 
 
 
 One Week. One Month 
 
 Sis Months. 
 
 One Teab. 
 
 Parts of Sand to 1 part of Cement. 
 
 2345 2345 2345 2345 
 
 92 
 165 
 170 
 193 
 215 
 218 
 
130 
 
 MAIN DRAINAGE WORKS. 
 
 In a similar series of tests with Rosendale cement mortars, the 
 increase in strength obtained bj' substituting fine for coarse particles 
 in the cement was much less marked. The coarse particles were 
 softer than those from Portland cement, and had, in themselves, some 
 power of cohesion. As previous tests had shown that fine-ground 
 Rosendale cements were stronger, with sand, than coarse-ground, it 
 was assumed that the superiority was due, not so much to the absence 
 of palpably coarse particles, as to the fact that the bulk of the cement 
 was more floury, and thus better adapted to coating and binding the 
 particles of sand. Probably natural American cement is as much 
 improved as is Portland cement by fine grinding, but in the case of 
 the former there would not be the same relative advantage in bolting 
 out the coarse particles after grinding. 
 
 The following series of tests may be of interest, on account of the 
 age of the specimens. The mortars were made with an English 
 Portland cement, both unsifted as taken from the cask, and also 
 after it had been sifted through the No. 120 sieve, by which process 
 about 35 per cent, of coarse particles was eliminated. 
 
 Table No. 12. 
 
 
 Neat Cement. 
 
 Cement, 1 ; Sand, 2. 
 
 Cement, 1 ; Sand, 5. 
 
 
 2 Tears. 
 
 4 Tears. 
 
 2 Tears. 
 
 4 Tears. 
 
 2 Tears. 
 
 4 Tears. 
 
 Ordinary Cement, un- 
 sifted 
 
 Cement which passed 
 No. 120 Sieve . . 
 
 603 
 374 
 
 387 
 211 
 
 339 
 
 478 
 
 493 
 580 
 
 182 
 250 
 
 202 
 284 
 
 This table, also, shows that fine cements do not give as high re- 
 sults tested neat as do cements containing coarse particles, even coarse 
 particles of sand. It also shows (what is often noticed) that neat 
 cements become brittle with age, and are apt to fly into pieces under 
 comparatively light loads. 
 
 The series of tests which follows was made for the purpose of as- 
 certaining what value, if any, for cementing purposes, was possessed 
 by the hard, coarse particles of Portland cement. Mortars were 
 made with an ordinary English Portland cement, and compared with 
 similar mortars made with the same cement, after sifting through the 
 No. 120 sieve, which retained 33 per cent, of coarse particles. 
 
APPENDIX A. 
 
 Table No. 13. 
 
 131 
 
 
 One Week. 
 
 One Month. 
 
 Six Months. 
 
 One Year. 
 
 Kind of Cement. 
 
 Parts of Sand to one part of Cement. 
 
 
 
 353 
 311 
 
 2 
 139 
 
 187 
 
 3 
 
 86 
 132 
 
 
 279 
 243 
 
 2 
 201 
 
 275 
 
 3 
 
 142 
 201 
 
 
 438 
 268 
 
 2 
 323 
 367 
 
 3 
 253 
 310 
 
 
 444 
 306 
 
 2 
 343 
 434 
 
 3 
 
 Ordinary Cement, unsifted . 
 
 Cement which passed No. 120 
 Sieve 
 
 271 
 338 
 
 As usual, the coarse cement was stronger neat, and weaker with 
 sand. Assuming that the 33 per cent, of coarse particles retained 
 by the sieve had no value as cement, acting merely as so much sand, 
 and assuming also that all which passed through the sieve was good 
 cement, it follows that the ordinary unsifted cement with two parts of 
 sand, made a mortar in which the proportion of real cement to sand 
 was .67 to 2.33, or about 1 to 3.5. Hence, the mortar made with 
 fine cement and three parts of sand should be as strong, or a little 
 stronger, than that made with the coarse cement and two parts of 
 sand. It will be seen that the results in the table sustain the assump- 
 tion very well. 
 
 If, then, the coarse particles are assumed to act merely as so 
 much sand, it will not lessen the efficiency of the cement to remove 
 its coarse particles, and to substitute actual sand in their place. This 
 was done in making the following series of tests. One set of bri- 
 quettes was made with ordinary cement, and another set with the 
 same cement, from which 33 per cent, of coarse particles had been 
 removed and replaced with fine sand. 
 
 Table No. 14. 
 
 
 One Week. 
 
 One Month. 
 
 Six Months. 
 
 One Tear. 
 
 Kind of Cement. 
 
 Parts of Sand to one part of Cement. 
 
 
 2 
 
 3 
 
 2 
 
 3 
 
 2 
 
 3 
 
 2 
 
 3 
 
 Ordinary Cement, unsifted, 
 
 Cement with 33 per cent, 
 coarse particles removed 
 and fine sand substituted. 
 
 139 
 101 
 
 86 
 67 
 
 201 
 160 
 
 142 
 
 100 
 
 324 
 
 253 
 
 253 
 
 206 
 
 343 
 305 
 
 271 
 240 
 
132 
 
 MAIN DRAINAGE WORKS. 
 
 These briquettes refused to break in accordance with the theory, 
 and the assumed hj^pothesis was not verified. It is evident that, for 
 making mortar, tlie coarse particles of Portland cement are superior 
 to ordinary sand, but much inferior to fine cement. In the mortars 
 made with the cement, in which the coarse particles had been replaced 
 with fine sand, the real proportions of cement to sand were 1 to 3.5 
 and 1 to 5. It will be noticed that the tensile strength was not re- 
 duced in like proportion. 
 
 Experiment No. 11. 
 
 While building masonry laid in American cement mortar it is some- 
 times desirable to increase the strength of the mortar temporarily or 
 in places. Rich Portland cement mortars are expensive, and those 
 with large proportions of sand are too porous for many purposes. 
 The desired strength can be gained by using, instead of the simple 
 American cement, the same cement mixed with a percentage of strong 
 Portland cement. 
 
 The following series of tests was designed to ascertain the compara- 
 tive strength of mortars made with a Rosendale cement, an English 
 Portland cement, and also a mixture composed of equal parts of 
 each : — 
 
 Table No. 15. 
 
 Kind of Mortar. 
 
 1 Week. 
 
 1 Month. 
 
 6 Months. 
 
 1 Tear. 
 
 Rosendale Cement, 1 ; Sand 2 . . 
 
 Rosendale Cement, 0.5, ") o i r> 
 Portland Cement, 0.5, / '^'^°"' " " 
 
 Portland Cement, 1 ; Sand, 2 . . . 
 
 26 
 
 79 
 
 126 
 
 60 
 138 
 163 
 
 125 
 
 268 
 279 
 
 180 
 273 
 323 
 
 In the foregoing tests the mortar made with mixed cement had an 
 unexpected strength, approximating to that of mortar made with pure 
 Portland cement. In the following series of tests of mortars made 
 with lime of Teil, a fine-ground French Portland cement, and the 
 lime and cement mixed, the strength of the mortar made with the 
 mixture is almost exactly a mean between those of the other two mor- 
 tars, as also the cost of the mixed cement is a mean between the costs 
 of the other two. 
 
APPENDIX A. 
 
 133 
 
 Table No. 16. 
 
 Kind of Mortar. 
 
 1 Week. 
 
 1 Month. 
 
 6 Months. 
 
 1 Tear. 
 
 Lime of Teil, 1 ; Sand, 2 , . . . 
 
 Lime of Teil, 0.5, \ ^ . ^ 
 Portland Cement, 0.5, / *'^""' " ' " 
 
 Portland Cement, 1 ; Sand, 2 . . . 
 
 40 
 100 
 170 
 
 65 
 135 
 265 
 
 150 
 255 
 350 
 
 195 
 ■290 
 365 
 
 The best Portland cements sometimes do not set within an hour, 
 which precludes their use for wet work. In such cases quick-setting 
 cement should be added to them. Roman cements can be procured 
 which will set in from one to five minutes. Mixtures of Roman and 
 Portland cements were often used on the Main Drainage Works. Such 
 mortars would set about as quickly as if made with Roman cement 
 alone, and would acquire great subsequent strength, due to the Port- 
 land cement contained in them. This was proved by many experi- 
 mental tests. 
 
 It is probable that mixtures of any good cements can be used with- 
 out risk ; but before adopting anj^ novel combination it would be wise 
 to test it experimentally. 
 
 Experiment No. 12. 
 
 Engineers are accustomed to require that only clean sand and water 
 shall be used in making mortar. Occasionally these requirements 
 cause delay and extra expense. This experiment was designed to as- 
 certain how much injury would be caused by the use of sand contain- 
 ing moderate proportions of loam. In mixing the mortar for these 
 briquettes, sand containing 10 per cent, of loam was used in the place 
 of clean sand. Each figure in the table is an average (in pounds per 
 square inch) of ten breakings. 
 
 Table No. 17. 
 
 EOSENDALE CEMENT, 1; SAND, 1.5; LOAM, .15. 
 
 One "Week. 
 
 One Month. 
 
 Six Months. 
 
 One Tear. 
 
 21 
 
 46 
 
 200 
 
 221 
 
 The tests do not give very decisive results. For one week and one 
 
134 
 
 MAIN DRAINAGE WORKS. 
 
 month tJie breaking loads are not much more than one-half what 
 would have been expected with clean sand. For six months and a 
 year they are fully equal to ordinary mortar. 
 
 Experiment No. 13. 
 
 This experiment was similar to the foregoing one, except that clay, 
 instead of loam, was added to the mortar. Clay, when dissolved or 
 pulverized, consists of an almost impalpable powder, with particles 
 fine enough to fill the interstitial spaces among the coarser particles 
 of cement. By adding cla}' to cement mortar a much more dense, 
 plastic, and water-tight paste is produced, which was occasionally 
 found convenient for plastering surfaces or stopping leaky joints. 
 Each figure in the Portland cement series of tests is an average from 
 about fifteen briquettes ; those in the Rosendale cement series are 
 averages from ten briquettes. 
 
 Table No. 18. 
 
 KOSENDALE CEMENT. 
 
 
 Cement, 2 ; 
 Clay, 1. 
 
 Cement, 1 ; 
 Clay, 1. 
 
 Cement, 1 ; 
 Sand, 1.5. 
 
 Cement, 1 ; 
 Sand, 1.5; 
 Clay, 0.15. 
 
 Cement, 1; 
 Sand, 1.5; 
 Clay, 0.3; 
 
 Cement, 1 ; 
 Sand, 1.5; 
 Clay, 0.45. 
 
 • 
 1 week . . . 
 
 32 
 
 23 
 
 50 
 
 52 
 
 34 
 
 33 
 
 1 month . 
 
 108 
 
 52 
 
 123 
 
 116 
 
 101 
 
 100 
 
 6 months . . 
 
 303 
 
 206 
 
 217 
 
 248 
 
 247 
 
 236 
 
 1 year . . . 
 
 208 
 
 209 
 
 262 
 
 290 
 
 265 
 
 261 
 
 PORTLAND CEMENT. 
 
 
 Cement, 2; 
 Clay, 1. 
 
 Cement, 1 ; 
 Clay, 1. 
 
 Cement, 1 ; 
 Sand, 2. 
 
 Cement, 1 ; 
 Sand, 2; 
 Clay, 0.2. 
 
 Cement, 1 ; 
 Sand, 2; 
 Clay, 0.4. 
 
 Cement, 1 ; 
 Sand, 2; 
 Clay, 0.6. 
 
 ] week . . . 
 
 185 
 
 192 
 
 150 
 
 197 
 
 185 
 
 145 
 
 1 month . . . 
 
 263 
 
 271 
 
 186 
 
 253 
 
 245 
 
 203 
 
 6 months 
 
 348 
 
 322 
 
 320 
 
 361 
 
 368 
 
 317 
 
 1 year . . . 
 
 303 
 
 301 
 
 340 
 
 367 
 
 401 
 
 384 
 
 The tests seem to show that the presence of clay in moderate 
 amounts does not weaken cement mortars. 
 
APPENDIX A. 135 
 
 It was feared that the presence of clay in mortars exposed to the 
 weather might tend to make them absorlD moisture and become disin- 
 tegrated. To ascertain whether this would be so, sets of briquettes 
 were made, one set of Portland cement and sand only, the other con- 
 taining also different amounts of clay. They were allowed to harden 
 in water for a week, and were then exposed on the roof of the office 
 building for two and one-half years, when they were broken. All of 
 the briquettes appeared to be in perfectly good condition, with sharp, 
 hard edges. Their average tensile strengths in pounds per square 
 inch are shown in the following table : — 
 
 Table No. 19. 
 
 Portland Cement 1 ; Sand 2 402 
 
 Clay 0.5 262 
 
 " " " "1.0 256 
 
 " " " "1.5 182 
 
 " " " "2.0 178 
 
 The mortars with clay show a very fair degree of strength, and 
 the tests confirm the belief that the presence of clay works little, if 
 any, harm. Tests of mortars made with lime and clay also gave 
 favorable results. Such mortars would stand up in water. The sub- 
 ject is worthy of further investigation. 
 
 Experiment No. 14. 
 
 Occasionally, for stopping leaks through joints in the sewers, it 
 was found convenient to use cement mixed with melted tallow. The 
 tallow congealed at once and held the water while the joint was being- 
 calked. Briquettes made of melted tallow mixed with Portland 
 cement and sand, equal parts, acquired in 1 week, a tensile 
 strength of about 40 pounds to the inch. After a month, six months, 
 and a year, they were little, if any, stronger. It was thought that 
 possibly the ammonia in the sewage might gradually saponify and dis- 
 solve out the grease, leaving the mortar to harden by itself. Bri- 
 quettes of cement and tallow were kept in water, to which a little 
 ammonia was added from time to time. After a year or two the bri- 
 quettes had swelled to about double their former size, but the cement 
 had acquired no strength. 
 
 Experiment No. 15. 
 
 Having occasion to build with concrete a large monolithic structure, 
 in which a flat wall would be subjected to transverse stress, it was 
 considered necessary to make experiments, to find the comparative 
 
136 
 
 MAIN DRAINAGE WORKS. 
 
 resistance to such stress of concrete made with different cements 
 and with different proportions of sand and stone. 
 
 The cements used in the tests were an English Portland and a 
 Rosendale, both good of their respective kinds. Medium coarse pit 
 sand was used, and screened pebbles about an inch or less in diameter. 
 The beams were ten inches square and six feet or less long. They were 
 made in plank moulds resting on the bottom of a gravel-pit about four 
 feet deep. After the concrete had hardened sufficiently, the moulds 
 were removed, and the undisturbed beams buried in the pit and left 
 for six months exposed to the weather. They were then dug out, and 
 broken with the results given in the table. The total breaking loads 
 are given, including one-half of the weights of the beams, which aver- 
 aged about 150 pounds per cubic foot. The constant, c, is obtained for 
 the formula : — 
 
 f w z=z centre breaking load in pounds. 
 
 1 d zzz depth of beam in inches. 
 X c, in which -{ 6 rr: breadth of beam in inches. 
 
 \ I -^zi distance between supports in feet. 
 
 [^ cz=. a, constant. 
 
 cV X I 
 I 
 
 Since c has an average value, and there were gene^-ally more beams 
 of one length than the other, the value of c as given does not exactly 
 correspond with either load in the table. 
 
 Table No. 20. 
 
 Proportion of Materials. 
 
 Average Centre Breaking 
 Weight in Pounds. 
 
 Average 
 Modulus of 
 Rupture in 
 Pounds. 
 
 Average 
 Value of c 
 in Pounds. 
 
 Cement. 
 
 Sand. 
 
 Stone. 
 
 Dist. between 
 
 Suijports, 
 
 2' 4^". 
 
 Dist. between 
 
 Supports, 
 5'. 
 
 Rosendale, 1 . 
 
 " 1 . 
 Portland, 1 . . 
 
 " 1 . . 
 
 " 1 . . 
 
 2 
 3 
 3 
 4 
 6 
 
 5 
 7 
 7 
 9 
 11 
 
 1,782 
 
 Beams broke 
 
 3,926 
 
 3,648 
 
 2,822 
 
 690 
 
 in handling. 
 
 1,995 
 
 1,190 
 
 67 
 
 176 
 146 
 112 
 
 3.7 
 
 9.8 
 8.1 
 6.2 
 
 The table shows that concrete has a rather low modulus, especially 
 when made of Rosendale cement. When transverse stress is to be 
 opposed it is very important to give ample time for the concrete to 
 harden. 
 
Plate XXXI. 
 
 4i- 4 3t 5 2i- 2 li 
 
 PAHTS or SAND TO ONE PAHT OF CEMENT. 
 
APPENDIX A. 137 
 
 EXPERISIENT No. 16. 
 
 Many of the main drainage sewers were either built or lined with 
 concrete, which was always smoothly plastered with a coat of mortar. 
 It was important that this surface coat should he especially adapted to 
 resist abrasion. This experiment was made to ascertain the best 
 mixture for the purpose. Different mortars were formed into blocks 
 1-1 inches square, and, after hardening under water for 8 months, 
 were ground down upon a grindstone. The blocks were pressed upon 
 the stone with a fixed pressure of about 20 pounds. A counter was 
 attached to the machine, and the number of revolutions required to 
 grind off 0.1 inch of each block was noted. The cements used in the 
 test blocks were a rather coarse English Portland and a fair Rosendale. 
 
 The curves (Plate XXXI.) show the results obtained. In making 
 these curves the resistance to abrasion opposed by the Portland cement 
 mortar in the proportion of one part cement and two parts sand is 
 assumed to be 100, and the resistance of other mortars is compared 
 with it. The effect of the grinding upon the test blocks is noted on 
 the curves, and explains the somewhat striking results. 
 
 It appears that cements oppose the greatest resistance to abrasion 
 when combined with the largest amount of sand which they can just 
 bind so firmly that it will grind off and not be pulled out. A little 
 less or a little more of sand may greatly lessen the resistance. For 
 any given cement the proper amount of sand would, probably, have 
 to be ascertained by experiment. 
 
 Experiment No. 17. 
 
 It is a prevalent belief among masons that cement, even when it 
 contains no free lime, and does not check, expands considerably after 
 setting. It is stated that brick fronts laid with cement mortar (espe- 
 ciall}^ of Portland cement) have been known to bulge, and even rise, 
 owing to expansion in the mortar. Experiments were made to ascer- 
 tain what truth there was in this belief. Several dozens of glass lamp- 
 chimneys were filled with mortars made of various brands of American 
 and Portland cements, both neat and with different admixtures of 
 sand. The chimneys were immersed in water, and, without exception, 
 began to crack within three days. New cracks appeared during the 
 following ten days, after which time hardly a square inch of glass 
 remained which did not show signs of fracture. This showed that 
 the cement certainty expanded, though very slowly, and that the ex- 
 pansion continued for about two weeks. None of the cracks opened 
 
138 MAIN DRAINAGE WORKS. 
 
 appreciably, however, so that the amount of expansion, which was 
 evidently slight, could not thus be even approximately determined. 
 
 A number of 10-inch cubes were then made of similar mortars, with 
 small copper tacks inserted io the centres of all the sides. Some of 
 these cubes were kept in the air, and others immersed in water, and 
 the sizes of all of them were measured frequently by callipers during 
 six months. The increase in size' did not in any case exceed .01 inch, 
 and may have been less. This indicated that, while cement mortars 
 do expand, the increase in bulk in any dimension does not exceed .001 
 part of that elimension, and is too slight to be of consequence. In 
 the case of the walls before referred to, supposing them to have been 
 80 feet high, with five ^-inch joints to each foot, the total height of 
 mortar would have been 100 inches, and the extreme expansion of the 
 whole could only have been .1 inch. It is probable that the appar- 
 ent rise was merely a difference in elevation caused by settlements of 
 partition or side walls laid with weaker and compressible mortar. 
 
 Experiment No. 18. 
 
 It having been reported that cement mortars in contact with wood 
 had sometimes been found to be disintegrated, as if they might have 
 been affected by the wood acids, this experiment was made to see if 
 any such effect could be detected. About a dozen boxes were made, 
 each formed of five different kinds of wood, viz., oak, hard-pine, white- 
 pine, spruce, and ash. The boxes were filled with different cement 
 mortars, and were some of them submerged in fresh and others in salt 
 water. Briquettes were also made of cements mixed with different 
 kinds of sawdust. At the end of a year no effect upon the cements 
 could anywhere be detected. 
 
 Experiment No. 19. 
 
 Engineers are accustomed to insist on cement mortars being used 
 before they have begun to set, and on their being undisturbed after 
 that process has begun. With cements that set quickly workmen are 
 tempted to retemper tlie mortar after it has begun to stiffen. Some 
 experiments were made on mortars which were undisturbed after 
 first setting, and others which were retempered from time to time. 
 Unfortunately all of the conditions of these tests were not accurately 
 recorded, and the results are not considered trustworthy. The follow- 
 ing series of tests, which represents an extreme case not met with in 
 actual practice, may be of interest. 
 
APPENDIX A. 
 
 139 
 
 A mortar made of one part of Portland cement and two parts of 
 sand was allowed to harden for a week. It was then pulverized, re- 
 tempered, and made into briquettes. These subsequently acquired the 
 following tensile strength in pounds per square inch : — 
 
 1 week . 7 
 
 1 month 13 
 
 6 months 49 
 
 2 years 93 
 
 Under the circumstances it is somewhat surprising that the mortar 
 developed as much strength as it did. Good tests to elucidate this 
 subject are much needed. 
 
 Experiment No. 20. 
 
 A brand of " Selenitic" cement was offered for use on the work, and 
 was said to possess great merits. It was made by treating an ordi- 
 nary American cement by a patented process. It was tested by com- 
 paring it with an untreated sample of the same cement of which it was 
 made. The following are the results of the tests : — 
 
 Table No. 2. 
 
 Mixture. 
 
 Kind of 
 Cement. 
 
 1 Day. 
 
 1 Week. 
 
 1 Month. 
 
 6 Months. 
 
 1 Tear. 
 
 Neat . . 
 Cement . 
 
 
 Untreated 
 Selenitic 
 
 
 124 
 149 
 
 185 
 168 
 
 140 
 171 
 
 164 
 
 282 
 
 186 
 273 
 
 Cement, 1 
 Sand, 1.5 
 
 
 Untreated 
 Selenitic 
 
 
 
 
 
 121 
 120 
 
 176 
 
 158 
 
 296 
 276 
 
 316 
 356 
 
 Cement, 1 
 Sand, 2 . 
 
 
 Untreated 
 Selenitic 
 
 
 
 
 
 92 
 103 
 
 154 
 133 
 
 259 
 226 
 
 805 
 276 
 
 Cement, 1 
 Sand, 4 . 
 
 
 Untreated 
 Selenitic 
 
 
 
 
 
 88 
 49 
 
 87 
 97 
 
 158 
 167 
 
 168 
 164 
 
 The breakings are somewhat irregular, but seem to show that this 
 cement was made somewhat stronger by the selenitic process of 
 treatment when tested neat, but was little, if at all, improved for use 
 as a mortar ; not enough, certainly, to compensate for the higher cost. 
 
APPENDIX B. 
 
 LIST OF OFFICERS CONNECTED WITH BOSTON 
 MAIN DRAINAGE WORKS, 
 
 Commission of 1875. 
 
 E. S. CHESBROUGH, C.E. 
 MOSES LANE, C.E. 
 C. F. FOLSOM, M.D. 
 
 Engineers. 
 
 City Engineers. 
 
 Joseph P. Davis 1876-1880. 
 
 Henry M. Wightman 1880-1885. 
 
 Principal Assistants to City Engineer. 
 
 Henry M. Wightbian 1876-1880. 
 
 Alphonse Fteley ^ 1880-1884. 
 
 Principal Assistant in Charge of Main Drainage WorTcs. 
 
 Eliot C. Clarke 1876-1885. 
 
 Assistant Engineers. 
 
 William Jackson 1876-1885. 
 
 Frederic P. Stearns 1880-1885. 
 
 Clemens Herschel 1878-1880. 
 
 George S. Rice 1877-1880. 
 
 George H. Crafts 1877-1881. 
 
 Seth Perkins 1877-1885. 
 
 Charles S. Gowen 1880-1881. 
 
 E. R. Howe 1877-1880. 
 
 F. A. May 1876-1880. 
 
 F. W. Ring 1876-1877. 
 
 K. Tappan 1876-1877. 
 
APPENDIX B. 
 
 141 
 
 Principal Superintendents of Construction. 
 Sewer Construction. 
 H. A. Carson. 
 
 Pumping- Static n . 
 S. H. Tarbell. 
 
 Joint Special Committee on Improved Sewerage. 
 1876. 
 
 Aldermen. 
 
 Alvah a. Burrage, Chairman. 
 Solomon B, Stebbins. 
 Thomas J. Whidden. 
 
 1877. 
 
 Aldermen. 
 
 Choate Burnham, Chairman. 
 Charles W. Wilder. 
 Lucius Slade. 
 
 1878. 
 
 Aldermen. 
 
 Thomas J. Whidden, Chairman. 
 Solomon B. Stebbins. 
 Lucius Slade. 
 
 Councilmen. 
 
 Eugene H. Sampson. 
 J. Homer Pierce. 
 Warren K. Blodgett. 
 Marcellus Day. 
 Albert H. Taylor. 
 
 Councilmen. 
 
 Eugene H. Sampson. 
 J. Homer Pierce. 
 Warren K. Blodgett. 
 Martin L. Ham. 
 George L. Thorndike. 
 
 Councilmen. 
 
 Eugene H. Sampson. 
 George L. Thorndike. 
 J. Homer Pierce. 
 Frederick B. Day. 
 James B. Richardson. 
 
 1879. 
 
 Aldermen. * 
 
 Lucius Slade, Chairman. 
 Solomon B. Stebbins. 
 Daniel D. Kelly. 
 
 Councilmen. 
 
 Isaac Rosnosky. 
 Thomas J. Denney. 
 John P. Brawley. 
 Daniel J. Sweeney. 
 Oscar B. Mowry. 
 
142 
 
 MAIN DEAINAGE WORKS. 
 
 1880. 
 
 Aldermen. 
 
 Lucius Slade, Chairman. 
 Asa H. Caton. 
 Geobge L. Thorndike. 
 
 Councilmen. 
 
 Daniel J. Sweeney. 
 Chaeles H. Plimpton. 
 Howard Clapp. 
 Malcolm S. Geeenough. 
 Benjamin Brintnall. 
 
 1881. 
 
 Aldermen. 
 
 Lucius Slade, Chairman. 
 William Woolley. 
 Charles H. Hersey. 
 
 Councilmen. 
 Howard Clapp. 
 Thomas J. Denney. 
 Malcolm S. Greenough. 
 Frank E. Farwell. 
 John E. Bowker. 
 
 1882. 
 
 Aldermen. 
 
 Lucius Slade, Chairman. 
 William Woolley. 
 Charles H. Hersey. 
 
 Councilmen. 
 
 Malcolm S. Greenough. 
 Thomas J. Denney. 
 Frank E. Farwell. 
 Prentiss Cummings. 
 Nathan G. Smith. 
 
 1883. 
 
 Aldermen. 
 
 Lucius Slade, Chairman. 
 William Woolley. 
 Thomas H. Devlin. 
 
 Councilmen. 
 
 Malcolm S. Greenough. 
 Thomas J. Denney. 
 Frank E. Farwell. 
 John B. Fitzpatrick. 
 Patrick J. Donovan. 
 
 1884. 
 
 Aldermen. 
 
 Lucius Slade, Chairman. 
 Charles H. Hersey. 
 Malcolm S. Greenough. 
 
 * Councilmen. 
 
 Thomas J. Denney. 
 Patrick J. Donovan. 
 Isaac Rosnosky. 
 J. Edward Lappen. 
 James B. Graham. 
 
APPENDIX B. 
 
 143 
 
 1885. 
 Aldermen. 
 
 Patrick J. Dokovan, Chairman. 
 George' Curtis. 
 William J. Welch. 
 
 Councilmen. 
 
 Edward P. Fisk. 
 J. Edward Lappen. 
 John Gallagher. 
 William H. Murphy. 
 Benjamin B. Jenks. 
 
ii 
 
3 Jiipi 
 
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