CIRCULAR 197 ILLINOIS STATE GEOLOGICAL SURVEY 557 I 6c no. 198 c, 1 STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. RINKS, Director DIVISION OF THE STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA CIRCULAR 198 GROUNDWATER POSSIBILITIES IN NORTHEASTERN ILLINOIS A Pr®Ilflnniiiinifflry GeelldDgsc lepent BY R.E. BERGSTROM, J. W. FOSTER, LIDIA F. SELKREGG, and W. A. PRYOR Service activities concerning groundwater are performed jointly by the Illinois State Geological Survey and the Illinois State Water Survey PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 19 5 5 QPD -* Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/groundwaterpossi198berg GROUNDWATER POSSIBILITIES IN NORTHEASTERN ILLINOIS A Preliminary Geologic Report By Robert E. Bergstrom, John W. Foster, Lidia F. Selkregg and Wayne A. Pryor ABSTRACT Groundwater possibilities for domestic, municipal, and indus- trial supplies in northeastern Illinois range from poor to excellent. This report summarizes the geologic conditions controlling the availability of groundwater and suggests ways to obtain it under the prevailing conditions. Maps are presented which show: 1) ground- water possibilities from sand and gravel deposits, 2) groundwater possibilities in shallow bedrock, and 3) depth to the Galesville sandstone, the principal water -yielding formation for industrial and municipal groundwater in northeastern Illinois. INTRODUCTION Water that occurs in the earth and that is tapped with varying success by farm, municipal, and industrial wells is one of our most valuable natural re- sources. In some areas it is readily available for all purposes - from small domestic supplies to gr,eat industrial or municipal supplies - whereas in other areas even a little groundwater is difficult to obtain in wells. The basic conditions that control the availability of water in the earth (groundwater) are natural and fixed. Skillful well design, construction, and management are extremely important factors in obtaining satisfactory amounts of groundwater, but these factors apply at any potential well site only if natu- ral geologic conditions favor the type of supply desired. For example, even the most elaborate and careful well construction does not obtain a groundwater supply for a large city at a site where all the earth formations to great depths are dense, tight materials which do not allow water to flow into the well. Northeastern Illinois has geologic conditions that make it one of the most favorable areas in the State for obtaining groundwater. Farm supplies from shallow sources are readily available in much of the area. Municipal and in- dustrial supplies are widely available from deep sources and are also locally available from shallow sources. The purpose of this report is to provide general information on the avail- ability of groundwater in nine counties: Cook, DuPage, Grundy, Kane, Kanka- kee, Kendall, Lake, McHenry, and Will. This region has an area of some 5000 square miles and a population of over 5,250,000. It includes densely populated [i] 2 ILLINOIS STATE GEOLOGICAL SURVEY and industrialized sections, such as Cook County, and sparsely populated agri- cultural districts. Evaluation of the groundwater possibilities within the re- gion, therefore, has taken into consideration both domestic and large-scale demands. This report is based on a study of the nine counties by six members of the Groundwater Division of the Illinois State Geological Survey: Robert E. Berg- strom, Merlyn B. Buhle, John W. Foster, James E. Hackett, Wayne A. Pryor, and Lidia F. Selkregg. It is the second of a series prepared to assist in water- supply improvement on the farms of Illinois * The Geological Survey is coop- erating in this program with the extension services of the Agricultural Engi- neering Department, University of Illinois. The region covered here is Agri- cultural Extension District 1, eastern part. We hope this report will improve the general understanding of groundwater occurrence and assist in the pro- curement of suitable groundwater supplies. The authors are happy to acknowledge the generous assistance given in this study by many drilling contractors of northeastern Illinois and by mem- bers of the State Water Survey, particularly W. B. Millis of Chicago. GEOLOGY OF THE REGION The main features of the northeastern Illinois landscape were developed during the geologically recent past, when great continental glaciers covered much of northern United States. From centers of snow accumulation in Canada: these vast ice sheets advanced southward, as well as in other directions. They scraped the land surface over which they moved, picked up and transported rock debris, and deposited most of the debris at the melting outer borders of the ice. j The glacial deposits, called drift, form an irregular surface blanket that , covers the solid layered bedrock in northeastern Illinois. In excavations, such as quarries and road cuts, and in deeply eroded stream valleys, the drift mantle has been removed and the underlying bedrock exposed. In most of the ; area drilling penetrates varying thicknesses of unconsolidated glacial materia before striking bedrock. Not only the deposits themselves but the form of ' some of the deposits were produced by glacial processes. For example, the ; prominent ridges that parallel Lake Michigan in McHenry, Lake, Kane, Cook,, DuPage, and Will counties are thick accumulations of mixed clay, silt, sand, pebbles, and boulders heaped up along the front of a melting glacier. These ridges are called moraines. Cook, Grundy, and Kankakee counties contain wide flat areas which were the sites of shallow glacial lakes. Some valleys ofj northeastern Illinois have broad sand and gravel flats which were built up by large streams fed by the melting glaciers. Because the great glaciations of the Ice Age occurred quite recently m geologic time, the landscape of northeastern Illinois is actually fairly young. An older landscape - carved in the bedrock largely before the glaciers advanc * The first report, Water Wells for Farm Supply in Central and Eastern Illi- nois, by John W. Foster and Lidia F. Selkregg, has been issued by the Illinois State Geological Survey as Circular 192, and is available free of charge from the Survey in Urbana. GROUNDWATER IN NORTHEASTERN ILLINOIS 3 into the area - would be found if the mantle of drift were stripped away De spite its burial beneath glacial deposits which locally attain a thickness of several hundred feet, the bedrock surface is not entirely beyond our range of study. Thousands of water wells drilled through the glacial drift into the bed- rock provide detailed information on the bedrock topography. The bedrock surface has hills and valleys just as the land surface does. Some surface valleys coincide with valleys in the bedrock, but in areas of very thick drift the surface and buried valleys may not correspond. In contrast to the complex, heterogeneous glacial deposits, the bedrock formations present a more orderly picture. They consist of layers of lime- stone shale and sandstone arranged one upon the other like the pages of a thick book Although they are firm, dense rocks now, they were originally de- posited as loose sediments in shallow seas which invaded the continent. They were buried and hardened into solid rock during the several hundred million years after the seas had retreated from northeastern Illinois. The rocks were later gently tilted from their original hormonal position, so that toda^ they a i P sou heastward 10 to 15 feet per mile. The tilted beds are cut by the Irosion surface beneath the glacial drift, producing rudely parallel belts thlt trend ap- proximately north-south, In McHenry, Lake, Cook, DuPage, Will, and Kanka kee counties, a lime stone -like rock, called dolomite, underlies the glacial nlath t W he e dr!ft. t0 ^ ~" W ' * ^ ^ ** "**~ ^ d "" tly «~ Beneath the 3000 or 4000 feet of layered rocks is ancient crystalline rock which forms the basement. The crystalline rock is mainly granite as shown by a few very deep wells in Illinois. Crystalline basement rock is at the sur- tuth D 7 T ^ ? anC ° 1S M ° Untains ° f Mi — » -d the Black Hills of SJSSSJ^f M haS ^^ marked Uplift - d de - — <* «" over- WATER IN THE EARTH well. W h« r i ^ ° CCUrS ln the S rOUnd and c °™* to the surface in springs and wells has long been regarded as somewhat mysterious. The details of its oc currence, source, quantity, quality, temperature, pressure, and movement are Ze and"' *? 7" 1 T^* P " Utaia « to «*«*W are re Z vely simple and well understood. y Water falling on or flowing over the ground seeps through openings be- ween loose particles of the soU and percolates downward _ | * w *'£ iepth, all openings in the loose surface material (such as glacial drift) and in •he underlying bedrock are filled with water. This water occurs in pores be 3wLT ^ ^ "^ 7 eViCeS ' ^ n0t ^ StreamS ° r lak6S (except only eln fih hl " eSt0ne , CaVeS) - Beca use rainfall continually contributes to or eplemshes the supply, groundwater is a renewable resource ts D Is' t UPPer l UrfaC u ° f the water - sa turated zone is called the water table, ts position is shown by the depth at which water stands in shallow wells, ormgs and excavations. It roughly parallels the surface topography rising P/aTstmpst nd int6rSeCtmg ^ *"*"* ""*" — -/ennU'str^^s, 4 ILLINOIS STATE GEOLOGICAL SURVEY Water from the saturated zone is not everywhere available for withdrawal by wells, as this is controlled by the details of the local geology. A bed of clay may contain a large volume of water per cubic foot but hold the water so tightly that a well drilled into it may be "dry." On the other hand, a bed of pea gravel may contain less water per cubic foot than the clay, but the water in the gravel is not held and can move quite readily between the grains and into a well bore. As the well is pumped, more water flows in. The problem involved in obtaining a groundwater supply, therefore, is to strike a "formation" that will transmit its water to the well bore. Most drilled wells that are "dry" are unsuccessful not because of lack of water in the rocks but because water -yielding (permeable) formations are not present. A special word should be said about the geology of artesian wells. Water that occurs in some of the deep permeable sandstone formations underlying northeastern Illinois comes from rainfall, which enters these rocks some dis- tance away, where they are close to the surface. Because relatively water- tight formations occur above the deep sandstones in northeastern Illinois, the water in the deep beds behaves somewhat differently from that in beds at shal- lower depths. It is under natural pressure and therefore may rise several hundred feet in a well that penetrates a deep sandstone. We call these wells artesian wells. In the days before the water from the deep sandstones was heavily exploited by industries and cities, some artesian wells flowed without pumping. WATER-YIELDING FORMATIONS The most important water -yielding deposits in the glacial drift above the bedrock are beds of clean, loose sand and gravel. They range from thin dis- continuous streaks to extensive beds tens of feet thick. Drilled wells are usually productive where the sand and gravel is a few feet or more thick and water-bearing. Where only thin streaks of sand and gravel are present in otherwise tight glacial drift, large -diameter dug wells are generally the only way of obtaining groundwater from the shallow drift. The grain size (texture) of sand and gravel deposits is extremely impor- tant in determining their water -yielding properties. Good water -yielding sands are coarser than sugar and nearly all the grains are the same size. The per- centage of clay and silt in sand and gravel deposits should be low because this fine material occupies the spaces between the larger grains and slows water movement. Few natural deposits have the uniform coarse textures that are ideal; however, a skillful drilling contractor, familiar with sand and gravel well construction, can by proper design and development often make a satis- factory well in formations that are fine-grained or not uniformly sorted, or in formations that contain some clay and silt. Much of the bedrock beneath the glacial drift in northeastern Illinois is a lime stone -like rock called dolomite. Groundwater in limestone and dolomite occurs in fractures and in channels dissolved out of the rock. The success of a water well drilled in limestone or dolomite, therefore, depends upon the well bore actually penetrating water -filled joints and channels. The thick dolomite in much of northeastern Illinois is well creviced and fractured, particularly in the upper part, so that it is an important source of GROUNDWATER IN NORTHEASTERN ILLINOIS 5 groundwater. The dolomite is especially good for groundwater at the many- places where it is overlain by drift containing substantial sand and gravel de- posits. On the other hand, where the drift is tight and non-water -yielding, the underlying dolomite is also commonly "tight." Some drilling contractors sub- stantially improve the performance of limestone and dolomite wells in the area by enlarging existing joints and channels with hydrochloric acid, which dis- solves part of the rock with which it comes in contact. Another important water -yielding rock of northeastern Illinois is sand- stone. It occurs at a depth of several hundred feet and more throughout the area. In southwestern Kendall County an important water -yielding sandstone lies just beneath the glacial drift. Water occurs in sandstone between the sand grains, just as it does in loose sand deposits. Therefore, the size and uniformity of the grains is ex- tremely important. Sandstone also contains variable amounts of cement, which binds the grains together. The amount of cement is another factor that affects the water yield. Tightly cemented sandstones are not good formations for water unless they are well jointed or fractured, like limestones. The deep sandstones of northeastern Illinois - the Gales ville sandstone in particular - and the shallower St. Peter sandstone are good groundwater sources because they are uniform in texture and loosely cemented. Less sat- isfactory for groundwater are the fine-grained tightly cemented near-surface sandstones of the Pennsylvanian system ("Coal Measures") in Grundy County. ILLINOIS STATE GEOLOGICAL SURVEY SUMMARY OF GROUNDWATER POSSIBILITIES BY COUNTIES This evaluation of groundwater possibilities for domestic, municipal, and industrial purposes is based upon geologic infor- mation in the files of the Illinois State Geological Survey and helpful suggestions by drilling contractors. The county discus- sions summarize possibilities in (1) sand and gravel, (2) shallow bedrock, and (3) deep sandstones. They may be used in conjunc- tion with figures 2, 3, and 4. Figure 1 is an index map of north- eastern Illinois. 5E. ILLINOIS STATE GEOLOGICAL SURVEY POSSIBILITIES FOR WELLS IN SAND AND GRAVEL • • • Best possibilities for the occurrence of water-bearing sand and gravel within the glacial drift. Groundwater for domestic and farm supply generally is obtainable in this area from small-diameter drilled wells completed in sand and gravel. The wells range in depth from 35 to over 200 feet, depending upon depth of water -yielding formation. Possibilities for municipal or industrial wells completed above bedrock are good to excellent, although some test drilling probably is necessary to locate the best formation and site for the construction of a high-capacity well. Fair to good possibilities for the occurrence of water- bearing sand and gravel within the glacial drift. Ground- water for domestic and farm supply is obtainable locally in this area from small-diameter drilled wells in sand and gravel. The wells range in depth from 35 to about 100 feet. Water -yielding sand and gravel probably is absent at many locations, so wells generally are drilled through the glacial drift into bedrock. Possibilities for municipal or industrial wells are poor to fair. Extensive test drilling is likely to be necessary to locate deposits suitable for the construction of high-capacity wells in sand and gravel. Most high-capacity wells penetrate a bedrock aquifer. Poorest possibilities for the occurrence of water-bearing sand and gravel within the glacial drift. Most wells obtain groundwater from bedrock below the glacial drift. Depth to bedrock generally is less than 50 feet. Shallow sands along the rivers are suitable locally for domestic and farm wells, but widespread thick sand and gravel beds generally are ab- sent. *f' 6 7_ 8 9 10 II I2E. 4 eFMC henry , j .pp^MS **M"l — 7"T~.:? T"" " ['■'■ """ r ^^ JW ^/^^\V^n^?W^fiH^^^r 1-' H r: rr ~:TTT:r; HrrH - rfir:r:rrr ~ ~ it.^*^.V.^*W i *r«yiV»4iiiI^4'li , j - u U.L: l: l; :. v: • • : .: I : ; : : • • 43 liii 41 40' 39 :m--^-"^-'« M 37! 36 lii 55| mmm, mm® •;«t '::::::::::::::::■:■■: »>.:■:,:;.::: ' : ://z:'.::;: ::::::::::::: 1: :::::::; : :: i : : , 1: :.:::.■:: , :::::::::::::!. T tjILw^tej- JA''.\:'M\\ ' . .. i . • : J i i lii"::*::::-"::::::: :"l r w^«^:-;j;i; ; :;j:-::-:;r:::-ic • L i • : l [ ; ^^r : -: i:::":j::»;;s:i:-:::" . 7V„. . ; \ \\ I ,^ K ^ ^. \ 7 ^KANKAKEE; - '. ■ • 10 ILLINOIS STATE GEOLOGICAL SURVEY POSSIBILITIES FOR WELLS IN UPPER BEDROCK FORMATIONS K^?5 wSm Dolomite lies directly beneath the glacial drift and yields groundwater at most locations through open crev- ices and channels. Most farm and domestic wells ob- taining water from dolomite penetrate the rock 15 to 75 feet, depending upon the number and character of the water -yielding cracks. Industrial and municipal wells obtaining groundwater from dolomite generally penetrate 50 to 250 feet. Dolomite lies directly beneath the glacial drift and generally has better -than-average water -yielding poten- tial because of abundance of crevices and channels. Dolomite lies directly beneath the glacial drift, but generally has less-than-average water -yielding potential. Shale or shaly dolomite bedrock is commonly found directly beneath the glacial drift. In some areas south of T. 38 N., it is necessary that wells in bedrock extend through 60 feet or more of non-water -yielding shale to penetrate water -yielding dolomite below. North of T.37 N., particularly in Kane County, much dolomite is inter - bedded w\th the shale and may yield groundwater from open cracks. Water -yielding St. Peter sandstone lies directly be- neath the glacial drift and is suitable for small -diameter drilled wells. Shale bedrock, generally 35 to 100 feet thick, lies directly beneath the glacial drift. Most drilled wells penetrate through non- water -yielding shale into water- bearing sandstone below. Pennsylvanian ("Coal Measures") bedrock lies di- rectly beneath the glacial drift. The formations are mostly non- water -yielding shales, but sandstone beds occur locally (as around Verona, Carbon Hill, Brace - ville, Gardner, and South Wilmington) and are suitable for domestic and farm wells. Conditions in these rocks generally are unfavorable for high-capacity wells. DesPlaines faulted area. Bedrock formations are broken and displaced, so the usual sequence of forma- tions rarely is found. Upper bedrock generally consists of tight shale more than 400 feet thick in some places. There are possibilities of high-capacity wells in deep sandstone, but shallow sand and gravel should be in- vestigated first. 5E_ 6 :~ rTiTi^: P: :T:n ^: :t:1 :::::: iiiti H H -ti ri": rr- riH H-j"t:ti SCALE 12 ILLINOIS STATE GEOLOGICAL SURVEY DEPTHS TO TOP OF THE GALESVILLE SANDSTONE The Galesville sandstone extends throughout northeastern Illinois. Its average thickness is approximately 135 to 160 feet. Like other bed- rock formations in the region, the sandstone dips southeastward. Its depth increases from about 600 feet in western Kendall County to over 2200 feet in southeastern Kankakee County. Hundreds of industrial and municipal water wells obtain water from the Galesville sandstone, considered the best bedrock aquifer in Illinois because of its consistent permeability and thick- ness. Many deep wells also obtain part of their yield from the shallower St. Peter sandstone and Trempeauleau dolomite and from the deeper Mt. Simon sandstone. To the south, the groundwater possibilities of the Galesville sandstone are con- trolled by water quality, which becomes poorer with depth, particularly south of the Illinois River and in Kankakee and southern Will counties. _ 5 . E __ . £ 46 ;;:Mc;" henry"! ." 14 ILLINOIS STATE GEOLOGICAL SURVEY COOK COUNTY Groundwater possibilities in sand and gravel beds in Cook County are best in the upland areas in the northwestern, south-central, and southern parts of the county. These water -yielding deposits are principally sand and fine to coarse gravel, which are in some places as much as 100 feet thick. They oc- cur mainly in the lower half of the glacial drift. Best possibilities for indus- trial and municipal supplies of water in sand and gravel are near Elgin, Bart- lett, Arlington Heights, and Orland Park; also locally elsewhere. In central Cook County and along the Des Plaines River southwest of Sum- mit, the glacial drift is thin and sand and gravel deposits are correspondingly thin or are absent. Here shallow sand deposits are mainly fine-grained or silty, and virtually all drilled wells penetrate solid bedrock for groundwater supplies. The Chicago Plain lies generally east of Homewood, Oak Forest, Ever- green Park, Justice, LaGrange, Bellwood, Niles, and Northfield. This low- land is underlain by silts and clays deposited on the floor of ancient Lake Chi- cago. Water-bearing sands are extremely scarce in the lake beds. The sur- face of the Chicago Plain is marked with more -or -less continuous ancient beach ridges and spits of clean sand, for example, the Glenwood Beach run- ning southeastward from Glenwood and the Wilmette spit fanning south- south- westward from Wilmette. The sands of these features are generally too thin to be suitable for water wells, but locally the sands extend to depths of 25 to 30 feet and are water-bearing in the lower part. A narrow band of beach sand along the present Lake Michigan shore yields groundwater to sand-point wells in scattered places. The common source of groundwater for domestic wells in Cook County is in the upper part of the dolomitic bedrock, lying immediately below the drift. Beneath the silts and clays of the Chicago Plain in the eastern part of Cook County, the dolomitic bedrock is relatively tight and locally not water -yielding. Areas where the shallow dolomite is particularly favorable for water wells are in the western half of T. 35 N., R. 14 E., near Chicago Heights, and in parts of Ts.38 and 39 N., R. 12 E., near LaGrange. Cook County is underlain by deeply buried sandstone, a reliable source of municipal and industrial water supplies. The Galesville sandstone ranges in depth from 1000 feet in northwestern Cook County to 1800 feet in the extreme southeastern part. Most municipal and major industrial water supplies in the \ county are obtained from this aquifer. { In north-central Cook County, in the vicinity of Des Plaines, bedrock for- mations have been severely broken and displaced, or faulted (fig. 3). Uncom- monly great thicknesses of shale are encountered locally within the Des Plaines faulted area, and dolomite formations may be thin or absent. Groundwater pos- sibilities in dolomite are therefore poorer here than they are in most of Cook County. DUPAGE COUNTY Thick glacial drift containing water-yielding sand and gravel deposits over- lies the dolomite in DuPage County. The most favorable areas for sand and mu- r, m- GROUNDWATER IN NORTHEASTERN ILLINOIS IS gravel wells are north of Naperville Within fi,* -, tic wells probably can be made in ne dri ft As de from'd *° """^ ^ appears that water-yielding sand and gravel deposi 111 ^ , SUPPli6S ' " nicipal consideration mighfbe found by t est in g ' A ong the De" P T a *? "" along the East and West Branches of the DuPage River in T I* *™ hurst the glacial drift is thin and generally un/avoraMe L^a^ef abundant water-filled crevices. Excelled Z shaikh '' C ° ntainS dolomite at Lombard, Glen Ellyn, Villa plrkWh e T T C ° nSt ™ Cted in the the Des Plaines River. ' Wheaton > Naperville, and along The deep sandstones, Galesville and Mt ^ extends' we t"- 2££ Xore:nn n S"^ P ° SSibUltleS '" ^^ ™"> in the the top of ITc'^u* San f St ° ne OCCUrs throughout Lake County. Depth to MCHENRY COUNTY Besttrs^orT ^^^ *" '*** ^ graVel beds are Z°°* >° excellent. >artl , high-capacity wells in sand and gravel are in the eastern part nt" ° h Beld6n ' GreenWO ° d ' Woodstock, Crystal Lake, and Algon^ ium. In this area the glacial drift that contains water-yielding deposits if 18 ILLINOIS STATE GEOLOGICAL SURVEY generally over 173 - thick . Sana ■££"££ £ £%£%?£L. -i^r^v^e^r^r^ - «* « some * *. dePOSits lie as deep as 200 feet. grou ndwater supplies can be ob- to the western two-th«d of the con y « of finding very favor . of the county the drift is less than 50 feet thick . ces ^ Groundwater generally can be obtained from open ««*^ dolomite that lies directly below the gl acial ^* » *^ ^ ^ J^ drill into the underlying dolomite. McHenry County. Depth to t °zi or::: tss^srr :i;r= r i * *. — weft to about 1100 feet along the eastern edge of the county. WILL COUNTY the drift and obtain water from open cracks «J C dolomite lies at or ' Des Plaines River and in extreme southern Will ^Count, near the surface, so water -yielding sands and gravels a« ^ scare P . sibilities for high-capacity wells in sand and 8'-^^*^™ £ t thick < HE and T. 34 N.. R. 14 E., where the drift is generally over and where widespread sand and **?££ B '£££'*i~T in southern Will West of the DuPage River and along the Kankakee K County, thick shale beds occur below ^^f*™^ ^netrate dolo-i these ^;"^S:S— " extreme southwestern; S Cour:-- b^the Pennsylvania, systen ^^ ^f j r i • 1 ,^ift These sandstones yield water to a numDer ox *.* D eep water-bearing ••^^"^^^fS^S^-- Galesville sandstone lies at a depth of aboutu lies deeper than about 1900 feet in the extreme -^-^JJ 1 ^^ Consideration should 1000 feet below sea level, as in southeastern Will County, be given to possible poor water quality. PLANNING HIGH-CAPACITY WELLS Most areas in northeastern Illinois are underlain by -^"^^ tions favorable for the construction of ^.^^^Z^erlL Jells GROUNDWATER IN NORTHEASTERN ILLINOIS I9 The best wells are generally those planned on the basis of all ,h» hydrologic information that is obtainable. geolog lc and The following log shows the sequence of formations th=»t «,. of the region. Well 1 of the Aluminum Co^Tl™^™^™" typical of deep sandstone wells. or less d A rmet n T94 C 7 TrM ' ^tf " t^ ' " *' P " MiUeI A ""*n Well Co., driller 1947, SE 1/4 sec. 17, T. 39 N., R. 12 E., Cook Co.; State Geo logical Survey sample set 16355; samples studied in 1950 E T. elll'- r* i C . ,_ i/^-H^b 1/2 ft. Hole diameter: 18 inches 22 1/? HZ6 /TS; ft i 2 ; 500ft ' : 10inCheS " 500-1126 1/2 ft.; 8 inches, ' 112b 1/2-1495 ft. Static water level: 361 ft. (1947). Thickness Depth Pleistocene series (feet) (feet) Unconsolidated glacial drift Silurian system ^ Niagaran dolomite, yellowish gray Alexandrian dolomite, whitish Ordovician system Maquoketa shale and thin dolomite Galena dolomite, yellowish brown Decorah dolomite, sandy Platteville dolomite, yellowish brown and gray Glenwood-St. Peter sandstone, silty shale and chert Oneota-Gunter dolomite, sandy Cambrian system Trempealeau dolomite, yellowish gray and brown Franconia sandstone, shale and dolomite Ironton-Galesville sandstone Eau Claire shale and sandstone Sand and gravel wells -~S~ ^=^ -- ~ =• ther CeT^ro t : POSlt / yi6ld m ° re Water t0 SpeC1 " C Wells *a„ any rally ^llowe™' ? , adVant ^ eS of sand ^nd gravel sources are gen- acterial CaU ^ As ^Jr b a *T' "* * '° m ° ■*"" "*« 'oratory test drilwTs? 8 ' ** ^^ bedS are s "»ered, ex- veiopm^t -f^^'^raj - ? "iff* has ofte - discouraged the gravel wells. It is often easier to design a deep rock 190 200 45 245 225 470 185 655 15 670 133 803 202 1005 30 1035 80 1115 75 1190 105 1295 175 1470 25 1495 20 ILLINOIS STATE GEOLOGICAL SURVEY well and to disregard the possibility of locating very favorable shallow water sources Figure 2 indicates the general possibilities of locating promising sand and gravel beds. In areas where conditions are favorable for the occurrence of sand and gravel deposits, it is good practice to test the glacial drift to the top of solid rock for the possible presence of water -yielding material. Such a test may find no suitable shallow water source, in which case a rock well may be necessary. A test that shows a promising sand and gravel bed should furnish basic information necessary for designing a high-capacity screened well. Test information should include a complete log of formations, samples of drill cut- tings at five-foot intervals, drilling characteristics, and static water level. If rotary equipment is used for the test, data should include mud loss, mud weight, size of mud pit, and use of hydraulic "pull-down." Bedrock wells Many variable conditions affect the design of a good high-capacity well in bedrock in northeastern Illinois. These include (1) thickness, depth, and per- meability of sandstones; (2) depth and crevicing of dolomites; (3) ability of for- mations to sustain open hole without casing or lining; (4) tendency of formations to yield silt or sand during heavy pumping; and (5) water quality and water- pressure potential. The State Geological Survey can furnish basic information on the first four conditions for prospective well locations, although specific data depends on the availability of information from prior drilling. Much subsurface information is available in the Geological Survey files. The State Water Survey furnishes basic information on water quality, pressure potential of various formations, and yields of existing wells. Wells completed in dolomite directly beneath glacial drift have surface casing seated in firm rock. There are strong possibilities of bacterial pollu- , tion where high-capacity wells obtain water from dolomite overlain by less thari 35 feet of glacial drift. Most deep sandstone wells in northeastern Illinois are cased through the Maquoketa shale into the top of the Galena dolomite, because many of the shale beds of the Maquoketa formation are too weak to sustain continuously an open hole. Lining also is desirable in the lower 30 to 50 feet of the St. Peter sand- stone, particularly in the shale bed generally found between the sandstone and ; the dolomite of the Oneota formation. In McHenry County and vicinity, the lowe, St. Peter also contains weak cherty zones which require lining. No other shale; or cherty zones above the Ironton-Galesville sandstone are sufficiently wide- spread to require plans for lining. The pumping of fine sand and silt has been a problem in a number of deep sandstone wells in this region. The State Geological Survey has been called upon frequently to identify the source of the materials so that corrective mea ures may be taken. The most common sources of earth material pumped with water are (1) silt and clay from glacial drift, caused by a break in surface casi or by poorly seated casing; (2) silt and clay from open crevices in dolomite, which may be directly beneath the drift; and (3) silt and fine sand from the St. Peter, lower Franconia, Ironton, or Galesville formations. GROUNDWATER IN NORTHEASTERN ILLINOIS 21 A small amount of caving and pumping of earth material is probably un- avoidable in high-capacity wells. However, attention to the following causes of excessive sand pumping should reduce the number and severity of sand-pumping problems: 1) drilling too small a hole in the Ironton-Galesville sandstone, which results in excessive velocities of water moving upward; 2) setting the pump at a level where turbulence in the vicinity of the pump bowls causes en- largement of the hole. Pump should be set opposite a firm dolomite or within a liner; 3) shooting the water -yielding sandstones with too much explosive and with too little regard for the condition of the sandstone. Sand probably caves readily from roofs of soft ledges which have been undercut by explosives. More uniform enlargement of the bore hole in the most permeable zones should de- crease sand pumping. PLANNING DOMESTIC AND FARM WELLS Northeastern Illinois is the most favorable large region in the state for ob- taining small private water supplies at minimum cost. Most private supplies are obtained from screened wells in sand and gravel or from unscreened (open hole) wells in dolomite below the drift. In western Kendall County, and locally in Grundy and Kane counties, private wells are drilled in firm sandstone Only in the southwestern part of Grundy County are geologic conditions in the bedrock locally unsuitable for small drilled wells. Most shallow bedrock formations in this area are tight shale. It is particularly important in such an area that wells be completed in water-bearing sand and gravel above rock wher- ever these permeable deposits can be located. These suggestions should be helpful in planning private water supplies: 1. Select a driller who has constructed wells that have proved trouble-free for a period of years. 2. Encourage the driller to set a commercial well screen if the well is to be completed in sand and gravel. A properly selected and installed screen is the best guarantee against sand pumping. In a sand bed that is barely suitable for a water source, a carefully selected well screen is necessary for maximum yield. 3. The State Department of Public Health discourages the use of well pits on Grade A milk farms. Such pits are unduly expensive when they are properly constructed for good san- itation. 4. If a rock well is in creviced dolomite where the glacial drift above the dolomite is less than about 35 feet thick, the water should have periodic bacterial analyses. Wells in creviced rock are more subject to pollution than other types of drilled wells because there is no filtering action. 5. In most areas in northeastern Illinois, one location on a property is probably as good as another, so far as ground- water possibilities are concerned, so it is best to drill the well in a convenient place that has good surface drainage. In parts of Grundy County, however, it may be necessary to locate wells at some distance from the house, if water- bearing sand and gravel deposits cannot be located nearby. 22 ILLINOIS STATE GEOLOGICAL SURVEY ROLE OF THE DRILLING CONTRACTOR 1 Every driller should provide his customer with an accurate log of ^ the well at the time it is completed. In accordance with the Mining Laws o II mo.s, I copy of the log should be sent to the State Geological Survey and to the State Water Survey. A good driller-s log includes a description of the formations rnformaUon on thematic water level and hasic ^^^[^^fj^ length and size of well screen and size of casing), and an indication of the capac- iy oft he well. As a service to drillers and property owners, log books may be obtained by the contractors without charge from the Geological Survey Maintaining a permanent record of the construction of a water well is of grease to tie property owner. This record should be kept with offxcxal prop- erty rlcords and delivered to a new owner when the property changes hands. Copies of records will be available at the State Geological Survey xf the driller provides them when the well is constructed. 2 It is desirable to construct the well so that the depth to water level can be me'asured with a tape or other device without removing pumping *^™*- 3 The top of the well should be constructed to prevent surface pollution from entering the well or seeping downward around the casing A good ^way £ prevent downward seepage of surface water is to pour an envelope of oncrete ^ around the casing to a depth of several feet and to make sure that surface waters drain away from the well. ,„„„„* n f ™»ti>r 4 Drillers should take special care to obtain the maximum amount of water from a poor formation in areas where groundwater conditions are ^ av °f* ble - Whereas almost anyone can obtain a suitable yield from an excellent sand and gravel formation, it takes a driller with experience and imagination to make the best use of a sand that is slow to respond to pumping. 5 Commercial well screens should be selected by the driller after a water, yielding bed has been penetrated and examined. The purpose of the wel screen [. not only to maintain an open hole and to admit water to the well but also to en- able the driller to pull the fine portion of the formation through the screen and ,, remove it from the well. This is called well "development," a process that re- quires that slot openings in the screen be carefully determined on the basis of ._ the size of grains in the water-yielding bed. One objection to using slotted casin, rather than commercial well screen is that the size of the slot openings rarely is appropriate for the particular formation. Use of slotted pipe or ^open-hot torn casing should be avoided except in very coarse sand and gravel beds where the , ability of the well to yield water far exceeds the demand made. , 6. The State Geological Survey files samples of drill cuttings received fron, drillers. It is particularly desirable in the case of school, industrial and mu- nicipal well construction to save samples at regular five-foot intervals for the entire depth of the well. These samples may be sent express collect to the Sur vey, where they will be studied and placed in the permanent sample library. ^ In- formation obtained from samples is vital in effective rehabilitation of old wells. GROUNDWATER IN NORTHEASTERN ILLINOIS 23 LARGE-DIAMETER WELLS Large-diameter wells that are excavated by hand, or better yet, by power auger or bucket still have their place. In northeastern Illinois, however, where conditions are generally favorable for small drilled wells, the large well has never found wide use. They are best adapted to areas where formations are tight and cannot yield water readily to a pump. Such conditions are found locally in several parts of Grundy County and in extreme southwestern Will and extreme western Kankakee counties. The chief advantage of a large well (say 2 to 5 feet in diameter) is that it can store large quantities of water. Short, intermittent pumping of a large well does not require immediate release of water from the surrounding formation The well can refill slowly over a period of many hours. Modern power equip- ment excavates large wells 50 to 100 feet or more in depth. Special sanitary precautions should be taken with large diameter wells (see Circular 14A, Illi- nois State Department of Public Health, Springfield). SUGGESTIONS FOR FURTHER READING A safe water supply: C. W. Klassen, Dept. of Public Health Circ. 14, 1951. Bedrock topography of Illinois: Leland Horberg, Illinois Geol. Survey Bull. 73, 1950. Chicago area water supply: A. M. Buswell, Max Suter, and H. E. Hudson, Jr., Illinois Water Survey Circ. 29, 1950. Cisterns: Illinois Dept. Public Health Circ. 129, 1949. Data on the ground waters of Lake County: Illinois Water Survey Circ. 17, 1935. Disinfection of water: Illinois Dept. Public Health Circ. 97, 1950. Geology of the Chicago region: J Harlen Bretz, Illinois Geol. Survey Bull. 65, Part I, General, 1939. Public ground-water supplies in Illinois: compiled by Ross Hanson, Illinois Water Survey Bull. 40, 1950. Rehabilitation of sandstone wells: W. B. Millis, Illinois Water Survey Circ. 23, 1946. Significance of Pleistocene deposits in the groundwater resources of Illinois: J. W. Foster, Econ. Geol., v. 48, no. 7, Nov. 1953. Stratigraphy and geologic structure of northern Illinois: F. T. Thwaites, Illi- nois Geol. Survey Rept. Inv. 13, 1927. The artesian waters of northeastern Illinois: C. B. Anderson, Illinois Geol. Survey Bull. 34, 1919. Water wells for farm supply in central and eastern Illinois: J. W. Foster and Lidia Selkregg, Illinois Geol. Survey Circ. 192, 1954. Topographic maps are available for most of the area covered in this report. For the Chicago region these maps are on a scale of approximately 2 1/2 inches to the mile, and in the remainder of the area they are on a scale of 1 inch to the mile. They are printed by quadrangles and can be obtained from the Illinois State Geological Survey, Urbana, Illinois, or from the United States Geological Survey, Washington 25, D. C, for 20 cents each. Index maps showing topographic map coverage of the State are free. Areal geologic maps, engraved in color on a scale of 2 1/2 inches to the mile are also available for the Chicago region. These can be obtained from the Illinois State Geological Survey for 15 cents each. ILLINOIS j&mrt 'ofjCiacofa, i CIRCULAR 198 ILLINOIS STATE GEOLOGICAL SURVEY URBAN A (17813—6-55) <^3£*>2