TN295 ■■'■■;■>,■■■■'■■■/■■■ iMlH ■1 JHHH| nHHHHHh 1111111 ■' ''■'■■'" ■ ';■..- ■ '■' Bl "' •■■" ■ ■' •'■ ■ ■ ' sBjSSi'BB' ''!' ''.''•''iv'''' 1 .- 1 ' ■''.''■i :i ffiffiSsS m : IB I WKm iiH ^c- >v.« ^ 0^ A> Cti ^ ... <*_ A> ... «>> .V.' V • • • » < * ^ J, " • » «' v-cr 'bV •*•_ s.0 v .»!•'* *> v * 1 • •" ^ * \f> q # '^.*-p ^°^ • > » \ * 1 %'*^L'* *> ^ *?* ^'.l'* ^ '• ^W&S jy O. ^ « , . <1 A> ... a^ *^Ei^- cS°: : **">. -. <> v B ^' ^ » V o. '• C, if <* «? -^ ■ . 7 • A Bureau of Mines Information Circular/1987 Cost Estimation Handbook for Small Placer Mines By Scott A. Stebbins UNITED STATES DEPARTMENT OF THE INTERIOR Information Circular 9170 Cost Estimation Handbook for Small Placer Mines By Scott A. Stebbins UNITED STATES DEPARTMENT OF THE INTERIOR Donald Paul Hodel, Secretary BUREAU OF MINES David S. Brown, Acting Director As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserving the environment and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration. IN 235 .11* no. 1)70 Library of Congress Cataloging-in-Publication Data Stebbins, Scott A. Cost estimation handbook for small placer mines. (Information circular / Bureau of Mines; 9170) Includes bibliographies. Supt. of Docs, no.: I 28.27: 9170 1. Hydraulic mining— Costs. I. Title. II. Series: Information circular (United States. Bureau of Mines); 9170. TN295.U4 [TN421] 622 s [622 '.32] 87-600145 For sale by the Superintendent of Documents. U.S Government Printing Office Washington, DC 20402 CONTENTS Abstract 1 Introduction 2 Acknowledgments 2 Section 1.— Placer Mine Design Exploration 3 Panning 4 Churn drilling 4 Bucket drilling 4 Rotary drilling 5 Trenching 5 Seismic surveys 5 Mining 5 Backhoes (hydraulic excavators) 6 Bulldozers 6 Draglines 6 Dredges 6 Front-end loaders 7 Rear-dump trucks 7 Scrapers 7 Processing 7 Conveyors 8 Feed hoppers 8 Jig concentrators 8 Sluices 8 Spiral concentrators 9 Table concentrators 9 Trommels 9 Vibrating screens 10 Sample mill design 10 Supplemental systems 13 Buildings 13 Camp facilities 13 General services and lost time 13 Generators 13 Pumps 14 Settling ponds 14 Environment 14 Cost estimation 15 Cost equations 15 Cost date adjustments 15 Site adjustment factors 16 Labor rates 17 Financial analysis 18 Bibliography 18 Section 2.— Cost Estimation Capital and operating cost categories 19 Capital costs 20 Exploration 20 Panning 21 Churn drilling 21 Bucket drilling 21 Trenching 21 General reconnaissance 21 Camp costs 21 Seismic surveying (refraction) 21 Rotary drilling 21 Helicopter rental 21 Development 22 Access roads 22 Clearing 23 Page Preproduction overburden removal 24 Bulldozers 24 Draglines 25 Front-end loaders 26 Rear-dump trucks 27 Scrapers 28 Mine equipment 29 Backhoes 29 Bulldozers 30 Draglines 31 Front-end loaders 32 Rear-dump trucks 33 Scrapers 34 Processing equipment 35 Conveyors 35 Feed hoppers 36 Jig concentrators 37 Sluices 38 Spiral concentrators 39 Table concentrators 40 Trommels 41 Vibrating screens 42 Supplemental 43 Buildings 43 Employee housing 44 Generators 45 Pumps 46 Settling ponds 47 Operating costs 48 Overburden removal 48 Bulldozers 48 Draglines 49 Front-end loaders 50 Rear-dump trucks 51 Scrapers 52 Mining 53 Backhoes 53 Bulldozers 54 Draglines 55 Front-end loaders 56 Rear-dump trucks 57 Scrapers 58 Processing 59 Conveyors 59 Feed hoppers 60 Jig concentrators 61 Sluices 62 Spiral concentrators 63 Table concentrators 64 Tailings removal 65 Bulldozers 65 Draglines 66 Front-end loaders 67 Rear-dump trucks 68 Scrapers 69 Trommels 70 Vibrating screens 71 Supplemental 72 Employee housing 72 Generators 73 Lost time and general services 74 Pumps 75 Bibliography 78 Appendix.— Example of cost estimate 79 ILLUSTRATIONS Page 1. Sample flow sheet, sluice mill 10 2. Sample flow sheet, jig mill 11 3. Sample flow sheet, table mill 12 4. Exploration cost summary form 21 5. Capital cost summary form 76 6. Operating cost summary form 77 A-l. Sample flow sheet 80 A-2. Capital cost summary form completed for example estimation 87 A-3. Operating cost summary form completed for example estimation 94 TABLES 1. Sample material balance, sluice mill 10 2. Sample material balance, jig mill 10 3. Sample material balance, table mill 10 4. Cost date indexes 17 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT BCY bank cubic yard LCY/h loose cubic yard per d/a day per year hour ft foot pm micrometer ft 2 square foot ft 2 /yd 3 square foot per min minute cubic yard min/h minute per hour ft/h foot per hour gpm gallon per minute St short ton h hour st/h short ton per hour h/shift hour per shift tr oz troy ounce hp horsepower tr oz/yd 3 troy ounce per cubic in inch yard kW kilowatt wt % weight percent kW/yd 3 kilowatt per cubic yd/h yard per hour yard yd 3 cubic yard lb/LCY pound per loose cubic yd 3 /d cubic yard per day yard yd 3 /ft 2 cubic yard per lb/yd pound per yard square foot lb/yd 3 pound per cubic yard yd 3 /h cubic yard per hour LCY loose cubic yard yr year LCY/a loose cubic yard per year COST ESTIMATION HANDBOOK FOR SMALL PLACER MINES By Scott A. Stebbins 1 ABSTRACT This Bureau of Mines publication presents a method for estimating capital and operating costs associated with the exploration, mining, and processing of placer deposits. To ensure represent- ative cost estimates, operational parameters for placering equipment and basic principles of placer mining techniques are detailed. Mining engineer. Western Field Operations Center. Bureau of Mines. Spokane, WA. INTRODUCTION In 1974, the Bureau of Mines began a systematic assess- ment of U.S. mineral supplies under its Minerals Avail- ability Program (MAP). To aid in this program, a technique was developed to estimate capital and operating costs associated with various mining methods. This technique, developed under a Bureau contract by STRAAM Engineers, Inc., was completed in 1975, then updated in 1983. During the course of the update, it was noted that few provisions were made for estimating the costs of small-scale mining and milling methods typically associated with placer min- ing. The popularity and widespread use of placer mining methods indicated that a cost estimating system for placer mining would be of value to prospectors, miners, investors, and government evaluators. This report has been written to aid those involved with placer mining in the estimation of costs to recover valuable minerals from placer deposits. It relies on the principle that cost estimates will be representative only if calculated for technically feasible mining operations. Because the design of such an operation can be difficult, provisions have been made to assist the user in achieving this goal. Section 1 of the report describes the processes involved in placering, and may be used to aid in designing a viable mine. Operational parameters for equipment commonly used in placer exploration, mining, and processing are discussed, as well as basic principles of successful placer mining techniques. If the reader is unfamiliar with this form of mining, section 1 should be thoroughly understood prior to estimating costs. Section 2 contains cost equations that enable the user to estimate capital and operating costs of specific placer techniques. Cost equations are designed to handle the wide variety of conditions commonly found in placer deposits. This allows the reader to tailor estimates to the characteristics of a particular deposit, which ensures representative costs. Although based primarily on gold placer operations, cost equations are valid for any other com- modity found in deposits of unconsolidated material. Equa- tions are geared to operations handling between 20 and 500 LCY/h of material (pay gravel plus overburden). Estimated costs are representative of operations in the western United States and Alaska, and are based on a cost date of January 1985. The appendix provides an example of placer mine design and cost estimation using the information contained in this report. This report is not intended to be an exhaustive discus- sion of placer mining. Many detailed texts have been writ- ten on this process, any one of which will assist the reader in method design. A number of these are listed in the bibliographies accompanying sections 1 and 2. ACKNOWLEDGMENTS A special debt is owed to the late George D. Gale, metallurgist, Bureau of Mines. This handbook, and many of the ideas and facts it contains, are the product of his ingenuity. SECTION 1.— PLACER MINE DESIGN The complete design of a placer mine involves the in- tegration of exploration, mining, processing, and sup- plemental systems for the efficient recovery of valuable minerals from an alluvial deposit. This design is the first step in accurate cost estimation. In this section, individual systems are categorized as follows: 1. Exploration.— The phase of the operation in which resources are delineated. Because the amount of time and effort spent on discovery is difficult to tie to any one specific deposit, only the processes of delineation and definition are costed. Field reconnaissance, drilling, and panning are representative of items in this category. 2. Mining.— Deposit development, material excavation and transportation, and feeding of the mill are all in- cluded in this category. Items such as clearing and over- burden removal are also included. 3. Processing.— Processing is defined as all tasks required to separate the desired mineral products from valueless material. 4. Supplemental.— Any items not directly related to mineral recovery, but necessary for the operation of the mine. These might include buildings, employee housing, and settling pond construction. Before designing a placer mining operation, the evaluator will need information concerning the deposit under evaluation. Preliminary information helpful in ex- ploration program, mine, mill, and supplemental function design includes 1 . Description of deposit access. 2 . Anticipated exploration and deposit definition requirements. 3 . An estimate of deposit geometry and volume. 4 . Distribution and location of valuable minerals within the deposit. 5 . Geologic characteristics, volume and depth of overburden. 6 . Depth, profile, and geologic characteristics of bedrock. 7 . Local topography. 8 . Physical characteristics and geologic nature of valuable minerals. 9 . Availability of water. 10. Availability of power. 11. Environmental considerations. 12. Labor availability and local wage scales. 13. Housing or camp requirements. Information should be as detailed as possible. By pro- viding such items as exact haul distances and gradients, accurate estimates of overburden thickness and deposit area, the evaluator will increase the precision of cost calculations. With the preceding information in hand and the help of the material contained in the following pages, the user will be able to design a technically feasible operation. The following sections will assist the evaluator in planning each phase of the mine. When designing systems for individual areas of operation, the evaluator must keep in mind that these systems will interact and must be compatible. For in- stance, hourly capacity of pay gravel excavation should equal mill feed rate, and the mill must be set up to easily accept gravel from the equipment used for material transportation. Most of the information contained in the following pages is based on average operating parameters and performance data for the various types of equipment used in placer min- ing. Costs and conclusions derived from this manual must be considered estimates only. Because of the many variables peculiar to individual deposits, the stated levels of equip- ment performance and costs may not be realized on any given job. EXPLORATION It can be safely stated that far more people seek placer deposits than actually mine them. Exploration for placer gold can be enjoyable work and has achieved a recreational status in the western United States. For the serious miner, however, exploration is only the initial phase of a complete mining operation. Consequently, it incurs a cost that must be repaid by the recovery of valuable minerals. For the purposes of this report, exploration is divided into two phases. The first phase involves locating the deposit, and the second consists of defining enough of a resource to either justify development or to eliminate the deposit from further consideration. Costs for the first phase of exploration are difficult to attribute to any one deposit. This type of exploration is typically regional in nature and deposit specifics are rarely considered. For cost estimation purposes, expenses associated with a specific deposit are the main concern. Only costs directly related to the definition of that particular deposit will be calculated. Accordingly, this discussion deals mainly with the deposit definition phase of exploration. Time, effort, and money spent on resource definition vary greatly from one deposit to the next. Some miners are satisfied with the degree of certainty obtainable with shovel, pan, and physical labor. Others, wishing more security, systematically trench or drill the deposit and process samples using some sort of mechanical concentrator. Still others, hoping for greater assurance, follow up drilling or trenching by bulk sampling using machinery intended for mining. These samples are then processed in a scaled-down version of the proposed mill. The extent of effort spent on deposit definition is related to 1. Degree of certainty desired. 2. Availability of capital. 3. Experience of the operator. 4. Historical continuity of similar or local deposits. It is intuitively obvious that the degree of certainty of success is related to the extent of exploration undertaken, and it is desirable to delineate the deposit as extensively as is practical prior to production. In many cases, however, lack of exploration capital and the need for cash-flow limit the exploration phase, and mining commences on the limited information at hand. Goals of a thorough explora- tion program include determination of 1. Deposit volume. 2. Deposit and overburden geometry. 3. Deposit grade. 4. Distribution of valuable minerals within the deposit. 5. Geological and physical characteristics of the valuable minerals. 6. Geological and physical characteristics of waste material. 7. Location, geology, and physical nature of the bedrock. 8. Water availability. 9. Environmental concerns. Much of the information needed to estimate costs of developing and operating a placer mine is gathered during deposit exploration. Consequently, costs estimated after ex- ploration are much more precise than estimates made prior to exploration. In section 2 of this report, two methods are presented for estimating exploration costs. With the first, a cost can be calculated by simply estimating the total resource of the deposit. This method is based on total exploration expen- ditures for several active placer operations, but is not con- sidered as precise as the second method. The second method requires that the evaluator design an exploration plan. This plan should include the type and extent of each exploration method required, for example 1. General reconnaissance, 5 days with a two-person crew. 2. Seismic surveying, 10,000 linear ft. 3. Churn drilling, 4,000 ft. 4. Trenching, 1,000 yd 3 . 5. Samples panned, 2,000. 6. Camp facilities, four people for 20 days. To aid in developing this plan, some techniques com- monly employed for sampling and subsurface testing of placer deposits are discussed in the following paragraphs. These include panning, churn drilling, bucket drilling, rotary drilling, trenching, and seismic surveying. waste during production. Skilled use of a gold pan during the mining sequence can make or break the small mining operation. CHURN DRILLING Methods of drilling placer deposits are quite varied, but the most common technique is churn drilling. Typically, the churn drill uses percussion to drive casing down through the material being sampled (in some instances, casing is not used). After a length of casing is driven, the contents are recovered (bailed), another length of casing is added, and the process is repeated. Depths are usually restricted to less than 150 ft, and hole diameters range from 4 to 10 in. One advantage of this method is that sample process- ing keeps pace with drilling, allowing good control of drill- hole depth and instantaneous logging. A churn drill is generally operated by two people; the driller operates the drill, bails the sample, and keeps track of the depth of each run; the panner estimates the volume of the samples, pans them as they are recovered, and logs the hole. Drilling rates average about 2 ft/h but can reach as much as 4 ft/h in clay, soil, sand, pebbles and soft bedrock. The machine is suitable for drilling through cemented gravels and permafrost, although productivity will diminish. Penetration is drastically reduced in ground con- taining boulders and in competent or hard bedrock. Samples recovered from churn drill casings are often subject to volume changes caused by compaction or expan- sion of material within the casing. Sample volume changes can also be caused by compaction around the bit forcing material out into the surrounding formation, and by material "run-in" due to high deposit water content. One or more of these conditions may be encountered in any one deposit, requiring the application of volume corrections. This task is often difficult and requires the experience of a qualified driller or engineer. BUCKET DRILLING PANNING One of the most versatile and common sampling devices in placer mining is the gold pan. It is used as a recon- naissance tool, a sampling tool, and a concentrate refining tool. With a gold pan, the prospector has the ability to, in effect, conduct his or her assay work on-site with immediate results. Although accuracy may be poor, the prospector can determine in the field if gold is present and in roughly what amounts. The gold pan uses gravity separation to concentrate heavy minerals. Pans come in a variety of sizes, ranging in diameter from 12 to 16 in. An experienced panner can concentrate approximately 0.5 yd 3 gravel daily. Because of this limited capacity, panning can be costly when large volumes must be processed; however, low capital expense, ease of use, versatility, and portability make the gold pan invaluable. Immediate feedback when exploring or mining is a prime advantage of the gold pan. This one feature is ex- tremely important for eliminating areas of low potential during exploration, and for separating pay gravel from Bucket drilling, although not as popular as churn drill- ing, has important applications in placer deposit evalua- tion. Under ideal conditions, this technique is relatively fast and provides large samples. In this system, a standard rotary drill is equipped with a special "bucket" bit con- sisting of a 30- to 48-in-diam cylinder, 3 to 4 ft long. The bit is driven down through the deposit, using the rotational force of the drill, until the cylinder is full. As the bit is withdrawn, a mechanism closes off the bottom of the bit retaining the sample. The process is then repeated until the desired depth is reached. Bucket drills perform best in sands, soils, pebbles, and clays. Progress is slow, and sometimes impossible, in ground containing boulders, cemented gravel layers, and bedrock. The size of the bit tends to disperse drilling force over a large area, thereby reducing the effective penetration rate. For this reason the bucket drill quickly becomes inefficient in hard or compact material. Problems are also encountered in saturated ground, where water often washes away a por- tion of the sample as the bit is withdrawn. Bucket drilling extracts a much larger sample than other drilling methods. Consequently, the influence of the bit on compaction and expansion of material is reduced. ROTARY DRILLING This type of drill, commonly used for drilling large- diameter blastholes in surface mining, has found limited use in placer exploration. The only way to obtain a sample with this machine is to analyze drill cuttings. Because the method does not provide a core, it is difficult to associate a volume with the recovered material, and it is hard to estimate the depth horizon of the sample. Rotary drills are useful in that they provide a fast, in- expensive way to determine the depth of bedrock. Holes pro- vided by rotary drills range from 6 to 15 in. in diameter and reach any depth required for placer mining. Virtually any material can be drilled, and penetration rates are far superior to any other placer drilling method. Regardless of the steps taken, however, it is difficult to accurately estimate deposit grade with samples obtained from rotary drilling. TRENCHING In fairly shallow, dry deposits, trenching with a backhoe is an extremely effective sampling technique. The procedure involves digging a trench to bedrock, then obtaining material from a channel taken down one side of the trench. This material is then measured and analyzed, providing a grade estimate. Another method relates an assay analysis of all the material extracted by the backhoe to the volume of the trench. The disadvantage of this method is the in- ability to determine the horizon of valuable mineral con- centration. With either method, large-volume samples are available at a low cost. In sampling situations, backhoes can excavate from 20 to 45 LCY/h. Sample control is typically good with little volume distortion or material dilution under properly con- trolled circumstances. Backhoes are relatively inexpensive, easy to operate, versatile, and readily available. The machine can dig a variety of formations, and digging depths as much 30 ft below the machine platforms are possible. In saturated ground, keeping the trench open for sampling is normally a major problem. SEISMIC SURVEYS In placer mining, bedrock depth plays a key role. Although not always the case, gold tends to concentrate near, on, or even in bedrock in a majority of placer deposits. Consequently, it is imperative to understand the nature of the bedrock and to design a mining method and select equip- ment based on its depth. One method of determining bedrock depth is seismic refraction or reflection. In simple terms, the technique in- volves bouncing sound energy off the relatively resistant bedrock to determine its depth. The method is much cheaper than drilling a series of holes and, if bedrock proves to be too deep for practical mining, may prevent unnecessary drilling. MINING Next, a method for excavation and and transportation of material contained in the deposit is needed. Mining methods are typically dictated by several basic factors. Deposit depth, size, and topography are of primary impor- tance. The geologic nature of the deposit and accompany- ing overburden both play key roles. Types of equipment ob- tainable locally, sources of power, and the availability of water are all important factors. In some cases, operators may simply feel more confident using one method of extrac- tion as opposed to another, even if local conditions are unfavorable. In any event, the mining method should be designed with one fundamental goal in mind: To extract pay gravel from the deposit and move it to the mill at the lowest possi- ble overall cost. Several basic concepts should be designed into the mining method to keep costs low. These include 1. Haul only pay gravel to the mill. Eliminate hauling and processing unprofitable material. 2. Handle both overburden and pay gravel as few times as possible. Do not pile overburden or tails on ground that is scheduled for excavation. 3. Locate the mill at a site that minimizes average pay gravel haul distance. In most instances, it is cheaper to pump water than to haul gravel. 4. Do not mine gravel that is not profitable even if it con- tains gold. Money is lost for every yard of gravel mined if that gravel does not contain enough value to pay for the cost of mining and processing. As can be seen, common sense plays a large role in the proper design of a placer mine. The same holds true for mine equipment selection. Countless combinations of equipment have been tried in attempts to effectively mine placer deposits. Equipment typically used in the western United States includes 1. Backhoes (hydraulic excavators). 2. Bulldozers. 3. Draglines. 4. Dredges. 5. Front-end loaders. 6. Rear-dump trucks. 7. Scrapers. Each type of equipment is suited to a particular task. In some instances, only one piece of equipment may be used to remove overburden, excavate and haul pay gravel, and place mill tailings and oversize (i.e., bulldozers). More often, several different types of equipment are utilized to take advantage of their specific attributes. When selecting placer mining equipment, the evaluator must consider two important concepts. First, the volume of earth in place is less than the volume of the same earth after excavation. This point is critical in cost estimation and must be remembered. Because placer gravel is relatively light, placer mining equipment is typically limited by volume capacity, not weight capacity. For this reason, mine equipment capacities and associated cost equations in this report are based on volume after accounting for material swell— in loose cubic yards. Resource estimates are typically stated in bank cubic yards— the volume before accounting for material swell. This has a significant meaning to the design of a placer mining system. To mine a 500,000-BCY deposit, equipment will have to move 570,000 LCY of gravel if the material swells 147c (typical for gravel deposits). Although the total weight of material moved is constant, equipment will have to move a larger volume of gravel than the in-place estimate indicates. As a result, the mining system should be designed around the total loose cubic yards of gravel to be moved, not the total bank cubic yards. Second, mine equipment equations in section 2 of this report are based on the maximum amount of overburden, pay gravel, and mill tails moved daily. Although average volume handled might be less, equipment must be selected to handle the maximum load. To aid in mine planning, and to obtain reasonable capital and operating mine costs, the following information will typically be required: 1. Total length and average width of haul and access roads. 2. Total surface area of deposit. 3. Nature of ground cover. 4. Topography of deposit area. 5. Total loose cubic yards of overburden, and maximum amount of overburden handled daily. 6. Total loose cubic yards of pay gravel, and maximum amount of pay gravel handled daily. 7. Total cubic yards of mill tails handled daily. 8. Type of equipment desired. 9. Average haul distances and gradients for overburden, pay gravel, and tailings. The following is a discussion of the principal types of equipment used in excavating and hauling overburden, placer gravel, and mill oversize and tails, and may be used to aid in mine design and equipment selection. BACKHOES (HYDRAULIC EXCAVATORS) The backhoe is one of the most efficient types of equip- ment for bedrock cleanup. It is most often used for the ex- traction of pay gravel, but can also be used for excavation of overburden. The machine has almost no capacity for transportation of material and for that reason is used in conjunction with either front-end loaders, trucks, or in some cases, bulldozers. Depending on bucket selection, the machine can handle a variety of ground conditions including clays, poorly sorted gravels, tree roots, and vegetation. Dig- ging depths of over 30 ft are obtainable with certain backhoes, but production capability decreases rapidly as maximum digging depth is approached. Backhoes typically used in the western United States are capable of excavating from 95 to 475 LCY/h. Sizes range from 105-hp machines with 0.5-yd 3 buckets to 325-hp units with 3.75-yd 3 buckets. Capacity is contingent upon digging difficulty, operator ability, swing angle, digging depth, and obstructions. The backhoe is ideal for situations where bedrock cleanup is critical, obstructions exist in the mining area, and other means of transporting gravel are available. BULLDOZERS The bulldozer represents an extremely versatile tool in placer deposit extraction, and is the most popular. It can be used for overburden removal, pay gravel excavation, bedrock cleanup, overburden and pay gravel transportation, road construction, tailings placement, and a variety of minor functions. The bulldozer is the only device capable of handling all tasks required for placer mining in a prac- tical manner and must be considered if capital is scarce. Although bulldozers can handle all placer mining func- tions, they are not necessarily the most efficient machine for any one task. With its ripping capacity, the bulldozer is capable of cleaning up bedrock; however, the backhoe is much more selective and efficient. The bulldozer can, and often is, used to transport gravel, but in most cases trucks, scrapers, and front-end loaders can each do the job cheaper if haul distances are more than a few hundred feet. In ad- dition, bulldozers are not well suited to more large volumes of gravel or to dig to excessive depths. In both instances, draglines exhibit superior performance. A major advantage of the bulldozer is its ability to ex- cavate, transport, and load the mill all in one cycle, eliminating the need for expensive rehandling. Dozer capacities for excavating and hauling range from 19 LCY/h for a 65-hp machine up to 497.5 LCY/h for a 700-hp dozer (based on a 300-ft haul distance). Capacity is dependent upon ripping requirements, operator ability, cutting distance, haul distance, digging difficulty, and haul gradient. Dozers are best suited for situations where deposit and overburden thicknesses are not excessive, few large obstruc- tions are present, and haul distances average less than 500 ft. DRAGLINES Draglines are well suited for excavating large quantities of overburden, gravel, and waste. Although their material transporting ability is limited, draglines with booms up to 70 ft long are capable of acting as the sole piece of mining equipment. As with the bulldozer, draglines can excavate overburden and pay gravel, load the mill, and remove tail- ings; however, draglines are relatively inefficient at bedrock cleanup, and do not handle difficult digging as well as backhoes or dozers. Depths of over 200 ft are obtainable with this type of machine, and when used in conjunction with front-end loaders or rear-dump trucks, large-capacity operations are possible. Draglines handle from 28 LCY/h for a 84-hp unit to 264 LCY/h for a 540-hp machine. Capacity is dependent upon bucket efficiency, swing angle, and operator ability. Draglines are ideal for overburden removal and for large, deep deposits where bedrock cleanup is not critical. They must, however, be matched with the right equipment (i.e., portable mills or gravel transportation machinery). DREDGES Cost estimation equations for dredging are not in- cluded in this report. Dredges, except for recreational units and small machines used in active channels, are designed for high-capacity excavation of specific placer environments. The machines are best utilized in large volume, relatively flat-lying deposits that occur below water level. Because of large capital investment requirements and a scarcity of ground suitable for large-scale dredging, they are uncom- mon in the western United States. Operating costs for large-capacity dredges average ap- proximately $0.70/yd 3 . Purchase and refurbishing costs are often more than $3 million, and can run over $10 million. In large-volume situations, dredges must be considered. Because suitable applications are rare, however, they have not been included in this report. FRONT-END LOADERS This versatile machine is capable of many functions. In the western United States, its primary use is hauling previously excavated gravels, and the subsequent loading of the mill. Although front-end loaders are not the most ef- ficient hauling unit, their self-loading ability provides many advantages. One is the elimination of the need to match the excavation machine with the haul unit. With a front- end loader, the excavator can operate at its own pace and simply stockpile material. The loader then feeds from the stockpile and transports gravel to the mill feed hopper. This removes the problem of matching excavator output with truck cycles or mill feed rates. The machine is also capable of removing and transport- ing mill oversize and tailings; however, front-end loaders are not particularly adept at excavating consolidated material. If overburden or gravel are at all compacted, a backhoe or bulldozer should be used for a primary excavation. Front-end loaders are capable of hauling from 24 LC Y/h for a 65-hp, 1-yd 3 machine to 348 LCY/h for a 690-hp, 12-yd 3 machine (based on a 500-ft haul distance). Capacity varies with haul length, haul gradient, operator ability, bucket efficiency, and type of loader. Front-end loaders are best utilized as haul units over distances of less than 1,000 ft. Their versatility makes them useful for pay gravel and overburden transportation, mill oversize and tailings removal, and general site cleanup. REAR-DUMP TRUCKS Trucks represent the least expensive method of material movement over long distances; however, since other machinery is required for loading, total gravel transporta- tion expenses over short distances may be higher than for front-end loaders or scrapers. Trucks generally serve two purposes: Material movement and mill feed. They have relatively low capital costs and require little maintenance compared to other placer equipment. Trucks do need fairly good road surfaces and require careful matching with loading equipment to achieve acceptable efficiency. Capacities for units at small placer operations range from 3 to 47.5 yd 3 . Trucks are most productive over haul distances of 1,000 to 10,000 ft and can travel faster than equivalent-sized scrapers or front-end loaders. Production capacities range from 32.3 LCY/h for a 3-yd 3 truck to 444.8 LCY/h for a 47.5-yd 3 truck (based on a 2,500-ft haul distance). Capacity is contingent upon loader capacity, haul distance, and haul gradient. Trucks are suited to operations where a fixed mill is situated more than 0.5 mile from the minesite. They are equally effective hauling pay gravel, overburden, or mill tailings and oversize, but must be accompanied by a method of material loading. SCRAPERS These machines are noted for their high productivity when used to transport overburden, pay gravel, and tail- ings. As with front-end loaders, scrapers are self-loading, although bulldozers or other scrapers often assist. They are capable of much higher speeds and greater capacity than front-end loaders, and exhibit haulage characteristics similar to rear-dump trucks. Scrapers, however, are more costly to purchase and maintain. Scrapers are limited in their ability to excavate con- solidated or unsorted material. A bulldozer equipped with a ripper must precede them in overburden or gravel that is not easily drifted. If boulders are present, they must either be blasted or removed by other means. The nature of the scraper-dumping mechanism renders them unsuitable for direct mill feed. When used to haul pay gravel, scrapers will typically unload near the mill, and bulldozers will then be used to feed material. Capacities range from 201 LCY/h for a 330-hp machine to 420 LCY/h for a 550-hp machine (based on a 1,000-ft haul distance). Capacity is contingent upon haul distance and gradient, and loading procedure. In placer mining, scrapers are best utilized for transpor- tation of unconsolidated overburden or mill tailings over distances ranging from 500 to 5,000 ft. PROCESSING Often the most difficult part of placer mining is achiev- ing the desired recovery of valuable minerals from mine- run gravel. The design of a successful mill is a specialized science and often proves difficult even for those actively in- volved in placer mining. Great care must be taken to en- sure the recovery of a high percentage of contained valuable minerals. Obviously, the profitability of an operation is directly related to the percentage of contained valuable minerals recovered by the mill. Although mill design can be difficult, the basic premise used in heavy mineral recovery is quite logical. In placer deposits, high-density minerals have been concentrated by combinations of natural phenomenon such as gravity, tur- bulent fluid flow, and differences in mineral density. Con- sequently, it would seem practical to utilize these conditions to further concentrate heavy minerals. This form of mineral recovery is referred to as gravity separation and is the basis for most placer mills. Gravity processes must consider both particle specific gravity and size for effective separation. Differences in specific gravity alone will not distinguish various materials. It is the differences in weights in a common medium that creates efficient separation. Consequently, a particle of high specific gravity and small size may react the same as a large particle with low specific gravity in a given fluid. If grav- ity separation is to be effective, size control must be im- plemented to take advantage of differences in particle specific gravity. Equipment used for gravity separation ranges from gold pans to prebuilt self-contained placer plants. In general, the most widely employed devices in the western United States are 1. Jig concentrators. 2. Sluices. 3. Spiral concentrators. 4. Table concentrators. 5. Trommels. 6. Vibrating screens. Of these devices, trommels and vibrating screens are used for particle size classification, and the remainder are forms of gravity concentrators. In addition, feed hoppers and conveyors are needed for surge capacity and material transportation. These items, which are commonly neglected in plant costing, must be carefully selected to ensure prop- er plant operation. Although the complete design of a placer recovery plant cannot be thoroughly covered in the space available here, three sample flowsheets illustrating basic placer mill design are included at the end of this section on processing. Along with a flow sheet detailing equipment type, size, and capa- city required for the mill, the following will be needed to obtain an accurate cost estimate using this report: 1. Maximum feed capacity of the mill. 2. A material balance illustrating feed, concentrate, and tailings rates. 3. The purpose of each gravity separation device (rougher, cleaner, scavenger, etc.). 4. Method of removal and transportation of mill tails and oversize. The following discussion details equipment used in gravity separation and may prove useful in mill design. CONVEYORS As material travels through a mill circuit, it can be moved by conveyor, pumped in a slurry, or transferred by gravity. In placer processing mills, material is most often transported in a slurry or by gravity. In some cases, however, conveyors are necessary. Conveyors are typically used for situations of extended transport where material need not be kept in a slurry, such as the removal of over- size or tailings. They provide an inexpensive method of transporting large quantities of material over fixed distances. In the case of placer processing plants, this distance typically ranges between 10 and 120 ft. Conveyors used in these plants are typically portable, and consequently come complete with framework and support system ready to operate. Conveyor capacity is related to belt width, belt speed, and material density. For most placer gravels, capacities range between 96 yd 3 /h for an 18-in-wide belt to 480 yd 3 /h for a 36-in-wide belt. FEED HOPPERS The initial piece of equipment in most mill circuits is a feed hopper. The hopper is used in conjunction with a feeder to smooth out material flow surges introduced by loading devices with fixed bucket sizes (front-end loaders, rear-dump trucks, etc.). Hoppers often contain a grizzly in order to reject large oversize material. The feeder, typically a vibrating tray located under the hopper, transfers gravel at an even rate to the circuit. Although the hopper-feeder combination may appear to be a minor piece of equipment, a steady flow of material through the mill is very impor- tant for effective gravity separation. Hopper capacity and feeder capacity are two separate items. Generally, hoppers are designed to hold enough material to provide a steady flow of gravel despite surges inherent in mining cycles. Feeders are set to provide the appropriate flow rate to the mill. So even though a hopper may have a 100-yd 3 capacity, the feeder might provide material at 20 ydVh. Feeders are not always used in placer mills. When they are not used, feed rate is regulated by the size of the open- ing in the bottom of the hopper. The cost estimation curves in this report calculate hopper-feeder costs based on feeder capacity, which typically equals mill capacity. Factors are provided for situations where feeders are not used. JIG CONCENTRATORS Jigs are gravity separation devices that use hindered settling to extract heavy minerals from feed material. They typically consist of shallow, perforated trays through which water pulsates in a vertical motion. In most instances, a bed made up of sized shot, steel punchings, or other "ragging" material is placed over the perforations to pro- mote directional currents required for separation. Slurried feed flowing over the bed is subjected to the vertical pulsa- tions of water, which tend to keep lighter particles in suspension while drawing down heavier constituents. These heavy minerals are either drawn through the bed and discharged from spigots under the jig or, if too large to pass through the perforations, are drawn off near the end of the machine. Lighter particles continue across and over the end of the jig as tailings. Jigs are sensitive to feed sizing. They are generally utilized for feeds ranging from 75 ^m to a maximum of 1 in, but recoveries improve if feed is well sized and kept to minus 0.25 in. Efficiency is maximized when feed materials have been deslimed and sized into a number of separate frac- tions for individual treatment. Optimum solids content for jig plant feed ranges from 35% to 50%— the object being to avoid excessive dilation of the material. Capacities for jigs range from 0.1 to 400 yd 3 /h and are dependent upon desired product as well as equipment size. SLUICES The most common gravity separation device used in placer mills, sluices are simple to construct, yet effective heavy mineral recovery tools. Sluice design is quite diverse and opinions differ widely with respect to capacity, riffle design, and recovery. In general, capacities and perfor- mances vary with box width and slope, gold particle size, nature of feed, and availability of water. Sluices are primarily used for rough concentration and are capable of processing poorly sorted feeds. As with other methods, however, recovery is related to the degree of previous sizing. Sluice design can be quite complex but usually is a mat- ter of trial and error. Several basic principles typically apply. Width is determined by the maximum and minimum volume of water available, the size and quantity of over- size feed that must be transported, and the slope. Length depends principally on the character of the gold. Coarse gold and granular gold settle quickly and are easily held in the riffles, while fine gold and porous gold may be carried some distance by the current. Velocity of the water is controlled primarily by the slope. In general, the sluice should be con- structed and installed so that water flowing through the box will transport oversized material and prevent sand from packing the riffles. If the surface of the water flowing through the sluice is smooth, the bottom of the sluice is probably packed with sand, allowing little gold to be saved. The desired condi- tion occurs when waves form on the surface of the water flowing through the sluice, and these waves, along with the wave-forming ridges of material on the bottom of the sluice, migrate upstream. This indicates an eddying or boiling ac- tivity on the lee side of the ridges, which maximizes gold recovery and tailings transport. Consequently, the sluice attains maximum efficiency when riffle overloading is incipient. Sluices are generally considered to be high-capacity units, with a 12-in-wide sluice box capable of handling 15 yd 3 /h if sufficient water is available. A 24-in-wide sluice can handle up to 40 yd 3 /h, and 48-in-wide sluices have reportedly processed up to 200 yd 3 /h. Of course, a sluice will handle as much gravel as the operator wants to push through it. However, to ensure reasonable recovery, capacity is limited by box width and slope, water availability, and feed characteristics. Feed slurry densities are highly variable and range from 1% to 35% solids by weight, averaging 10%. Water use can be reduced significantly if the larger of the oversize is eliminated from the feed. Sluices require no power to operate unless a pump is needed to transport water or slurry. One disadvantage of the sluice is the necessity to halt operations in order to recover concentrates. SPIRAL CONCENTRATORS Spirals are used infrequently in the western United States but may be applicable for certain types of feed. These gravity separation devices exhibit several desirable features. They accept sized slurry directly, and require no energy to operate other than perhaps pumps for material feed. Pumps can be excluded if gravity feed is used. Selec- tivity is high because of adjustable splitters within the slurry flow. Spirals can be used to produce a bulk concen- trate, scavenge valuable minerals from tailings, or in some instances, recover a finished concentrate. The ability to pro- duce a finished concentrate will be limited to feeds that con- tain a higher concentration of desired product than typically found in most gold placer feeds. To save space, two or three spiral starts are constructed around a common vertical pipe. This arrangement takes lit- tle floor space, allowing banks of multiple units to be set up for large-capacity requirements. In this situation, slurry distributors are required to sectionalize feed for individual spirals. Maximum feed rates vary according to feed particle den- sity, size, and shape. Rates generally range from 1.0 to 1.4 yd 3 /h roughing down to 0.3 to 0.5 yd 3 /h cleaning per start. Feed slurry density is typically less than 25% solids by weight, necessitating the use of larger pumps than needed for jigs or tables. TABLE CONCENTRATORS Concentrating tables (shaking tables) are one of the oldest methods of mechanical gravity concentration. Although capable of handling a variety of feed types and sizes, their optimum use is wet gravity cleaning of fine con- centrates ranging from 15 jum to 1/8 in. The unit consists of a large, flat, smooth table, slightly tilted, with riffles at- tached to the surface. A longitudinal reciprocating motion is introduced to the deck by means of a vibrating mechanism or an eccentric head action. Although limited in capacity, tables have the advantage of being easily adjustable by regulating the quantity of wash water and altering the tilt angle of the deck. The results of these changes are immediately observable on the table. With the addition of splitters, efficient control of high-grade concentrate recovery, middling recovery, and tailings pro- duction is possible. Solids content for table feeds averages approximately 25% by weight. Stroke length and speed are adjusted ac- cording to feed. Long strokes at slow speeds are used for coarse feeds; fine material responds better to short strokes at higher speeds. A reciprocating speed of 280 to 380 strokes/min will handle most feeds. Table capacities range from 0.05 to 8 yd 3 /h and depend on desired product as well as equipment size. TROMMELS This machine is the most common size classification device used in gold placer mills and is well suited for this task if properly designed. Trommels consist of a long rotating cylinder that is typically divided into two sections. In the first section, lengths of angle iron or similar material are fastened to the inside of the rotating drum. These act as lifters to carry feed up the side of the rotating cylinder. As material reaches the top of the rotation, it falls back to the bottom of the cylinder and breaks upon impact. This action, along with water introduced under pressure, serves to break up compacted soils and clays, and liberate valuable minerals. The second section consists of perforations in the cylinder walls positioned along the length of the drum. Typically, perforation size will graduate from 1/8 in, to 3/16 in, to 1/4 in as the feed progresses down the trommel. Sized fractions are drawn directly below the section of the trommel in which they are separated. They generally flow to either a vibrating screen to be sized further or to a gravity separation device. Oversize material is discharged out the end of the trommel as waste. Trommels are particularly well adapted to placer feeds because of their ability to handle a diversity of feed sizes and to break up material in the scrubber section. Capacity ranges from 10 to 500 yd 3 /h and is dependent on feed characteristics, screen perforation sizes, and machine size. Water requirements are contingent upon the amount of washing desired. 10 VIBRATING SCREENS Vibrating screens are often used for secondary size classification in circuits treating alluvial ores and, in some cast's, may provide primary sizing. The machines consist of a deck, or decks, containing inclined screening surfaces that are vibrated in either a rectilinear or elliptical motion. Screening medium can be woven wire cloth, parallel bars, or punched sheet metal. High capacity, ease of installation, and reasonable operating costs have all contributed to the popularity of vibrating screens. The practical minimum size limitation for production screens is about 100 mesh, although 325-mesh separations have been achieved. Capacity is, of course, dependent on many factors. These include type of material, amount of oversize, amount of undersize, moisture content, particle shape, screen opening size, and screen medium. In general, from 0.40 to 0.75 ft 2 of screen surface area will be needed for every cubic yard of feed handled per hour. SAMPLE MILL DESIGN It is not possible to provide complete instruction on mill design within the constraints of this manual. Mills must be planned with the intention of treating the size, shape, and grade characteristics of a specific feed. Sample gold mill flowsheets shown in figures 1, 2, and 3 are included to aid the evaluator in cost estimation only. They are provided to demonstrate that, in most instances, material will have to be fed, washed, sized, and separated for proper recovery. Tables 1, 2, and 3 provide sample material balances for these mills. Table 1. — Sample material balance, sluice mill (Specific gravity: Gold, 17.50; waste, 2.81) Feed Concentrate Feed Concentrate Tails Rate yd 3 /d. . 120 0.1 119.9 Composition wt%.. 100 0.08 99.92 Specific gravity 2.81 2.82 2.81 Grade trozAu/yd 3 .. 0.040 42.24 0.005 Gold distribution: tr oz/d 4.8 4.224 0.576 °/o 100 88 12 Table 2.— Sample material balance, jig mill (Specific gravity: Gold, 17.50; waste, 2.65) Tails Rate yd 3 /d.. 700 0.1 699.9 Composition wt %. . 100 0.01 99.99 Specific gravity 2.65 2.71 2.65 Grade trozAu/yd 3 .. 0.030 199.50 0.002 Gold distribution: tr oz/d 21.0 19.95 1.05 % 100 95 5 Table 3.— Sample material balance, table mill (Specific gravity: Gold, 17.50; waste, 2.73) Rate yd 3 /d . Composition wt % . Specific gravity Grade tr oz Au/yd 3 . Gold distribution: tr oz/d Feed Concentrate Tails 250 100 2.73 0.045 0.2 0.08 2.75 53.44 249.8 99.92 2.73 0.002 11.25 100 10.688 95 0.562 5 10-st capacity rear-dump truck Oversize 4- Plus 0.5 in (7.5 yd 3 /h) Conveyor Dump Tails (4.49 yd 3 /h) Mine-run gravel (12 yd 3 /h) I Feed hopper Feed belt Trommel Minus 0.5 in (4.5 yd 3 /h) Sluice Concentrates (0.01 yd 3 /h) Panning Gold product (200 gpm) -> Water Settling pond Pump Recycled water Figure 1.— Sample flow sheet, sluice mill. Dragline 11 Plus 4 in (5 yd 3 /h) Plus 1.5 in (20 yd 3 /h) ' Waste (28 yd 3 /h) Scavenger sluice Gold product Waste (1.5 yd 3 /h) Black sand (0.49 yd 3 /h) Mine-run gravel (70 yd 3 /h) Grizzly (800 gpm) Minus 4 in Vibrating screen Minus 0.5 in (30 yd 3 /h) Jig sump Jig pump Dewatering bin Cleaner jig Gold and black sands (0.5 yd 3 /h) I Final jig Concentrate (0.01 yd 3 /h) I Panning Gold product Minus 1.5 to plus 0.5 in (15 yd 3 /h) Sluice Waste (15 yd 3 /h)' Plus 0.5-in nuggets — fe Sluice Minus 0.5-in nuggets h -^ Rougher jig Jig tray ^ w Min I js 0.125-in concen (2 yd 3 /h) I Plus 0.125-in nuggets trate Gold product -► Water Settling pond Pump Recycled water Dump Figure 2.— Sample flow sheet, jig mi 12 Bulldozer Mine-run gravel (25 yd 3 /h) Oversize (8.25 yd 3 /h) Conveyor r Minus 0.25 in (5.25 yd 3 /h) Feed hopper Feed belt Trommel Minus 0.125 in (5 yd 3 /h) (500 gpm) +\ Minus 0.0625 in (6.5 yd 3 /h) Waste "(0.49 yd 3 /h) Conveyor Waste (0.49 yd 3 h) Coarse sluice Concentrate (0.1 yd 3 /h) Coarse table 4_^\ Middling sluice r\ * Concentrate (0.2 yd 3 /h) Middling table — >«- Concentrates (0.01 yd 3 /h) y\ Panning Fines sluice Fines table Oversize (14.75 yd 3 /h)~ Concentrates ' (0.01 yd 3 /h) r\ \ + ». Tails (15.25 yd 3 /h) Concentrate (0.2 yd 3 /h) Vibrating screen Minus 0.125 in (0.5 yd 3 /h) I Fines sluice Gold product I Waste (0.49 yd 3 /h) I Settling pond Pump Dump Recycled water- Figure 3.— Sample flow sheet, table mill. 13 SUPPLEMENTAL SYSTEMS Commonly neglected in costing and design work, sup- plemental systems gain importance in placer operations. Because of the relative low cost of placer mining and mill- ing equipment and systems, the expenses associated with supplemental items represent a larger percentage of the total cost than with other types of mining. For costing pur- poses, any system, structure, or equipment not directly related to production but necessary for continued operation is categorized as supplemental. These include 1. Buildings. 2. Camp facilities. 3. General services and lost time. 4. Generators. 5. Pumps. 6. Settling ponds. Each item included in the supplemental section should be examined to determine if it is needed at a particular operation. To aid in this determination and to assist in cost estimation of supplemental items, the following informa- tion will prove helpful: 1. Location and elevation of available water in reference to the millsite. 2. Ecological sensitivity of the area. 3. An estimate of the number and capacity of pumps needed. 4. Maximum hourly capacity of mill. 5. Building requirements. 6. An estimate of workforce size. BUILDINGS Many placer operators consider any building to be a lux- ury; however, if weather is a factor or if operators desire to safely store equipment, some buildings will be needed. Typically, a small placer mine will have one structure that serves as a shop, a concentrate cleanup area, and a storage room. More elaborate operations, or those in areas of bad weather, will cover the mill and often construct several small storage sheds. These buildings are usually temporary structures of minimal dimensions constructed of wood or metal. The size of each building must be estimated for costing purposes. For the typical operation, the main structure will be capable of housing the largest piece of mobile equipment at the mine with enough additional room for maintenance work. Shops often have concrete floors, and power and water facilities are typically provided. Storage sheds are usually of minimum quality, have a wood floor if any at all, and often contain power for lighting. Factors for all these variables are provided in the building cost estimation curve. by the workers in their trailers with an allowance provided for the cost of food. To calculate the expense of camp facilities, it is necessary to estimate the number of people staying at the mine. Guidelines for this estimate are provided with the cost equations in section 2 of this report. It must be remembered that the number of people working at any one operation can be quite variable, and if the number of in- tended or actual employees is available, this figure must be used. GENERAL SERVICES AND LOST TIME Compared with other methods of mineral recovery, placer mining is relatively inefficient. Because of limits in workforce size, delays and tasks not directly related to min- ing have a noticeable effect on productivity. This inefficiency strongly influences costs associated with placer mining, and must be taken into account. In placer mining, most costs associated with inefficiency can be attributed to three distinct areas: 1. Equipment downtime. 2. Site maintenance. 3. Concentrate refinement. Specific expenses can be further delineated. 1. Equipment downtime. A. Productivity lost by the entire crew because of breakdown of key pieces of equipment. B. Productivity lost by individual operators because of breakdown of single pieces of equipment. C. Labor charges of outside maintenance personnel. 2. Site maintenance. A. Road maintenance. B. Stream diversion. C. Drainage ditch construction and maintenance. D. Site cleanup. E. Reclamation grading and recontouring. F. Settling pond maintenance. G. Mill relocation. 3. Concentrate refinement. A. Concentrate panning. B. Mechanical separation. C. Amalgamation. Estimates indicate that in placer mining up to 37% of the total labor effort is spent on the above tasks. The lost time and general services cost curve must be used in all placer mine cost estimates. GENERATORS CAMP FACILITIES The provision of facilities for workers is an important part of placer operations. In most situations, workers will stay at the site during the mining season to take advan- tage of good weather. The needs of these workers must be met, and that typically involves providing living quarters and food. In almost all cases, employee housing at placer mines consists of mobile homes or trailers with a minimum amount of support equipment. Cooking is generally done In all but the most simple gravity separation mills, power will be needed to operate equipment. A minor amount of power will also be required for camp functions. Typically, power is provided by one of three sources: 1. Individual diesel engines driving each piece of equipment. 2. Diesel generators. 3. Electrical power brought in through transmission lines. The third source generally requires excessive initial capital expenditures. Transmission lines are considered only 14 when the mill capacity is well over 200 ydVh, existing transmission lines are located near the site, or the mine life is expected to be 15 yr or more. Power source selection should be based on lowest overall cost and minimum en- vironmental impact. For most small- to medium-sized gravity separation mills in remote locations, diesel generators are selected to provide power. Cost estimation curves in this report are based on diesel generators providing all power to mill equipment. Electric power costs contained in individual processing equipment operating cost curves account for diesel generator operating costs. PUMPS Water, used to wash gravel and to initiate slurrying of the feed, is typically introduced as gravel enters the trom- mel or screen. More water is added as needed throughout the circuit to dilute the slurry or assist in washing. To pro- vide adequate washing, this water must be introduced under pressure which, in many cases, necessitates the use of pumps. Pumps will also be needed if mill water is to be recycled through settling ponds. Under certain cir- cumstances, one pump can handle all tasks required in a placer processing plant utilizing recycled water. It is preferable to minimize the use of pumps by taking advan- tage of gravity. Water use is dependent on several factors, including 1. Washing required to properly slurry feed. 2. Type of separation equipment used. 3. Availability of water. 4. Size and nature of valuable mineral constituents. For costing purposes, the evaluator must estimate the volume of water pumped per minute and the pumping head. A separate estimate must be made for each pump. Water requirements can either be calculated using parameters given in the processing portion of section 1, or roughly estimated using the following equation: Water consumption (gpm) = 94.089(X) 0546 , where X = maximum cubic yards of mill feed handled per hour. This equation provides the total gallons of water per minute consumed by the mill. Although not technically ac- curate, for the purposes of this report, head may be estimated as the elevation difference between the pipe outlet at the mill or upper settling pond, and the pump intake. SETTLING PONDS With the current level of environmental awareness, it is almost assured that mill water will have to be treated prior to discharge. Placer mines typically recycle mill ef- fluent through one or more settling ponds to control en- vironmental impact. To calculate the cost of settling pond construction using this report, only the maximum mill feed rate is required. Cost curves provide the construction expense of unlined ponds sized to comply with most regulations. In some in- stances, the pond will have to be lined with an impervious material. This is often required in ecologically sensitive areas, or in situations where underlying soils do not properly filter mill effluent, thereby increasing the turbidity of nearby streams. A factor is provided in the settling pond cost curve for impervious linings. ENVIRONMENT Enviromental costs are often decisive in placer mine economic feasibility. Costs associated with water quality control and aesthetics are inescapable and can represent a significant percentage of total mining expenses. Methods to minimize ecological disturbance are now considered an integral function of the mining sequence and are treated as such in cost estimation. Stream siltation from mill effluent and land disturbance from excavation are the main environmental problems fac- ing placer miners. Reduction of water quality is often the biggest problem, and many techniques have been devised to lessen the impact caused by mill operation. One method involves limiting mill operation to short periods of time, thus allowing effluent to disperse before additional mill discharge is introduced. Often the mill is designed with the intent of using as little water as possible for valuable mineral separation. The most common solution is mill water recirculation facilitated by the construction of settling ponds. These ponds are used to hold mill effluent until par- ticulate matter has settled; water from the ponds is then reused in the mill circuit. Mining of alluvial deposits necessitates disturbance of large areas of land. Typically all trees, brush, grasses, and ground cover will be cleared. This task alone may present a major stumbling block, because some States restrict open burning. Next, a layer of overburden is removed to expose the deposit. Finally, the valuable mineral-bearing gravel can be excavated. Current technology suggests that control of land dis- turbance be incorporated into the mining sequence. Mill tailings and oversize are typically dumped back into worked-out areas. Soil cover and overburden are removed just prior to pay gravel excavation, then hauled to mined- out areas to be graded and contoured over replaced tails. Often the surface is revegetated. In most instances, the operator will have no choice but to implement ecological control and reclamation procedures. Operators are typically required to post a bond to cover the cost of reclaiming mined lands, and if the surface is left disturbed, these bonds will be forfeited. Regulations vary from State to State, and may appear difficult and confusing at first; however, by contacting in- formation services at State capitals, operators will be directed to the agencies concerned. These agencies will detail regulations concerning placer operation and will also point out which Federal agencies might be involved (U.S. Forest Service or U.S. Bureau of Land Management). In most instances, contact will have to be made with both State 15 and Federal agencies. Typically, meeting environmental re- quirements for the State will satisfy Federal regulations. As stated earlier, environmental control is an integral part of mine and mill design, and costs are treated accord- ingly. Equations are provided for calculating the cost of mill tails and oversize placement. Expenses associated with grading and contouring are contained in the lost time and general services curve. An equation is also provided for the construction of settling ponds, if water is to be recycled. Bond costs are not included since requirements are highly variable. One other cost may arise that is not covered in section 2. This is the expense of replanting, and usually ranges from $100 to $200 per acre. COST ESTIMATION After selecting exploration, mining, milling, and sup- plemental techniques, the next step in cost estimation is the choice of appropriate cost curves. If the evaluator has completed the mine design prior to attempting cost estima- tion, this task consists of simply going through section 2 of this report and selecting the proper equations. The list of capital and operating categories at the beginning of sec- tion 2 will aid in choosing individual curves. Costs used in deriving the estimation equations were collected from several sources. These include 1. Placer mine operators. 2. Mine equipment suppliers. 3. Published cost information services. In all cases, cost figures quoted in the text and points used in cost equation derivations are averages of all data available. A bibliography of cost information publications follows section 2. Many of these sources contain both cost and capacity information and can be used to supplement this manual. Cost estimation methodology in this handbook is based on the Bureau's Cost Estimation System (CES), first published in 1977 as "Capital and Operating Cost Estima- tion System Handbook," by STRAAM Engineers, Inc. Pro- cedures for cost estimation using this report closely follow that publication. The cost estimation portion of this report is divided into operating and capital costs. Cost equations are similar for both with the only difference appearing in the units of the final answer. Capital costs are given in total dollars expended and operating costs in dollars per year. Using the appropriate curves, a separate cost is calculated for each capital and operating cost item. Only costs directly associated with the operation under evalua- tion need be calculated. All other cost items should be ig- nored. After calculation, item costs should be entered on the respective capital and operating cost summary forms (see figures 5 and 6 in section 2). Upon summation of individual expenses, a contingency may be added to both capital and operating costs. It is dif- ficult to anticipate every condition that may arise at a par- ticular operation, and the purpose of the contingency is to account for unforeseen expenditures. This figure is typically based on the degree of certainty of the evaluation in rela- tion to available information, and ranges from 10% to 20%. Cost per cubic yard of pay gravel processed is deter- mined by dividing the sum of all annual operating costs by the total amount of pay gravel processed per year. Summa- tion of individual capital expenditures produces the total capital cost. Use of the individual curves is described in the follow- ing paragraphs. COST EQUATIONS Capital and operating costs are divided into labor, equip- ment, and supply categories. One, two, or all three of these categories will be present in each cost equation. The sum of costs from each of these categories provides the total cost for any single cost item. To facilitate cost adjustments respective to specific dates, the labor, equipment, and supply classifications are further broken down into subcategories. Typically, each cost item will have a number of site ad- justment factors. These are provided to account for characteristics specific to a particular deposit. These fac- tors determine the precision of the final cost, so they must be selected and used carefully. Assistance in determining the correct use of a factor, or in understanding the parameters involved in a cost item, may be found in the preceding pages. To further improve cost estimates, labor rates are also adjustable. Rates can vary greatly for small placer opera- tions. For this reason, adjustments can be made to the fixed rates used in this report for specific known rates at in- dividual operations. COST DATE ADJUSTMENTS All cost equations were calculated in January 1985 dollars. Costs calculated for any particular cost item are broken down into specific categories and subcategories to facilitate adjustment to specific dates. These include Labor. 1. Mine labor. 2. Processing labor. 3. Repair labor. Equipment. 1. Equipment and equipment parts. 2. Fuel and lubrication. 3. Electricity. 4. Tires. Supplies. 1. Steel items. 2. Explosives. 3. Timber. 4. Construction materials. 5. Industrial materials. For placer mining, most general maintenance and non- overhaul repairs are accomplished by the equipment operator, so repair labor rates are assumed to be equal to those of the operator. If information available to the evaluator indicates that this is not the case, repair labor 16 portions of the total labor cost are stated to facilitate adjustment. Equipment operating costs are broken down into respec- tive percentages contributed by parts, fuel and lubrication, electricity, and tires. These percentages, listed immediately following the cost equations, are used to calculate specific costs for each subcategory so that they may be updated. Supply costs are broken down and handled in a similar manner. Cost date indexes for the preceding subcategories are provided in table 4. These and other cost indexes are up- dated every 6 months and are available from the Bureau of Mines, Western Field Operations Center, East 360 Third Avenue, Spokane, WA 99202. To adjust a cost to a specific date, divide the index for that date by the index for January 1985, and multiply the resulting quotient by the cost calculated for the respective subcategory. An example of such an update follows. Example Cost Update Calculate the cost in July 1985 dollars of extracting and moving pay gravel 300 ft over level terrain using bulldozers. Assume a 200-LCY/h operation, and use the operating cost equations provided in the operating costs— mining- bulldozers portion of section 2. Operating costs per LCY (from section 2): Equipment operating cost 0.993(200)"° 43 ° Labor operating cost 14.01 (200)"° 945 January 1 985 total Subcategory costs per LCY (from section 2): Equipment parts Fuel and lubrication Operator labor Repair labor 0.47 0.53 0.86 0.14 $0,102 $0,102 $0,094 $0,094 $0,102 .094 .196 $0,048 $0,054 $0,081 $0,013 Update indexes Subcategory July 85/Jan. 85 Quotient (from table 4): Equipment parts Equipment Fuel and lubrication . Fuel Operator labor Mine labor Repair labor Mine labor Updated costs per LCY: Equipment parts Fuel and lubrication Operator labor Repair labor July 1985 total cost per LCY. 362.3/360.4 630.7/636.2 $11.98/$11.69 $11.98/$11.69 1.005 x $0,048 0.991 x $0,054 1.025 x $0,081 1.025 x $0,013 1.005 0.991 1.025 1.025 $0,048 .054 .083 .013 .198 SITE ADJUSTMENT FACTORS As stated earlier, adjustment factors determine the precision for cost estimates and must be used carefully. Several factors are provided for each curve, and their use will significantly alter the calculated cost. The following example illustrates factor use. Example Adjustment Factor Application Calculate the cost of extracting pay gravel in a hard dig- ging situation and moving it 800 ft up an 8% gradient us- ing bulldozers. Assume a 200-LCY/h operation (January 1985 dollars), and use the operating cost and adjustment factor equations provided in the operating costs— mining- bulldozers portion of section 2. Operating costs per LCY (from section 2): Equipment operating cost 0.993(200)"° 43 ° = $0,102 Labor operating cost 14.01 (200)"° 945 = .094 January 1985 total 196 Factors (from section 2): Distance F = 0.00581(800)° 9 ° 4 = 2.447 Gradient F c = i.041el°° 15 < 80) l = 1.174 Digging difficulty 1 .670 Used equipment: Equipment U„ = 1 .206(200)"° ° 13 = 1.126 Labor U, = 0.967(200)° ° 15 = 1 .047 Factored cost per LCY: From total cost equation for bulldozers: [$0,102(1.126) + $0,094(1.047)] x 2.447 x 1.174 x 1.670 = January 1985 total cost per LCY $1 .023 The 500% increase in operating cost, from $0,196 to $1,023 per loose cubic yard, demonstrates the dramatic ef- fect of using the proper factors. If a cost category contains a factor not applicable to the deposit in question, then simply leave that factor out of the total cost equation. The variables inserted in the factor equations are generally self-evident. An exception to this is the digging difficulty factor. Parameters for this factor are based on the following: 1. Easy digging.— Unpacked earth, sand, and gravel. 2. Medium digging.— Packed earth, sand, and gravel, dry clay, and soil with less than 25% rock content. 3. Medium to hard digging.— Hard packed soil, soil with up to 50% rock content, and gravel with cobbles. 4. Hard digging.— Soil with up to 75% rock content, gravel with boulders, and cemented gravels. It can be seen from these parameters that many deposits will fall into one of the last two categories. Digging difficulty has a dramatic effect on the cost of extraction, so these fac- tors must be chosen carefully. Bulldozer and backhoe curves both contain a digging difficulty factor. Other excavation equipment, such as draglines, scrapers, and front-end loaders, are generally suited for special digging conditions and are not used in harder ground. Consequently, no digging difficulty factor is provided for these. 17 Table 4.— Cost date indexes 1 Mining labor 2 Equip- ment and repair parts Fuel and lubrication Elec- tricity Tires Bits and steel Explo- sives Tim- ber Construc- tion ma- terial 3 1 Unless otherwise noted, based on U.S. Bureau of Labor Statistics (BLS) "Producer Price Indexes,' 2 Based on BLS "Employment and Earnings: Average Hourly Earnings, Mining." 3 Based on Engineering and News Record "Market Trends: Building Cost." 4 January. 5 July. 6 January (base cost year for this report). base year 1967 100. Indus- trial material 1960 . $2.61 85.8 95.5 100.1 113.1 97.1 94.5 92.1 99 95.3 1961 . 2.64 87.3 97.2 100.7 109.9 97.2 97.0 87.4 97 94.8 1962 . 2.70 87.5 96.1 101.9 94.7 95.8 97.0 89.0 96 94.8 1963 . 2.75 89.0 95.1 101.1 96.9 95.7 100.4 91.2 98 94.7 1964 . 2.81 91.2 90.7 100.3 97.6 97.0 100.0 92.9 98 95.2 1965 2.92 93.6 92.8 100.3 98.8 97.9 99.6 94.0 97 96.4 1966 . 3.05 96.5 97.4 99.8 101.3 98.7 98.1 100.1 99 98.5 1967 . 3.19 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100 100.0 1968 . 3.35 105.7 98.1 100.9 102.7 101.9 102.3 117.4 127 102.5 1969 . 3.61 110.4 99.6 102.2 98.3 107.0 104.7 131.6 108 106.0 1970 . 3.85 115.9 101.0 106.6 105.4 115.1 106.7 113.7 109 110.0 1971 . 4.06 121.4 106.8 115.5 110.3 121.8 113.3 135.5 133 114.0 1972 . 4.41 125.7 108.9 123.9 111.3 128.4 115.2 159.4 151 117.9 1973 . 4.73 130.7 128.6 132.6 115.7 136.2 120.1 205.2 154 125.9 1974 . 5.21 152.3 223.4 172.3 141.6 178.6 150.0 207.1 167 153.8 1975 . 5.90 185.2 257.5 209.7 155.4 200.9 178.0 192.5 186.3 171.5 1976 . 6.42 198.9 276.6 226.7 172.8 215.9 187.2 233.0 205.5 182.4 1977 . 6.88 213.7 308.1 257.0 181.5 230.3 193.1 276.5 237.7 195.1 1978 . 7.67 232.8 321.0 279.5 192.0 253.5 208.7 322.1 247.7 209.4 1979 . 8.50 256.2 444.8 305.3 219.6 283.5 225.6 354.3 269.28 236.5 1980" 8.70 275.4 582.4 334.8 236.9 297.3 237.1 336.3 280.86 260.3 1980s 9.08 290.9 693.3 376.0 250.4 300.4 254.4 327.3 289.05 275.6 1981" 9.78 304.9 736.0 393.9 256.2 322.8 268.5 331.6 298.25 289.9 1981 s 10.07 324.0 818.4 429.9 269.6 338.7 292.8 330.1 312.11 306.0 1982 4 10.58 337.0 802.9 454.0 271.6 343.1 293.2 310.6 324.74 311.7 1982 s 10.91 346.1 777.1 471.5 272.6 337.4 294.8 319.2 330.56 313.0 1983" 11.10 348.6 727.1 482.6 285.4 333.2 300.4 324.2 342.01 314.0 1983 5 11.31 352.7 694.9 492.2 256.6 341.3 302.8 372.5 357.28 316.6 1984 4 11.56 354.3 669.7 492.0 258.0 354.1 301.3 353.2 355.52 319.2 19845 11.62 358.2 674.6 525.5 256.3 357.2 312.4 343.3 357.90 324.0 1985 6 11.69 360.4 636.2 524.9 262.0 357.4 313.4 343.2 358.32 323.2 1985 5 11.98 362.3 630.7 540.3 246.0 354.6 312.1 354.9 363.63 324.3 LABOR RATES The cost of labor in placer mining is highly variable and cannot be precisely estimated in every case. For the pur- poses of this report, only two separate labor rates are used: $15.69/h for mining functions, and $15.60/h for milling. These rates apply to operation, maintenance, installation, and construction labor. The labor portions of each specific cost category are broken out and in this way can be adjusted to the estimator's particular labor rate. To accomplish this, multiply the labor cost for each category by the ratio of desired labor rate to mining or milling labor rate ($15.69/h or $15.60/h). The following example illustrates this adjustment. Example Labor Rate Adjustment Calculate the cost of extracting and moving pay gravel 300 ft over level terrain using bulldozers with an operator labor cost of $18.00/h. Assume a 200-LCY/h operation ( January 1985 dollars), and use the operating cost equations provided in the operating costs— mining-bulldozers portion of section 2. Operating costs per LCY (from section 2): Equipment operating cost 0.993(200)"° 430 Labor operating cost 14.01(200)° 945 January 1985 total Labor adjustment: Labor operating cost per LCY ($1 8.00/$1 5.69) x $0,094 Adjusted cost per LCY: Equipment operating cost Labor operating cost January 1985 total cost per LCY $0,102 .094 .196 .108 .102 .108 .210 Labor rates are based on wage scales for the western United States (including Alaska) and include a 24% burden. This burden consists of 9.8% workers compensation in- surance, 7.0% Social Security tax, 3.7% State unemploy- ment insurance, and 3.5% Federal unemployment tax. If other costs such as health and retirement benefits are to be included, they must be added to an estimated labor rate. To familiarize the reader with the use of this cost estimating system, an example of a complete cost estimate is included in the appendix. is FINANCIAL ANALYSIS The purpose of this report is to provide an estimate of capital and operating costs for small placer mines. A distinc- t ion must be made between a cost estimate and an economic feasibility analysis. Capital and operating costs are simply two separate variables in a complete economic analysis. To determine the economic feasibility of an operation, the evaluator must consider each of the following: 1. Recoverable value of commodity. 2. Local, State, and Federal taxes. 3. Capital depreciation. 4. Depletion allowances. 5. Desired return on investment. 6. Costs and methods of project financing. 7. Inflation. 8. Escalation. 9. Environmental intangibles. Economic feasibility analysis is a subject in itself, and will not be covered here. The preceding list is included to emphasize the following: A prospect is not economically feasible simply because the apparent commodity value ex- ceeds the total capital and accrued operating costs calculated from this manual. The costs associated with the preceding list are real and must be considered when determining the feasibility of a prospect. Any attempt to provide guidelines for determina- tion of feasibility based solely on estimates of capital and operating costs would be highly misleading. There is no quick and easy way to account for the wide variety of situa- tions encountered in economic analysis. Each one of the preceding items must be examined individually to provide accurate economic feasibility estimates, and a complete cash-flow analysis is the only way to ensure that proper results are obtained. To accomplish this, all yearly income and expenses must be tabulated. Then the rate of return over time must be calculated from the resultant profits or losses. The evaluator must consider all factors influencing income and include all expenses as well as account for the value of money over time and choose an acceptable rate of return. In brief, the operator will have to receive adequate revenues from commodities recovered to 1. Cover all operating expenses. 2. Recover initial equipment expenditures. 3. Provide for equipment replacement. 4. Cover all exploration and development costs. 5. Pay taxes. 6. Compensate for inflation and cost escalation. 7. Supply a reasonable profit. Only when enough revenue is produced to cover all of the above can an operation be considered economically feasible. BIBLIOGRAPHY Adorjan, L.A. Mineral Processing. Paper in Mining Annual Review 1984. Min. J. (London), 1984, pp. 217-219. Bertoldi, M.J. Preliminary Economics of Mining a Thick Coal Seam by Dragline, Shovel-Truck, and Scraper Mining Systems. BuMines IC 8761, 1977, 27 pp. Daily, A. Valuation of Large, Gold-Bearing Placers. Eng. and Min. J., v. 163, No. 7, July 1962, pp. 80-88. Earll, F.N., K.S. Stout, G.G. Griswald, Jr., R.I. Smith, F.H. Kelly, D.J. Emblen, W.A. Vine, and D.H. Dahlem. Handbook for Small Mining Enterprises. MT Bur. Mines and Geol. Bull. 99, 1976, 218 pp. Gardner, E.D., and P.T. Allsman. Power-Shovel and Dragline Placer Mining. BuMines IC 7013, 1938, 68 pp. Jarrett, B.M. Development Document for Final Effluent Limita- tions Guidelines and New Source Performance Standards for the Ore Mining and Dressing Point Source Category. U.S. EPA Docu- ment 440/1-82/061, 1982, 656 pp. Levell, J.H., V.V. Thornsberry, W.G. Salisbury, and D.A. Smith. 1983 Mineral Resource Studies: Kantishna Hills and Dunkle Mine Areas, Denali National Park and Preserve, Alaska. Volume II. Ap- pendix A (contract S0124031, Salisbury & Dietz, Inc.). BuMines OFR 129(2)-84, 1984, pp. 1-232. Macdonald, E.H. Alluvial Mining: The Geology, Technology, and Economics of Placers. Chapman and Hall (London), 1983, 508 pp. McLellan, R.R., R.D. Berkenkotter, R.C. Wilmot, and R.L. Stahl. Drilling and Sampling Tertiary Gold-Bearing Gravels at Badger Hill, Nevada County, Calif. BuMines RI 7935, 1974, 50 pp. Schumacher, O.L. Placer Gold— Production and Cost History of an Alaska Placer Gold Mine. Western Mine Eng.— Min. Cost Serv- ice reprint, Spokane, WA, 1985, 5 pp. Sharp, A. P., and A.D. Cook. Safety Practices in Churn Drilling at Morenci Branch, Phelps Dodge Corp., Morenci, Ariz. BuMines IC 7548, 1950, 22 pp. Stout, K.S. The Profitable Small Mine, Prospecting to Operation. McGraw-Hill, 1984, pp. 83-98. Taggart, A.F. Ores and Industrial Minerals. Sec. 11 in Handbook of Mineral Dressing. Wiley, 1945, 140 pp. Terrill, I. J., and J.B. Villar. Elements of High-Capacity Gravity Separation. CIM Bull, v. 68, No. 757, May 1975, pp. 94-101. Thoenen, J.R., and E.J. Lintner. Churn-Drill Performance. BuMines RI 4058, 1947, 48 pp. Thomas, B.I., D.J. Cook, E. Wolff, and W.H. Kerns. Placer Min- ing in Alaska: Methods and Costs at Operations Using Hydraulic and Mechanical Excavation Equipment With Non-Floating Washing Plants. BuMines IC 7926, 1959, 34 pp. West, J.M. How To Mine and Prospect for Placer Gold. BuMines IC 8517, 1971, 43 pp. Wilson, E.D. Gold Placers and Placering in Arizona. AZ Bur. Geol. and Min. Tech. Bull. 168, 1961, 124 pp. 19 SECTION 2.— COST ESTIMATION CAPITAL AND OPERATING COST CATEGORIES Section 2 contains equations for estimating capital and operating costs associated with placer mining. Equations are provided for the following items. Capital costs: Operating costs: Exploration: Overburden removal: Panning Bulldozers Churn drilling Draglines Bucket drilling Front-end loaders Trenching Rear-dump trucks General Scrapers reconnaissance Mining: Camp costs Backhoes Seismic surveying Bulldozers Rotary drilling Draglines Helicopter rental Front-end loaders Development: Rear-dump trucks Access roads Scrapers Clearing Processing: Preproduction Conveyors overburden removal: Feed hoppers Bulldozers Jig concentrators Draglines Sluices Front-end loaders Spiral concentrators Rear-dump trucks Table concentrators Scrapers Tailings removal: Mine equipment: Bulldozers Backhoes Draglines Bulldozers Front-end loaders Draglines Rear-dump trucks Front-end loaders Scrapers Rear-dump trucks Trommels Scrapers Vibrating screens Processing equipment: Supplemental: Conveyors Employee housing Feed hoppers Generators Jig concentrators Lost time and general Sluices services Spiral concentrators Pumps Table concentrators Trommels Vibrating screens Supplemental: Buildings Employee housing Generators Pumps Settling ponds Included in this section are summary forms (figs. 4-6) that may be used to aid in total capital and operating cost calculations. A bibliography of cost information sources is provided at the end of this section. The appendix contains a complete sample cost estima- tion. This sample will familiarize the reader with cost estimation techniques used in this report. 20 CAPITAL COSTS EXPLORATION Two methods are presented for calculating exploration o»t.- Method l allows tlie e\aluator to roughly estimate costs with a minimum of information. Method 2 requires a detailed exploration plan and provides the user with a much more precise cost. Method 1: If information concerning exploration of a deposit is not available, the following equation may be used to estimate an exploration capital cost. It must be em- phasized, however, that costs calculated from this equation can be very misleading, and it is recommended that a de- tailed exploration program be designed if possible and that costs be assigned using method 2. As stated in section 1, the amount of exploration re- quired is a highly variable function of many factors. This equation is based on estimated exploration costs for several successful placer operations, but these deposits may have little in common with the one being evaluated. The base equation is applied to the following variable: X == Total estimated resource, in bank cubic yards (BCY) Base Equation: Exploration capital costs . .Y c = 0.669(X) 0849 00,000 10,000 1 ,000 10, 300 100 000 1 ,000,000 10, ( XX TOTAL RESOURCE, bank cubic yards Exploration capital costs An exact breakdown of expenses included in this cost is not available. In general, exploration is a labor-intensive task. Unless the deposit is extremely remote, a large share of the exploration cost will be attributed to labor. If the deposit is remote, costs of access equipment (helicopters, etc.) will become a factor. Method 2: Excellent cost data for most exploration func- tions may be found in the Bureau's Cost Estimation System (CES) Handbook (IC 9142). Functions covered in that publication include Helicopter rental rates. Sample preparation and analysis costs. Drill capacities and costs for core, rotary, and hammer drills. Survey charges. Labor rates. Travel costs. Ground transportation costs. Field equipment costs. Geological, geophysical, and geochemical exploration technique costs. Costs directly related to placer mining from the above list are summarized in the following tabulations. Several items particular to placer mining are not covered in the CES Handbook. These items, for which costs follow, include Panning. Churn drilling. Bucket drilling. Trenching. CAPITAL COSTS 21 Exploration Cost Tabulations: As in the CES Hand- book, costs are given in dollars per unit processed (cubic yard, sample, foot drilled, etc.). The product of the unit cost and the total units processed constitutes the total capital cost for any particular method of exploration. Total explora- tion costs consist of the sum of these individual exploration method expenses. A summary sheet for these calculations is shown in figure 4. EXPLORATION-PANNING Average cost per sample $2.10 Cost range $1.90-$2.60 Cost variables Labor efficiency and material being panned. EXPLORATION-CHURN DRILLING Average cost per foot $45 Cost range $20-$70 Cost variables Depth of hole, material being drilled, site access, and local competition. EXPLORATION-BUCKET DRILLING Average cost per foot $9.20 Cost range $5-$20 Cost variables Depth of hole, material being drilled, and site access. EXPLORATION-TRENCHING Average cost per cubic yard $7.10 Cost range $2.25-$28.50 Cost variables Labor efficiency, material being sampled, site access, equipment owner- ship, sampling method, and total volume of work to be done. CES Exploration Cost Tabulations: Some of the more pertinent exploration cost items presented in the CES Hand- book (IC 9142) are summarized in the following. A de- tailed description of these items can be found in that publication. EXPLORATION-GENERAL RECONNAISSANCE Average cost per worker-day $195 Cost range $175-$210 Cost variables Deposit access, terrain, and labor efficiency. EXPLORATION-CAMP COSTS Average cost per worker-day $30 Cost range $19-$41 Cost variables Deposit remoteness, terrain, access, and climate. EXPLORATION-SEISMIC SURVEYING (REFRACTION) Average cost per linear foot $1.50 Cost range $1.00-$2.50 Cost variables Labor efficiency, deposit access, and terrain. EXPLORATION-ROTARY DRILLING Average cost per foot $6.50 Cost range $2.00-$11.50 Cost variables Depth of hole, material being drilled, and site access. EXPLORATION-HELICOPTER RENTAL Average cost per hour $395 Cost range $305-$590 Cost variables Passenger capacity, payload capacity, cruise speed, and range. EXPLORATION COST SUMMARY FORM Capital cost calculation: General reconnaissance . . worker-days x $ /worker-day Camp costs worker-days x $ /worker-day Panning samples x $ /pan Churn drilling ft drilled x $ /ft Bucket drilling ft drilled x $ /ft Trenching yd 3 x $ /yd 3 Seismic surveying linear ft x $ /linear ft Rotary drilling ft drilled x $ /ft Helicopter time h x $ /h x$ / x$ / x$ / x $ / x$ / x$ / x$ / x$ / Total Figure 4.— Exploration cost summary form. ■22 CAPITAL COSTS DEVELOPMENT— ACCESS ROADS Capital Cost Equation: This equation provides the cost per mile of road construction to the deposit and between various facilities. Costs include clearing and excavation, but do not account for any blasting or gravel surfacing that may be required. The equation is applied to the following variable: X = Average width of roadbed, in feet. The following assumptions were made in estimating road costs: 1. Side slope, 25 r /i. 3. Moderate digging 2. Moderate ground cover. difficulty. 100,000 Base Equation: Access road capital cost .Y c = 765.65(X)°- 922 The capital cost consists of 68% construction labor, 13% parts. I6 r /f fuel and lubricants, and 3% tire replacement. Brush Factor: The original equation is based on the assumption that ground cover consists of a mixture of brush and trees. If vegetation is light (i.e., consisting mainly of brush or grasses), the total cost per mile (covered with brush) must be multiplied by the factor obtained from the follow- ing equation: F B = 0.158(X) 0325 . Forest Factor: If ground cover is heavy (i.e., consisting mainly of trees), the total cost per mile (covered with trees) must be multiplied by the factor obtained from the follow- ing equation: F F = 2.000(X)-° 079 . Side Slope Factor: If average side slope of the terrain is other than 25%, the factor obtained from the following equation must be applied to the total cost per mile: P _ Q 633gl0. 021 (percent slope)] Surfacing Factor: If gravel surfacing is required, the cost per mile must be multiplied by the following factor to account for the additional labor, equipment, and supply costs: F G = 6.743. Blasting Factor: In hard-rock situations, blasting may be required. Should this be the case, the cost obtained from the following equation must be added to total access road cost. o 10,000 1 ,000 100 AVERAGE ROADBED WIDTH, feet Development capital costs - Access roads F H = [12,059. 18(X) 0534 ] x [miles of roadbed requiring blasting]. Total Cost: Access road capital cost is determined by [(Y c x F B x F F x F s x F G ) x total miles] + F H . This total cost is then entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 23 DEVELOPMENT— CLEARING Capital Cost Equation: This equation provides the total capital cost of clearing brush and timber from the sur- face of a deposit prior to mining. Costs include labor, equip- ment, and supplies required to completely strip the surface of growth, and to dispose of debris. The equation is applied to the following variable: X = Total acreage to be cleared. The following assumptions were made in estimating clearing costs: 1. Level slope. 2. Moderate ground cover. Base Equation: Clearing capital cost Y c = 1,043.61(X) 0913 The capital cost consists of 68% construction labor, 18% fuel and lubricants, 12% parts, and 2% steel supplies. Slope Factor: The original equation is based on the assumption that the slope of the surface overlying the deposit is nearly level. If some slope is present, the factor obtained from the following equation must be applied to the clearing capital cost: F = 942e' 0008(percent sl °P e " Brush Factor: Ground cover is assumed to consist of a mixture of brush and small trees. If the surface is covered with only brush and grasses, the following factor must be applied to the cost: F B = 0.250. Forest Factor: If the surface is forested, capital cost must be multiplied by the following factor: F F = 1.750. Total Cost: Clearing capital cost is determined by (Y„ x Fo x F„ x F ) v C S B x F'- This total cost is then entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. * ' 10 □ 1 00 000 T3 h- m D cr - i . nnn 10 100 TOTAL SURFRCE RRER, acres lopment capital costs - Clearing ,000 24 CAPITAL COSTS PREPRODUCTION OVERBURDEN REMOVAL— BULLDOZERS Capital Cost Equations: These equations provide the cost of excavating and relocating overburden using bulldozers. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by bulldozer. The base equations assume the following: 1. No ripping. 4. Dozing distance, 300 ft. 2. Cutting distance, 5. Average operator ability. 50 ft. 6. Nearly level gradient. 3. Efficiency, 50 min/h. Base Equations: Equipment operating cost Y E 0.993(X)-°- 430 Labor operating cost Y L = 14.0KX)- 0945 Equipment operating costs average 47% parts and 53% fuel and lubrication. Labor operating costs average 86% operator labor and 14% repair labor. Distance Factor: If the average dozing distance is other than 300 ft, the factor obtained from the following equa- tion must be applied to total cost per loose cubic yard: F D = 0.00581(distance) 0904 . Gradient Factor: If the average gradient is other than level, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F = 1 041e'°- 015 ' pera ' m K 1 ' adient, l Ripping Factor: If ripping is required, total operating cost must be multiplied by the following factor, this will account for reduced productivity associated with ripping: F D = 1.595. 0. 100 ^s. Equipment ^ Labor 10 100 1,000 CAPACITY, maximum loose cubic yards par hour Overburden removal capital costs - Bulldozers Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e Labor factor U, 1.206(X)- 0013 0.967(X) 0015 Digging Difficulty Factor: Parameters given in the discussion on site adjustment factors in section 1 should be used to determine if a digging difficulty factor is required. If so, one of the following should be applied to total cost per loose cubic yard: easy digging medium .0.830 F u , medium-hard digging 1.250 digging 1.000 F H , hard digging . . . 1.670 Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e ) + Y L (U,)] x F D x F G x F H x Fr . To obtain overburden removal capital cost, the total cost per loose cubic yard must be multiplied by total amount of overburden handled by bulldozer prior to production. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 25 PREPRODUCTION OVERBURDEN REMOVAL— DRAGLINES Capital Cost Equations: These equations provide the cost of excavating overburden using draglines. Costs are reported in dollars per loose cubic yard of overburden han- dled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by dragline. The base curves assume the following: I .000 Base Equations: Equipment operating costs.. x E Labor operating costs Y L = 12.19(X)-° 888 Y E = 1.984(X)-°- 390 Equipment operating costs consist of 67% parts and 33% fuel and lubrication. Labor operating costs consist of 78% operator labor and 22% repair labor. Swing Angle Factor: If the average swing angle is other than 90°, the factor obtained from the following equa- tion must be applied to the total cost per loose cubic yard: F s = 0.304 (swing angle) 0269 . 1. Bucket efficiency, 0.90. 3. Swing angle, 90°. (0 0.100 a 2. Full hoist. 4. Average operator ability. ^*"*-» Equipment ^ Lctoor 10 100 1,000 CAPACITY, maximum loose cubic yards per hour Overburden removal capital costs - Draglines Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U Labor factor U, = 1.162(X)-°- 017 = 0.989(X) 0006 Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e ) + Y L (U,)] x F s . To obtain the overburden removal capital cost, the total cost per loose cubic yard must be multiplied by the total amount of overburden handled by dragline prior to production. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 26 CAPITAL COSTS PREPRODUCTION OVERBURDEN REMOVAL— FRONT-END LOADERS Capital Cost Equations: These equations provide the cost of relocating overburden using wheel-type front-end loaders. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the tol lowing variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by front-end loader. The base equations assume the following: 1. Haul distance, 500 ft. 3. Inconsistent operation. 2. Rolling resistance, 4. Wheel-type loader, nearly level gradient. 1 .000 Base Equations: Equipment operating cost Labor operating cost . . . . Y E = 0.407(X)-0-225 Y L = 13.07(X)-°936 Equipment operating costs average 22% parts, 46% fuel and lubrication, and 32% tires. Labor operating costs average 90% operator labor and 10% repair labor. Distance Factor: If the average haul distance is other than 500 ft, the factor obtained from the following equa- tion must be applied to the total cost per loose cubic yard: » . 1 00 Equ 1 pmen t Labor 10 100 1,000 CRPRCITY, maximum loose cubic yards per hour Overburden removal capital costs - Front-end loaders F D = 0.023(distance) 0616 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%-, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F (i = 0.877e IOO46l P elct ' nt Biadicnt)|_ Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e = 1.162(X)-0-° 17 Labor factor U, = 0.989(X)°°°6 Track-Type Loader Factor: If track-type loaders are used, the following factors must be applied to the total cost obtained from the base equations: Equipment factor T e = 1.378 Labor factor T, = 1.073 Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e ) (T e ) + Y L (U,) (T,)] x F D x F G . To obtain the overburden removal capital cost, the total cost per loose cubic yard must be multiplied by the total amount of overburden handled by front-end loader prior to produc- tion. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 27 PREPRODUCTION OVERBURDEN REMOVAL— REAR-DUMP TRUCKS Capital Cost Equations: These equations provide the cost of hauling overburden using rear-dump trucks. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden, and tails moved hourly by rear- dump truck. The base equations assume the following: 1. Haul distance, 2,500 ft. 4. Average operator 2. Loader cycles to fill, 4. ability. 3. Efficiency, 50 min/h. 5. Rolling resistance, 2%, nearly level gradient. Base Equations: Equipment operating costs . . Y E = 0.602(X)-0-296 Labor operating cost Y L = 11.34(X)-°89i Equipment operating costs consist of 28% parts, 58% fuel and lubrication, and 14% tires. Labor operating costs con- sist of 82% operator labor and 18% repair labor. Distance Factor: If average haul distance is other than 2,500 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F D = 0.093(distance)0-3". Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: f = 0.907e[°' 049, P ercent gradient)I_ Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e = 0.984(X)°°ie Labor factor U, = 0.943(X)°-°2i Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e ) + Y L (U,)] x F D x F G . O.QIO ~~"* Equipment \ Labor 10 100 I ,000 CRPRCITY, maximum I oosa cubic yards per hour Overburden removal capital costs - Rear-dump trucks To obtain the overburden removal capital cost, the total cost per loose cubic yard must be multiplied by the total amount of overburden handled by truck prior to production. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 28 CAPITAL COSTS PREPRODUCTION OVERBURDEN REMOVAL— SCRAPERS Capital Cost Equations: These equations provide the cost of excavating and hauling overburden using scrapers. Costs are reported in dollars per loose cubic yard of over- burden handled. The equations are applied to the follow- ing variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by scraper. I .000 The base curves assume the following: Standard scrapers. 4. Average haul distance, Rolling resistance, 6%, 1,000 ft. nearly level gradient. 5. Average operator Efficiency, 50 min/h. ability. Base Equations: Equipment operating cost. .Y E Labor operating cost Y L 0.325(X)-"-2io 12.01(X)-0-93o Equipment operating costs consist of 28% parts, 58% fuel and lubrication, and 14% tires. Labor operating costs con- sist of 82% operator labor and 18% repair labor. Distance Factor: If average haul distance is other than 1,000 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F L) = 0.01947(distance) 0577 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 6%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F, = 0.776e IO047 'p < -' ra ' lU K^dK-ntu o.oio "— — Equipment x LobDr I 00 I , 000 CAPACITY , maximum loose cubic yards per hour Overburden removal capital costs - Scrapers Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e = 1.096(X)-oooe Labor factor U, = 0.845(X)°°34 Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e ) + Y L (U,)] x F D x F G . To obtain the overburden removal capital cost, the total cost per loose cubic yard must be multiplied by the total amount of overburden handled by scraper prior to production. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 29 MINE EQUIPMENT— BACKHOES Capital Cost Equation: This equation furnishes the cost of purchasing the appropriate number and size of hydraulic backhoes needed to provide the maximum re- quired production. Costs do not include transportation, sales tax, or discounts. The equation is applied to the following variable: X = Maximum loose cubic yards of pay gravel moved hourly by backhoe. The following capacities were used to calculate the base equation: 105 hp 95 to 200 LCY/h 135 hp 175 to 275 LCY/h 195 hp 250 to 375 LCY/h 325 hp 350 to 475 LCY/h These capacities are based on the following assumptions: Medium digging difficulty. Average operator ability. Swing angle, 60° to 90°. 4. Maximum digging depth, 0% to 50%. 5. No obstructions. to l_ a D b 100 000 a _l t— a. cr i n . nnn 10 1 00 I , 000 CAPACITY, maximum loose cubic yards per hour Mine equipment capital costs - Backhoes Base Equation: Equipment capital cost . . . Y c = 84,132.01e l000350(X)1 Equipment capital costs consist entirely of the equipment purchase price. Digging Depth Factor: If average digging depth is other than 50% of maximum depth obtainable for a par- ticular make of backhoe, the factor obtained from the follow- ing equation must be applied to total capital cost: F D = 0.04484(D)°™>, where D = percent of maximum digging depth. Used Equipment Factor: This factor accounts for the reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: Fu = 0.386. Digging Difficulty Factor: Parameters given in the discussion on site adjustment factors in section 1 should be used to determine if a digging difficulty factor is required. If so, one of the following should be applied to total capital cost: F H , easy digging . . 1.000 F H , medium-hard F H , medium digging 1.556 digging 1.330 F H , hard digging . . 1.822 Total Cost: Backhoe capital cost is determined by Y c x F D x Fu x F H . This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 30 CAPITAL COSTS MINE EQUIPMENT— BULLDOZERS Capital Cost Equation: This equation furnishes the cost of purchasing the appropriate size and number of crawler dozers needed to provide the maximum required production. Costs do not include transportation, sales tax, or discounts. The equation is applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden, and waste moved hourly by bulldozer. The following capacities were used to calculate the base equation: 65 hp 19.0 LCY/h 80 hp 31.5 LCY/h 105 hp 56.5 LCY/h 140 hp 82.0 LCY/h .000,000 200 hp 126.0 LCY/h 335 hp 263.5 LCY/h 460 hp 334.0 LCY/h 700 hp 497.5 LCY/h The above capacities are based on the following assumptions: 1. Straight "S" blades. 2. No ripping. 3. Average operator ability. 4. Cutting distance, 50 ft. 5. Dozing distance, 300 ft. 6. Efficiency, 50 min/h. 7. Even, nearly level gradient. 10,000 100 .0 CAPACITY, maximum I oosb cubic yards per hour Mine equiment capital costs - Bulldozers Base Equation: Equipment capital cost. .Y c = 3,555.96(X)0 806 Equipment capital costs consist entirely of equipment pur- chase price. Distance Factor: If average dozing distance is other than 300 ft, the factor obtained from the following equa- tion must be applied to capital costs. This will correct for the addition or reduction of equipment required to main- tain maximum capacity: F D = 0.01549(distance)o?32. Gradient Factor: If the average gradient is other than level, the factor obtained from the following equation must be applied to total capital cost. This will correct for the ad- dition or reduction of equipment required to maintain max- imum capacity. (Favorable haul gradients should be entered as negative, uphill haul gradients as positive.) P = 1.041e'°' 015, P ercent gradient!) Digging Difficulty Factor: Variations from the base digging difficulty will necessitate changes in equipment size to maintain production capacity. Parameters given in the discussion on site adjustment factors in section 1 should be used to determine if a digging difficulty factor is required. If so, one of the following should be applied to total capital cost: F H easy digging . . 0.863 F H medium digging 1.000 digging 1.197 F H hard digging . . 1.509 Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: Fu = 0.411. Total Cost: Bulldozer capital cost is determined by Y c x F H x F D x F G x Fu. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 31 MINE EQUIPMENT— DRAGLINES Capital Cost Equation: This equation furnishes the cost of purchasing the appropriate size dragline needed to provide the maximum required production. Costs do not in- clude transportation, sales tax, or discounts. The equation is applied to the following variable: X= Maximum loose cubic yards of pay gravel, overburden, and waste moved hourly by dragline. The following capacities were used to calculate the base equation: 84 hp ... 28 LCY/h 110 hp. . .47 LCY/h 148 hp . . . 66 LCY/h 170 hp. . .75 LCY/h I ,000,000 190 hp . . . 94 LCY/h 263 hp . . . 132 LCY/h 289 hp . . . 188 LCY/h 540 hp . . . 264 LCY/h The above capacities are based on the following assumptions: 1. Bucket efficiency, 0.90. 2. Full hoist. 3. Swing angle, 90°. 4. Average operator ability. Base Equation: Equipment capital cost 10,000 10 100 1,000 CRPflCITY, maximum I oqsq cubic yards per hour Mine equipment capital costs - Draglines Y c = . 16,606. 12(X)o-678 Equipment capital costs consist entirely of the equipment purchase price. Swing Angle Factor: If the average swing angle is other than 90 °, the factor obtained from the following equa- tion must be applied to total capital cost. This factor will compensate for equipment size differences required to ob- tain the desired maximum capacity: F s = 0.450(swing angle) 180 . Used Equipment Factor: This factor accounts for the reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: Fu = 0.422. Total Cost: Dragline capital cost is determined by Y r x F s x F„. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 32 CAPITAL COSTS MINE EQUIPMENT— FRONT-END LOADERS Capital Cost Equation: This equation provides the cost of purchasing the appropriate size and number of wheel- type front-end loaders needed to supply the maximum re- quired production. Costs do not include transportation, sales tax, or discounts. The equation is applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden, and waste moved hourly by front-end loader. The base equation was calculated using the following capacities: 1.00-yd 3 bucket, 3.50-yd 3 bucket, 65 hp 24.00 LCY/h 200 hp . . 129.50 LCY/h 1.50-yd 3 bucket, 4.50-yd 3 bucket, 80 hp .... 34.50 LCY/h 270 hp . .171.00 LCY/h 1.75-yd 3 bucket, 6.50-yd 3 bucket, 105 hp . . . 38.50 LCY/h 375 hp . .234.00 LCY/h 2.25-yd 3 bucket, 12.00-yd 3 bucket, 125 hp .. .56.25 LCY/h 690 hp . .348.00 LCY/h 2.75-yd 3 bucket, 155 hp . . .66.00 LCY/h ID L a w 100 000 o _i 10 000 1 a 100 1,0 CAPACITY, maximum loose cubic yards per hour Mine equipment capital costs - Front-end loaders The above capacities are based on the following assumptions: 1. Haul distance, 500 ft. 4. 2. Rolling resistance, 2%, 5. nearly level gradient. 6. 3. Inconsistent operation. Wheel-type loader. Efficiency, 50 min/h. General purpose bucket, heaped. Base Equation: Equipment capital cost. . .Y c = 2,711. 10(X)° - 896 Equipment capital costs consist entirely of the equipment purchase price. Distance Factor: If the average haul distance is other than 500 ft, the factor obtained from the following equa- tion must be applied to the capital cost. This will correct for the addition or reduction of equipment required to main- tain maximum capacity. (If tracked loaders are to be used, the maximum haul distance should not exceed 600 ft.) F D = 0.033(distance) 0552 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to the total capital cost. This will correct for the addition or reduction of equip- ment required to maintain maximum capacity: F = 0.888e 10 041l P ercent Kradient)]_ Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life. F v = 0.386. Track-Type Loader Factor: If track-type loaders are used, the factor obtained from the following equation must be applied to total capital cost. This factor will account for the decrease in production efficiency and the difference in equipment cost: F T = 0.414(X)0272. by Total Cost: Front-end loader capital cost is determined Y n X F n X F r . X F„ X F. T- This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 33 MINE EQUIPMENT— REAR-DUMP TRUCKS Capital Cost Equation: This equation furnishes the cost of purchasing the appropriate size and number of diesel rear-dump trucks needed to provide the maximum required production. Costs do not include transportation, sales tax, or discounts. The equation is applied to the following variable: X =Maximum loose cubic yards of pay gravel, overburden, and waste moved hourly by rear-dump truck. The following capacities were used to calculate the base equation: 3.0-yd 3 truck 32.3 LCY/h 5.0-yd 3 truck 53.4 LCY/h 6.0-yd 3 truck 63.6 LCY/h 8.0-yd 3 truck 83.5 LCY/h 10.0-yd 3 truck 104.2 LCY/h truck 444.8 LCY/h 12.0-yd 3 truck 124.5 LCY/h 16.0-yd 3 truck 163.9 LCY/h 22.8-yd 3 truck 223.5 LCY/h 34.0-yd 3 truck 326.3 LCY/h 47.5-yd 3 The above capacities are based on the following assumptions: 1. Diesel rear-dump trucks. 2. Loader cycles to fill, 4. 3. Haul distance, 2,500 ft. 4. Rolling resistance, 2%, nearly level gradient. 100 000 10.000 10 100 1,000 CRPRCITY, maximum loose cubic yards psr hour Mine equipment capital costs - Rsai — dump trucks Base Equation: Equipment capital cost. . .Y c = 472.09CX) 1 139 Equipment capital costs consist entirely of the equipment purchase price. Distance Factor: If the average haul distance is other than 2,500 ft, the factor obtained from the following equa- tion must be applied to capital cost. This will correct for the addition or reduction of equipment required to main- tain maximum capacity: F D = 0.06240(distance)o 364. Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to total capital cost. This will correct for the addition or reduction of equipment required to maintain the maximum capacity. (Favorable haul gradient should be entered as negative, uphill haul grades as positive.) Fp = 0.896e'° 056( P ercent gradient)). Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: Frj = 0.243. Total Cost: Truck capital cost is determined by Y c x F D x F G x F„. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 34 CAPITAL COSTS MINE EQUIPMENT— SCRAPERS Capital Cost Equation: This equation furnishes the cost of purchasing the appropriate size and number of scrapers needed to provide maximum required production. Costs do not include transportation, sales tax, or discounts. The equa- tion is applied to the following variable: X= Maximum loose cubic yards of pay gravel, over- burden, and waste moved hourly by scraper. The following capacities were used to calculate the base equation: 330 hp 201 LCY/h 550 hp 420 LCY/h 450 hp 323 LCY/h The above capacities are based on the following assumptions: 1. Standard scrapers. 2. Rolling resistance, 6%, nearly level gradient. 3. Average haul distance, 1,000 ft. 4. Average operator ability. 5. Dozing distance, 300 ft. 6. Efficiency, 50 min/h. Base Equation: Equipment capital cost 100 000 • 10,000 1 3 100 1 ,0 CRPHC I T Y t max i mum I oosg cub i c yards pe r hour Mine equipment capital costs - Scrapers Y c = l,744.42(X)0-934 Equipment capital costs consist entirely of the equipment purchase price. Distance Factor: If the haul distance is other than 1,000 ft, the factor obtained from the following equation must be applied to the total capital cost. This will correct for the addition or reduction of equipment required to main- tain maximum production capacity: F D = 0.025 (distance) 0539 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 6%, the factor obtained from the following equation must be applied to total capital cost. This will correct for the addition or reduction of equipment required to maintain the maximum production capacity. (Favorable haul gradients are entered as negative, uphill haul gradients as positive.) F G = 0.776e l0047l P elcenl uradienti]. Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: F,r = 0.312. Total Cost: Scraper capital cost is determined by Y c x F D x F G x Fu. This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 35 PROCESSING EQUIPMENT— CONVEYORS Capital Cost Equation: This equation furnishes the cost of purchasing and installing the appropriate size con- veyors needed to meet maximum required production. A separate cost must be calculated for each conveyor in the circuit. The cost includes associated drive motors and elec- trical hookup. Equipment transportation, sales tax, and dis- counts are not accounted for. The equation is applied to the following variable: X=Maximum cubic yards of material moved hourly by conveyor. The following capacities were used to calculate the base equation: 18-in-wide 30-in-wide conveyor 96 yd 3 /h conveyor 320 yd 3 /h 24-in-wide 36-in-wide conveyor 192 yd 3 /h conveyor 480 yd 3 /h Base Equation: Equipment capital cost Y c = 4,728.36(X) 0287 The capital cost consists of 89% equipment purchase price, 8% installation labor, and 3% construction materials. Length Factor: If the required conveyor length is other than 40 ft, the factor obtained from the following equation must be applied to the calculated capital cost. This factor is valid for conveyors 10 to 100 ft long: F L = 0.304(length)0-33o. Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: Fu = 0.505. Total Cost: Conveyor capital cost is determined by Y c x F L x F n . This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. — 100 000 10.000 10 100 1.000 CAPACITY, maximum cubic yards of material moved per hour Processing equipment capital costs -Conveyors 36 CAPITAL COSTS PROCESSING EQUIPMENT— FEED HOPPERS Capital Cost Equation: This equation furnishes the cost of purchasing and installing the appropriate size vibrating feeder needed to meet maximum required produc- tion. The cost includes associated drive motors, springs, and electrical hookup, plus the expense of a hopper. Equipment transportation, sales tax, and discounts are not accounted for. The equation is applied to the following variable: X = Maximum cubic yards of material handled hourly by feed hopper. The following capacities were used to calculate the base equation: 12-in-wide unit 16 yd 3 /h 24-in-wide unit 211 yd 3 /h 36-in-wide unit 522 yd 3 /h The above capacities are based on the following assumptions: 1. Unsized feed. 2. Feed density, 2,300 lb/yd 3 . Base Equation: Equipment capital cost Y c = 458.48(X) 0470 The capital cost consists of 82% equipment purchase price, 14% construction and installation labor, and 4% steel. 1 m L a T3 S io.ooo o _) cr Q_ cr i . nnn 10 100 1,000 CAPACITY, maximum cubic yards of feed treated per hour Processing equipment capital costs - Feed hoppers Hopper Factor: In many instances a vibrating feeder may not be required. If a hopper is the only equipment needed, multiply the calculated cost by the factor obtained from the following equation. This factor will account for material and labor required to construct and install a hopper: F H = 0.078ei° 00172< F R x F L „ This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 41 PROCESSING EQUIPMENT— TROMMELS Capital Cost Equation: This equation furnishes the cost of purchasing and installing the appropriate size trom- mels needed to meet maximum required production. Cost includes associated drive motors, piping, and electrical hookup. Equipment transportation, sales tax, and discounts are not accounted for. The equation is applied to the follow- ing variable: X = Maximum cubic yards of feed handled hourly by trommels. The following capacities were used to calculate the base equation: 3.0-ft diam 3.5-ft diam 4.0-ft diam 4.5-ft diam 40 yd 3 /h. 5.0-ft diam 50 ydVh. 5.5-ft diam 85 yd 3 /h. 7.0-ft diam 150 yd 3 /h. . 250 yd 3 /h. . 300 yd 3 /h. . 500 yd 3 /h. The above capacities are based on the following assumptions: 1. Trommels are sec- tioned for scrubbing and sizing. 2. Gravity feed. 3. Feed density, 2,300 lb/yd 3 . 00,000 - - ^s , - 10.000 10 100 1,000 CRPRCITY, max i mum cubic yards of feed treated per hour Processing equipment capital costs - Trommels Base Equation: Equipment capital cost. 7,176.21(X) 0559 The capital cost consists of 64% equipment purchase price, 26% construction and installation labor, and 10% construc- tion materials. Used Equipment Factor: This factor accounts for the reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: F L . = 0.516. Total Cost: Trommel capital cost is determined by This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 42 CAPITAL COSTS PROCESSING EQUIPMENT— VIBRATING SCREENS Capital Cost Equation: This equation furnishes the cost of purchasing and installing the appropriate size and number ol' vibrating screens needed to meet maximum re- quired production. Cost includes installation and electrical hookup of both the screens and the associated drive motors. Equipment transportation, sales tax, and discounts have not been taken into account. The equation is applied to the following variable: X = Maximum cubic yards of feed handled hourly by vibrating screens. The following capacities were used to calculate the base equation: 30-ft 2 screen 96-ft 2 screen surface 47 yd : 7h surface 150 yd 3 /h 56-ft 2 screen 140-ft 2 screen surface 87 ydVh surface 218 yd 3 /h 60-ft 2 screen surface 93 yd 3 /h The above capacities are based on the following assumptions: 1. An average of 0.624 ft 2 2. Feed solids, of screen is required for 3,120 lb/yd 3 , every cubic yard of 3. Gravity feed, hourly capacity. Base Equation: Equipment capital cost. . . Y ( . = 1,870. 20(X) 06:!1 The capital cost consists of 75% equipment purchase price, I0 r /r construction and installation labor, and 15% construc- tion materials. I ,000,000 £ 100.000 10,000 • 10 100 1,000 CRPflCITY, maximum cubic yards of feQd treated per hour Processing equipment capital costs - Vibrating screens Capacity Factor: If anticipated screen capacity is other than 0.624 ft 2 /yd 3 of hourly feed capacity, the calculated capital cost must be multiplied by the following factor. This will account for the increase or reduction in equipment size required to maintain production: F ( . = 1.322(C) 0629 , where C = anticipated capacity in square feet per cubic yard of hourly feed. Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: F l} = 0.565. by Total Cost: Vibrating screen capital cost is determined Y ( . x F c x F LI . This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 43 SUPPLEMENTAL— BUILDINGS Capital Cost Equation: This equation provides the cost of materials and construction for any buildings needed at the site. These may include storage sheds, shops, or mill buildings. Costs do not include sales tax, material transpor- tation, or discounts. A separate cost must be calculated for each building, and the equation is applied to the following variable: X = Estimated floor area, in square feet. Building costs are based on the following assumptions: I 00 . 000 1. Average quality tem- porary structures. 2. Steel frame with metal siding and roofing. 3. Concrete perimeter foundations with wood floors. 4. Electricity and lighting provided. Base Equation: Capital cost Y c = 34.09(X) a907 The capital cost consists of 34% construction labor, 41% con- struction materials, and 25% equipment. Cement Floor Factor: If a cement floor is required, the cost calculated from the base equation must be multiplied by the factor obtained from the following equation: F c = 1.035(X) 0008 . Plumbing Factor: If plumbing is required, the follow- ing factor must be applied to the total capital cost: F p = 1.013(X) 0002 . Foundation Factor: If a concrete foundation and wood floor are not needed, multiply the capital cost by the factor obtained from the following equation. This will account for the cost of wood blocks and sills for the foundation: F F = 0.640(X) 0026 . Total Cost: Building capital cost is determined by 10,000 ,000 FLOOR RRER, square feet Supplemental capital costs - Buildings Y„ x F„ x F„ x F„ This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 44 CAPITAL COSTS SUPPLEMENTAL— EMPLOYEE HOUSING Capital Cost Equation: Costs of purchasing, outfitting, and installing trailers for workers living at the minesite are provided by this equation. Costs are based on fair qual- ity single-wide trailers capable of meeting minimum building code requirements. Costs do not include sales tax, equipment transportation, or discounts. The equation is ap- plied to the following variable: X = Average loose cubic yards of overburden and pay gravel handled hourly. The following capacities were used to calculate the base equation: 25 LCY/h . . 3.1 workers 150 LCY/h . 6.6 workers 50 LCY/h . . 4.2 workers 400 LCY/h . 9.9 workers The above capacities are based on the following assumptions: 1. Average workforce for 2. Two workers per placer mines in the trailer, western United States 3. Trailers contain cook- ( including Alaska). ing facilities. Base Equation: Capital cost Y c = 7,002.51(X) - 418 The capital cost consists of 90% equipment purchase price, T7c construction and installation labor, and 3% construc- tion materials. 10,000 100 1,000 CAPACITY, avGrogg Ioqsg cubic yards pay gravel plus overburden mined per hour Supplemental capital costs - Employee housing Used Equipment Factor: This factor accounts for the reduced expense of purchasing used trailers. The adjusted cost is obtained by multiplying the calculated capital cost by the following factor: F LI = 0.631. Workforce Factor: The equation used to compute labor for capital cost estimation is: Workforce = 0.822(X)' 0.415 If the workforce for the operation under evaluation is known, and is different than that calculated from the above equation, the correct capital cost may be obtained from the following equation: Y r = (Number of workers) x 8,608.18. Total Cost: Employee housing capital cost is deter- mined by Y c * F . This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 45 SUPPLEMENTAL— GENERATORS Capital Cost Equation: This equation provides the cost of puixhasing and installing the appropriate size generator required to meet maximum production. Cost includes in- stallation and connection through the fuse box, and allows for mill, mine, camp, and ancillary function power consump- tion. Costs do not include equipment transportation, sales, tax, or discounts. The equation is applied to the following variable: X = Maximum cubic yards of feed handled per hour. The following capacities were used to calculate the base equation: 10-kVV 75-kW generator ... 10 yd 3 /h generator . . . 125 yd 3 /h 30-kW 125-kW generator ... 40 yd 3 /h generator . . . 200 yd 3 /h 45-kW 250-kW generator ... 75 yd 3 /h generator . . . 400 yd 3 /h The above capacities are based on the assumption that 0.57 kW is needed for every cubic yard of mill capacity. This is average for a mine with a basic plant containing trom- mels, conveyors, mechanical gravity separation devices (jigs or tables), and other necessary ancillary equipment. In all cases, a slightly higher rated generator has been selected for costing purposes to account for demand surges and miscellaneous electrical consumption, such as camp elec- tricity. A factor is provided below for operations with power consumption rates other than 0.57 kW/yd 3 . 10,000 ,000 1 ,000 10 100 MILL CflPRCITY, maximum cubic yards of feed treated per hour Supplemental capital costs - Generators Base Equation: Equipment capital cost. 1,382.65(X) - 604 The capital cost consists of 75% equipment purchase price, 19% construction and installation labor, and 6% construc- tion materials. Alternate Power Consumption Factor: If anticipated power consumption rate is other than 0.57 kW/yd 3 mill capacity, the capital cost must be multiplied by the factor obtained from the following equation: F p = 1.365(P) 061g , where P = anticipated power consumption rate. Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: F v = 0.481. Total Cost: Generator capital cost is determined by Y, F D xF, This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. Ui CAPITAL COSTS SUPPLEMENTAL— PUMPS Capital Cost Equation: This equation furnishes the cost of purchasing and installing the appropriate size of pump needed for each particular function (i.e., providing Irish mill water, recirculating spent water through settling ponds, etc.). If more than one pump is required, a separate cost must be calculated for each installation. Guidelines for pump requirements are listed in section 1. In general, however, at least one pump will be required if water is recycled through settling ponds. Costs of diesel-driven cen- trifugal pumps, polyvinyl chloride (PVC) pipe, and pump and pipe installation labor are all considered. Costs of equip- ment transportation, sales tax, and discounts are not in- cluded. The equation is applied to the following variable: X = Maximum gallons per minute of water handled. The following capacities were used to calculate the base equation: 0.50-hp pump . 2.00-hp pump . 5.25-hp pump . 50 gpm 200 gpm 500 gpm 10.50-hp pump . . 18.50-hp pump . . 37.00-hp pump . . 1,000 gpm 1,750 gpm 3,500 gpm 10,000 0! L o ui 1 ,000 a _i a: Q_ cr 100 1 D 100 1 ,000 10, c PUMP CAPACITY, maximum gal Ions per minute Supplemental capital casts - Pumps The above capacities are based on the following assumptions: 1. Total head of 25 ft. 2. Diesel-powered pumps. Abrasion-resistant steel construction. Total engine-pump ef- ficiency of 60%. Base Equation: Equipment capital cost. 63.909(X) 0618 The capital cost consists of 70% equipment purchase price, 22 r/ f construction materials, and 8% construction and in- stallation labor. Head Factor: If total pumping head is other than 25 ft, the factor calculated from the following equation will correct for changes in pump size requirements. The product of this factor and the original cost will provide the ap- propriate figure: F H = 0. 125(H) 6:i? , where H = total pumping head. Used Equipment Factor: This factor accounts for reduced capital expenditure of purchasing equipment hav- ing over 10,000 h of previous service life: F v = 0.615. Total Cost: Pump capital cost is determined by Y c * F H x Fu . This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. CAPITAL COSTS 47 SUPPLEMENTAL— SETTLING PONDS Capital Cost Equation: This equation furnishes the cost of settling ponds for waste-water treatment. Costs of labor and equipment operation for site selection, size deter- mination, rough surveying, excavation, ditching, grading, and placement of sized gravel are all included. The equa- tion is applied to the following variable: X = Maximum mill water consumption, in gallons per minute. If the water consumption rate is not known, one can be estimated from the following equation: X = 94.089(Y) 0546 , where Y = maximum cubic yards of mill feed handled per hour. The following capacities were used to calculate the base equation: 400 gpm 1,426-yd 3 900 gpm 600 gpm 1,426-yd 3 liquid capacity. 2,139-yd 3 liquid capacity 1,400 gpm 3,208-yd 3 liquid capacity 4,991-yd 3 liquid capacity The above capacities are based on the following assumptions: 1. Pond located in mined- out area. 2. Excavated by bulldozer. 3. Capable of holding 12 h of waste water produced by mill. 4. Based on jig plant water consumption rate. 10,000 1 000 100 in 1 10 100 1,000 10,000 MILL WRTER CONSUMPTION, maximum gallons per minute Supplemental capital costs - Sett I i ng ponds Base Equation: Capital cost. . . Y c 3.982(X) ' 952 The capital cost consists of 75% construction labor, 13% fuel and lubrication, and 12% equipment parts. Liner Factor: In order to meet water quality standards, some settling ponds must be lined with an impervious material. If such a liner is required, total capital cost must be multiplied by the factor calculated from the following equation: This factor covers cost of the liner and associated installation labor: F L = 27.968(X)-°- 314 . Total Cost: Settling pond capital cost is determined by Y c >< F L . This product is subsequently entered in the appropriate row of the tabulation shown in figure 5 for final capital cost calculation. 48 OPERATING COSTS OVERBURDEN REMOVAL— BULLDOZERS Operating Cost Equations: These equations provide the cost of excavating and relocating overburden using bulldozers. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the till lowing variable: X Maximum loose cubic yards of pay gravel, overburden, and tails moved hourly by bulldozer. The base equations assume the following: I .000 1. No ripping. 2. Cutting distance, 50 ft. 3. Efficiency, 50 min/h. Base Equations: 4. Dozing distance, 300 ft. 5. Average operator ability. 6. Nearly level gradient. Equipment operating cost. Labor operating cost Y K = 0.993(Xr - 430 Y,' = 14.0KX)- 0945 Equipment operating costs average 47% parts and 53% fuel and lubrication. Labor operating costs average 86% oper- ator labor and 14% repair labor. oi 0.100 a o O.OIO ^^ Equipment Labor 10 I 00 1 , 000 CAPACITY, maximum loose cubic yards per hour Overburden removal operating costs - Bulldozers Distance Factor: If the average dozing distance is other than 300 ft, the factor obtained from the following equa- tion must be applied to total cost per loose cubic yard: F„ = 0.00581(distance) a904 . Gradient Factor: If the average gradient is other than level, the factor obtained from the following equation must be appled to the total cost per loose cubic yard: 1.041e" fill Ki-iulivnli) Ripping Factor: If ripping is required, total operating cost must be multiplied by the following factor. This will account for the reduced productivity associated with ripping: F K = 1.595. Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: Equipment factor U, Labor factor U, 1.206(X)-°- 013 0.967(X) 0015 Digging Difficulty Factor: Parameters given in the discussion on site adjustment factors in section 1 should be used to determine if a digging difficulty factor is required. If so, one of the following should be applied to total cost per loose cubic yard: F H , easy digging . 0.830 F H , medium-hard F„, medium digging 1.250 digging 1.000 F H , hard digging . 1.670 Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U ) + Y L (U,)] x F D x F G x F H x F R . The total cost per loose cubic yard must then be multiplied by the total yearly amount of overburden handled by bulldozer. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 49 OVERBURDEN REMOVAL— DRAGLINES Operating Cost Equations: These equations provide the cost of excavating overburden using draglines. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by dragline. The base curves assume the following: 1. Bucket efficiency, 3. Swing angle, 90°. 0.90. 4. Average operator 2. Full hoist. ability. Base Equations: Equipment operating cost. . . Y E =1.984(X)-° 390 Labor operating cost Y L =12.19(X)-°-8«> Equipment operating costs consist of 67% parts and 33% fuel and lubrication. Labor operating costs consist of 78%- operator labor and 22% repair labor. Swing Angle Factor: If average swing angle is other than 90°, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F s =0.304(swing angle) 0269 . Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: — Equipment N Lc±Jor 10 100 1,000 CRPHCITY , max i mum I oose cub i c yards per hour Overburden removal operating costs - Draglines Equipment factor U e = 1.162(X)-«oi7 Labor factor . . .'. U, = 0.989(X)oooe Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e ) + Y L (U,)] x F s . The total cost per loose cubic yard must then be multiplied by the total yearly amount of overburden handled by dragline. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. ;>o OPERATING COSTS OVERBURDEN REMOVAL— FRONT-END LOADERS Operating Cost Equations: These equations provide t he cost of relocating overburden using wheel-type front- end loaders. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by front-end loader. The base equations assume the following: 1. Haul distance, 500 ft. 3. Inconsistent operation. 2. Rolling resistance, 2%, 4. Wheel-type loader nearly level gradient. Base Equations: Equipment operating cost. . . Y R = 0.407(X)" 225 Labor operating cost Y, =13.07(X)-°^e Equipment operating costs average 22% parts, 46% fuel and lubrication, and 32%- tires. Labor operating costs average 909; operator labor and 10% repair labor. Distance Factor: If average haul distance is other than 500 ft, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F 1) =0.023(distance)" 61fi . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F r = 0.877e |lu)46l P L ' ra ' nt K'«dientl| Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: I .000 (0 0. 100 Equipment Lcbor 10 100 1,000 CflPRCITY, maximum I aoss cubic yards per hour Overburden removal operating costs - Front-end loaders Equipment factor U e = 1.162(X)-°-°" Labor factor U, = 0.989(X)°.ooe Track-Type Loader Factor: If track-type loaders are used, the following factors must be applied to the total cost obtained from the base equations: Equipment factor T e = 1.378 Labor factor T, = 1.073 Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U e XT e ) + Y L (U,XT,)] x F D x F G . The total cost per loose cubic yard must then be multiplied by the total yearly amount of overburden handled by dragline. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 51 OVERBURDEN REMOVAL— REAR-DUMP TRUCKS Operating Cost Equations: These equations provide the cost of hauling overburden using rear-dump trucks. Costs are reported in dollars per loose cubic yard of over- burden handled. The equations are applied to the follow- ing variable: X=Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by rear dump truck. The base equations assume the following: 4. Average operator ability. 5. Nearly level gradient. 1. Haul distance, 2,500 ft. 2. Loader cycles to fill, 4. 3. Efficiency, 50 min/h. Base Equations: Equipment operating cost . . . Y E =0.602(X)-° 296 Labor operating cost Y L =11.34(XH- 891 Equipment operating costs consist of 28% parts, 58% fuel and lubrication, and 14% tires. Labor operating costs con- sist of 82% operator labor and 18% repair labor. Distance Factor: If average haul distance is other than 2,500 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F D =0.093(distance) 0311 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F<- = 0.907e' 0049l P e, ' cent gradient)] Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: Equipment factor U e =0.984(X)-°° 16 Labor factor U,=0.943(X)o°2i Total Cost: Cost per loose cubic yard of overburden is determined by 0. 100 0.010 ^-Eq jipment \ Labor 10 1 00 I , 000 CflPRCITY, maximum loose cubic yards per hour Overburden removal operating costs - Rear-dump trucks [Y E (U e +Y L (U,)] x F D x F G- The total cost per loose cubic yard must then be multiplied by the total yearly amount of overburden handled by truck. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. 52 OPERATING COSTS OVERBURDEN REMOVAL— SCRAPERS Operating Cost Equations: These equations provide the cost of excavating and hauling overburden using scrapers. Costs are reported in dollars per loose cubic yard of overburden handled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by scraper. The base curves assume the following: 1. Standard scrapers. 2. Rolling resistance, 6V( , nearly level gradient. 3. Efficiency, 50 min/h. 4. Haul distance, 1,000 ft. 5. Average operator ability. Base Equations: Equipment operating cost. . . Y F =0.325(X)-°- 21() Labor operating cost Y, =12.01(X)- 0f »° Equipment operating costs consist of 48% fuel and lubrica- tion, 347f tires, and 18% parts. Labor operating costs con- sist of 88/? operator labor and 12% repair labor. Distance Factor: If average haul distance is other than 1,000 ft, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F|,=0.01947(distance) or ' 77 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 6%, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F (; = 0.776e |no47l P l ' ra ' ,u KnidiontH. Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: Equipment factor U e =1.096(X)-°-°°e Labor factor U. = 0.845(X)°-°*» a oi 0. ■ Equipment ^ Labor ID 100 1,000 CRPFCITY, maximum loose cubic yards par hour Overburden removal operating costs - Scrapers Total Cost: Cost per loose cubic yard of overburden is determined by [Y E (U,) + Y L (U,)] x F D x F G . The total cost per loose cubic yard must then be multiplied by the total yearly amount of overburden handled by scraper. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 53 MINING— BACKHOES Operating Cost Equations: These equations provide the cost of excavating pay gravel using backhoes. Costs are reported in dollars per loose cubic yard of pay gravel han- dled. The equations are applied to the following variable: X= Maximum loose cubic yards of pay gravel moved hourly by backhoe. The base equations assume the following: 1. Easy digging 4. Average operator difficulty. ability. 2. Swing angle, 60° to 5. No obstructions 90°. (boulders, tree roots, 3. Up to 50% of etc.). maximum digging depth. Base Equations: 95-200 LCY/h: Equipment operating cost . . .Y E =8.360(X)- 1019 Labor operating cost Y L =-17.53(XH-«» 175-275 LCY/h: Equipment operating cost . . .Y E =11,44(X)- 1021 Labor operating cost Y L =17.25(XH-°°° 250-375 LCY/h: Equipment operating cost . . .Y E =15.17(X)- 1003 Labor operating cost Y L =19.97(X)-! ° 17 350^75 LCY/h: Equipment operating cost . . .Y E =22.59(Xh 0995 Labor operating cost Y L =16.55(X)-°9" Equipment operating costs consist of 38% parts and 62% fuel and lubrication. Labor operating costs consist of 88%' operator labor and 12% repair labor. Digging Depth Factor: If average digging depth is other than 50% of maximum, the factor obtained from the following equation must be applied to the total cost per loose cubic yard of pay gravel: F D =0.09194(percent of maximum digging depth) 0608 . Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: Equipment factor U e =1.078(X)-° 003 Labor factor U, = 0.918(X)0-02i Digging Difficulty Factor: Parameters given in the discussion on site adjustment factors in section 1 should be used to determine if a digging difficulty factor is required. io 0.100 0.010 - \ \ \ \ \ X \ \ \ \^> N 100 1,000 CRPRCITY, maximum loose cubic yards per hour Equipment Labor Mining operating costs - Backhoes If so, one of the following should be applied to total cost per loose cubic yard of pay gravel: F H , easy digging . . . 1.000 F H , medium-hard F H , medium digging 1.500 digging 1.250 F H , hard digging 1.886 Total Cost: Cost per loose cubic yard of pay gravel is determined by [Y e (U e ) + Y L (U,)] x F D x F H . The total cost per loose cubic yard must then be multiplied by the total yearly amount of pay gravel handled by backhoe. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. .V! OPERATING COSTS MINING— BULLDOZERS Operating Cost Equations: These equations provide the cost of excavating and relocating pay gravel using bulldozers. Costs are reported in dollars per loose cubic yard of pay gravel handled. The equations are applied to the following variable: X=Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by bulldozer. The base equations assume the following: 1. No ripping. 2. Cutting distance, 50 ft. 3. Efficiency, 50 min/h. 4. Dozing distance, 300 ft. 5. Average operator ability. 6. Nearly level gradient. Base Equations: Equipment operating cost. Y F =0.993(X)-0430 Labor operating cost Y L =14.01(X)-° 945 Equipment operating costs average 47% parts and 53% fuel and lubrication. Labor operating costs average 86% operator labor and 14% repair labor. Distance Factor: If average dozing distance is other than 300 ft, the factor obtained from the following equa- tion must be applied to the total cost per loose cubic yard: F.^O.OOSSKdistance) 0904 . 0.010 ^•^ Equ i omen t N Labor 100 1,000 CRPflCITY, maximum I qqsq cubic yards per hour Mining operating costs - Bulldozers Gradient Factor: If average gradient is other than level, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F . = 1 041e |0015, P e,cent gradient)] Ripping Factor: If ripping is required, total operating cost must be multiplied by the following factor. This will account for reduced productivity associated with ripping: F R = 1.595. Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: Equipment factor U e =1.206(X)-ooi3 Labor factor U, = 0.967(X)°-°i5 Digging Difficulty Factor: Parameters given in the discussion on site adjustment factors in section 1 should be used to determine if a digging difficulty factor is required If so, one of the following should be applied to total cost per loose cubic yard. F H , easy digging . . . 0.830 F H , medium-hard F H , medium digging 1.000 digging 1.250 F H , hard digging 1.670 Total Cost: Cost per loose cubic yard of pay gravel is determined by [Y E (U e )+Y L (U,)]xF D xF G xF H xF R . The total cost per loose cubic yard must then be multiplied by total yearly amount of pay gravel handled by bulldozer. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 55 MINING— DRAGLINES Operating Cost Equations: These equations provide the cost of excavating pay gravel using draglines. Costs are reported in dollars per loose cubic yard of pay gravel han- dled. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by dragline. The base curves assume the following: 1. Bucket efficiency, 0.90. 2. Full hoist 3. Swing angle, 90°. 4. Average operator ability. Base Equations: Equipment operating cost. . . Y E = Labor operating cost Y L = T.984(X)-°-390 12.19(XH-888 Equipment operating costs consist of 67% parts and 33% fuel and lubrication. Labor operating costs consist of 78% operator labor and 22% repair labor. Swing Angle Factor: If the average swing angle is other than 90°, the factor obtained from the following equa- tion must be applied to total cost per loose cubic yard: F s =0.304(swing angle) 0269 . Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by the factors obtained from the following equations: Equipment factor U e =1.162(X)-° 017 Labor factor U| = 0.989(X) 0006 Total Cost: Cost per loose cubic yard of pay gravel is determined by [Y lJ CU e )+Y L (U I )]xF s . The total cost per loose cubic yard must then be multiplied by the total yearly amount of pay gravel handled by dragline. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. 0) 0. a ^*^ Equ i pmen t ^ Lcbor 10 100 1,000 CRPRCITY, maximum loose cubic yards pGr hour Mining operating costs - Draglines 56 OPERATING COSTS MINING— FRONT-END LOADERS Operating Cost Equations: These equations provide the cost of hauling pay gravel using wheel-type front-end loaders. Costs are reported in dollars per loose cubic yards of pay gravel handled. The equations are applied to the following variable: X=Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by front-end loaders. The base equations assume the following: 1. Haul distance, 500 ft. 3. Inconsistent operation. 2. Rolling resistance, 2%, 4. Wheel-type loader, aearly level gradient. Base Equations: Equipment operating costs . . Y E = 0.407(X)-°225 Labor operating costs Y L = 13.07(X)-0936 Equipment operating costs average 22% parts, 46% fuel and lubrication, and 32% tires. Labor operating costs average 90% operator labor and 10% repair labor. Distance Factor: If the average haul distance is other than 500 ft, the factor obtained from the following equa- tion must be applied to total cost per loose cubic yard: F D = 0.023(distance) 0616 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F r = 0.877e l0046( P elcent Kradient)|_ Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e = 1.162(Xr 0017 Labor factor II = 0.989(X)° 006 I .000 0.100 0.010 Equ 1 pmen t Lcbor 100 1,000 CAPACITY, maximum I oosq cubic yards per hour Mining operating costs - Front-end loaders Track-Type Loader Factor: If track-type loaders are used, the following factors must be applied to total cost ob- tained from the base equations: Equipment factor T e = 1.378 Labor factor T, = 1.073 Total Cost: Cost per loose cubic yard of pay gravel is determined by [Y E (U e XT e )+ ■ Y L (U,XT,)]x F D x F G . The total cost per loose cubic yard must then be multiplied by total yearly amount of pay gravel handled by front-end loader. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 57 MINING— REAR-DUMP TRUCKS Operating Cost Equations: These equations provide the cost of hauling pay gravel using rear-dump trucks. Costs are reported in dollars per loose cubic yard of pay gravel. The equations are applied to the following variable: X= Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by rear dump truck. The base equations assume the following: 1. Haul distance, 2,500 ft. 2. Loader cycles to fill, 4. 3. Efficiency, 50 min/h. Base Equations: Equipment operating cost. 4. Average operator ability. 5. Rolling resistance, 2%, nearly level gradient. Y F =0.602(X)-0 296 Labor operating cost Y L =11.34(XH>89i Equipment operating costs consist of 28% parts, 58% fuel and lubrication, and 14% tires. Labor operating costs con- sist of 82% operator labor and 18% repair labor. Distance Factor: If average haul distance is other than 2,500 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F D =0.093(distance) 0:J11 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F =0.907e IOO49l P ercent tn" adient) l. Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service'life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e =0.984(X) 0016 Labor factor U,=0.943(X)0 02i Total Cost: Cost per loose cubic yard of pay gravel is determined by [Y E (U c )+Y L (U,)]xF D xF G . ^~" Equ i pmen t \ Labor 10 100 1,000 CAPACITY, maximum loose cubic yards per hour Mining operating costs - Rear-dump trucks The total cost per loose cubic yard must then be multiplied by the total yearly amount of pay gravel handled by rear- dump truck. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. 58 OPERATING COSTS MINING— SCRAPERS Operating Cost Equations: These equations provide the cost of excavating and hauling pay gravel using scrapers. Costs are reported in dollars per loose cubic yard of pay gravel handled. The equations are applied to the following variables: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by scraper. The base equations assume the following: 1. Standard scrapers. 4. Haul distance, 1,000 I .000 2. Rolling resistance, 6%, nearly level gradient. 3. Efficiency, 50 min/h. ft. Average operator ability. Base Equations: Equipment operating cost. . . Y E =0.325(X) 0210 Labor operating cost Y L '=12.01(X)-°- 930 Equipment operating costs consist of 48% fuel and lubrica- tion, 34% tires, and 18% parts. Labor operating costs con- sist of 88^ operator labor and 12% repair labor. Distance Factor: If average haul distance is other than 1,000 ft, the factor obtained from the following equation must be applied to the total cost per loose cubic yard: F„=0.01947(distance) " 7 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 6%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F r = 0.776e IOO47, P t ' m -' nt Kradientll, Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e =1.096(X)-°-°° 6 Labor factor U, = 0.845(X)°°34 0) 0.100 — Equipment ^ Labor 10 100 ! ,000 CRPflCITY, maximum I qqsq cubic yards per hour Mining operating costs - Scrapers Total Cost: Cost per loose cubic yard of pay gravel is determined by [Y E (U e )+Y L (U,)]xF D xF G . The total cost per loose cubic yard must then be multiplied by the total yearly amount of pay gravel handled by scraper. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 59 PROCESSING— CONVEYORS Operating Cost Equations: These equations provide the cost of moving gravel using conveyors. Costs are reported in dollars per cubic yard of gravel handled and in- clude the operating cost of the conveyor along with the drive. The equations are applied to the following variable: X = Maximum cubic yards of material moved hourly by conveyor. The base equations assume the following: 1. Conveyors, 40 ft long. 3. Nearly level setup. 2. Feed, 3,120 lb/yd 3 . Base Equations: Equipment operating cost. . .Y E = 0.218(X)-°- 561 Labor operating cost Y L = 0.250(X)" 702 Equipment operating costs average 72% parts, 24% elec- tricity, and 4% lubrication. Labor operating costs consist entirely of repair labor. Conveyor Length Factor: If conveyor length is other than 40 ft, factors obtained from the following equations must be applied to respective portions of the operating costs. These factors are valid for conveyors 10 to 100 ft long: Equipment factor L e = 0.209(length) 0431 Labor factor L, = 0.245(length)° 39 ° Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of base operating costs must be multiplied by the following factors: Equipment factor U e = 1.155 Labor factor .U, = 1.250 3 u 0.0101- E 0.001 1 I ^\ "V. ^^ Equipment ! ^ Labor I 1 ! 10 100 1,000 CAPACITY, maximum cubic yards of material moved per hour Processing operating costs - Conveyors Total Cost: mined by Cost per cubic yard of gravel is deter- [Y E (L e XU e ) + Y L (L,XU,)]. The total cost per cubic yard must then be multiplied by the total yearly amount of feed handled by conveyor. (A separate operating and total yearly cost must be calculated for each conveyor in the circuit.) This product is subsequent- ly entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. till OPERATING COSTS PROCESSING— FEED HOPPERS Operating Cost Equations: These equations provide cost of material transfer using vibrating feeders. Costs are reported in dollars per cubic yard of feed and include the operating cost of the hopper, feeder, and drive motor. The equations are applied to the following variable: X = Maximum cubic yards of feed handled hourly by feed hopper. The base equations assume the following: I. Unsized feed. 2. Feed solids, 2,300 lb/yd 3 . Base Equations: Equipment operating cost. . Labor operating cost Y, 0.033(Xr 0344 o.oi7(xr - 295 Equipment operating costs consist of 88% parts, 6% elec- tricity, and %'7( lubrication. Labor operating costs consist entirely of repair labor. Hopper Factor: In many installations, a vibrating feeder is not used, and pay gravel feeds directly from the hopper. If this is the case, no operating cost for feeders is required. Used Equipment Factor: If a feeder with over 10,000 h of previous service life is to be used, the following factors must be applied to respective operating costs to account for increased maintenance and repair requirements: Equipment factor U e = 1.176 Labor factor U, = 1.233 Total Cost: Cost per cubic yard of feed is determined by [Y K (U.) + Y,(U,)]. The total cost per cubic yard must then be multiplied by total yearly amount of feed handled by feed hopper. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. 0.010 w 0.001 "*"- Equ i pmen t 1 "**^> Labor 10 100 1,000 CRPRCITY, maximum cubic yards af feed treated per hour Processing operating costs - Feed hoppers OPERATING COSTS 61 PROCESSING— JIG CONCENTRATORS Operating Cost Equations: These equations provide the cost of gravity separation using jig concentrators. Costs are reported in dollars per cubic yard and include the operating cost of the jigs and associated drive motors. The equations are applied to the following variable: X = Maximum cubic yards of feed handled hourly by jig concentrators. The base equations assume the following: 100.000 4. Slurry density, 40% solids. 5. Gravity feed. 1. Cleaner service. 2. Hourly capacity, 0.617 yd 3 /ft 2 . 3. Feed solids, 3,400 lb/yd 3 . Base Equations: Equipment operating cost. . . Y E = 0.113(Xr 0328 Supply operating cost Y s = 0.002(X) _0 184 Labor operating cost Y L = S^OSfX)" 1 268 Equipment operating costs consist of 40% parts, 34% elec- tricity, and 26% lubrication. Supply operating costs consist entirely of lead shot for bedding material. Labor operating costs consist of 66% operator labor and 34% repair labor. Rougher-Coarse Factor: If jigs are to be used for rougher service or a coarse feed, higher productivity will be realized. To compensate for this situation, the following factor must be applied to total operating cost: F D = 0.344. I .000 0. 100 ^.Equipment. x Labor _Supp las 0.1 1.0 10.0 100.0 1 ,000.0 CRPRCITY, maximum cubic yards of fesd treated per hour Processing operating costs - Jig concentrators Used Equipment Factor: If jig concentrators with over 10,000 h of service life are to be used, the following factors must be applied to respective operating costs to account for increased maintenance and repair requirements: Equipment factor U e = 1.096 Labor factor U? = 1.087 Total Cost: Cost per cubic yard of feed is determined by r s + Y L (U,)] x Fr . [Y E (U) + Y c The total cost per cubic yard must then be multiplied by the total yearly amount of feed handled by jig concentrators. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. 62 OPERATING COSTS PROCESSING— SLUICES Operating Cost Equations: These equations provide the cost of gravity separation using sluices. Costs are reported in dollars per cubic yard of feed and consist en- tirely of the expense of periodic concentrate cleanup. The equation is applied to the following variable: X = Maximum cubic yards feed handled hourly by sluice. The base equations assume the following: 1. Steel plate 4. Length-to-width ratio construction. 4:1. 2. Angle iron riffles. 5. Gravity feed. 3. Feed solids, 3,400 lb/yd 3 . Base Equation: Labor operating cost ... Y, = 0.337(Xr° 6:ifi Labor operating costs consist entirely of feed adjustment and cleanup labor. Costs of maintenance labor and parts are negligible. Wood Sluice Factor: If wood sluices are to be used, an allowance must be made for periodic sluice replacement. To account for this, an equipment cost must be added to total cost, and labor cost must be multiplied by the following factor: Equipment cost Y E Labor factor W, 0.00035(X) 0383 1.141 w O.OOI "-Lctrar 1 10 100 1,000 CRPRCITY, maximum cubic yards of feed treated per hour Processing operating costs - Sluices Total Cost: Cost per cubic yard of feed is determined by fY,(W,) + Y R ]. The total cost per cubic yard must then be multiplied by total yearly amount of feed handled by sluices. This product is subsequently entered in the appropriate row of the tabula- tion shown in figure 6 for final operating cost calculation. OPERATING COSTS 63 PROCESSING— SPIRAL CONCENTRATORS Operating Cost Equations: These equations provide the cost of gravity separation using spiral concentrators. Costs are reported in dollars per cubic yard of feed and in- clude the operating cost of the spirals and slurry splitters only. The equations are applied to the following variable: X = Maximum cubic yards of feed handled hourly by spiral concentrators. The base equations assume the following: 1. Rougher service. 2. Solids per start, 1.75 st/h. 3. Feed solids, 3,400 lb/yd 3 . Base Equations: Equipment operating cost . Labor operating cost 4. Slurry density, 10% solids. 5. Gravity feed. $0.0007/yd 3 0.755(X)-°- 614 Equipment operating costs consist entirely of parts. Labor operating costs consist entirely of operator labor, with the operator performing functions such as lining replacement. Cleaner-Scavenger Factor: If spirals are to be used for cleaning or scavenging, throughput is reduced. The following factors must be applied to respective operating costs: Equipment factor C e = 2.429 Labor factor C, = 1.796 S i.oooo . 1 000 (X tr W 0.0001 — _ — ^Lc±io = r Equipment 10 100 1,000 CRPRCITY, maximum cubic yards of feed treated par hour Processing operating costs - Spiral concentrators Used Equipment Factor: Because spiral concentrators have no moving parts, they enjoy a long service life. Generally, only the liners require periodic replacement. For this reason, the operating costs asscociated with spirals are typically constant throughout the life of the machine. Total Cost: Cost per cubic yard of feed is determined by [0.0007(C e ) + Y L (C,)]. The total cost per cubic yard must then be multiplied by the total yearly amount of feed handled by spiral concen- trators. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. 64 OPERATING COSTS PROCESSING— TABLE CONCENTRATORS Operating Cost Equations: These equations provide the cost of gravity separation using table concentrators. Costs are reported in dollars per cubic yard of feed and in- clude the operating cost of the tables and associated drive motors. The equations are applied to the following variable: X = Maximum cubic yards of feed handled hourly by table concentrators. The base equations assume the following: 1. Cleaner service. 3. Slurry density, 25% 2. Feed solids, 3,400 solids. lb/yd :i . 4. Gravity feed. 10.00 Base Equations: Equipment operating cost. Labor operating cost 1.326(X)-o"43 1.399(X)-0-783 Equipment operating costs consist of 87% parts, 7% elec- tricity, and 6% lubrication. Labor operating costs consist of 67% operator labor and 33% repair labor. Rougher-Coarse Factor: If the tables are to be used for rougher service or a coarse feed, higher productivity will be realized. To compensate for this situation, the following factors must be applied to both equipment and labor operating costs: Equipment factor R e = 0.415 Labor factor R, = 0.415 Used Equipment Factor: If table concentrators with over 10,000 h of service life are to be used, the following factors must be applied to the respective operating costs to account for increased maintenance and repair requirements: Equipment factor U = 1.217(X)-° 002 Labor factor U, = 1.12HX)- 0026 1 .00 -"•Equl pment ^Lcfcor 1 1 1.0 10.0 100.0 D flCITY, maximum cubic yards of feed treated per hour Processing operating costs - Table concentrators Total Cost: Cost per cubic yard of feed is determined by [Y E (R e XU t .)+Y L (R,XU,)]. The total cost per cubic yard must then be multiplied by the total yearly amount of feed handled by table concen- trators. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 65 PROCESSING— TAILINGS REMOVAL— BULLDOZERS Operating Cost Equations: These equations provide the cost of removing and relocating tailings using bulldozers. Costs are reported in dollars per cubic yard of tailings moved. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden, and tails moved hourly by bulldozer. The base equations assume the following: 1. Efficiency, 50 min/h. 3. Average operator 2. Dozing distance, 300 ability. ft. 4. Nearly level gradient. 1 .000 Base Equations: Equipment operating cost . Labor operating cost . . . . . Y E = 0.993(X)-°i30 Y L = 14.01(X)-°945 Equipment operating costs average 47% parts, and 53% fuel and lubrication. Labor operating costs average 86% operator labor and 14% repair labor. Distance Factor: If average dozing distance is other than 300 ft, the factor obtained from the following equa- tion must be applied to total cost per loose cubic yard: F D =0.00581(distance)0 904. Gradient Factor: If average gradient is other than level, the factor obtained from the following equation must be applied to total cost per loose cubic yard: Fr = 1.041e' 0015l P ercent gradient)]_ Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e =1.206(X)-°°i3 Labor factor U, = 0.967(X)°oi5 Total Cost: Cost per cubic yard of tailings is deter- mined by [Y E (U e ) + Y L fU,)] xF D xF G . ■ 1 — ■ "\Eq Liipment Labor 10 100 1,000 CAPACITY, maximum loose cubic yards per hour Processing operating costs - Tai I i ngs removal - Bui I dozers The total cost per cubic yard must then be multiplied by the total yearly amount of tailings moved by bulldozer. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. tw OPERATING COSTS PROCESSING— TAILINGS REMOVAL— DRAGLINES Operating Cost Equations: These equations provide the cost of removing and relocating tailings using draglines. Costs are reported in dollars per cubic yard o f tailings moved. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden, and tails moved hourly by dragline. The base equations assume the following: 1. Bucket efficiency, 3. Swing angle, 90°. 2. 0.90. Full hoist. 4. Average operator ability. Base Equations: Equipment operating cost. . Labor operating cost Y E = 1.984(X)-°-390 Y,' = 12.19(X)-°888 Equipment operating costs consist of 67% parts, 33% fuel and lubrication. Labor operating costs consist of 78% operator labor and 22% repair labor. Swing Angle Factor: If average swing angle is other than 90°, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F s =0.304(swing angle) 0269 . Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U c =1.162(X)-° 017 Labor factor U, = 0.989(X)°oo6 ^*"""-- Equipment ^ Lc±)or 10 100 1,000 CAPACITY, maximum loose cubic yards per hour Processing operating costs - Tai I i ngs removal - Dragl i nes Total Cost: Cost per cubic yard of feed is determined by [Y E (U e ) + Y L (U,)] xF s . The total cost per cubic yard must then be multiplied by the total yearly amount of tailings moved by dragline. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 67 PROCESSING— TAILINGS REMOVAL— FRONT-END LOADERS Operating Cost Equations: These equations provide the cost of removing and relocating tailings using wheel- type front-end loaders. Costs are reported in dollars per cubic yard of tailings moved. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden, and tails moved hourly by front-end loader. The base equations assume the following: 1. Haul distance, 500 ft. 3. Inconsistent operation. 2. Rolling resistance, 2%, 4. Wheel-type loader, nearly level gradient. 1 .QQQ Base Equations: Equipment operating cost . . Labor operating cost Y E = 0.407(X)-0-225 Y L = 13.07(X)"0-936 Equipment operating costs average 22% parts, 46% fuel and lubrication, and 32% tires. Labor operating costs average 90% operator labor and 10% repair labor. Distance Factor: If average haul distance is other than 500 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F D =0.023(distance) 0616 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F r = 0.877e [0046( P ercent gradient>]_ Equipment Labor O.OIO 10 100 1,000 CRPRCITY, maximum loose cubic yards per hour Processing operating costs - tai I i ngs removal - Front-end loaders Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e =1.162(X)-° 017 Labor factor U!=0.989(X) oo6 Track-Type Loader Factor: If track-type loaders are used, the following factors must be applied to total cost ob- tained from the base equations: Equipment factor T e = 1.378 Labor factor T,=1.073 by Total Cost: Cost per cubic yard of tailings is determined [Y E fU e XT e )+Y L (U,XT,)] x F D x F G . The total cost per cubic yard must then be multiplied by the total yearly amount of tailings moved by front-end loader. This product is subsequently entered in the ap- propriate row of the tabulation shown in figure 6 for final operating cost calculation. 68 OPERATING COSTS PROCESSING— TAILINGS REMOVAL— REAR-DUMP TRUCKS Operating Cost Equations: These equations provide the cost of removing and relocating tailings using rear-dump trucks. Costs are reported in dollars per cubic yard of tail- ings moved. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, overburden . and tails moved hourly by rear- dump truck. The base equations assume the following: 1. Haul distance, 4. Average operator I .000 2,500 ft. 2. Loader cycles to fill, 4. i 3. Efficiency, 50 min/h. Base Equations: Equipment operating cost. Labor operating cost ability. Rolling resistance, 2%, nearly level gradient. Y E = 0.602(X)-0296 Y L = 11.34(X)-o.89i Equipment operating costs consist of 28% parts, 58% fuel and lubrication, and 14% tires. Labor operating costs con- sist of 82% operator labor and 18% repair labor. Distance Factor: If average haul distance is other than 2,500 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: Fi^O.OgSfdistance) -'". Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 2%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F ( . = 0.907e |lu)49l P l ' lc '' nt Kradicntll. Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of the base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U e =0.984(X)°° 1 6 Labor factor U I = 0.943(X) 0021 Total Cost: Cost per cubic yard of tailings is deter- mined by [Y E (U e )+Y L (U,)] xF D xF G . 0. 100 Equipment \ Labor 10 1 00 1 , 000 CAPACITY, maximum loose cubic yards per hour Processing operating costs - Tai I ings removal - Rear-dump trucks The total cost per cubic yard must then be multiplied by the total yearly amount of tailings moved by truck. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS 69 PROCESSING— TAILINGS REMOVAL— SCRAPERS Operating Cost Equations: These equations provide the cost of removing and relocating tailings using scrapers. Costs are reported in dollars per cubic yard of tailings moved. The equations are applied to the following variable: X = Maximum loose cubic yards of pay gravel, over- burden, and tails moved hourly by scraper. The base curves assume the following: 1. Standard scrapers. 4. .000 Rolling resistance, 6%, nearly level gradient. Efficiency, 50 min/h. Base Equation: Equipment operating cost . Labor operating cost Haul distance, l.UUU ft. oi Average operator ability. "O Ul □ u Y E = 0.325(X)- 0210 ID z r- (X 12.0KX)- 0930 Equipment operating costs consist of 48% fuel and lubrica- tion, 34% tires, and 18% parts. Labor operating costs con- sist of 88% operator labor and 12% repair labor. Distance Factor: If average haul distance is other than 1,000 ft, the factor obtained from the following equation must be applied to total cost per loose cubic yard: F D = 0.01947(distance) 0577 . Gradient Factor: If total gradient (gradient plus roll- ing resistance) is other than 6%, the factor obtained from the following equation must be applied to total cost per loose cubic yard: JT =0 77fie'0-0 47, P ercent gradient)] i ou Equ 1 pmen t Labor 10 100 1,000 CAPACITY, maximum loose cubic yards per hour Processing operating costs - Tai i ings removal - Scrapers Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of base operating costs must be multiplied by factors obtained from the following equations: Equipment factor U 1.096(X) -0.006 Labor factor U~ = 0.845(X) 0034 Total Cost: Cost per cubic yard of tailings is determin- [Y E (U e ) + Y L (U,)] x F D x F G . The total cost per cubic yard must then be multiplied by total yearly amount of tailings moved by scraper. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. OPERATING COSTS PROCESSING— TROMMELS Operating Cost Equations: These equations provide the cost of processing gravel using trommels. Costs are reported in dollars per cubic yard of gravel handled. The equations are applied to the following variable: X = Maximum cubic yards of gravel processed hourly by trommels. The base equations assume the following: 1. Trommels are sec- 2. Associated electric tioned for scrubbing motor operating costs and sizing. are included. Base Equations: -0.403 Equipment capital cost Y E = 0.217(X) Labor operating cost Y,' = 0.129(X)-° 429 Equipment operating costs average 63% parts, 26% elec- tricity, and 11% lubrication. Labor operating costs consist entirely of maintenance and repair labor. Used Equipment Factor: These factors account for added operating expenses accrued by equipment having over 10,000 h of previous service life. The respective equip- ment and labor portions of base operating costs must be multiplied by the following factors: Equipment factor U = 1.194 Labor factor U, = 1.310 Total Cost: Cost per cubic yard of gravel is determin- ed bv [Y R (U.) + Y,(U,)]. The total cost per cubic yard must then be multiplied by the total yearly amount of gravel processed by trommels. This product is subsequently entered in the appropriate row of the tabulation shown in figure 6 for final operating cost calculation. a T3 CD ID O ^"N L O ^"*** Equ I pmsn t 1 L 0.010 ^"^ Labor co a ■a H a CJ z 1- (X w 0.001 3 100 ! ,0 CAPACITY, max i mum cubic yards af feod treated per hour Processing operating costs - Trommels OPERATING COSTS 71 PROCESSING— VIBRATING SCREENS Operating Cost Equations: These equations provide the cost of processing gravel using vibrating screens. Costs are reported in dollars per cubic yard of gravel handled. The equations are applied to the following variable: X = Maximum cubic yards of gravel processed hourly by vibrating screen. The base equations assume the following: 1. An average of 0.624 ft 2 of screen is re- quired for every cubic yard of hourly capacity. Base Equations: Equipment operating cost Labor operating cost Equipment operating costs average 73% parts, 19% elec- tricity, and 8% lubrication. Labor operating costs consist entirely of maintenance and repair labor. Capacity Factor: If anticipated screen capacity is other than 0.624 ft 2 /yd 3 hourly feed capacity, the respective operating costs must be multiplied by factors obtained from the following equations: C = 1.267(C) 0575 , Mine-run gravel (100 yd 3 /h) Feed hopper Oversize Trommel (25 yd 3 /h) m ■* fe. ^ w Minus 0.25 in (20 yd 3 /h) Rougher jig Concentrate (5 yd 3 /h) r-\ Cleaner jig Concentrate (0.1 yd 3 /h) Final jig Concentrate (0.03 yd 3 /h) Panning Gold product _^ Waste — _ (20 yd 3 /h) *~ Sluice Concentrate (0.01 yd 3 /h) S\ Minus 0.125 in (5 yd 3 /h) Cleaner jig Concentrate (0.1 yd 3 /h) Figure A-1— Sample flow sheet. CAPITAL COSTS 81 Exploration (p. 20) Reconnaissance 20 worker-days x $195/worker-day = $3,900 Churn drilling 1,400 ft x $45/ft = 63,000 Trenching 2,000 yd 3 x $7.10/yd 3 = 14,200 Panning 1,200 samples x $2.10/sample = 2,520 Helicopter 8 h x $395/h = 3,160 Camp 180 worker-days x $30/worker-day = 5,400 Exploration capital cost = $92,180 x 1.025 (labor) $94,485 Access roads (p. 22) 22-ft wide 4 miles long 20% side slope Forested 600 ft blasting Base cost Y c = 765.65(22)° 922 = Labor $13,236 x 0.68 x 1.025 = Parts $13,236 x 0.13 x 1.005 = Fuel $13,236 x 0.16 x 0.991 = Tires $13,236 x 0.03 x 0.939 = Forest factor F F = 2.000(22)-° 079 = Side slope factor Fg = 0.633e [0021(20)] = Blasting factor F H = [12,059.18(22)°- 534 ] x (600/5,280) = Access road capital cost = [($13,426 x 1.567 x 0.963 x 4] + 7,140 $13,236/mile $9,225 1,729 2,099 373 $13,426/mile 1.567 0.963 7,140 $88,180 Clearing (p. 23) 6 acres 10% side slope Forested Base cost Y r = 1,043.61(6)°- 913 $5,358 Labor $5,358 x 0.68 x 1.025 Parts $5,358 x 0.12 x 0.991 Fuel $5,358 x 0.18 x 1.006 Steel $5,358 x 0.02 x 0.992 Slope factor F g Forest factor F 9 42e [0.008(10)] F $3,735 637 970 106 $5,448 1.020 1.750 Clearing capital cost = [$5,448 x 1.020 x 1.750] $9,725 82 Preproduction overburden removal (p. 24) 30,000 LCY 250 LCY/h 3.000-ft haul + 8% haul gradient plus rolling resistance Used scraper Equipment cost Y E = 0.325(250)-°- 21 ° = $0.102/LCY Parts $0,102 x 0.18 x 1.005 = $0,018 Fuel and lubrication $0,102 x 0.48 x 0.991 = 0.049 Tires $0,102 x 0.34 x 0.939 = 0.033 $0.100/LCY Labor cost Y L = 12.01(250r°- 93 ° = $0.071/LCY Labor $0,071 x 1.00 x 1.025 = $0.073/LCY Distance factor F D = 0.01947(3,000)°- 577 = 1.975 Gradient factor F G = 0.776e [0047(8)] = 1.130 Used equipment U e = 1.096(250)-° 006 = 1.060 U[ = 0.845(250)° ° 34 = 1.019 Overburden removal capital cost = [($0,100 x 1.060) + ($0,073 x 1.019)] x 1.975 x 1.130 x 30,000 $12,077 Mine equipment— backhoes (p. 29) 100 LCY/h 80% maximum digging depth Medium-hard digging Base cost Y r 84,132.01e [0 ° 0350<1 °° )] Equipment $119,389 x 1.00 x 1.005 Digging depth factor F D = 0.04484(80)°- 790 Digging difficulty factor F H = $119,389 = $119,986 1.429 1.556 Backhoe capital cost = ($119,986 x 1.429 x 1.556) $266,792 Mine equipment— bulldozers (p. 30) 100 LCY/h 400-ft average haul distance -8% average haul gradient Used equipment Base cost Y c = 3,555.96(100)°- 806 Equipment $145,531.00 x 1.00 x 1.005 Distance factor F D = 0.01549(400)°- 732 Gradient factor F G = 1.041e [0015( - 8)] Used equipment factor Fjj Bulldozer capital cost = ($146,259 x 1.244 x 0.923 x 0.411) . = $145,531 = $146,259 1.244 0.923 0.411 $69,022 83 Mine equipment— front-end loaders (p. 32) 100 LCY/h Two machines, 50 yd 3 /h each 800-ft average haul + 6% haul gradient plus rolling resistance Base cost Y c = 2,711.10(50)° 896 = $90,245 Equipment $90,245 x 1.00 x 1.005 = $90,696 Distance factor F D = 0.033(800)°- 552 = 1.321 Gradient factor F G = 0.888e t0041(6)) = 1.136 Front-end loader capital cost = (2 x $90,696 x 1.321 x 1.136) $272,207 Mine equipment— scrapers (p. 34) 250 LCY/h 3,000-ft average haul +8% haul gradient plus rolling resistance Used equipment Base cost Y c = 1,744.42(250) - 934 = $302,919 Equipment = $302,919 x 1.00 x 1.005 = $304,434 Distance factor F D = 0.025(3,000) - 539 = 1.871 Gradient factor F G = 0.776e [0047(8)] = 1.130 Used equipment factor Fjj = 0.312 Scraper capital cost = ($304,434 x 1.871 x 1.130 x 0.312) $200,817 Processing equipment— conveyors (p. 35) 70 ydVh 40 ft long Base cost Y c = 4,728.36(70)°- 287 = $16,005 Equipment price $16,005 x 0.89 x 1.005 = $14,316 Installation labor $16,005 x 0.08 x 1.025 = 1,312 Construction materials $16,005 x 0.03 x 1.015 = 487 Conveyor capital cost = ($14,316 + $1,312 + $487) $16,115 Processing equipment— feed hoppers (p. 36) 100 yd7h Base cost Y c = 458.48(100)° 47 ° = $3,993 Equipment price $3,993 x 0.82 x 1.005 = $3,291 Installation labor $3,993 x 0.14 x 1.025 = 573 Steel $3,993 x 0.04 x 0.992 = 158 Feed hopper capital cost = ($3,291 + $583 + $158) $4,022 84 Processing equipment— rougher jig (p. 37) 20 ydVh Base cost Y c = 6,403.82(20)°- 595 = $38,067 Equipment price $38,067 x 0.62 x 1.005 = $23,720 Installation labor $38,067 x 0.12 x 1.025 = 4,682 Construction materials $38,067 x 0.26 x 1.015 = 10,046 Rougher factor F R = 0.531 Rougher jig capital cost = [($23,720 + $4,682 + $10,046) x 0.531] $20,416 Processing equipment— cleaner jigs (p. 37) 2 at 5 ydVh Base cost Y c = 6,403.82(5) 0595 = $16,685 Equipment price $16,685 x 0.62 x 1.005 = $10,396 Installation labor $16,685 x 0.12 x 1.025 = 2,052 Construction materials $16,685 x 0.26 x 1.015 = 4,403 Cleaner jigs capital cost = [$10,396 + $2,052 + $4,403) x 2] $33,702 Processing equipment— final jig (p. 37) 0.2 ydVh Base cost Y c = 6,403.82(0.2) - 595 = $2,458 Equipment price $2,458 x 0.62 x 1.005 = $1,532 Installation labor $2,458 x 0.12 x 1.025 = 302 Construction materials $2,458 x 0.26 x 1.015 = 649 Final jig capital cost = ($1,532 + $302 + $649) $2,483 Processing equipment— sluice (p. 38) 50 yd 3 /h Base cost Y c = 113.57(50)° 567 = $1,044 Construction labor $1,044 x 0.61 x 1.025 = $653 Construction materials $1,044 x 0.39 x 1.015 = 413 Sluice capital cost = ($653 + $413) . $1,066 Processing equipment— sluice (p. 38) 20 ydVh Base cost Y c = 113.57(20)°- 567 = $621 Construction labor $621 x 0.61 x 1.025 = $388 Construction materials $621 x 0.39 x 1.015 = 246 Sluice capital cost = ($388 + $246) $634 85 Processing equipmment— trommel (p. 41) 100 LCY/h Base cost Y c = 7,176.21(100)°- 559 Equipment price $94,166 x 0.64 x 1.005 Installation labor $94,166 x 0.26 x 1.025 Construction materials $94,166 x 0.10 x 1.015 Trommel capital cost = ($60,568 + $25,095 + $9,558) $94,166 $60,568 25,095 9,558 $95,221 Supplemental— main building (p. 43) 1,680 ft 2 Cement floor Plumbing added Base cost Y c = 34.09(1,680)°- 907 = $28,707 Equipment $28,707 x 0.25 x 1.005 = $7,213 Construction labor $28,707 x 0.34 x 1.025 = 10,004 Construction materials $28,707 x 0.41 x 1.015 = 11,946 Cement floor factor F c = 1.035(1,680) 0008 = 1.098 Plumbing factor F p = 1.013(1,680) 0002 = 1.028 Main building capital cost = [($7,213 + $10,004 + $11,946) x 1.098 x 1.028] $32,918 Supplemental— sheds (p. 43) 2 at 216 ft 2 each Base cost Y c = 34.09(216) - 907 Equipment $4,467 x 0.25 x 1.005 Construction labor $4,467 x 0.34 x 1.025 Construction materials $4,467 x 0.41 x 1.015 Shed capital costs = [($1,122 + $1,557 + $1,859) x 2] $4,467 $1,122 1,557 1,859 $9,076 Supplemental— employee housing (p. 44) 100 LCY/h pay gravel 250 LCY/h overburden 350 LCY/h total Used trailers Base cost Y c = 7,002.51(350)° 418 = $81,035 Equipment $81,035 x 0.90 x 1.005 = $73,296 Construction labor $81,035 x 0.07 x 1.025 = 5,814 Construction materials $81,035 x 0.03 x 1.015 = 2,468 Used trailer factor Fy = 0.631 Employee housing capital cost = [($73,296 + $5,814 + $2,468) x 0.631] . . $51,476 86 Supplemental— generators (p. 45) 100-LCY/h mill feed Base cost Y c = 1,382.65(100) - 604 = $22,321 Equipment $22,321 x 0.75 x 1.005 = $16,824 Construction labor $22,321 x 0.19 x 1.025 = 4,347 Construction materials $22,321 x 0.06 x 1.015 = 1,359 Generator capital cost = ($16,824 + $4,347 + $1,359) $22,530 Supplemental— pumps (p. 46) 100-LCY/h mill feed 80-ft head Water consumption (p. 47) = 94.089Q00) - 546 = 1,163 gpm Base cost Y c = 63.909(1,163)° 618 = $5,013 Equipment $5,013 x 0.70 x 1.005 = $3,527 Installation labor $5,013 x 0.08 x 1.025 = 411 Construction materials $5,013 x 0.22 x 1.015 = 1,120 Head factor F H = 0.125(80)°- 637 = 2.038 Pump capital cost = [($3,527 + $411 + $1,120) x 2.038] $10,308 Supplemental— settling ponds (p. 47) 1,163 gpm Base cost Y c = 3.982(1,163)°- 952 = $3,300 Construction labor $3,300 x 0.75 x 1.025 = $2,537 Fuel and lubrication $3,300 x 0.13 x 0.991 = 425 Equipment parts $3,300 x 0.12 x 1.005 = 397 Settling pond capital cost = ($2,537 + $425 + $397) $3,360 87 CAPITAL COST SUMMARY FORM Item Cost Exploration: Method 1 cost $ Method 2 cost 94,485 Development: Access roads 88,180 Clearing 9,725 Preproduction overburden removal: Bulldozers Draglines Front-end loaders Rear-dump trucks Scrapers 1 2,077 Mine equipment: Backhoes 266,792 Bulldozers 69,022 Draglines Front-end loaders 272,207 Rear-dump trucks Scrapers 200,81 7 Processing equipment: Conveyors 16,115 Feed hoppers 4,022 Jig concentrators 56,601 Sluices 1 ,700 Spiral concentrators Table concentrators Trommels 95,221 Vibrating screens Supplemental: Buildings 41 ,994 Camp 51 ,476 Generators 22,530 Pumps 1 0,308 Settling ponds 3,360 Subtotal 1,316,632 Contingency (1 0%) 131,663 Total 1,448,295 Figure A-2.— Capital cost summary form completed for example estimation. S8 OPERATING COSTS Overburden removal— scrapers (p. 52) 250 LCY/h 3,000-ft average haul distance +8% average haul gradient plus rolling resistance Used equipment Equipment Y E = 0.325(250)-°- 210 = $0.102/LCY Parts $0,102 x 0.18 x 1.005 = $0,018 Fuel and lubrication $0,102 x 0.48 x 0.991 = 0.049 Tires $0,102 x 0.34 x 0.939 = 0.033 $0,100 Labor Y L = 12.01(250)-°- 930 = $0.071/LCY Labor $0,071 x 1.00 x 1.025 = $0,073 Distance factor F D = 0.01947(3,000) - 577 = 1.975 Gradient factor F G = 0.776e [0047(8)! = 1.130 Used equipment factor U e = 1. 096(250)" 0006 = 1.060 U, = 0.845(250) 0034 = 1.019 Overburden removal cost [(0.100 x 1.060) + (0.073 x 1.019)] x 1.975 x 1.130 = $0.403/LCY Annual scraper operating cost = $0.403/LCY x 375,000 LCY/a $151,125 Mining— backhoes (p. 53) Pay gravel excavation 100 LCY/h 80% maximum digging depth Medium-hard digging difficulty Equipment Y E = 8.360(100r 1019 = $0.077/LCY Parts $0,077 x 0.38 x 1.005 = $0,029 Fuel and lubrication $0,077 x 0.62 x 0.991 = _ 0.047 $0,076 Labor Y L = 17.53(100r 1009 = $0.168/LCY Labor $0,168 x 1.00 x 1.025 = $0,172 Digging depth factor F D = 0.09194(80) 0608 = 1.320 Digging difficulty factor F H = 1.500 Backhoe mining cost = [(0.076 + 0.172)] x 1.320 x 1.500 = $0.491/LCY Annual backhoe operating cost = $0.491/LCY x 150,000 LCY/a $73,650 89 Mining— front-end loaders (p. 56) Pay gravel haulage 100 LCY/h total Two 50-LCY/h loaders 800-ft average haul distance + 6% average haul gradient plus rolling resistance Equipment Y E = 0.407(50)" - 225 = $0.169/LCY Parts $0,169 x 0.22 x 1.005 = $0,037 Fuel and lubrication $0,169 x 0.46 x 0.991 = 0.077 Tires $0,102 x 0.32 x 0.939 = 0.051 $0,165 Labor Y L = 13.07(50)-°- 936 = $0.336/LCY Labor $0,336 x 1.00 x 1.025 = $0,344 Distance factor F D = 0.023(800) 0616 = 1.413 Gradient factor F G = 0.877e [0046(6)] = 1.156 Pay gravel transportation cost = (0.165 + 0.344) x 1.413 x 1.156 = $0.831/LCY Annual front-end loader operating cost = $0.831/LCY x 150,000 LCY/a $124,650 Processing— conveyors (p. 59) 70 yd 3 /h Equipment Y E = 0.218(70)-°- 561 Parts $0,020 x 0.72 x 1.005 Electricity $0,020 x 0.24 x 1.029 Lubrication $0,020 x 0.04 x 0.991 Labor Y L = 0.250(70)-°- 702 Labor $0,013 x 1.00 x 1.025 Conveyor operating cost = (0.020 + 0.013) = $0.033/yd 3 Annual conveyor operating cost = $0.033/yd 3 x 105,000 yd 3 /a $0.020/yd 3 $0,014 0.005 0.001 $0,020 $0.013/yd 3 $0,013 $3,465 Processing— feed hoppers (p. 60) 100 LCY/h total Equipment Y E = 0.033(100r - 344 = Parts $0,007 x 0.88 x 1.005 = Electricity $0,007 x 0.06 x 1.029 = Lubrication $0,007 x 0.06 x 0.991 = Labor Y L = 0.017(100)- °- 295 = Labor $0,004 x 1.00 x 1.025 = Feed hopper operating cost = (0.007 + 0.004) = $0.011/LCY Annual feed hopper operating cost = $0.011/LCY x 150,000 LCY/a $0.007/LCY $0,006 0.0004 0.0004 $0,007 $0.004/LCY $0,004 $1,650 90 Processing— rougher jig (p. 61) 20 ydVh Equipment Y E = 0.113(20)-°- 328 = Parts $0,042 x 0.40 x 1.005 = Electricity $0,042 x 0.34 x 1.029 = Lubrication $0,042 x 0.26 x 0.991 = Supplies Y s = 0.002(20r 0184 = Industrial materials $0,001 x 1.00 x 1.003 = Labor Y L = 3.508(20)" 1268 = Labor $0,079 x 1.00 x 1.025 = Rougher service factor F R = Rougher jig operating cost = (0.043 + 0.001 + 0.081) x 0.344 = $0.043/yd 3 Annual rougher jig operating cost = $0.043/yd 3 x 30,000 yd 3 /a . . . . $0.042/yd 3 $0,017 0.015 0.011 $0,043 $0.001/yd 3 $0,001 $0.079/yd 3 $0,081 0.344 $1,290 Processing— cleaner jigs (p. 61) 2 at 5 yd 3 /h Equipment Y E = 0.113(5)-°- 328 Parts $0,067 x 0.40 x 1.005 Electricity $0,067 x 0.34 x 1.029 Lubrication $0,067 x 0.26 x 0.991 Supplies Y s = 0.002(5)-° 184 Industrial materials $0,001 x 1.00 x 1.003 Labor Y L = 3.508(5)" 1268 Labor $0,456 x 1.00 x 1.025 Cleaner jig operating cost = (0.067 + 0.001 + 0.467) = $0.535/yd 3 Annual cleaner jig operating cost = $0.535/yd 3 x 15,000 yd 3 /a. $0.067/yd 3 $0,027 0.023 0.017 $0,067 $0.001/yd 3 $0,001 $0.456/yd 3 $0,467 $8,025 91 Processing— final jig (p. 61) 0.2 yd 3 /h Equipment Y E = 0.113(0.2)-°- 328 Parts $0,192 x 0.40 x 1.005 Electricity $0,192 x 0.34 x 1.029 Lubrication $0,192 x 0.26 x 0.991 Supplies Y s = 0.002(0.2)-° 184 Industrial materials $0,003 x 1.00 x 1.003 Labor Y L = 3.508(0.2)" 1268 Labor $26,999 x 1.00 x 1.025 Final jig operating cost = (0.193 + 0.003 + 27.674) = $27.870/yd 3 Annual final jig operating cost = $27.870/yd 3 x 300 yd 3 /a . . . $0.192/yd 3 $0,077 0.067 0.049 $0,193 $0.003/yd 3 $0,003 $26.999/yd 3 $27,674 $8,361 Processing— sluices (p. 62) 50 yd 3 /h Labor Y L = 0.377(50)-°- 636 Labor $0,031 x 1.00 x 1.025 Sluice operating cost = $0.032/yd 3 Annual sluice operating cost - $0.032/yd 3 x 75,000 yd 3 /a $0.031/yd 3 $0,032 $2,400 92 Processing— Sluices (p. 62) 20 ydVh Labor Y L = 0.377(20)-°- 636 Labor $0,056 x 1.00 x 1.025 Sluice operating cost = $0.057/yd 3 Annual sluice operating cost = $0.057/yd 3 x 30,000 yd7a $0.056/yd 3 $0,057 $1,710 Processing— Tailings removal— bulldozers (p. 65) 100 LCY/h 400-ft average haul distance -8% average haul gradient Equipment Y E = 0.993(100)-°- 430 = $0.137/LCY Parts $0,137 x 0.47 x 1.005 = $0,065 Fuel and lubrication $0,137 x 0.53 x 0.991 = 0.072 $0,137 Labor Y L = 14.01(100)-°- 945 = $0.180/LCY Labor $0,180 x 1.00 x 1.025 = $0,185 Distance factor F D = 0.00581(400)° 904 = 1.307 Gradient factor F G = 1.041e [0015( - 8)] = 0.923 Used equipment factor U e = 1.206(100)-° 013 = 1.136 Uj = 0.967(100) 0015 = 1.036 Tailings removal cost = [(0.137 x 1.136) + (0.185 x 1.036)] x 1.307 x 0.923 = $0.419/LCY Annual bulldozer operating cost = $0.419/LCY x 150,000 LCY/a $62,850 Processing— trommels (p. 70) 100 yd 3 /h Equipment Y E = 0.217(100r°- 403 Parts $0,034 x 0.63 x 1.005 Electricity $0,034 x 0.26 x 1.029 Lubrication $0,034 X 0.11 x 0.991 Labor Y L = 0.129(100)-°- 429 Labor $0,018 x 1.00 x 1.025 Trommel operating cost = ($0,035 + $0,018) = $0.053/yd 3 Annual trommel operating cost = $0.053/yd 3 x 150,000 yd 3 /a $0.034/yd 3 $0,022 0.009 0.004 $0,035 $0.018/yd 3 $0,018 $7,950 93 Supplemental— housing (p. 72) 100 LCY/h pay gravel 250 LCY/h overburden 350 LCY/h total Supplies Y s = 1.445(350)-°- 583 Fuel $0,047 x 0.05 x 0.991 Industrial materials $0,047 x 0.95 x 1.003 = $0.047/LCY $0,002 0.045 $0,047 Housing operating cost = $0.047/LCY Annual housing operating cost = $0.047/LCY x 525,000 LCY/a $24,675 Supplemental— lost time and general services (p. 74) 100-yd 3 /h mill feed Equipment Y E = 0.142(100) 0004 = $0.145/LCY Fuel $0,145 x 0.53 x 0.991 = $0,076 Parts $0,145 x 0.47 x 1.005 = 0.068 $0,144 Labor Y L = 2.673(100)-°' 524 = $0.239/LCY Labor $0,239 x 1.00 x 1.025 = $0,245 Lost time and general service cost = ($0,144 + $0,245) = $0.389/LCY Annual lost time and general service cost = $0.389/LCY x 675,000 LCY/a $262,575 Supplemental— pumps (p. 75) 100 ydVh mill feed 1,163 gpm 80-ft head Equipment Y E = 0.007(1, 163) 0713 = Fuel and lubrication $1,074 x 0.59 x 0.991 = Parts $1,074 x 0.41 x 1.005 = Labor Y L = 0.004(1163) - 867 = Labor $1,819 x 1.00 x 1.025 = Head factor H e = 0.09K80) - 735 = H, = 0.054(80) 0893 = Pump operating cost = [($1,071 x 2.279) + ($1,864 x 2.739)] = $7.546/h Annual pump operating cost = $7.546/h x 1,500 h/a $1.074/h $0,628 0.443 $1,071 $1.819/h $1,864 2.279 2.739 $11,319 ** 788 4b'3 94 OPERATING COST SUMMARY FORM Item Annual cost Overburden removal: Bulldozers $ Draglines Front-end loaders Rear-dump trucks 151,125 Scrapers Mining: Backhoes 73,650 Bulldozers Draglines Front-end loaders 124,650 Rear-dump trucks Scrapers Processing: Conveyors 3,465 Feed hoppers 1 ,650 Jig concentrators 1 7,676 Sluices 4,110 Spiral concentrators Table concentrators Tailings removal: Bulldozers 62,850 Draglines Front-end loaders Rear-dump trucks Scrapers Trommels 7,950 Vibrating screens Supplemental: Employee housing 24,675 Lost time and general services 262,575 Pumps 11,319 Subtotal 745,695 Contingency (1 0%) 74,570 Total 820,265 Cost per cubic yard pay gravel = total annual cost divided by pay gravel mined per year. $820,265/150,000 LCY/a = $5.47/LCY Final cost per cubic yard pay gravel $5.47 Figure A-3.— Operating cost summary form completed for example estimation. ^? *t> »' ^ . » • o . ^-i. 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