Cost Estimation Handbook for Small Placer Mines
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';>,'/ TN295 iMlH JHHH|1 nHHHHHh ' 1111111 ''''" ';..- '' "' •" •' Bl ' 1 1 ' ''!' ' :i sBjSSi'BB' ''.''•''iv'''' .- ''.''i ffiffiSsS m : IBI WKm iiH >v.« ^c- ^ 0^ .V.' V • • • » < * ^ J, " • » «' A> Cti ^ ... <*_ A> ... «>> v-cr 'bV ^°^ ^ * '^.*-p •*•_ v \f> q # •" 1 s.0 .»!•'* *> v * 1 • %'*^L'* *> * • > » \ '• <l^ o ~>^W&S jy ^ *?* ^'.l'* ^ ^% J«K- * ** -lw-V O. « , . <1 A> ... <a ^ • o. <j5°x. : • y\^ r+t* Vk I a° v. / ^v /, v • v^v\. * v-^v v^-v . v^v V v^v va :»^o ^^ft o^MM?» j>a^ *^Ei^- cS°: : **">. -. ^' B ^ <> v » 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 Page Abstract 1 Preproduction overburden removal 24 Introduction 2 Bulldozers 24 Acknowledgments 2 Draglines 25 Front-end loaders 26 Rear-dump trucks 27 Section 1.—Placer Mine Design Scrapers 28 Mine equipment 29 Exploration 3 Backhoes 29 4 Panning Bulldozers 30 4 Churn drilling Draglines 31 4 Bucket drilling Front-end loaders 32 5 Rotary drilling Rear-dump trucks 33 5 Trenching Scrapers 34 Seismic surveys 5 Processing equipment 35 Mining 5 Conveyors 35 Backhoes (hydraulic excavators) 6 Feed hoppers 36 6 Bulldozers Jig concentrators 37 6 Draglines Sluices 38 6 Dredges Spiral concentrators 39 7 Front-end loaders Table concentrators 40 Rear-dump trucks 7 Trommels 41 7 Scrapers Vibrating screens 42 Processing 7 Supplemental 43 8 Conveyors Buildings 43 Feed hoppers 8 Employee housing 44 8 Jig concentrators Generators 45 Sluices 8 Pumps 46 Spiral concentrators 9 Settling ponds 47 Table concentrators 9 Operating costs 48 Trommels 9 Overburden removal 48 Vibrating screens 10 Bulldozers 48 mill design 10 Sample Draglines 49 Supplemental systems 13 Front-end loaders 50 Buildings 13 Rear-dump trucks 51 facilities 13 Camp Scrapers 52 lost time 13 General services and Mining 53 Generators 13 Backhoes 53 14 Pumps Bulldozers 54 14 Settling ponds Draglines 55 Environment 14 Front-end loaders 56 estimation 15 Cost Rear-dump trucks 57 equations 15 Cost Scrapers 58 Cost date 15 adjustments Processing 59 16 Site adjustment factors Conveyors 59 17 Labor rates Feed hoppers 60 Financial analysis 18 Jig concentrators 61 Bibliography 18 Sluices 62 Spiral concentrators 63 Section 2.—Cost Estimation Table concentrators 64 Tailings removal 65 Capital and operating cost categories 19 Bulldozers 65 Capital costs 20 Draglines 66 Exploration 20 Front-end loaders 67 Panning 21 Rear-dump trucks 68 Churn drilling 21 Scrapers 69 Bucket drilling 21 Trommels 70 Trenching 21 Vibrating screens 71 General reconnaissance 21 Supplemental 72 Camp costs 21 Employee housing 72 Seismic surveying (refraction) 21 Generators 73 Rotary drilling 21 Lost time and general services 74 Helicopter rental 21 Pumps 75 Development 22 Bibliography 78 Access roads 22 Clearing 23 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 2 ft square foot 2 3 ft /yd 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 yd3 cubic yard lb/LCY pound per loose cubic yd 3/d cubic yard per day 3 2 yard yd /ft 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- mining techniques. If the reader is unfamiliar with this ment of U.S. mineral supplies under its Minerals Avail- form of mining, section 1 should be thoroughly understood ability Program (MAP). To aid in this program, a technique prior to estimating costs. was developed to estimate capital and operating costs Section 2 contains cost equations that enable the user associated with various mining methods. This technique, to estimate capital and operating costs of specific placer developed under a Bureau contract by STRAAM Engineers, techniques. Cost equations are designed to handle the wide Inc., was completed in 1975, then updated in 1983. During variety of conditions commonly found in placer deposits. the course of the update, it was noted that few provisions This allows the reader to tailor estimates to the were made for estimating the costs of small-scale mining characteristics of a particular deposit, which ensures and milling methods typically associated with placer min- representative costs. Although based primarily on gold ing. The popularity and widespread use of placer mining placer operations, cost equations are valid for any other com- methods indicated that a cost estimating system for placer modity found in deposits of unconsolidated material. Equa- mining would be of value to prospectors, miners, investors, tions are geared to operations handling between 20 and 500 and government evaluators. LCY/h of material (pay gravel plus overburden). Estimated This report has been written to aid those involved with costs are representative of operations in the western United placer mining in the estimation of costs to recover valuable States and Alaska, and are based on a cost date of January minerals from placer deposits. It relies on the principle that 1985. cost estimates will be representative only if calculated for The appendix provides an example of placer mine design technically feasible mining operations. Because the design and cost estimation using the information contained in this of such an operation can be difficult, provisions have been report. made to assist the user in achieving this goal. This report is not intended to be an exhaustive discus- Section 1 of the report describes the processes involved sion of placer mining. Many detailed texts have been writ- in placering, and may be used to aid in designing a viable ten on this process, any one of which will assist the reader mine. Operational parameters for equipment commonly in method design. A number of these are listed in the used in placer exploration, mining, and processing are bibliographies accompanying sections 1 and 2. discussed, as well as basic principles of successful placer ACKNOWLEDGMENTS A special debt is owed to the late George D. Gale, of the ideas and facts it contains, are the product of his metallurgist, Bureau of Mines. This handbook, and many ingenuity. SECTION 1.—PLACER MINE DESIGN The complete design of a placer mine involves the in- 5 . Geologic characteristics, volume and depth of tegration of exploration, mining, processing, and sup- overburden. plemental systems for the efficient recovery of valuable 6 . Depth, profile, and geologic characteristics of minerals from an alluvial deposit. This design is the first bedrock. step in accurate cost estimation. 7 . Local topography. In this section, individual systems are categorized as 8 . Physical characteristics and geologic nature of follows: valuable minerals. 9 . Availability of water. Exploration.—The phase of the operation in which 1. 10. Availability of power. resources are delineated. Because the amount of time and 11.