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IC 
 
 9040 
 
 Bureau of Mines Information Circular/1985 
 
 Environmental Issues Related to Mineral 
 Development in the Stillwater Complex, 
 MT 
 
 By Michael T. Nigbor, Stephen R. Iverson, and Paul C. Hyndman 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 75! 
 
 Mines 75th a^ 
 
(AJ^UMtJjs. | W^ ^ 
 
 Information Circular 9040 
 
 Environmental Issues Related to Mineral 
 Development in the Stillwater Complex, 
 MT 
 
 By Michael T. Nigbor, Stephen R. Iverson, and Paul C. Hyndman 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 Donald Paul Hodel, Secretary 
 
 BUREAU OF MINES 
 Robert C. Horton, Director 
 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 
 
 °F degree Fahrenheit 
 
 ft foot 
 
 ft 3 cubic foot 
 
 ft^/yr square foot per year 
 
 g/h gram per hour 
 
 gpm/ft 2 gallon per minute 
 
 min 
 
 ml* 
 
 urn 
 
 mph 
 
 MW 
 
 NTU 
 
 
 per square foot 
 
 h 
 
 hour 
 
 in 
 
 inch 
 
 in/yr 
 
 inch per year 
 
 kW 
 
 kilowatt 
 
 lb 
 
 pound 
 
 minute 
 
 milliliter 
 
 micrometer 
 
 mile per hour 
 
 megawatt 
 
 nephelometric 
 turbidity unit 
 
 lb/acre pound per acre 
 
 ug/m 3 
 
 microgram per cubic meter 
 
 pet percent 
 
 ppm part per million 
 
 tpd ton (short) per day 
 
 tpy ton (short) per year 
 
 wt pet weight percent 
 
 yd 3 cubic yard 
 
 yr year 
 
 Library of Congress Cataloging in Publication Data: 
 
 Nigbor, Michael T 
 
 Environmental issues related to mineral development in the Still- 
 water Complex, MT. 
 
 (Information circular ; 9040) 
 
 Bibliography: p. 32-33. 
 
 Supt. of Docs, no.: I 28.27: 9040. 
 
 1, Mineral industries— Environmental aspects— Montana. I. Iverson, 
 Stephen R. II. Hyndman, Paul C. III. United States. Bureau of Mines. 
 IV. Title. V. Title: Stillwater Complex, Montana. VI. Series: Infor- 
 mation circular (United States. Bureau of Mines) ; 9040. 
 
 TN295.U4 [TD195.M5] 622s [338.2'74] 85-600062 
 
 
 f\0< 
 

 PREFACE 
 
 This report provides information on the environmental issues associ- 
 ated with mining strategic minerals in the Stillwater Complex, MT. It 
 is not an environmental impact statement and is not meant to serve as 
 one. Its purpose is informational; it is intended for use by planners 
 in the minerals field. If any of the potential operations discussed in 
 this report should become reality, separate, site-specific environmen- 
 tal impact statements will be required. 
 
 In general, the scenarios used to estimate production ranges were 
 constructed with the goal of domestic mineral self-sufficiency in mind. 
 Beyond this, political and policy issues associated with such mining 
 operations were not considered. 
 
 The reader is reminded that the mining operations described are based 
 on hypothetical scenarios. At the time this report was prepared, only 
 the 1,000- tpd platinum-group metal (PGM) operation had any firm plans 
 associated with it. The authors are aware of no plans to produce Cr or 
 Ni from deposits in the Stillwater Complex. 
 
Ill 
 
 CONTENTS 
 
 Page 
 
 Abstract. 1 
 
 Introduction 2 
 
 General description of the Stillwater Complex 2 
 
 Regulatory environment 3 
 
 Operation descriptions 6 
 
 Chromium 6 
 
 PGM 7 
 
 Nickel-copper 9 
 
 Land issues 12 
 
 Tailings disposal plans 12 
 
 Chromite tailings 12 
 
 PGM tailings — Minneapolis Adit site 12 
 
 PGM tailings — Hertzler Ranch site. 13 
 
 Nickel-copper tailings 14 
 
 Combined tailings 14 
 
 Tailings pond reclamation 14 
 
 Chromite tailings 14 
 
 PGM tailings 15 
 
 Nickel-copper tailings 15 
 
 Ferrochrome smelter waste 15 
 
 Waste rock 17 
 
 Land use changes 17 
 
 Visual impacts 18 
 
 Summary of land issues 18 
 
 Water issues 21 
 
 Surface waters baseline quality 21 
 
 Mine drainage water quality 23 
 
 New source performance standards 24 
 
 Ferrochrome smelter waste water 24 
 
 Nickel-copper processing waste water 26 
 
 Diversion of streams 26 
 
 Summary of water issues 27 
 
 Air issues 27 
 
 Baseline air quality 27 
 
 Ferrochrome smelter gas emissions 28 
 
 Dust 30 
 
 Other air issues 30 
 
 Other issues 31 
 
 Noise 31 
 
 Power, transportation, and housing 31 
 
 Conclusions 31 
 
 References 32 
 
 ILLUSTRATIONS 
 
 1. General geology of study area, showing the Stillwater Complex 3 
 
 2. Looking west across the Stillwater River at the Mouat chromite and Ni-Cu 
 
 areas 4 
 
 3 . Geologic map of the Mouat Mine area 5 
 
 4 . Plan map of Cr mine-mill-smelter facilities 6 
 
 5 . Plan map of PGM mine-mill facilities .• 7 
 
ILLUSTRATIONS — Continued 
 
 Page 
 
 6. Minneapolis Adit, main haulage for PGM operations..... 8 
 
 7. Plan map of tailings pond at Hertzler Ranch area for PGM operations, high 
 
 production rate 9 
 
 8. Hertzler Ranch area. 10 
 
 9. Plan map of combined operations, a hypothetical worst case 10 
 
 10. Verdigras Creek 11 
 
 11. Upstream and centerline methods of constructing tailings dams 13 
 
 12. Waste rock terracing method 17 
 
 13. Visual effects of PGM mining operations at the low production rate 19 
 
 14. Visual effects of combined operations, a hypothetical worst case 19 
 
 15. Visual effects of Ni-Cu open pit from Beartooth Ranch 20 
 
 16. Visual effects of Ni-Cu open pit from Woodbine Falls 20 
 
 17. Water sample locations 21 
 
 18. Ferrochrome smelter water treatment system 26 
 
 19. Wind roses from the Stillwater River Valley.' 28 
 
 20. Ferrochrome smelter air control system 29 
 
 TABLES 
 
 1. Revegetation species used in reclamation 14 
 
 2. Water quality regulatory standards 22 
 
 3. Surface water samples exceeding regulatory standards 22 
 
 4. New source performance standards for Ni mining and milling 24 
 
 5. New source performance standards for Pt mining and milling 24 
 
ENVIRONMENTAL ISSUES RELATED TO MINERAL DEVELOPMENT 
 IN THE STILLWATER COMPLEX, MT 
 
 By Michael T. Nigbor, Stephen R. Iverson, and Paul C. Hyndman 
 
 ABSTRACT 
 
 This Bureau of Mines publication identifies the significant environ- 
 mental issues associated with the potential development of strategic 
 and critical minerals in the Stillwater Complex, MT. The Stillwater 
 Complex contains deposits of Cr, platinum-group metals (PGM), and Ni. 
 Issues that must be addressed prior to minerals development include the 
 effects mining, milling, and smelting will have on the land, water, and 
 air, and methods of minimizing the environmental impacts. 
 
 ^Mining engineer, Denver Research Center, Bureau of Mines, Denver, CO. 
 
 ^Mining engineer, Western Field Operations Center, Bureau of Mines, Spokane, WA. 
 
INTRODUCTION 
 
 Our Nation depends on foreign sources 
 for a host of mineral products. One of 
 the Bureau's main goals is to minimize 
 such dependence, by conducting research 
 that leads to technology for better uti- 
 lizing domestic resources. The Bureau 
 also maintains current statistics on 
 import dependence, production, and 
 recycling (J_) . 3 
 
 The strategic and critical minerals is- 
 sue has been described in the literature. 
 A recent publication, "World Index of 
 Strategic Minerals: Production, Exploi- 
 tation, and Risk" (2^, provides a very 
 complete summary of the issue. 
 
 A potential domestic source of some 
 strategic minerals is the Stillwater Com- 
 plex, in south-central Montana. It is a 
 geologic structure that contains deposits 
 of Cr, PGM, and Ni. The Nation's largest 
 known resources of Cr and PGM are located 
 here (3). Nickel deposits are smaller, 
 but still significant. The PGM deposits 
 are possibly economic to mine, and in 
 fact are being evaluated by the Stillwa- 
 ter Mining Co. for economic viability. 
 The Cr and Ni deposits are not considered 
 economic to mine at today's prices. 
 
 Certain environmental issues could af- 
 fect the development of domestic strate- 
 gic and critical deposits such as those 
 in the Stillwater Complex. Environmental 
 
 regulations resulting from the National 
 Environmental Policy Act, the Clean Water 
 Act, the Clean Air Act, and others set 
 standards for the development of mineral 
 deposits by requiring the consideration 
 of environmental impacts and the limita- 
 tion of certain types of waste discharges 
 (4). This report attempts to identify 
 the major environmental issues in the 
 Stillwater Complex, to describe baseline 
 conditions, and to suggest solutions to 
 environmental problems related to poten- 
 tial strategic mineral development. With 
 this information and with adequate plan- 
 ning, development can occur in a timely 
 fashion without undue environmental 
 impacts. 
 
 In determining environmental issues, 
 the strategy taken was to assume two sce- 
 narios for each commodity, one low-end 
 scenario and one high-end scenario. The 
 low- and high-end scenarios were estab- 
 lished by analysis of minimum economic 
 size, most likely mining method, size of 
 resource, current technological limita- 
 tions, and current market consumption. 
 The low- and high-end scenarios can be 
 thought of as resulting in minimum and 
 maximum potential environmental effects, 
 respectively. In this way, the most 
 likely production rates were bounded by 
 the low- and high-end scenarios. 
 
 GENERAL DESCRIPTION OF THE STILLWATER COMPLEX 
 
 The Stillwater Complex is a magraatic 
 segregation geologic structure 1 to 5 
 miles wide and 28 miles long. It is 
 located about 60 miles southwest of Bil- 
 lings, MT (fig. 1). The complex occurs 
 in the Beartooth Mountains of the Rocky 
 Mountain physiographic province. The 
 complex is oriented in a northwest- 
 southeast direction. 
 
 The complex is cut on the southeast 
 third by the Stillwater River Valley, 
 a broad, glaciated, northeast-trending 
 valley (fig. 2). Elevation at the valley 
 floor is about 5,000 ft above sea level. 
 
 ■^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this report. 
 
 Chrome Mountain, in the northwest third, 
 is the highest point in the complex, 
 about 10,000 ft above sea level. 
 
 The West Fork Stillwater River cuts the 
 complex about 5 miles northwest of the 
 Stillwater River. The West Fork Stillwa- 
 ter River runs in a narrow canyon, the 
 floor of which is about 6,500 ft above 
 sea level at the complex. The East Boul- 
 der River cuts the complex 5 miles far- 
 ther along in a similar steep canyon. 
 The Boulder River Valley forms the ter- 
 minus of the complex on the northwest. 
 The Boulder River has an elevation of 
 about 5,000 ft above sea level at the 
 complex and runs essentially south-north. 
 Northeast of the Stillwater Complex, the 
 Boulder and Stillwater Rivers flow into 
 
© 
 
 LEGEND 
 Sedimentary rocks 
 Stillwater Complex 
 Metamorphic rocks 
 Mines (inactive) 
 ) Gish (Cr) 
 Mouat (Cr) 
 Mouat (Ni-Cu) 
 Stillwater (PGM) 
 Benbow (Cr) 
 
 \ MON 
 
 
 MONTANA 
 
 Study a 
 
 FIGURE 1. - General geology of study area, 
 showing the Stillwater Complex. 
 
 the Yellowstone River, which in turn 
 flows to the Missouri River. 
 
 Northeast of the complex, the topog- 
 raphy changes from mountainous to more 
 gentle terrain. Mesas and hogbacks sep- 
 arated by broad valleys give way to 
 
 rolling topography. South and west of 
 the complex, the topography again becomes 
 mountainous in the Beartooth Range, 
 with some peaks exceeding 14,000 ft in 
 elevation. 
 
 Mining activity in the Stillwater Com- 
 plex includes past mining of chromite (5- 
 6_) , current development of PGM, and ex- 
 ploration for Ni and Cu. 
 
 The Stillwater Complex is a layered 
 magma intrusive, consisting of three ma- 
 jor units: the Basal, Ultramafic, and 
 Banded zones. Nickel, copper, chromium, 
 and PGM occur in high concentrations in 
 specific zones of the complex. In the 
 Basal zone, Ni occurs as pentlandite in 
 pyrrhotite and Cu occurs as chalcopyrite. 
 Chromium occurs as chromite in the Ultra- 
 mafic zone, and the PGM occur as several 
 platinum-group sulfides in the Banded 
 zone. The Ni-Cu sulfides are generally 
 in discontinuous irregular layers. The 
 chromite occurs in several lenses and 
 layers, alphabetically designated, with 
 two layers, the G and H zones, being 
 the thickest and most continuous. The 
 platinum-group sulfides occur in an al- 
 most continuous zone 3 to 6 ft thick. 
 
 The geology of the Stillwater Complex 
 has been discussed in the literature (7- 
 8). Geologic maps of the Stillwater Com- 
 plex area and the Mouat Mine area are 
 shown as figures 1 and 3. 
 
 REGULATORY ENVIRONMENT 
 
 The regulatory environment (the envi- 
 ronmental and mine development regula- 
 tions and agencies) is complex; however, 
 a brief description is presented here. 
 
 The National Environmental Policy Act 
 (NEPA) of 1969 directs all Federal agen- 
 cies to provide environmental impact 
 statements (EIS's) to the U.S. Council on 
 Environmental Quality before proceeding 
 with any major action that significantly 
 affects the environment. NEPA' s require- 
 ments are supplemented by the Montana 
 Environmental Policy Act (MEPA) . MEPA's 
 more stringent requirements would super- 
 sede those of NEPA. MEPA and NEPA re- 
 quirements extend to both State and Fed- 
 eral lands within Montana. 
 
 In the Stillwater Complex, mining oper- 
 ations can potentially be on U.S. Forest 
 
 Service (USFS) land and private lands. 
 Montana Department of State Lands (DSL) 
 administers the 1971 Montana Metal Mine 
 Reclamation Act (formerly the Hard Rock 
 Mining Act) , which applies to all lands 
 within Montana. DSL has sole regulatory 
 authority on patented mining claims with- 
 in Federal lands. DSL requires that a 
 reclamation plan be submitted and ap- 
 proved as part of an application for an 
 operating permit. A bond would also be 
 posted to ensure that adequate funds are 
 reserved for future land reclamation (9) . 
 DSL would regulate mining activity on 
 both Federal and private lands. 
 
 USFS regulates mining activity under a 
 number of laws, including the 1872 Mining 
 Law and amendments, the Organic Admini- 
 stration Act of 1897, the Mining and 
 
FIGURE 2. - Looking west across the Stillwater River at the Mouat chromite and Ni-Cu areas. 
 
 Mineral Policy Act of 1970, the National 
 Materials and Minerals Policy, Research, 
 and Development Act of 1980, and a number 
 of Executive (Presidential) Orders. USFS 
 manages surface resources on unpatented 
 mining claims and issues permits for op- 
 erations primarily limited to facilities 
 and uses of forest lands. 
 
 A proposed PGM operation at the Min- 
 neapolis Adit would be an example of 
 a combined Federal-State jurisdiction. 
 Most of the proposed mine is in a na- 
 tional forest, while the associated sur- 
 face facilities are on private land. 
 Before the company can commercially de- 
 velop its mineral properties, it requires 
 an operating permit from DSL, an approval 
 
 of its plan of operations from USFS, and 
 air and water quality permits from the 
 Montana Department of Health and Environ- 
 mental Sciences (MDH&ES) . An EIS must 
 be prepared in accordance with MEPA and 
 NEPA requirements to be used as a guide 
 for approval of permits and operation 
 plans. A draft EIS on the project ( 10 ) 
 was filed jointly by DSL and USFS in 
 1985. 
 
 An EIS must contain data on base- 
 line conditions, the proposed operation, 
 alternatives to the proposed operation, 
 and its environmental impacts. Most of 
 this information would be provided in 
 the application(s) for a raining permit 
 filed by the developer with DSL, USFS, 
 
Scale, ft 
 
 Q Quaternary alluvium 
 
 LEGEND 
 
 t ■ ■ ■ ■ ■ i Archean hornfels regionally 
 *■ ' ■ > r ^' metamorphosed 
 
 [;■;;; Pji;'.;^ Paleozoic sedimentary rocks * Mines 
 
 ® Mouat (Cr) 
 © Mouat (Ni-Cu) 
 
 Aqmg Archean quartz monzonite 
 
 i * ■ »] Archean banded zone 
 
 IV*. .1 (platinum group within this zone) © Stillwater (PGM) 
 
 y/AJS/A Archean ultramafic zone * — » — » Thrust fault 
 
 V/iii/A (chromite bands within this zone) 
 
 I i ' ■ ! ' A t>J 1 1 1 1 Archean basal zone 
 
 (Ni-Cu sulfides) 
 
 FIGURE 3. - Geologic map of the Mouat Mine area. 
 
 or both. The result is that the devel- 
 oper bears the expense of generating the 
 data for the EIS that is required before 
 an agency can grant a mining permit. 
 
 Beyond the requirements for a mining 
 permit and an EIS, each operation in the 
 Stillwater Complex would also need per- 
 mits to discharge waste into the air and 
 water. These requirements are estab- 
 lished in the Clean Air Act and the Clean 
 Water Act and are administered by the En- 
 vironmental Protection Agency (EPA) or 
 the State if it has approved programs. 
 
 EPA has promulgated regulations limit- 
 ing the types and amounts of various 
 pollutants allowed from mining, mill- 
 ing, and smelting operations. In par- 
 ticular, regulations called new source 
 performance standards (NSPS) for mining, 
 milling, and smelting have recently been 
 
 issued (11). These regulations would 
 have an impact on any potential mineral 
 operations in the Stillwater Complex. 
 
 The Montana Department of Natural Re- 
 sources and Conservation (DNR&C) admini- 
 sters air and water pollution regulations 
 under State law. In accordance with an 
 agreement between the EPA and DNR&C, 
 DNR&C administers EPA's air and water 
 programs within the State of Montana, 
 thereby streamlining the permit process. 
 The agreement basically states that Mon- 
 tana's program has been reviewed by the 
 EPA and approved as being at least as 
 rigorous as the national program. 
 
 Other requirements before a mineral 
 operation can go into production in- 
 clude permits required by the U.S. Mine 
 Safety and Health Administration, the 
 U.S. Occupational Safety and Health 
 
Administration, and various local author- 
 ities. Most of these permits are related 
 to the health and well-being of workers 
 and not directly to environmental issues. 
 
 The Montana Hardrock Mining Impact Board 
 requires that a company supply prepay- 
 ment for estimated socioeconomic impacts 
 due to planned mining operations. 
 
 OPERATION DESCRIPTIONS 
 
 Two scenarios were selected for Cr op- 
 erations: the low-end scenario was based 
 on a production rate of 1,000 tpd ore and 
 the high-end scenario used 2,500 tpd ore. 
 Operations outside this range were con- 
 sidered unlikely, based on engineering 
 considerations, the nature of demand for 
 Cr , and the extent of the resources. 
 
 Two scenarios were selected for PGM op- 
 erations , based on recent development 
 in the area and demand for PGM. The low- 
 end scenario used a production rate of 
 1,000 tpd, and the high-end scenario used 
 4,000 tpd. 
 
 Only one scenario was used for Ni-Cu 
 operations. The production rate selected 
 was 27,500 tpd ore, with 24,800 tpd 
 waste. This size is speculative, as 
 very few solid engineering data were 
 available. 
 
 The following three sections provide 
 basic information on potential Cr , PGM, 
 and Ni-Cu mining and milling operations 
 in the Stillwater Complex. 
 
 CHROMIUM 
 
 Two scenarios were examined for a mine- 
 mill-furnace, chromite-to-f errochrome fa- 
 cility. The low-end scenario included a 
 1,400-tpd mine, 1,000-tpd mill, and 750- 
 tpd furnace to produce 230 tpd of high- 
 carbon f errochrome. The high-end scenar- 
 io included a 3,500-tpd mine, 2,500-tpd 
 mill, and 1,800-tpd furnace to produce 
 545 tpd of high-carbon ferrochrome. Op- 
 erational lives for the two scenarios 
 would be 35 and 14 yr , respectively. For 
 both scenarios, the mine will operate 
 5 days per week and the mill will operate 
 7 days per week. Total speculative re- 
 sources in the G and H zones are 13 mil- 
 lion tons of chromite averaging 21 pet 
 Cr 2 3 . Figure 4 shows the potential lo- 
 cation of the facilities. 
 
 The mine would consist of a 12,000- 
 ft main haulage adit, a 1,600-ft under- 
 ground shaft, and underground facilities 
 to service the workers and equipment 
 
 during shrinkage stope mining of the two 
 chromite ore zones. The 4,000-ft Monte 
 Alto Adit would be rehabilitated and 
 extended about 7,800 ft to intersect the 
 G and H zones at an elevation of 5,470 
 ft. A rapid-tunneling machine could be 
 used to drive the 10- by 10-ft adit. 
 
 The 12-ft-diam service shaft collar 
 would be located about 700 ft west of the 
 face of the H zone on the No. 5 
 of the old Mouat Mine. The lowest 
 of the shaft, the 5470, would be 
 200 ft north of the main haulage 
 
 level 
 
 level 
 
 about 
 
 adit 
 
 and about 9,800 ft from the Monte Alto 
 
 LEGEND 
 
 1 Monte Alto Adit 
 
 2 Coarse ore stockpile and crusher 
 
 3 Fine ore stockpile 
 
 4 Mill and enqueuing building 
 
 5 Dry and shop 
 
 6 Bnquetted mill concentrate stockpile 
 
 7 Smelter leed stockpiles, coal char, 
 limestone, and quartz 
 
 8 Ferrochrome smelter area 
 
 9 Sag storage a 
 TO Sludge storage area 
 1 1 Ferrochrome stockpile 
 
 12 Office buildings 
 
 13 Tailings storage area 
 M Site of old tailings area. 1943 
 15 Site of old tailings area. 1953-61 
 
 FIGURE 4. - Plan map of Cr mine-mill-smelter 
 facilities. 
 
portal. The shaft would have nine sta- 
 tions above the main haulage about 180 ft 
 apart. 
 
 Ore would be mined using the shrink- 
 age stope methods utilized previously at 
 the Mouat Mine (_5_ ) . The s topes would be 
 about 200 ft long and 170 ft high along 
 dip. They would be separated horizon- 
 tally by 20-ft-wide pillars. Raises 
 would be bored from the level above. Ore 
 haulage would be by battery motors on the 
 intermediate levels and by trolley or 
 diesel motor on the main haulage level. 
 The ore would be moved to the main haul- 
 age level by ore passes and then by motor 
 to the coarse ore stockpile at the mill. 
 About 10 pet of the ore would remain in 
 the mine as ground support pillars. 
 
 Mine-run ore would be crushed to minus 
 3/8 in and ground to minus 35 mesh (minus 
 0.02 in) in a rod mill. Regrinding would 
 be done in a ball mill. The undersize 
 material would be fed to the spirals in 
 the gravity separation circuit. Mill 
 heads are expected to assay about 21 pet 
 Cr203, the concentrate about 40 pet 
 Cr203, and the tails about 5 pet 0^03, 
 for a recovery rate of 88 pet Cr203. 
 About 46 pet of the feed material would 
 report to the concentrates. 
 
 The grinding and gravity concentrating 
 processes for chromite would use no chem- 
 icals ( 6_) . The quality of the water is 
 expected to be approximately the same as 
 that of the surface water in the vicin- 
 ity. Tailings would be piped about 1.5 
 miles north of the mine site to a tail- 
 ings dam at the St rat ton Ranch area 
 (fig. 4). 
 
 The concentrates would be agglomerated 
 to a plus 8-mesh (1/8-in) size and fed 
 to a sealed, submerged electric arc fur- 
 nace to produce high-carbon ferrochrome. 
 This ferrochrome would be acceptable for 
 use in the production of austenitic 
 stainless steel (12). At the present 
 time, no steel smelter in the United 
 States is known to use this process; how- 
 ever, at least one smelter in Japan does 
 have such a process. 
 
 PGM 
 
 The two sizes selected for PGM opera- 
 tions were 1,000 tpd and 4,000 tpd ore. 
 
 In general, operations of these sizes 
 would fill a portion of the domestic need 
 for PGM under normal and severe crisis 
 scenarios, respectively. Other consid- 
 erations, such as size of reserves and 
 the physical characteristics of the ore, 
 also entered into the size selection 
 process. 
 
 For the 1,000-tpd case, mining would 
 be by shrinkage s toping. Rubber-tired 
 vehicles would be used to haul ore and 
 waste from the mine. Waste rock would 
 be stored in a dump at the mine por- 
 tal. Waste rock production would be ex- 
 pected to be about 150 tpd. Mine life 
 is estimated conservatively at 20 yr. 
 Figure 5 shows the location of proposed 
 facilities. 
 
 The Minneapolis Adit (fig. 6) will be 
 the main entrance to the mine and serve 
 as the main haulageway. The mine waste 
 rock dump would be located near the por- 
 tal. The mill, shop, and other surface 
 facilities would be located nearby, as 
 shown in figure 5. 
 
 PGM milling would be by the froth flo- 
 tation method using a low-pH process. 
 Ore would be crushed, ground, and floated 
 using a potassium amyl xanthate collector 
 and a polyglycol ether frothing agent. 
 Carboxy methyl cellulose and CuSO^ would 
 
 FIGURE 5. - Plan map of PGM mine-mill facilities. 
 
FIGURE 6. - Minneapolis Adit, main haulage for PGM operations. 
 
 be added as conditioners. Additional in- 
 formation on the milling process can 
 be found in other Bureau publications 
 
 ( n-u) . 
 
 Tailings would be disposed of in a 
 lined tailings pond at the same site 
 (fig. 5). Approximately 87 pet of the 
 processed mill feed would be tailings. A 
 tailings dam would be constructed using 
 the centerline method (15) . 
 
 Several changes are needed in order to 
 achieve 4,000-tpd capacity in PGM mining 
 and milling operations. In-mine crushing 
 and belt haulage would be used instead 
 of rubber-tired haulage to transport ore 
 out of the mine. A decline from the West 
 Fork area to the ore zone would be added 
 to gain access to additional reserves. 
 Waste rock would continue to be hauled by 
 rubber-tired vehicles to the dump site 
 near the portal, but the amount would 
 increase to about 600 tpd. 
 
 The tailings area at the Minneapolis 
 Adit is not large enough to store 20 yr 
 
 of production at 4,000 tpd. Utilization 
 of cut-and-fill s toping would reduce the 
 amount of material in the tailings pond 
 by returning about 50 pet of the material 
 to the stopes as backfill, but even then, 
 the tailings area at the Minneapolis Adit 
 is barely large enough to accommodate 
 20 yr of production. 
 
 Therefore, the tailings area would be 
 moved to a secondary site known as Hertz- 
 ler Ranch (figs. 7-8), which is large 
 enough to store this amount of tailings. 
 This site was selected based on an in- 
 depth study of alternative tailings pond 
 sites in the area (10). 
 
 The mill would remain located near the 
 Minneapolis Adit. It would use the same 
 flotation process described above. The 
 tailings would be separated into two size 
 fractions. The coarse (150-mesh) materi- 
 al would be slurried and pumped back into 
 the mine as backfill material. The fine 
 fraction would be slurried and pumped to 
 the Hertzler Ranch tailings pond. 
 
FIGURE 
 rate. 
 
 Contour interval, 
 200 ft 
 
 7. - Plan map of tailings pond gt Hertzler Ranch area for PGM operations, high production 
 
 The tailings slurried to the pond would 
 contain an inadequate amount of coarse 
 material for dam construction, so borrow 
 material from the area would be used. 
 Suitable material for dam construction 
 can be removed from the pond site before 
 mining commences. The impermeable geo- 
 logic conditions at the Hertzler Ranch 
 site make pond lining unnecessary (10). 
 
 Concentrated ore from both the 1,000- 
 tpd and 4,000-tpd operations would be 
 shipped elsewhere for refining. Truck 
 
 haulage would be 
 concentrate. 
 
 used to transport the 
 
 NICKEL-COPPER 
 
 An open pit is the mining method most 
 likely to be used to extract Ni-Cu ore 
 from the Basal zone of the Stillwater 
 Complex. A proposed plan is to develop 
 a section of this zone located within a 
 large rotated block (faulted section of 
 the complex) . This block also contains 
 
10 
 
 FIGURE 8. - Hertzler Ranch area. 
 
 Ni-Cuand PGM pond 
 
 'Nye 
 
 *°\ 
 
 Ni-Cu pit i 
 
 Beartooth t 
 Ranch 
 
 ^Woodbine 
 Campground 
 
 
 
 <^^ ~/~ V_-^4]9f-l— l«J^J=-*= 
 
 
 //h 
 
 a^ i — i — * Columbus 
 
 
 //?10r 
 
 " 24 miles 
 
 / 
 
 
 
 /A 
 
 ond Iffy 
 
 
 LEGEND 
 Paved road 
 
 
 Gravel road 
 
 €ws 
 
 
 *-^-t- Railroad 
 
 s 
 
 
 Slurry pipeline 
 
 — < Mine adits 
 © West Fork PGM (hypothetical) 
 
 PGM mill 
 
 
 © Level 5 Cr (existing) 
 
 -«,4 
 
 
 ® Minneapolis (existing) 
 @ Monte Alto (partially completec 
 *® Photo locations 
 
 A Figures 1 3 and 1 4 
 
 8 Figure 15 
 
 C Figure 16 
 
 1 
 
 i j 
 
 Scale, mi 
 
 FIGURE 9. - Plan map of combined operations, a hypothetical worst case. 
 
 the chromite zones at the old Mouat Cr 
 operation. Figure 9 is a surface plan 
 view showing the potential open pit, 
 dump, and processing facilities, as well 
 as PGM and Cr operations included in a 
 worst case scenario. The Ni-Cu mine life 
 is expected to be 18 yr. 
 
 The ore zone would be mined by standard 
 open pit techniques using shovels and 
 mine trucks. A rate of 27,500 tpd ore 
 and 24,800 tpd waste is proposed. A pri 
 mary crusher would be located at the east 
 side of the pit. Crushed ore would be 
 conveyed downhill at no more than a -16 
 
11 
 
 slope. The conveyor would be enclosed 
 and strong enough to withstand the depo- 
 sition of overlying mine waste. At the 
 base of the dump, a transfer station 
 would direct ore toward the milling fa- 
 cilities near river level. To the north 
 a service road would be extended from 
 the Mouat Mine road. Verdigras Creek 
 (fig. 10) would be diverted above the pit 
 and redirected north about 3,000 ft to 
 Mountain View Lake. An equipment mainte- 
 nance facility and mine truck parking 
 would be located just north of the pit. 
 
 Conveyed ore would be stockpiled adja- 
 cent to the processing facilities. The 
 mill feed rate would be 20,500 tpd, 7 
 days per week. Initial processing would 
 involve grinding the feed to minus 250 
 mesh using semiautogenous mills and ball 
 mills. Bulk sulfide flotation would be 
 
 used to recover Ni and Cu. The rougher 
 concentrate would be cleaned twice to 
 remove Fe and insolubles. A total of 
 19,500 tpd of rougher tails averaging 
 0.075 pet Ni and 0.045 pet Cu would be 
 disposed of in a tailings pond facility, 
 and 940 tpd of cleaner concentrates would 
 be sent to the leaching circuit. 
 
 The proposed leach process would be 
 similar to the two-stage Cl-0 2 leach cur- 
 rently being tested by the Bureau (16). 
 In a batch process , cleaner concentrate 
 would be mixed with reclaimed water and 
 recycled solutions. This pulp would be 
 autoclaved, and CI and compressed air 
 would be added. After 5 h, 94 to 99 pet 
 of the Ni and Cu would be ionized in so- 
 lution. The high-grade Ni-Cu solution 
 would be recovered using wash water. 
 A waste product amounting to 866 tpd, 
 
 FIGURE 10. - Verdigras Creek. 
 
12 
 
 containing Fe and gangue minerals , would 
 be disposed of in the tailings pond. 
 Copper would be electrowon, and nickel 
 
 would be precipitated; 40 tons of Ni and 
 34 tons of Cu would be recovered daily at 
 78- and 67-pct recoveries, respectively. 
 
 LAND ISSUES 
 
 The land issues category contains the 
 most significant environmental issues 
 found in the study. Mining, milling, and 
 refining typically involve significant 
 land use changes. 
 
 Solid wastes, including waste rock from 
 mining, tailings from milling, and sludge 
 from Cr smelting, would create a dispo- 
 sal problem that would have its primary 
 effects on the land. Choice of disposal 
 sites would be a significant problem in 
 the Stillwater Complex. Much of the area 
 is too mountainous, at too high an eleva- 
 tion, or situated on unstable geologic 
 features, and would not make good dispo- 
 sal sites. 
 
 The chemical composition of the tail- 
 ings to be generated is not cause for un- 
 due concern. However, the sludge from 
 ferrochrome production might require spe- 
 cial handling and storage methods to en- 
 sure that any potentially hazardous com- 
 pounds are properly contained. 
 
 In the following sections, these land 
 issues are discussed: tailings dispo- 
 sal, smelter waste, waste rock, land use 
 changes, visual impact, and reclamation 
 plans. 
 
 TAILINGS DISPOSAL PLANS 
 
 The tailings dams for all disposal 
 plans would be instrumented and moni- 
 tored. Instrumentation would include 
 piezometers to monitor the phreatic sur- 
 face within the dams. Frequent inspec- 
 tion and periodic surveys of the dam face 
 would be conducted to detect any dam 
 movement. Monitor wells, installed down- 
 drainage from the dams, would be sampled 
 periodically to check for seepage. 
 
 Chromite Tailings 
 
 For both scenarios, the chromite tail- 
 ings pond would be located at the Strat- 
 ton Ranch site (fig. 4). The pond would 
 have an average height of 50 ft and a 
 maximum height of 75 ft, and would occupy 
 
 approximately 40 acres at the end of the 
 mine life. 
 
 The tailings dam would be constructed 
 of tailings using the upstream method. 
 A cross section of a typical upstream dam 
 is shown in figure 11. This type of con- 
 struction is the least expensive and 
 should result in a stable dam since there 
 are relatively few fines in these tail- 
 ings . Seepage through or under the dam 
 would be collected by a toe drain and re- 
 turned to the pond. The chemical compo- 
 sition of chromite tailings is relatively 
 inert, making pond lining unnecessary. 
 
 In the event of combined Cr, PGM, 
 and Ni-Cu operations, the large Hertzler 
 Ranch site (fig. 9) would be used, and 
 the Stratton Ranch would not be needed. 
 The amount of tailings generated by Cr 
 operations would be negligible compared 
 with the amounts generated by PGM and Ni- 
 Cu operations. 
 
 PGM Tailings — Minneapolis Adit Site 
 
 Two different areas have been chosen 
 for PGM tailings disposal, depending on 
 the scenario. For the low-end scenario, 
 the Minneapolis Adit site would be used 
 (figs. 5-6). This pond would have an 
 average height of 80 ft and a maximum 
 height of 100 ft, and would occupy an es- 
 timated 75 acres. For the high-end sce- 
 nario, the Hertzler Ranch site would 
 be used (fig. 8). This pond would have 
 an average depth of 40 ft and a maximum 
 height of 75-ft, and would occupy an es- 
 timated 380 acres. 
 
 In the low-end scenario case, the tail- 
 ings dam would be constructed using the 
 centerline method of construction (fig. 
 11). This type of dam would be more ex- 
 pensive than an upstream-constructed dam, 
 but would be structurally stronger. This 
 dam would be relatively high and would be 
 located near a county highway, so struc- 
 tural integrity would be important. This 
 dam would be constructed with a blanket 
 or toe drain to keep the phreatic surface 
 
13 
 
 £ 
 
 Pond 
 
 >& 
 
 \\\ \\\ 
 
 /// \\\ 
 
 Fine tailing (slimes 
 
 J^ * * « 
 
 * wm7 ' ^~ mv&zmr 
 
 ^ Original ground 
 surface 
 
 Coarse tailing (sands) 
 
 Starter dam 
 
 UPSTREAM SPIGOTING METHOD 
 
 Cyclone 
 
 Water and slimes 
 released to pond, 
 
 Sands distributed and compacted 
 on downstream slope 
 
 Slimes 
 
 Initial dike 
 (compacted in layers) 
 
 CENTERLINE METHOD 
 FIGURE 11. - Upstream and centerline methods of constructing tailings dams. 
 
 in the dam at acceptable levels. Any 
 seepage would be returned to the pond. 
 
 The bottom surface of the pond and 
 the upstream face of the dam would be 
 lined to minimize seepage under the pond 
 and possible contamination of ground 
 water. Monitor wells installed down- 
 drainage from the pond would be sampled 
 periodically to check for seepage. 
 
 PGM Tailings — Hertzler Ranch Site 
 
 In the high-end scenario for PGM opera- 
 tions, the tailings area would be located 
 at the Hertzler Ranch. Since cut-and- 
 fill stoping is the mining method in this 
 scenario, borrow material would be used 
 to construct the tailings dam. This ma- 
 terial would be scraped from the pond 
 area at the beginning of operations. The 
 pond location was chosen to minimize dam 
 size and height. The tailings dam would 
 
 be constructed using standard earth dam 
 techniques (15) . 
 
 The impermeable shale that underlies 
 the Hertzler Ranch site makes a liner un- 
 necessary. Instead, a toe drain and sump 
 would collect any seepage and return it 
 to the pond. 
 
 A perennial stream running in Robinson 
 Draw must be diverted around the tail- 
 ings area. This diversion, shown in fig- 
 ure 7, would reduce the amount of runoff 
 water the pond and dam will be required 
 to handle. 
 
 A pond liner should be unnecessary, but 
 the sand and gravel overlying the pond 
 would be scraped off to minimize leakage 
 under the dam. Geologic data indicate 
 that an average of 15 ft of alluvium 
 needs to be removed to expose the shale. 
 Monitor wells, piezometers, and surveys 
 would ensure that the pond and dam are 
 performing properly. 
 
14 
 
 Nickel-Copper Tailings 
 
 Only two sites in the area are capable 
 of holding the estimated 81 million yd 3 
 (128 million tons) of tailings produced 
 over the 18-yr life of the mine. These 
 sites are the Hertzler Ranch and Horseman 
 Flats, which could hold 100 million yd 3 
 (155 million tons) and 159 million yd 3 
 (252 million tons) of tailings, respec- 
 tively. The Hertzler Ranch site is about 
 6.5 miles north and down-drainage from 
 the proposed Ni-Cu mill site (figures 7 
 and 8) . The Horseman Flats site is about 
 4 miles northwest of the mill site and 
 about 850 ft higher in elevation, which 
 would entail pumping the tailings uphill 
 (fig. 9). At present, the Hertzler Ranch 
 seems to be the most viable site since 
 sufficient water is available from the 
 Stillwater River for a mill at the pres- 
 ent site. The major environmental prob- 
 lems would apply to either tailings site. 
 
 Combined Tailings 
 
 In the event of combined Cr, PGM, and 
 Ni-Cu operations, the Hertzler Ranch site 
 would be used to contain tailings from 
 all three operations. This pond would be 
 an average of 75 ft high, be constructed 
 in two terraces, have a maximum height of 
 125 ft, and cover an estimated 650 acres 
 at the end of mining. 
 
 Two tailings dams would be constructed 
 using tailings from the Ni-Cu and Cr 
 operations. The first dam would be con- 
 structed to form the upper terrace at 
 5,000 ft elevation. The upper terrace 
 
 would hold about 60 pet of the tailings. 
 The lower terrace would crest at 4,900 ft 
 elevation and contain the balance of the 
 tailings. 
 
 In order for all of the tailings gener- 
 ated by combined operations to be con- 
 tained on the site, all of the alluvium 
 from the site must be removed and stock- 
 piled. This is an estimated 425 million 
 ft 3 of material, which would be used dur- 
 ing reclamation at the end of mining. 
 
 Both dams would be constructed using 
 the centerline method described previous- 
 ly. Instrumentation would be installed 
 to ensure proper performance. The creek 
 diversion mentioned earlier would be re- 
 quired in this scenario, also. 
 
 TAILINGS POND RECLAMATION 
 
 Chromite Tailings 
 
 The chromite tailings pond is expected 
 to cover approximately 40 acres at the 
 Stratton Ranch site at the conclusion of 
 mining. The material should be relative- 
 ly uniform and porous, and dry quickly. 
 The tailings area would be contoured to 
 more closely resemble natural surround- 
 ings after it has dried. 
 
 The tailings area from previous Mouat 
 Cr mine operations has been successfully 
 revegetated by The Anaconda Company (10) . 
 That area has been seeded with a mixture 
 of grasses and forbs, heavily fertilized, 
 and irrigated periodically. Revegetation 
 species were seeded at between 23 and 31 
 lb of live seed per acre. Species used 
 are listed in table 1. 
 
 TABLE 1. - Revegetation species used in reclamation (10) 
 
 Common name 
 
 Scientific name 
 
 Approximate seed rate 
 
 (pure live seed), 
 
 lb/acre 
 
 Sheep fescue or Idaho fescue 
 
 
 4-5 
 
 
 4-5 
 4-5 
 
 Festuoa ovina or Festuca 
 idahoenis. 
 
 3-4 
 3-4 
 
 
 
 3-4 
 .5 
 
 
 
 .5 
 
 
 2-3 
 
15 
 
 A similar program of revegetation would 
 be expected to be successful on tailings 
 generated by future Cr raining. To com- 
 pletely revegetate this area would re- 
 quire 2 to 3 yr. 
 
 PGM Tailings 
 
 For the low-end production rate of 
 1,000 tpd, the tailings pond would be lo- 
 cated at the Minneapolis Adit site (fig. 
 5) and would occupy about 75 acres. Max- 
 imum height would be about 100 ft. The 
 PGM tailings would contain a greater pro- 
 portion of fines than the chromite tail- 
 ings and would not dry quickly. 
 
 Once the tailings dam reaches its maxi- 
 mum height, revegetation of the dam face 
 could begin. The relatively steep slope 
 of the dam face (approximately 30 pet) 
 would probably make more involved reveg- 
 etation efforts necessary. Techniques 
 such as straw mulch crimping and netting 
 would probably be used to help hold the 
 seed until germination. 
 
 Revegetation of the tailings pond sur- 
 face would have to wait until it has 
 dried sufficiently. Until then, chemi- 
 cal dust suppressants could be applied to 
 reduce fugitive dust. Mine waste rock 
 could be spread over the surface of the 
 area during the winter to increase its 
 load-bearing capacity. Soil scraped from 
 the site before the pond was constructed 
 could then be spread over the surface of 
 the pond. If soil is not used to cap the 
 pond, revegetation would be much more 
 difficult and expensive. Fertilizer, 
 mulching, and irrigation rates would be 
 increased. Biomass production would be 
 lower, lengthening the time to full rec- 
 lamation by as much as 2 yr. 
 
 For the high-end production rate of 
 4,000 tpd, the Minneapolis Adit tailings 
 pond location is not large enough, so the 
 Hertzler Ranch site is assumed to be 
 used. A detailed reclamation plan has 
 already been established for this site 
 ( 10) . A brief description of it follows. 
 
 After operations cease, the tailings 
 area would be recontoured into a gentle 
 dome. This will encourage precipitation 
 to drain off the tailings instead of 
 percolating through them. Approximate- 
 ly 2 ft of waste rock from the mining 
 
 operation would be used to cap the area 
 and increase its load-bearing capacity. 
 Approximately 18 in of topsoil and sub- 
 soil scraped from the site before the 
 pond was constructed would be spread over 
 the rock. Revegetation using the species 
 listed in table 1 along with a few addi- 
 tional trees and shrubs would complete 
 the reclamation. After reclamation, the 
 area should be similar to the current 
 stony grassland ( 17 ) and is expected to 
 be suitable for grazing, the current land 
 use for that area. 
 
 Nickel-Copper Tailings 
 
 Reclamation would be the same as for 
 the PGM tailings reclamation plan dis- 
 cussed in the previous section, but on a 
 larger scale. After operations cease, 
 recontouring to a more natural shape 
 would commence. Waste rock from the open 
 pit would be used to cap the area. Top- 
 soil stripped from the pond area before 
 construction would be spread over the 
 rock. Revegetation using species listed 
 in table 1 and a few trees and shrubs 
 would complete the reclamation. The area 
 would appear similar to the present area 
 but would be 100 to 150 ft higher. 
 
 FERROCHROME SMELTER WASTE 
 
 The ferrochrome smelter produces two 
 types of solid waste that require dis- 
 posal: sludge from venturi scrubbers 
 and slag from the smelter. Of the two, 
 sludge is the more difficult prob- 
 lem because of the high organic con- 
 tent. Smelter slag is essentially vit- 
 rified silicates and should be fairly 
 nonreactive. 
 
 The ferrochrome smelter emits signif- 
 icant amounts of gas containing partic- 
 ulates. The particulates are removed 
 from the gas by a venturi scrubber as a 
 sludge. 
 
 Sludge recovery from the venturi scrub- 
 bers would amount to 30 tpd and 72 tpd 
 (11,000 tpy and 26,000 tpy) for the low 
 and high production rates, respectively. 
 The sludge, after filtering to remove wa- 
 ter, would be permanently stored on-site 
 and would require a double-lined pit. 
 This 40-ft-deep pit would be made by 
 
16 
 
 excavating to 20 ft of depth and bounding 
 the excavation by 20-ft-high walls. An 
 area of 3,500 ft 2 /yr is needed for the 
 low-end scenario and 8,500 ft 2 /yr for the 
 high-end scenario. Up to 8 wt pet of the 
 sludge would be organic material ( 18) . 
 Monitor wells would be installed to warn 
 of seepage. 
 
 Alternate methods of handling the 
 sludge would include recycling it back to 
 the briquetting operation, disposing of 
 it by including it with the mill tail- 
 ings, or possibly using it in making 
 blocks for permanent solid storage. 
 These alternate methods require further 
 study to identify their potential. 
 
 Organic matter emitted can be par- 
 tially captured using scrubbers for 
 closed or sealed furnaces and baghouses 
 for open furnaces. These control systems 
 recover a solid waste sludge and dust; 
 respectively. A sealed furnace and 
 scrubber system, as previously mentioned, 
 was chosen for the ferrochrome produc- 
 tion segment of the chromite operation 
 because a higher percentage of organic 
 matter would be recovered. In a previ- 
 ous study (18), five ferroalloy furnaces 
 were tested for generation and emission 
 of particulate and organic matter. Even 
 though no high-carbon-f errochrome-produc- 
 ing furnaces were tested, general results 
 comparing open and closed (sealed) fur- 
 naces are applicable. It is reported 
 that scrubbers are much more efficient 
 than baghouses in recovering organic 
 matter. The major evidence is that the 
 covered furnaces tested generated more 
 organic matter per megawatt hour but 
 emitted less into the atmosphere after 
 the scrubber. Open furnaces tested gen- 
 erated less per megawatt hour but emitted 
 more into the atmosphere after the 
 baghouse. 
 
 Concentrations of benzo(a)pyrene (BaP) 
 emitted as exhaust gas into the atmos- 
 phere from three ferroalloy plants ex- 
 ceeded the discharge multimedia environ- 
 mental goals (DMEG) of the EPA, whose 
 recommended value is 0.02 p.g/m 3 ( 18) . 
 DMEG's are used as reference points and 
 are not regulatory policy. Sampling in- 
 dicated none of the solid wastes would be 
 classified as hazardous, although all but 
 
 one operation exceeded DMEG-re commended 
 values for land disposal of BaP. Treated 
 water discharge from the two covered 
 smelter furnace control systems contained 
 no polynuclear aromatics. Biphenyl was 
 found in the emission samples from the 
 two covered furnaces, suggesting the com- 
 pound may also be present in discharged 
 solid wastes. In chlorination treatment 
 systems there is a possibility of form- 
 ing polychlorinated biphenyls from the 
 biphenyls. 
 
 The dewatered scrubber sludge accumu- 
 lated from the waste water treatment sys- 
 tem would contain various organic com- 
 pounds. Until additional information is 
 available regarding safe disposal, all 
 smelter sludge would be retained as solid 
 waste. 
 
 Slags are vitrified silicates similar 
 in content to scrubber sludge. Molten 
 slag would be dumped into pits open at 
 one end to permit removal after quench- 
 ing and granulation (18) . The slag pit 
 should be concrete-lined and sealed to 
 prevent pollution of ground water. Ex- 
 cess quenching water would be contained 
 within the pit and used during the next 
 slag dumping. The granulated slag can be 
 stockpiled as waste or used as road base. 
 
 Reclamation of smelter slag and scrub- 
 ber sludge would occur during operations, 
 and very little reclamation would be 
 needed after operations cease. Reclama- 
 tion of slag would be a fairly simple 
 process. The dump size would be pre- 
 planned and the pile shaped to have a 
 more natural appearance. Dumping and 
 reclamation would be similar to the oper- 
 ations of the Ni-Cu mine waste dump dis- 
 cussed in the next section. 
 
 Smelter sludge from the venturi scrub- 
 bers would be stored in double-lined 
 pits. Several pits would be needed al- 
 though the number would depend on opera- 
 tion size. As each pit is filled it 
 would be covered with an impermeable 
 liner similar to the one used underneath 
 the waste. Monitor wells would be in- 
 stalled to warn of seepage. Topsoil 
 would be placed over the liner. Hydro- 
 mulching and tree planting would reduce 
 erosion. 
 
17 
 
 WASTE ROCK 
 
 A method has been proposed for dumping 
 Ni-Cu mine waste rock, that would lessen 
 the visual impact. Waste would be trans- 
 ported to the base of the dump area and 
 placed in low lifts or terraces. Three 
 main advantages of using this method 
 would be the ability to adjust the dump 
 slope to conform to the natural topogra- 
 phy, the ability to revegetate the dump 
 slope after each lift is completed, and 
 the ability to create a more stable dump. 
 
 Operations of this method would in- 
 volve transporting waste by truck from 
 the pit, downhill to the base of the pre- 
 planned dump area. Each lift would be 
 about 10 ft high or higher, depending on 
 mine truck size and dumping method. Ini- 
 tial dumping of each lift would be at the 
 peripheral crest of the previous lift to 
 form a 10-ft-high berm. 
 
 For this plan to work properly, trucks 
 must dump waste on a given lift while 
 positioned on that lift (fig. 12). The 
 trucks would then be partially hidden 
 behind the initial berm, reducing vis- 
 ual impact. A bulldozer would intermit- 
 tently level the spoils piles to provide 
 a drivable base for the following lift 
 construction. A hydromulch sprayer would 
 be used to establish vegetation. Small 
 trees similar to species in the area 
 would also be planted. 
 
 In the conventional technique, waste 
 rock would be dumped near the pit in a 
 manner such that the face of the waste 
 pile is constantly "active and cannot be 
 vegetated. Each load would be dumped 
 over the previous load, but the dumping 
 elevation would be kept constant and the 
 waste pile would be extended out horizon- 
 tally. Some of the dump may be vegetated 
 during operations after that area becomes 
 
 inactive, but a large percentage of the 
 dump would remain active until operations 
 cease. 
 
 Reclamation would be done both during 
 and after operations cease. Erosion and 
 sedimentation impacts would differ de- 
 pending on which of the two dumping meth- 
 ods is chosen. Conventional dumping 
 techniques make vegetation efforts impos- 
 sible until after operations cease. The 
 multiple-lift approach allows vegetation 
 during operations, reducing erosion and 
 sedimentation of waters downslope. 
 
 The pit could be recontoured by blast- 
 ing to form a more continuous slope rath- 
 er than leaving benches. A more natural 
 talus slope appearance would result. 
 Another approach is to leave the benches 
 intact and lay topsoil on each level. 
 Grasses and trees could be planted to 
 minimize erosion as well as to improve 
 the visual appearance. The stream diver- 
 sion would be removed, allowing Verdigras 
 Creek to flow into the pit, forming a 
 small lake similar to Mountain View Lake. 
 Water redirected into the pit would need 
 a permanent channel. Some blasting and 
 rock removal may be needed. 
 
 LAND USE CHANGES 
 
 Approximately 25,000 acres in and 
 around the Stillwater Complex were ana- 
 lyzed for major land use categories (17). 
 About 50 pet of the area is undeveloped 
 national forest, wilderness area, and 
 private land. The land serves as wild- 
 life habitats and as camping, hiking, 
 fishing, and hunting areas. Agriculture 
 uses about 42 pet of the area; livestock 
 grazing is the most prevalent agricul- 
 tural use. Residential, recreational, 
 and mining activities make up the re- 
 mainder of land uses of the area. Most 
 
 Mine truck 
 
 Bulldozer 
 
 Hydromulcher 
 
 FIGURE 12. - Waste rock terracing method. 
 
18 
 
 people live in four communities: Nye, 
 Dean, Fishtail, and Absarokee. Approxi- 
 mately 50 vacation homes are located in 
 the area, as well as 2 commercial guest 
 ranches and 2 campgrounds. Mining and 
 exploration activities make up about 
 1 pet of the land use in the study area. 
 
 Mining of Cr, PGM, and Ni would repre- 
 sent a significant change in land use for 
 the region. Tailings areas would be lo- 
 cated on grazing land and remove it from 
 service for a period of time ranging from 
 15 to 30 yr. After the mines are closed, 
 the tailings areas can be revegetated to 
 be used again for grazing. The undevel- 
 oped land at the Ni-Cu open pit would be 
 permanently altered. Reclamation after 
 mining would minimize impact. Other land 
 that would be used for mine, mill, and 
 smelter building sites would be changed 
 from agricultural and residential use to 
 industrial use. 
 
 Since infrastructure such as roads , 
 transmission lines, and rail would be 
 upgraded, it is likely that other small 
 businesses and industries would choose to 
 locate in the area. Many of these busi- 
 nesses would probably supply goods and 
 services to the growing mining community. 
 
 In total, Cr operations would require 
 about 90 acres for the low-end scenario 
 and 125 acres for the high-end scenario. 
 PGM operations would require 160 acres 
 for the low-end scenario and 400 acres 
 for the high-end scenario. Nickel-copper 
 operations would require 900 acres. The 
 total land used for all mining opera- 
 tions, if all were conducted simulta- 
 neously, would be 1,425 acres, or about 
 6 pet of the land in the study area. 
 
 VISUAL IMPACTS 
 
 The major visual impact would result 
 from the Ni-Cu pit and dump, which cover 
 a total of about 350 acres. The other 
 significant visual impact would be from 
 the ferrochrome smelter and its tall 
 stack. The remaining facilities would 
 create limited and local visual impacts. 
 
 The Ni-Cu pit and dump would be visi- 
 ble for several miles in the Stillwater 
 Valley. It would be the only facility 
 visible from the Beartooth Ranch, Wood- 
 bine Falls (0.5 mile east of Woodbine 
 
 Campground) , and the Absaroka Beartooth 
 Wilderness. The ferrochrome plant and 
 the Ni-Cu pit and dump would be visible 
 for at least 6 miles downstream. Other 
 features such as the tailings dams and 
 mill facilities would only be visible 
 from the road for short distances (figs. 
 13-16). 
 
 The chromite tailings would cover an 
 area of about 40 acres. The PGM tailings 
 would cover 75 acres for the low-end case 
 and 380 acres for the high-end case. The 
 Ni-Cu tailings dam would cover about 350 
 acres. The tailings dams would be up to 
 125 ft high. The Ni-Cu tailings area 
 would be visible from parts of the road 
 leading to the Benbow Mine. 
 
 Solid waste from the ferrochrome smelt- 
 er would eventually occupy an area of 
 about 20 acres. A 30-day supply of feed 
 material for the smelter would be stored 
 on 1 acre of land near the smelter. Some 
 of the material, such as the coal char, 
 may be covered or stored in large bins 
 for protection from the weather. 
 
 Other items that will visually impact 
 the area are as follows: (1) a pipeline 
 for Ni-Cu tailings, which would be visi- 
 ble from the road between the Ni-Cu mill 
 and the Hertzler Ranch tailings site, 
 (2) a railroad spur, and (3) power lines, 
 which would be visible between the city 
 of Columbus and the ferrochrome smelter, 
 a distance of about 35 miles. 
 
 To a large extent , visual impacts can- 
 not be avoided, owing to limited siting 
 options and high visibility throughout 
 the valley. Use of blend-in colors for 
 buildings and use of the multiple-lift 
 waste rock disposal method described ear- 
 lier should reduce negative impact. 
 
 SUMMARY OF LAND ISSUES 
 
 The most significant land issues iden- 
 tified in this study are — 
 
 1. Disposal of tailings, including 
 sound dam design and reclamation. 
 
 2. Disposal of ferrochrome smelter 
 waste. 
 
 3. Changing land use patterns from 
 agriculture and recreation to mining and 
 mineral processing. 
 
 Adequate technology exists to permit 
 sound tailings pond construction and 
 
19 
 
 (D 
 
 => 
 
 (D 
 
 E 
 a 
 U 
 
 u 
 
 -o 
 o 
 
 Q. 
 O 
 
 O 
 
 Q_ 
 
 o 
 (/) 
 u 
 
 O 
 
 
 0) 
 
 E 
 a 
 U 
 
 Q. 
 O 
 
 E 
 o 
 u 
 
 o 
 I/) 
 u 
 
 D 
 
 - 
 
 > 
 
 LU 
 Qi 
 
 ID 
 O 
 
20 
 
 Dumps 
 
 FIGURE 15. - Visual effects of Ni-Cu open pit from Beartooth Ranch. Camera location is shown 
 on figure 9 (£>)• 
 
 ■*,:* \ 
 
 
 Pit 
 
 FIGURE 16. - Visual effects of Ni-Cu open pit from Woodbine Falls. Camera location is shown 
 on figure 9 (C). 
 
21 
 
 reclamation. Additional research is 
 needed to more accurately describe the 
 nature of ferrochrome smelter solid 
 waste, before sound disposal plans for 
 permanent storage of this waste can be 
 
 drawn up. The noted change in land use 
 patterns is largely unavoidable during 
 the term of active mining. After mining, 
 land use would return to earlier patterns 
 of agriculture and recreation. 
 
 WATER ISSUES 
 
 Water quality is very important to res- 
 idents and visitors and is quite likely 
 the most important environmental issue in 
 this area. The generally high baseline 
 water quality is a source of pride to 
 residents. Fishing is a major recre- 
 ational activity. In general, water is- 
 sues associated with the proposed mines 
 can be dealt with effectively. 
 
 In this section, baseline water qual- 
 ity, control of mine drainage water and 
 tailings pond water, and water treatment 
 for the Cr smelter are discussed. 
 
 SURFACE WATERS BASELINE QUALITY 
 
 Sample analyses from three separate 
 studies are combined in this section to 
 show the overall surface water quality of 
 the Stillwater Complex. Anaconda con- 
 tracted Camp Dresser and McKee, Inc., to 
 complete a baseline environmental study 
 as part of Anaconda's operating permit 
 application for its proposed Stillwater 
 project (18). Hydrologic monitoring en- 
 tailed monthly, biweekly, and irregularly 
 timed measurements of streamflow for a 
 1-yr period (June 1980 to June 1981). 
 Five stations were established on the 
 Stillwater River and seven stations on 
 its tributaries. These samples points 
 are shown on figure 17 as numbers 18 and 
 20-30. 
 
 The Stillwater PGM Resources Co. con- 
 tracted Beak Consultants, Ltd., to pre- 
 pare a baseline environmental study of 
 the East Boulder River and Dry Fork areas 
 ( 19) . Thirty surface water sample loca- 
 tions were used in Beak's report, but of 
 these only eight were used in the Bu- 
 reau's analysis. These samples are shown 
 on figure 17 as numbers 4 through 11. 
 Sampling was conducted over a 1-yr period 
 beginning April 1981 and ending April 
 
 1982. Each station was monitored up to 
 17 times in that year, which was similar 
 to the sampling done by Anaconda. 
 
 The Bureau sampled surface waters dur- 
 ing the month of June 1984 specifically 
 for this report. An attempt was made to 
 fill in gaps from previous studies in or- 
 der to gain a picture of the water qual- 
 ity of the entire Stillwater Complex; the 
 one-time sampling was used to gain addi- 
 tional data points. The 14 Bureau sam- 
 ples are shown in figure 17 as numbers 
 1-3, 12-17, 19, and 31-34. 
 
 Although the two industry surface water 
 studies involved analyzing samples for 
 many parameters, the Bureau analysis con- 
 cerns only parameters that have been 
 given regulatory standards, (table 2). 
 The Bureau analyses are limited to only 
 
 LEGEND 
 
 X Mines 
 @ Gish (Cr) 
 @ Mouat (Cr) 
 (S) Mouat (Ni-Cr) 
 @ Stillwater (PGM) 
 @ Benbow (Cr) 
 
 G- Water sample 
 
 FIGURE 17. - Water sample locations. 
 
22 
 
 part of this list, as identified in table 
 2. The industry surface water studies 
 included all parameters listed. 
 
 TABLE 2. - Water quality regulatory 
 standards (20) 
 
 Parameter 
 
 Standard, ppm 
 
 Ag 1 
 
 0.05 
 
 As 
 
 .05 
 
 Ba 1 
 
 1.00 
 
 Cd 
 
 .01 
 
 CI 1 
 
 250 
 
 Cr 
 
 .05 
 
 Cu 
 
 1.00 
 
 F 1 
 
 2.4 
 
 Fe , ..... 
 
 .3 
 
 Hs 
 
 .002 
 
 Mn 
 
 .05 
 
 Pb 
 
 .05 
 
 Se 
 
 .01 
 
 Zn 
 
 5.00 
 
 Sulfate 1 
 
 250 
 
 
 10 
 
 Total dissolved solids 1 ... 
 
 500 
 2 100 
 
 
 5 
 
 ^ot analyzed by Bureau. 
 2 Number of bacteria per 100 mL. 
 
 Surface water samples that exceeded the 
 regulatory standards are given in table 
 3. The data given in this table repre- 
 sent the maximum values obtained during 
 the 1-yr period. Parameters that ex- 
 ceeded the standards were Cd, Cr, Fe, Mn, 
 Pb, fecal bacteria, and turbidity. 
 
 Cadmium standards at eight sample sites 
 exceeded in the Stillwater River Valley. 
 Seven of these assayed 0.02 ppm Cd. Sam- 
 ple 25 had the highest value at 0.03 ppm, 
 indicating a higher background for Cd in 
 the West Fork drainage. Sample 12, lo- 
 cated farther up the West Fork, did not 
 show Cd values exceeding regulatory 
 standards. It is believed that high Cd 
 values in the surface water are the re- 
 sult of natural background and are not 
 due to any point source discharge (19). 
 Surface water samples taken during peak 
 flow periods (May and June) show highest 
 metal concentrations. This may be due to 
 higher concentrations of suspended sol- 
 ids; only Bureau samples were filtered to 
 remove the solids. Manganese, chromium, 
 lead, and fecal values exceeded regula- 
 tory standards during peak flows in sev- 
 eral of Anaconda's samples. Sample 32 (a 
 Bureau sample) , which assayed 0.082 ppm 
 Cr (greater than regulatory standards), 
 
 TABLE 3. - Surface water samples exceeding regulatory standards 
 
 Sample 1 
 
 Element , ppm 
 
 Fecal 
 coliform 2 
 
 Turbidity, 3 
 
 
 Cd 
 
 Cr 
 
 Fe 
 
 Mn 
 
 Pb 
 
 NTU 
 
 5 
 
 a 
 
 a 
 
 a 
 
 0.02 
 
 .02 
 
 .02 
 
 a 
 
 .02 
 
 .03 
 
 .02 
 
 .02 
 
 a 
 
 .02 
 
 a 
 
 a 
 a 
 a 
 a 
 a 
 a 
 0.14 
 a 
 a 
 a 
 a 
 a 
 a 
 .082 
 
 a 
 a 
 a 
 0.57 
 1.3 
 a 
 16 
 .31 
 1.1 
 
 a 
 
 1.6 
 
 .57 
 
 a 
 
 a 
 
 0.06 
 
 .06 
 
 a 
 
 .09 
 
 a 
 
 a 
 
 .28 
 
 a 
 
 a 
 
 a 
 
 a 
 
 a 
 
 a 
 
 NA 
 
 a 
 a 
 a 
 a 
 a 
 0.09 
 a 
 a 
 a 
 a 
 a 
 a 
 a 
 a 
 
 a 
 a 
 a 
 a 
 a 
 a 
 a 
 a 
 a 
 a 
 920 
 a 
 a 
 a 
 
 a 
 
 6 
 
 a 
 
 7 
 
 14.0 
 
 18 
 
 a 
 
 20 
 
 a 
 
 21 
 
 a 
 
 23 
 
 a 
 
 24 
 
 a 
 
 25 
 
 a 
 
 27 
 
 a 
 
 28 
 
 a 
 
 29 
 
 a 
 
 30 
 
 a 
 
 
 NA 
 
 a Did not exceed standard. NA Not analyzed, 
 Sample locations are shown on figure 17. 
 2 Number of bacteria per 100 mL. 
 3 Analyzed by Beak Consultants, Ltd. 
 
23 
 
 was also taken during peak flow. At this 
 location, an intermittent stream was 
 flowing through a mine waste dump at the 
 Benbow chromite mine. This sample was 
 filtered to remove suspended solids. 
 High Cr values may be due to chromite 
 dumps and abandoned tailings ponds where 
 fresh water is able to filter through. 
 
 High Mn and turbidity values from sam- 
 ples 5 through 7 (19) may also be a re- 
 sult of peak flow. Generally high values 
 from Cd and Fe throughout the year indi- 
 cate natural background and not a point 
 source. Fecal coliform exceeded regula- 
 tory standards in sample 28. The high 
 coliform counts reflect the presence of 
 cattle in the area. Water quality of the 
 Stillwater River is characterized as good 
 to excellent, while its tributaries are 
 characterized as poor to good. Surface 
 water quality of the East Boulder River 
 is rated generally high at upper eleva- 
 tions but deteriorates somewhat with 
 downstream distance (19). 
 
 In utilizing all sample data, an anal- 
 ysis of the surface water quality of the 
 entire Stillwater Complex can be at- 
 tained. The quality of water from major 
 rivers draining north through the complex 
 is good to excellent. High metal values 
 from tributaries in the complex indicate 
 local sources. Downstream at lower ele- 
 vations where cattle grazing is promi- 
 nent, degradation of water quality is 
 evident. The tributaries within and to 
 the south of the complex can be classi- 
 fied as poor to good. 
 
 MINE DRAINAGE WATER QUALITY 
 
 Mine drainage from several adits in the 
 Stillwater Complex was sampled and ana- 
 lyzed for water quality. Samples were 
 taken by the Bureau from the Benbow Mine, 
 the Mouat Mine, the Verdigras Creek Adit, 
 and the Gish Mine. Samples were taken by 
 Camp Dresser and McKee ( 17 ) from the Min- 
 neapolis Adit, the Mouat Mine, and the 
 Verdigras Creek Adit. 
 
 Samples taken by the Bureau were taken 
 in accordance with EPA-recommended meth- 
 ods (20) . Samples were filtered at 0.45 
 (j.m and acidified with HNO3. Samples were 
 analyzed for 16 cations, as listed in 
 
 table 2. Of the samples taken by the 
 Bureau, only one from the Mouat Mine ex- 
 ceeded water quality criteria for any 
 constituent. A Cr level of 0.082 ppm was 
 measured in this sample. The EPA cri- 
 terion for Cr is 0.05 ppm. EPA water 
 quality criteria are stated in terms of 
 total Cr (both hexavalent and trivalent). 
 In its hexavalent state, Cr has been 
 shown to be toxic and is suspected of 
 being carcinogenic ( 21 ) . Hexavalent Cr 
 is known to cause nasal irritation, and a 
 positive correlation between cancer and 
 exposure to hexavalent Cr has been noted. 
 Trivalent Cr, the other common valence 
 state, has been shown to be much less 
 toxic and is not suspected of being 
 carcinogenic. 
 
 Samples taken by Camp Dresser and McKee 
 indicated that a few constituents regu- 
 larly exceeded EPA criteria. Minneapolis 
 Adit samples had no constituent analyses 
 that averaged above EPA criteria. Mouat 
 Mine sample averages exceeded EPA crite- 
 ria for Fe, Mn, and Se. Verdigras Creek 
 Adit sample averages exceeded EPA crite- 
 ria for sulfate, Fe, and Mn (19). The 
 Verdigras Creek Adit is located in the 
 Basal zone of the complex (fig. 1). This 
 area contains sulfides, and the water is- 
 suing from this adit reflects the compo- 
 sition of the rock in the area. 
 
 In general, mine drainage samples ex- 
 hibited water quality higher than might 
 be expected. Exceptions to this were 
 rare. Sulfides in the PGM zone are a 
 relatively low proportion of the ore, and 
 water running through the Minneapolis 
 Adit has little opportunity to acquire 
 significant metal content. The unreac- 
 tive nature of chromite in the Benbow, 
 Mouat, and Gish Mines contributes to the 
 low metals content of water issuing from 
 these adits. The Verdigras Creek Adit is 
 located in the more chemically reactive 
 Basal zone, and the water issuing from 
 this adit is of lower quality. 
 
 In all samples, the pH was near neu- 
 tral. This is due to the lack of pyrite 
 in the rocks of the Stillwater Complex. 
 The neutral pH contributed to the low 
 metal concentrations found in mine drain- 
 age water since solubility of most .metals 
 is very low at neutral pH. 
 
24 
 
 NEW SOURCE PERFORMANCE STANDARDS (11) 
 
 Waste water discharges from mining, 
 milling, and smelting activities in the 
 Stillwater Complex would be regulated by 
 the Clean Water Act, New operations 
 would be considered "new sources." Regu- 
 lations concerning effluent limitations 
 were issued December 3, 1982. New source 
 performance standards are the most strin- 
 gent, because new mines and mills would 
 "have the opportunity to install the best 
 and most efficient waste water treatment 
 technologies." 
 
 The ore mining category has been di- 
 vided into subcategories covering various 
 ores and processes. There are existing 
 subcategories for Ni mining and ferro- 
 chrome production. A new subcategory for 
 Pt mining was created recently; however, 
 no subcategory for Cr mining currently 
 exists. Both the Ni and Pt ore subcate- 
 gories have been reserved, meaning that 
 final determinations of effluent limi- 
 tations will be set by the permitting 
 authority (Montana Department of State 
 Lands) on a case-by-case basis. New 
 source performance standards for Ni and 
 Pt mining have been issued in final form 
 and are outlined in tables 4 and 5. 
 Mines and mills processing more than 
 5,000 tons of Ni ores in 1 yr have efflu- 
 ent limitations listed in table 4. Mines 
 and mills processing Pt ores (other than 
 placer deposits) have effluent limita- 
 tions listed in table 5. 
 
 New source performance standards for 
 froth flotation mills require a zero dis- 
 charge. Both the Pt and Ni operations 
 discussed in this report would use froth 
 flotation and would be subject to this 
 requirement. Chromium operations use a 
 
 TABLE 4. - New source performance 
 standards for Ni mining and 
 milling, parts per million (11) 
 
 TABLE 5. - New source performance 
 standards for Pt mining and 
 milling, parts per million (11) 
 
 Parameter 
 
 24-h max 
 
 30 
 
 -day av 
 
 Total sue 
 
 >pended 
 
 30 
 
 1.0 
 
 .1 
 
 .3 
 
 1.0 
 
 1.0 
 
 
 20 
 
 As 
 
 .5 
 
 Cd 
 
 .05 
 
 Cu 
 
 .15 
 
 Pb 
 
 .5 
 
 
 .5 
 
 Parameter 
 
 Cd .T. 
 
 Cu 
 
 Hg 
 
 Pb 
 
 Zn 
 
 24-h max 
 
 30-day av 
 
 0.10 
 
 0.05 
 
 .03 
 
 .15 
 
 .002 
 
 .001 
 
 .6 
 
 .3 
 
 1.5 
 
 .75 
 
 gravity process and might not be subject 
 to it. 
 
 Zero discharge means that all process 
 water must be contained within the mill- 
 tailings pond circuit. The mill must not 
 discharge waste water anywhere except to 
 a contained tailings pond where excess 
 water would evaporate. Seepage through 
 the tailings dam or under the pond must 
 be prevented or recovered. 
 
 There are two exceptions to this re- 
 quirement. If contaminants that inter- 
 fere with milling tend to build up in the 
 closed circuit, then a "bleed" stream may 
 be allowed, subject to the limitations 
 given in tables 4 and 5. If a 10-yr, 
 24-h storm occurs, a temporary discharge 
 of tailings pond water may be allowed, 
 subject to limitations given in tables 4 
 and 5. 
 
 It is expected that Cr, Ni , and PGM 
 operations would be required to adhere to 
 the zero discharge requirement and that 
 they would be capable of meeting it. 
 
 FERROCHROME SMELTER WASTE WATER 
 
 Scrubbers used to clean furnace off- 
 gasses are a potential source of water 
 pollution (22) , because scrubber dis- 
 charge water generally contains a high 
 concentration of suspended solids and or- 
 ganic matter (sludge) ( 18) . A sealed 
 furnace has been suggested for this oper- 
 ation partly because it requires less 
 water than an open furnace. Off gas vol- 
 umes would be much less; thus, smaller 
 scrubbers and a smaller water treatment 
 system would be needed. Metals and or- 
 ganics in the discharge water may leach 
 or percolate from the sludge (23) . All 
 water from the scrubbers would be recy- 
 cled, and the dewatered sludge would be 
 stored in lined disposal ponds. 
 
25 
 
 The dusts and sludges generated from 
 furnaces are primarily particles less 
 than a micrometer in size, consisting of 
 oxides of Cr, Ca, Mg, and other elements, 
 in widely varying proportions depending 
 on the product being made. The sludges 
 from covered furnaces may also contain, 
 in quantities of up to 8 pet, vari- 
 ous types of organic compounds. Polycy- 
 clic organic matter (POM) content may be 
 as high as 65 pet of the organics (5 pet 
 of the sludge). Polynuclear aromatic 
 hydrocarbons (PNA) , including the known 
 carcinogens, benzo(a)pyrene (BaP), 
 indeo(l ,2,3-cd)pyrene, and others, may 
 occur in significant concentrations. 
 Another constituent of sludges may be 
 phenol, which is probably derived from 
 electrode binding materials in covered 
 furnaces (18). 
 
 A leachate test of emission control 
 dusts of a ferrochrome furnace, conducted 
 by the ferroalloy industry, showed that 
 Cr exceeded by 10 times the EPA water 
 quality criteria for classification as 
 hazardous (20) . Neither the slag nor 
 scrubber sludge, also tested, exceeded 
 EPA criteria, indicating their stability. 
 Although this test was made by the Ferro- 
 alloy Association Environmental Commit- 
 tee, they feel it is not representative 
 of actual dust characteristics. Signifi- 
 cant doubt exists as to actual character- 
 istics of smelter dust. 
 
 High concentrations of PNA are likely 
 in the scrubber water and sludge, and 
 previous work indicates that up to 90 pet 
 of this type of material can be adsorbed 
 on suspended particles. Therefore, it is 
 likely that the sludges in the lagoons 
 and landfills from covered furnaces con- 
 tain high concentrations of PNA, possibly 
 exceeding the minimum limits for acute 
 toxicity for effluent solid wastes (23). 
 The aqueous solubility of PNA's is unaf- 
 fected by solution pH, so no chemical pH 
 control can be taken. 
 
 Chemical treatment, clarif ier-f loccu- 
 lators, sand filters, and recirculation 
 would be required to meet the water ef- 
 fluent standards for electric ferroalloy 
 furnaces when scrubbers are used (22) . 
 
 Waste water purification normally con- 
 sists of solids removal by settling in 
 unlined ponds or filtration before any 
 
 chemical treatment of the water; thus, 
 the solids and the potential organics 
 contained within receive essentially no 
 treatment. Scrubber sludge is normally 
 disposed of in settling ponds. When a 
 pond is filled, a new one is constructed 
 or the old one is dredged for reuse. The 
 Ferroalloy Association estimates 85 pet 
 or more of all sludge wastes nationwide 
 are disposed of in landfills or lagoons, 
 and less than 15 pet are recycled, re- 
 claimed, or sold. Industry sources state 
 that sludges are essentially self-sealing 
 within a pond, so no linear or imperme- 
 able soil condition is necessary (18) . 
 However, sludge from the potential smelt- 
 er would be dewatered and stored in a 
 double-lined disposal site. 
 
 A general waste water treatment system 
 for ferroalloy production is shown in 
 figure 18. The process needed for Cr 
 production may not contain all of the 
 stages shown, but figure 18 gives an ap- 
 propriate general scheme of what might be 
 expected in waste water control. The 
 diagram is explained by Williams (15): 
 The pH is raised to about 11, and 
 sufficient chlorine is added to 
 maintain a free residual, followed 
 by sedimentation. This step oxi- 
 dizes phenol and cyanide (to cya- 
 nite) and phosphates and manganese 
 are precipitated. In the second 
 step, additional chlorine is added 
 and the pH is lowered to 7.0 by a 
 suitable acid. With a reaction 
 time of 60 minutes, the cyanate is 
 oxidized to CO2 and N2« In the 
 third step, the pH is lowered to 
 2.5 and sulfur dioxide is added. 
 After a reaction time of about 30 
 minutes, the hexavalent Cr is re- 
 duced to the trivalent state. The 
 fourth step consists of raising the 
 pH to 8.2, adding a polyelectro- 
 lyte and allowing sedimentation. 
 At this point, the trivalent chro- 
 mium is removed and final clar- 
 ification is accomplished. With a 
 sufficiently low overflow rate and 
 addition of flocculants in suffi- 
 cient quantities, a concentration 
 of 25 mg/L (milligrams per liter) 
 suspended solids can be attained 
 and metals can be reduced to low 
 
26 
 
 Sludge 
 disposal 
 or metal 
 recovery 
 
 0.5-gpm/ft 
 rise rate 
 at pH 8.2 
 
 FIGURE 18. - Ferrochrome smelter water treatment system. (From Williams (\6). 
 
 levels. Sand filtration of the fi- 
 nal clarifier effluent, with back- 
 wash returned to the clarifier, 
 can reduce suspended solids concen- 
 trations to 15 mg/L or less. After 
 filtration, the water may be recy- 
 cled back to the scrubbers. 
 Water needed for the smelting process can 
 be acquired from a well, directly from 
 the Stillwater River, or from the milling 
 process. Because all waste water is to 
 be recycled, makeup water would be mini- 
 mal (i.e., makeup for evaporation). 
 
 NICKEL-COPPER PROCESSING WASTE WATER 
 
 Detailed data on the characteristics 
 of waste water from the Ni-Cu process 
 are not available. However, a general 
 description of waste water disposal is 
 possible. 
 
 Water and reagents used in the bulk 
 flotation stage of the process would gen- 
 erally be recirculated. However, some 
 water and reagents would report to the 
 
 tailings pond with the tailings. Clari- 
 fied water would be decanted from the 
 tailings pond and reused. Excess water 
 would evaporate. 
 
 Waste water from the leach circuit 
 would be neutralized with lime and sent 
 to the tailings pond where it would ei- 
 ther be recycled or evaporate. Sludge 
 residue from the leaching circuit would 
 be neutralized with lime, slurried, and 
 sent to the tailings pond (18) . The zero 
 discharge requirements should be attain- 
 able in the planned Ni-Cu process. 
 
 DIVERSION OF STREAMS 
 
 Verdigras Creek runs though the middle 
 of the Ni-Cu zone and would need to be 
 diverted away from the open pit. The 
 creek would be diverted about 3,000 ft 
 west to Mountain View Lake (fig. 5), 
 which would reduce water pollution by 
 reducing the amount of water flowing 
 through the Ni-Cu pit. 
 
27 
 
 Water in Verdigras Creek is cur- 
 rently of lower quality than water in 
 other streams in the area because it 
 flows through the Ni-Cu zone. The di- 
 version is expected to increase water 
 quality in Verdigras Creek by routing 
 the creek through less reactive geologic 
 formations. 
 
 An unnamed creek shown in figure 7 
 would also need to be diverted for the 
 high-end PGM scenario, the Ni-Cu scenar- 
 io, and the combined operations scenario. 
 Diversion reduces the possibility that 
 heavy runoff from this creek would enter 
 the tailings pond. The creek would be 
 diverted to the east around the planned 
 dam. 
 
 SUMMARY OF WATER ISSUES 
 
 Baseline studies show that water qual- 
 ity in the Stillwater Complex ranges from 
 poor to good. Table 3 shows that samples 
 occasionally exceeded standards for Cd, 
 Cr, Fe, Mn, Pb, fecal bacteria, and tur- 
 bidity. Generally, the poorest samples 
 were taken during the spring, when flows 
 
 and suspended solids were high. Mine 
 drainage water quality was better than 
 expected; only one sample exceeded crite- 
 ria for Cr. 
 
 New source performance standards for Ni 
 and Pt mining and milling call for zero 
 discharge of process water, with a few 
 exceptions. A performance standard has 
 not been set for Cr mining and milling. 
 The processes that would be used in the 
 Stillwater Complex should be able to 
 achieve these standards. 
 
 The characteristics of Cr smelter waste 
 water are unclear. Some evidence ex- 
 ists suggesting that high concentrations 
 of organic compounds may be present in 
 sealed-furnace smelters. If so, waste 
 water treatment would be needed, and an 
 appropriate technique is suggested. Ad- 
 ditional research is indicated. 
 
 In summary, existing technology should 
 allow any mining operation except ferro- 
 chrome smelting to meet water quality 
 regulations. Ferrochrome smelting waste 
 water has unknown characteristics and may 
 pose treatment problems. 
 
 AIR ISSUES 
 
 
 With the exception of the ferrochrome 
 smelter, air quality issues seem to be 
 less significant than land or water is- 
 sues. In this section, information is 
 presented on the baseline air quality and 
 emissions from the ferrochrome smelter 
 and other sources. 
 
 BASELINE AIR QUALITY 
 
 The climate of the Stillwater Complex 
 is mountainous continental. Large varia- 
 tions in elevation (from 5,000 to 10,000 
 ft) cause large variations in local cli- 
 mate and precipitation. Mountain ridges 
 and valleys redirect prevailing winds. 
 During feasibility studies for potential 
 PGM operations, weather and air quality 
 sampling stations were established at 
 several points in the Stillwater Complex 
 (17) . These stations recorded tempera- 
 ture, wind speed, wind direction, precip- 
 itation, total suspended particulates, 
 and other parameters. Data presented 
 
 here are primarily from the Stillwater 
 River Valley because it would be the lo- 
 cation of the most activity. 
 
 Average temperature in the Stillwater 
 River Valley is 45° F. The date of the 
 first frost is mid-September, while the 
 last frost occurs in mid- June. Annual 
 temperature range is about 50° F, winter 
 to summer. Temperatures at higher eleva- 
 tions are much lower, and freezing tem- 
 peratures may occur at any time at eleva- 
 tions over 7,500 ft. Timberline in the 
 area is at about 9,700 ft. Precipitation 
 in the valley ranges between 5 and 60 
 in/yr. One-third to one-half of the pre- 
 cipitation occurs in April, May, and 
 June. The smallest amount of precipita- 
 tion occurs in the winter months of No- 
 vember through March. Annual precipita- 
 tion at the Minneapolis Adit is estimated 
 to be about 20 in/yr, while annual pre- 
 cipitation at the Hertzler Ranch site is 
 estimated to be about 15 in/yr (17). 
 
28 
 
 Persistent westerly winds blowing down 
 the Stillwater River Valley and occa- 
 sional southerly chinook winds tend to 
 reduce snow accumulations in the valley. 
 At higher elevations , an increasing pro- 
 portion of precipitation occurs as snow. 
 At elevations over 7,500 ft, over 75 pet 
 of the precipitation occurs as snow (17) . 
 
 A diurnal wind pattern typical of moun- 
 tain valleys exists in the Stillwater 
 River Valley. Daytime upslope winds and 
 nighttime downslope winds are caused by 
 heating from the sun. Prevailing wester- 
 ly winds tend to reduce the upslope con- 
 dition because they blow down the valley. 
 Strong downslope winds are channeled by 
 the valley and are common in the winter 
 to early spring months. Wind speed and 
 direction roses are shown in figure 19. 
 
 Data on the inversion heights in the 
 Stillwater River Valley have not been 
 complied, but data are available for 
 
 30 pel 
 
 30 pel 
 
 12-4 p.m. 4-8 p.m 8-12 midnight 
 
 DIURNAL WIND DIRECTION ROSES 
 
 similar valleys, and estimates have been 
 made based on these data. 
 
 Very strong nighttime temperature in- 
 versions are likely to occur, owing to 
 intense cooling under clear nighttime 
 skies. These inversions are expected to 
 be most intense during the winter months. 
 Inversion height is estimated to be about 
 500 ft above the valley floor (17). Per- 
 sistent westerly winds, common in the 
 valley, will reduce the frequency and in- 
 tensity of these inversions. During the 
 winter, winds under 5 mph occur less than 
 5 pet of the time. 
 
 When strong temperature inversions ex- 
 ist, mixing under the inversion is poor 
 and pollutants can become trapped in the 
 valley. Poor air quality can result. As 
 mentioned above, this condition would 
 be most likely to occur during the win- 
 ter months on days when strong winds are 
 absent. 
 
 Measurements of total suspended partic- 
 ulates in the Stillwater River Valley 
 averaged between 14 and 20 yg/m 3 . The 
 Federal standard is 260 ug/m 3 , and the 
 Montana standard is 200 yg/m 3 . All re- 
 corded measurements fell well below these 
 standards (17) . However, both Federal 
 and State clean air regulations use the 
 principle of "no significant deteriora- 
 tion" of air quality, meaning that per- 
 mits granted by these authorities will 
 require that emissions not "significant- 
 ly" change total suspended particulates 
 levels in the valley. Increments of de- 
 terioration may be allowed at the discre- 
 tion of the permit authority. 
 
 ; 20 pel 
 
 ,30 pet 
 
 Wind speed class (mph) 
 2 7 11 18 25 
 
 WIND SPEED ROSE 
 
 FIGURE 19. - Wind roses from the Stillwater 
 River Valley. 
 
 FERROCHROME SMELTER GAS EMISSIONS 
 
 The submerged electric arc furnace 
 (fig. 20) is sealed and produces an off- 
 gas rich in CO. The offgas is scrubbed 
 (particulates removed) by use of a high- 
 energy venturi scrubber (wet process). 
 Gaseous effluents include mainly CO, fol- 
 lowed by volatilized metallics, sulfur 
 oxides, cyanides, phenols, and oil, and 
 are usually treated by combustion (22) . 
 Normally, the CO-rich gas is flared, but 
 here in order to decrease pollution and 
 increase energy efficiency, it is pro- 
 posed to be used as fuel to dry mill con- 
 centrates. The effectiveness of flares 
 
29 
 
 Electrodes 
 / \ 
 
 Bag house 
 
 Water Water 
 
 FIGURE 20. - Ferrochrome smelter air control system. 
 
 . Option of 
 ' flaring gas 
 
 Co-rich gas 
 
 for fuel 
 
 to dryer 
 
 scrubber control 
 for the proposed 
 
 or burning in general for destroying 
 higher molecular weight organic matter is 
 questionable, since test data show that 
 organics survive even in gases from open 
 furnaces, which burn vigorously. 
 
 The general trend for submerged arc 
 ferroalloy production facilities is to 
 use an open-type furnace with a, baghouse 
 to remove particulates from the gas 
 stream. About 70 pet of all submerged 
 arc ferroalloy furnaces in the United 
 States in May 1980 were open furnaces 
 with baghouses (22). However, a sealed 
 furnace with venturi 
 equipment was chosen 
 chromite refining. CO gas can be recov- 
 ered from this type of furnace, and 
 smaller scale pollution control devices 
 are utilized because smaller volumes of 
 gas are produced by the furnace. All 
 covered furnaces in the United States use 
 scrubbers as control equipment rather 
 than baghouses. Gas from sealed furnaces 
 contains fumes, particulates, high con- 
 centrations of CO, some CO2 and H 2 , and 
 several types of organic matter. The 
 high CO content of the offgas makes it 
 potentially explosive and hazardous to 
 breathe. A baghouse for collection of 
 offgas particulates would be hazardous 
 because of the high CO content and the 
 toxic and volatile nature of the gas. A 
 typical ferrochrome smelter air control 
 system is shown in figure 20. 
 
 The EPA reports that sealed furnaces 
 have much lower gas emission rates than 
 open furnaces (22) . The power require- 
 ments for their control systems are usu- 
 ally much lower than those for open 
 
 furnaces. Open furnace control equipment 
 must handle gas volumes typically 50 
 times greater than the volumes from 
 sealed furnaces. Even 20 to 35 pet of 
 the energy supplied to a closed furnace 
 can be recovered by fueling processing 
 equipment such as dryers, pellet fur- 
 naces, and sintering machines with C0- 
 rich gas from the furnace. Only about 2 
 pet of the power used in operating sealed 
 furnaces is needed for pollution control. 
 
 The control systems should be well 
 sealed and the work areas ventilated. 
 Mechanical seals are used around the 
 electrodes on a sealed furnace, and the 
 feed mix is added through sealed chutes 
 (22). No gas or fume is allowed to es- 
 cape from the furnace cover, and only 
 a minimal secondary hood airflow is re- 
 quired. There is no air leakage into the 
 furnace, so combustion is prevented. Two 
 advantages of the sealed furnace are 
 reduced escape of gas and fumes from 
 the furnace cover and a lower cover 
 temperature. 
 
 About 173 and 411 tpd of gases are at- 
 tributable to smelting for the low- and 
 high-end scenarios, respectively. Com- 
 puter modeling would be required to esti- 
 mate the impact such emissions would have 
 on air quality, but some major character- 
 istics can be identified. The relatively 
 high volume of gases could significantly 
 affect air quality in the Stillwater 
 River Valley on occasions. The prevail- 
 ing westerly winds may tend to clear the 
 valley most of the time, but possible 
 strong temperature inversions on calm 
 winter mornings may trap pollutants in 
 
30 
 
 the valley. On days when strong inver- 
 sions are present, CO and particulates 
 from the smelter combined with CO and 
 particulates from automobiles and fire- 
 places could lower air quality. 
 
 Tapping fumes would be controlled by a 
 hood and fan sending gaseous effluents to 
 a baghouse or another scrubber. When the 
 furnace is tapped, fumes occur as a re- 
 sult of (1) burning the C plug out of the 
 taphole, (2) oxidation of hot metal, and 
 (3) vaporization of organics in the C 
 used as a lip liner when opening or seal- 
 ing the taphole. Emissions when tapping 
 are of short duration and are partially 
 captured by the taphole emission control 
 system. Fumes not captured are vented 
 and dispersed through the building's roof 
 monitors. Although the fumes could con- 
 tain hazardous organic compounds, their 
 concentrations are rapidly reduced by 
 dilution with air. Most plants have sys- 
 tems that capture the particulates in a 
 baghouse. Most other fumes and dust oc- 
 cur as metallic components similar to the 
 alloy during transfer, cooling, grinding, 
 and packing of the alloy. All water from 
 the scrubbers would be recycled. 
 
 DUST 
 
 Several potential sources of dust 
 exist, but detailed data to quantify 
 amounts do not. A general description of 
 these potential sources follows. 
 
 During the lifetimes of the PGM, Ni-Cu, 
 and chromite projects, periods will oc- 
 cur when portions of the tailings ponds 
 are dry and are potential sources of fu- 
 gitive dust. Such areas cannot be reveg- 
 etated until they are dry enough to sup- 
 port mechanical equipment, but chemical 
 dust suppressants could be used to effec- 
 tively minimize the problem. Chemical 
 composition of the tailings should not 
 pose any health risks as they are not 
 known to contain asbestiform minerals or 
 other irritants. Chromium in the tail- 
 ings would be in the less hazardous tri- 
 valent state and would be present in low 
 concentrations . 
 
 The Ni-Cu open pit is another poten- 
 tial source of dust. Haul roads in the 
 mine, blasting, and crushing are poten- 
 tial sources of dust. Most of these 
 sources can be effectively controlled, 
 however. Haul roads can be periodically 
 watered, blasting can be designed to min- 
 imize fines production, and dust from the 
 crusher would be contained in a baghouse, 
 as required by current regulations. It 
 is impossible to quantify the amount of 
 dust generated by the various operations, 
 but existing technology is generally ef- 
 fective in controlling emissions from 
 these types of sources. 
 
 OTHER AIR ISSUES 
 
 The most significant air issue not al- 
 ready addressed is the possibility of 
 residential air pollution caused by auto- 
 mobiles, wood-burning stoves, and fire- 
 places. As previously mentioned, strong 
 air temperature inversions are possible 
 in the valley during the winter months. 
 A large proportion of the expanded pop- 
 ulation of the area would be expected 
 to use stoves and fireplaces. Smoke and 
 CO from stoves and fireplaces could be 
 trapped in the valley by the inversion, 
 resulting in poor air quality. Catalytic 
 converters could be installed on pri- 
 vate wood-burning stoves to alleviate the 
 problem but would probably have to be 
 required by local ordinance. 
 
 The persistent prevailing westerly 
 winds during the winter months will tend 
 to reduce the occurrence of this condi- 
 tion. Less than 5 pet of winter mornings 
 would be susceptible to inversion-caused 
 pollution. 
 
 Mine ventilation air may contain sus- 
 pended particulates. This air exhaust 
 would contain respirable dust, nitrous 
 fumes from blasting, and diesel vehicle 
 exhaust. Amounts should be relatively 
 low and are not expected to impact air 
 quality. 
 
OTHER ISSUES 
 
 31 
 
 
 NOISE 
 
 Potential sources of frequent noise 
 would be haulage trucks and blasting in 
 the Ni-Cu open pit, as well as main 
 ventilation fans for the underground 
 mines; some noise would also be associ- 
 ated with the ferrochrome smelter. In- 
 frequent noise would come from trains 
 bringing in supplies and transporting 
 products to market. 
 
 POWER, TRANSPORTATION, AND HOUSING 
 
 Twin transmission lines could be con- 
 structed between Columbus and the ferro- 
 chrome smelter, 45 MW for the low-end 
 scenario and 110 MW for the high-end sce- 
 nario. The present 50 kW transmission 
 line is insufficient to meet the needs of 
 any potential operation. This line would 
 have to be upgraded in order to support 
 the increase in population resulting from 
 mining. The PGM and Ni-Cu mining would 
 need substantially less power than the 
 chromite mine-mill-smelter complex. 
 
 The road between Columbus and the mine- 
 mill sites would probably have to be up- 
 graded to accommodate the increased traf- 
 fic load resulting from mining. Heavy 
 equipment would probably be brought in by 
 rail, thus reducing the amount of road 
 upgrading. 
 
 A spur rail line from Columbus to the 
 mill area would be necessary for the Cr 
 mine-mill-smelter complex. Trains could 
 better handle the large volume of flux, 
 coal, and other material needed for pro- 
 ducing ferrochrome, and could transport 
 the ferrochrome to a main rail line. The 
 spur line could also be used to bring in 
 mine, mill, and smelter equipment. 
 
 Most people employed by these potential 
 operations would reside in Stillwater 
 County, which had a population of 5,597 
 in 1980. Chromium operations would em- 
 ploy 90 to 200 people, PGM operations 
 would employ 170 to 520 people, and Ni-Cu 
 operations would employ 150 to 300 peo- 
 ple. Assuming an average of two depen- 
 dents for each employee, the population 
 increase would be 220 to 600 people for 
 Cr operations, 510 to 1,560 people for 
 PGM operations, and 450 to 900 people for 
 Ni-Cu operations. The percentage popu- 
 lation increases for Stillwater County 
 would be 5 to 11 pet for Cr operations, 9 
 to 30 pet for PGM operations and 8 to 16 
 pet for Ni-Cu operations. Combined oper- 
 ations would result in a 22- to 57-pct 
 increase in the population of Stillwater 
 County. 
 
 The towns of Nye, Fishtail, Absaroka, 
 and Columbus would experience growth due 
 to these operations. Nye and Fishtail 
 (both unincorporated) are nearest to the 
 operations and are the smallest of the 
 communities. Housing constructed in 
 these communities would include single- 
 family homes, trailers, and apartments. 
 The school of Nye may have to be ex- 
 panded. Police and fire protection in 
 the upper part of the valley may have to 
 be increased. 
 
 Sufficient lead time would be required 
 for local officials to plan for orderly 
 growth if mining operations become real- 
 ity. Once detailed mine plans have been 
 formulated, local officials can prepare 
 plans for roads, schools, fire protec- 
 tion, and police services. Costs can be 
 estimated and suitable taxes and bonds 
 instituted. This process could take over 
 2 yr to complete. 
 
 CONCLUSIONS 
 
 In this report, the environmental is- 
 sues of potential development of strate- 
 gic and critical minerals in the Stillwa- 
 ter Complex were discussed. Specific 
 land, water, air, and other environmental 
 
 issues were identified and analyzed as to 
 how they would relate to mining of Cr, 
 PGM, and Ni-Cu deposits located in the 
 Stillwater Complex. 
 
32 
 
 Chromium would be mined underground 
 using shrinkage stoping methods. Mill- 
 ing would be by gravity concentration. 
 Smelting would be done on-site using a 
 sealed furnace. Mill feedrate would 
 range from 1,000 to 2,500 tpd ore. 
 
 PGM would be mined underground using 
 shrinkage stoping or cut-and-fill stoping 
 methods. Milling would be by froth flo- 
 tation using a low-pH method. Concen- 
 trate would be refined elsewhere. Mill 
 feedrate ranges from 1,000 to 4,000 tpd 
 ore. 
 
 Nickel-copper ore would be mined using 
 open-pit methods. Milling would be by 
 froth flotation and Cl-0 2 leach. Refin- 
 ing would be by electrolysis and precipi- 
 tation. Mill feedrate would be about 
 27,500 tpd ore. 
 
 The most significant environmental 
 isssues center around the ferrochrome 
 plant. This plant would produce a sludge 
 high in organic content. The plant would 
 
 be highly visible and require significant 
 amounts of electric power. 
 
 The Ni-Cu open pit and dump would be 
 visible during active mining. The tail- 
 ings pond resulting from the operation 
 would require an area of over 600 acres . 
 
 PGM mining would also be highly visible 
 during active mining. The area required 
 for tailings disposal ranges from 75 to 
 300 acres depending on size and mining 
 method. 
 
 Technology for reclamation and minimi- 
 zation of environmental effects seems to 
 be well defined, with the exception of 
 sludge disposal for the ferrochrome 
 smelter. Zero net waste water discharge 
 should be achievable for all operations. 
 Reclamation technology for all solid 
 waste (except ferrochrome smelter sludge) 
 is available and sound. Visual impact 
 and land use changes are unavoidable 
 effects. 
 
 REFERENCES 
 
 1. U.S. Bureau of Mines. Mineral Com- 
 modity Summaries 1984, 185 pp. 
 
 2. Hargreaves , D. , and S. Fromsen. 
 World Index of Strategic Minerals: 
 Production, Exploitation, and Risk. 
 Facts on File, Inc., New York, NY, 1983, 
 299 pp. 
 
 3. Jolly, J. H. Platinum-Group Met- 
 als. Ch. in Mineral Facts and Prob- 
 lems, 1980 Edition. BuMines B 671, 1981, 
 pp. 683-706. 
 
 4. Golden, J., R. P. Ouellette, S. Sa- 
 ari, and P. N. Cheremisinof f . Environ- 
 mental Impact Data Book. Ann Arbor Sci., 
 1979, 864 pp. 
 
 5. Price, P. M. Mining Methods and 
 Costs, Mouat Mine, American Chrome Co., 
 Stillwater County, Mont. BuMines IC 
 8204, 1963, 58 pp. 
 
 6. Sullivan, G. V., and G. F. Worken- 
 tine. Benef iciating Low-Grade Chromites 
 From the Stillwater Complex, Montana. 
 BuMines RI 6448, 1964, 28 pp. 
 
 7. Page, N. J., and W. J. Nokleberg. 
 Geologic Map of the Stillwater Complex, 
 Montana. U.S. Geol. Surv. Misc. Invest. 
 Series Map 1-797, 1974, 5 plates. 
 
 8. Bow, C. , C. Wolfgram, A. Turner, 
 S. Barnes, J. Evans, M. Zdepski, and 
 A. Boudreau. Investigations of the How- 
 land Reef of the Stillwater Complex, Min- 
 neapolis Adit Area: Stratigraphy, Struc- 
 ture, and Mineralization. Econ. Geol., 
 v. 77, 1982, pp. 1481-1492. 
 
 9. Perlmutter, S. J. Montana Envi- 
 ronmental Permit Directory. MT Environ. 
 Qual. Counc, 1982, 27 pp. 
 
 10. Montana Department of State Lands 
 and U.S. Forest Service. Draft Environ- 
 mental Impact Statement, Stillwater Min- 
 ing Co. Stillwater Project, Stillwater 
 County. 1985, 259 pp.; available from MT 
 Dep. State Lands, Helena, MT. 
 
 11. Federal Register. U.S. Environ- 
 mental Protection Agency. Ore Mining and 
 Dressing Point Source Category Effluent 
 Guidelines and New Source Performance 
 Standards. V. 47, No. 233, Dec. 3, 1982, 
 pp. 54597-54621. 
 
 12. Yamada, K. Stainless Steelmaking 
 by the LD-AOD Process. Ch. in Iron and 
 Steelmaker. Iron and Steel Soc. AIME, 
 1982, pp. 29-33. 
 
33 
 
 13. Morrice, E. Pilot Mill Flotation 
 of Anorthositic Platinum-Palladium Ore 
 From the Stillwater Complex. BuMines 
 RI 8763, 1983, 8 pp. 
 
 14. Baglin, E. G. , J. M. Gomes, and 
 M. M. Wong. Recovery of Platinum-Group 
 Metals From Stillwater Complex, Mont., 
 Flotation Concentrates by Matte Smelt- 
 ing and Leaching. BuMines RI 8717, 1982, 
 15 pp. 
 
 15. Williams, R. E. Waste Production 
 and Disposal in Mining, Milling, and Met- 
 allurgical Industries. Miller Freeman, 
 San Francisco, CA, 1975, 489 pp. 
 
 16. Smyres, G. A. Chlorine-Oxygen 
 Leaching of Complex Sulfide Concentrates. 
 AIME preprint A7786, 1977, 9 pp. 
 
 17. The Anaconda Company. Operating 
 Permit Application for a Platinum/Palla- 
 dium Mine, Stillwater County, Montana. 
 Unpublished report, 1981, 3 v., 600 pp.; 
 available from MT Dep. State Lands, 
 Reclam. Div. , Helena, MT. 
 
 18. Westbrook, W. Ferroalloy Fur- 
 naces: Generation and Emission of Par- 
 ticulate and Organic Matter. Paper in 
 
 39th Electric Furnace Conference Proceed- 
 ings. Iron and Steel Soc. AIME, 1981, 
 pp. 226-242. 
 
 19. Beak Consultants, Ltd. Surface 
 Water Resources for the Stillwater PGM 
 Resources Project. Unpublished report, 
 Tech. Rep. 4, 1982, pp. 41-48; available 
 from MT Dep. State Lands, Reclam. Div., 
 Helena, MT. 
 
 20. U.S. Environmental Protection 
 Agency. Quality Criteria for Water. 
 1976, 260 pp. 
 
 21. National Research Council. Medi- 
 cal and Biological Effects of Environmen- 
 tal Pollutants: Chromium. Natl. Acad. 
 Sci., Washington, DC, 1974, 155 pp. 
 
 22. U.S. Environmental Protection 
 Agency. Background Information for Stan- 
 dards of Performance: Electric Submerged 
 Arc Furnaces for Production of Ferroal- 
 loys. Volume I: Proposed Standards. 
 EPA-450/2-74-018a, 1974, 174 pp. 
 
 23. . Level 1 Environmental As- 
 sessment of Electric Submerged-Arc Fur- 
 naces Producing Ferroalloys. EPA-600/2- 
 82-083, 1981, 333 pp. 
 
 ■frU.S. CPO: 1985-505-019/20,091 
 
 INT.-BU.OF MINES,PGH.,PA. 28080 
 
33 
 

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