INTRODUCTION 



This paper describes and evaluates revegetation treat- 

 ments of an acid mine spoils area on a surface mine in the 

 western United States. Spoils on this area had not pro- 

 duced vegetation for 18 years. The value of lime as an 

 amendment on acid spoils has long been recognized. 

 Little has been done, however, in the West to show 

 whether mixing organic mulch into acid spoils with a 

 rotary tiller and seeding by various methods will enhance 

 the establishment of vegetation on unfavorable sites. 



DESCRIPTION OF AREA 



The Blackbird copper/cobalt mine is in the heart of the 

 Salmon National Forest about 25 air miles (40 km) west 

 and south of Salmon, Idaho. Its ownership has changed 

 several times since it opened in 1893, and its operation 

 was intermittent until 1967. Demands for cobalt in World 

 Wars I and II stimulated its operation. Later, at the onset 

 of the Korean War, ore production and milling operations 

 expanded. Peak production was in 1958, and operation 

 continued| until 1960. After a temporary shutdown, it re- 

 opened in 1963 with both a surface pit and an under- 

 ground operation. Production was not profitable, though, 

 and it closed again in 1967. 



Physiography of the general area is a succession of 

 rugged high ridges with steep hillsides and deep, narrow 

 draws, most of which are drained by perennial streams. 

 Elevation of the general mine area ranges between 6,600 

 and 8,200 feet (2 012 and 2 500 meters). Annual precipi- 

 tation averages 22 to 35 inches (56 to 89 cm). The 

 dominant vegetation of the area is lodgepole pine (Pinus 

 contorta) with some subalpine fir (Abies lasiocarpa). 

 Spruce (Picea spp.), can be found on north- and east- 

 facing slopes. The understory consists of huckleberry 

 (Vaccinium spp ), Oregon grape (Berberis repens), 

 spirea (Spiraea spp.), pinegrass (Calamagrostis rube- 

 scens), and some forbs. On disturbed sites, such as road 

 cuts, the major vegetation is composed of bitterbrush 

 (Purshia tridentata), alder (Alnus spp ), rose (Rosa 

 woodsii), bluebunch wheatgrass (Agropyron spicatum), 

 Idaho fescue (Festuca idahoensis), hairgrass (Des- 

 champsia caespitosa), western yarrow (Achillea millefo- 

 lium), and penstemon (Penstemon fruticosus). Rocks 

 in the Blackbird district are mostly quartzites and meta- 

 morphosed Precambrian sediments. Occasional mas- 

 sive intrusions of chalcopyrite, cobaltite, pyrite, and pyr- 

 rhotite occur in mineralized lenses; the first two minerals 

 are high grade ores, the other two are waste sulfide 

 minerals. 



Over the years, spoil material, which contained pyritic 

 and sulfide minerals, was dumped in large piles on steep 

 slopes in the draw at the head of Meadow Creek. This 

 dump has a volume of more than one million cubic yards 

 (765 000 m 3 ). High winds, rain, and snowmelt constantly 

 erode the surface of these waste piles and thereby 

 expose fresh mineral elements to oxidation. When these 

 sulfide minerals are exposed to oxygen, either in the air or 

 when dissolved in water, oxidation produces acids 

 (chiefly sulfuric) and other such substances as terrous 

 and ferric sulfates. The following equations express 

 these basic chemical reactions (Sorensen and others 

 1980): 



FeS, + FLO + 3-1/2 O,— FeSO. + FLSO, ( 1 ) 



2 2 2 424*' 



and 



2 FeS0 4 + 1/2 2 + FLS0 4 -Fe 2 (S0 4 ) 3 + H 2 (2) 



The sulfuric acid produced in these reactions acidifies the 

 overburden materials and dissolves heavy metal 

 compounds. 



The products of sulfide mineral oxidation make it 

 difficult, if not impossible, to establish vegetation without 

 modifying the overburden. The leaching of acid and toxic 

 metals described above, plus continuing erosion of the 

 waste material in the mine dump during the past 20 or 

 more years, has made the Blackbird mine a massive 

 producer of sulfuric acid, as well as of copper and iron 

 ions. Acid and heavy metals have eliminated all the fish, 

 benthic organisms, and most of the streamside 

 vegetation in Blackbird Creek and have eliminated the 

 anadromous fishery in Panther Creek, downstream to the 

 Salmon River. 



As yet unanswered questions at the Blackbird Mine 

 are: 



• Can the production and drainage of acid and other 

 pollutants be mitigated? If so, would the mitigation 

 method be environmentally and esthetically 

 acceptable? 



• Would the cost of mitigation be reasonable? Will 

 the mitigation system perpetuate itself, or will it 

 require continuous management? 



This problem is at least twofold. Part of it is the 

 continuous production of acid and other toxic materials 

 that result from constant exposure of the spoils area to 

 erosion. The other part is the flow of water from 

 underground mine tunnels. 



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