INTRODUCTION 



Abatement of acid drainage arising from the 

 oxidation of sulfide mineral mining wastes stored 

 on the land surface has probably never been 

 accomplished on an operational scale, short of 

 completely submerging the waste under water. 

 Submergence is an effective but limited treat- 

 ment. Effective abatement programs are notice- 

 ably absent from the acid mine drainage literature. 

 However, this is not to imply that some abatement 

 has not been realized in the past. Where abate- 

 ment has been realized, it is more traceable to 

 nature and time than to any conscious act of 

 people. 



Lime, topsoil covers, and vegetation have been 

 suggested as a means of reducing the acid mine 

 drainage (AMD) problem. The efficacy of vegeta- 

 tion as an erosion control agent cannot be 

 doubted. Vegetation can break the cycle of ero- 

 sion continually exposing new unoxidized sul- 

 fides. It has also been suggested that topsoil and 

 vegetation might create a sufficient oxygen de- 

 mand in the root zone to reduce sulfide mineral 

 oxidation (Brant and others 1971), but the reali- 

 zation of this is not documented. 



This paper presents the results of a 5-year 

 study of the soil-water ionic concentrations of 

 copper, iron, and sulfate — common components 

 of AMD in thewestern United States. The results of 

 the study highlight the intractability of the prob- 

 lem. 



METHODS 



The study site is on the Blackbird copper-cobalt 

 mine on the Salmon National Forest near Salmon, 

 Idaho. The study site and mine property have been 

 described by Farmer, Richardson, and Brown 

 (1 976). The overburden waste pile at the study site 

 contains approximately 1 .1 . million cubic yards (1 

 million cubic meters); the maximum fill depth is 

 estimated to be 75 ft (23 m); the elevation of the 

 site is 7,760 ft (2 365 m). The waste pile is about 25 

 years old. 



During May and June of 1 974, some 45 access 

 holes were drilled to depths varying from 4 to 61 ft 

 (1 .2 to 1 8.6 m). These holes were spread along two 

 line transects 200 ft (61 m) apart. Each transect 

 was about 240 ft (73 rn) long on nearly level 

 ground. Porous ceramic cup soil-water samplers 

 were installed in each hole. In holes more than 1 

 ft (3 m) deep the samplers were constructed after 



the suggestions of Wood (1 973). Prior to installa- 

 tion, each ceramic cup was washed at least three 

 times with IN HCL and rinsed with deionized 

 water. 



Shortly after the soil-water samplers were in- 

 stalled, the surface 8 to 1 inches (200 to 250 mm) 

 of overburden was removed from one of the line 

 transects. This shallow excavation extended the 

 full length of the transect, 240 ft (73 m), for about 

 100 ft (30 m) to either side of the transect. This 

 excavation was replaced with local forest topsoil 

 and shallow subsoils. The operation resulted in an 

 area topsoi led with 8 to 1 inches (200 to 250 mm) 

 of native soils with no change in the surface 

 elevation. 



During topsoiling, 1 ,800 lb/acre (2 030 kg/ha) of 

 burnt lime (CaO) was incorporated into the topsoil. 

 The topsoiled area sat fallow during the summer. 

 In early October 1 974, an additional 4,000 lb/acre 

 (4 470 kg/ha) of burnt lime was incorporated into 

 the topsoil. The topsoiled area was heavily re- 

 seeded to a mixture of native and introduced 

 grasses, was fertilized with 1,300 lb/acre (1 420 

 kg/ha) of liquid 10-34-0, and mulched with 2,700 

 lb/acre (3 050 kg/ha) of wood fiber. In July 1 975, 

 the topsoiled area was refertilized with 225 lb/ 

 acre (254 kg/ha) of a slow release 26-3-5 fertilizer. 

 In September 1975, the revegetated area was 

 relimed with 4,500 lb/acre (5 080 kg/ha) of agri- 

 cultural crushed limestone. 



These operations resulted in two line transects 

 of soil-water samplers. One transect was untreat- 

 ed and completely devoid of vegetation; the waste 

 dump had never revegetated naturally. The other 

 transect, for a width of about 200 ft (61 m), was 

 topsoiled, limed, and revegetated to a heavy stand 

 of grass, about 2,500 lb/acre (2 800 kg/ha) air-dry 

 weight in the second growing season. 



The soil-water samplers were evacuated with a 

 vacuum pump driven by a one-third horsepower 

 electric motor. A portable electric generator sup- 

 plied electricity. Between sample dates the 

 samplers were left under vacuum. They were also 

 reevacuated 24 hours priortothecollection of the 

 soil-water sample. Sample size varied consider- 

 ably, both spatially and temporally, from a few 

 milliliters to nearly a liter. Regardless of sample 

 size, the entire sample was removed on each 

 sample date. 



Soil-water samples were stored in clean poly- 

 propylene 250 ml bottles. The samples were not 

 acidified, but were refrigerated and transported 

 back to the laboratory. Analyses for copper, total 



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