PUBLIC HEALTH ASSESSMENT
DEL NORTE, RIO GRANDE COUNTY, COLORADO
Summitville Consolidated Mining Corp., Inc. (SCMCI), a subsidiary of Galactic Resources, operated a heap leach gold extraction mine from July 1986 through October 1991. The Emergency Response Branch of the Environmental Protection Agency (EPA) assumed operation and maintenance responsibility on December 16, 1992, after SCMCI declared bankruptcy. EPA has moved waste piles, capped the mine pits, and plugged mine adits (former underground workings in South Mountain) in an effort to prevent discharge of untreated water to Wightman Fork. The Wightman Fork drains into the Alamosa River, which flows into Terrace Reservoir. Terrace Reservoir is used for irrigation of farm land in the San Luis Valley.
Surface water is the main environmental medium the Summitville Mine site has impacted and is the primary transport mechanism carrying contaminants from the site. Three main sources--the heap leach pad, french drain, and Reynolds Adit and other associated acid drainages--have released contaminated water from the mine site. The contaminants are cyanide and heavy metals from the heap leach pad and french drain and heavy metals and sulfate from acid drainage.
ATSDR has classified this site as no apparent public health hazard. Although ATSDR has determined that human health effects are unlikely, we have recommended further sampling of surface water for heavy metals in order to evaluate the long-term impact, if any, on downstream users of Alamosa River water. ATSDR recommends that remediation at the Summitville Mine site continue so that environmental impacts from metal and hydrogen ion loading to the Alamosa River are lessened. No adverse human health effects are anticipated from metals in drinking water, soil, crops, fish, livestock, or wildlife in the Alamosa River basin. However, we recommend that studies on these potential pathways for human exposure continue. Private well samplings in the San Luis Valley, approximately 20 miles downstream of the mine site, suggest that mine drainage has had no widespread effect on well water quality. Most private wells in the San Luis Valley have metals below federal drinking water standards. However, we recommend a private well sampling program to confirm 1995 results and assure residents that their drinking water is safe. Cyanide in Alamosa River water is not at levels of public health concern because of treatment of on-site water containing cyanide and volatilization and dilution of cyanide in the creeks and river.
In cooperation with local, state, and federal agencies, the Agency for Toxic Substances and Disease Registry (ATSDR) has evaluated the public health significance of the Summitville Mine site in Del Norte, Colorado. Although ATSDR has determined that human health effects are unlikely, we have recommended further sampling of surface water for heavy metals in order to evaluate the long-term impact, if any, on downstream users of Alamosa River water.
ATSDR, in Atlanta, Georgia, is a federal agency within the U.S. Department of Health and Human Services. The Superfund law (Comprehensive Environmental Response, Compensation, and Liability Act of 1980 [CERCLA]) as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA) requires ATSDR to conduct health assessments of hazardous waste sites proposed for the National Priorities List (NPL).
This public health assessment (PHA) and the risk assessments that the U.S. Environmental Protection Agency (EPA) is releasing on the Summitville site have distinctly different purposes (1,2). The PHA evaluates the overall public health significance of the site and focuses on preventing or reducing exposure to hazardous substances. EPA's risk assessments (on human health and ecological risks) focus on the current and potential threat to people and the environment and how to establish clean-up levels that will protect them.
ATSDR received comments on the initial release of this public health assessment from staff of the Colorado Department of Public Health and Environment, the Colorado Department of Natural Resources, and EPA's contractor. Responses to comments received during the second release (the public comment period) are in Appendix Three. We concurred with most of the comments on these releases and have included revisions in this document.
Summitville Mine lies in the San Juan Mountain Range of the Rocky Mountains, approximately 18 miles southwest of Del Norte in Rio Grande County, Colorado [Figure 1]. The Rio Grande National Forest surrounds the mine site. The site was an open pit heap leach gold mining operation, conducted near the Continental Divide at an elevation of more than 11,000 feet. Wightman Fork Creek bounds the site on the north, Cropsy Creek on the east, and South Mountain on the southwest [Figure 1]. The disturbed area of the site covers approximately 550 acres (3). Contaminants from the site drain into Wightman Fork, which flows into the Alamosa River [Figures 1 and 2]. Terrace Reservoir, located on the Alamosa River, provides water for irrigating farm lands. EPA placed the Summitville Mine on the NPL in May 1994 (4).
Mining began at Summitville around 1870 with placer gold mining of alluvial deposits in streams (3). Open cut mining on gold-bearing quartz veins followed the placer mining. Underground mining of the veins, using adits and shafts, replaced open cut mining. The latest owner of the mine is Summitville Consolidated Mining Corp., Inc (SCMCI), a subsidiary of Galactic Resources Ltd. SCMCI mined from July 1986 through October 1991 and abandoned the site in December 1992 (3). SCMCI mined the gold ore, crushed it, and heaped it on a lined pad (the heap leach pad). Workers enclosed a portion of the valley where Cropsy Creek ran (44 acres area and 100 feet deep) and moved the creek to construct the heap leach pad (5). A solution of sodium cyanide, leaching through the ore, extracted gold. Wells set above the liner recovered the gold and other metals from the sodium cyanide leachate. Technicians transported the solution of cyanide and metals to a gold-recovery facility, where they produced silver and gold bullion (6). They reused the sodium cyanide solution.
The Emergency Response Branch of the Environmental Protection Agency (EPA) assumed operation and maintenance responsibility on December 16, 1992, after SCMCI declared bankruptcy (7). SCMCI left 160 million gallons of contaminated water within approximately 5 feet of overtopping the containing dike. EPA promptly responded to the threat of a release of cyanide and metal-bearing fluid from the heap leach pad by maintaining water treatment systems. During 1993 and 1994, they also reduced acid drainage from the site by plugging the mine adits (former underground workings in South Mountain) and providing and maintaining treatment systems. They moved waste rock to the mining pit and capped it to control further leaching of metals and acidic discharges (7). EPA's primary objectives at the Summitville Mine site include improving the quality of water flowing from the mine site into Wightman Fork, preventing any adverse human health effects, and reducing any negative environmental effects (8).
EPA formed a Response Engineering and Analytical Contract (REAC) Team in January 1993. The team evaluated existing records (1986-1993), conducted on-site sampling, and provided data for incorporation into the site assessment and ecological evaluation. EPA contractor Morrison Knudsen compiled a master database with on-site and off-site information, including data on downstream areas (9). EPA is directing the completion of remedial actions.
Several groups help with community relations and provide technical assistance to EPA. A Technical Assessment Group formed in February 1993 collects and disseminates information locally (10). Governor Roy Romer appointed a Summitville Advisory Committee in May 1993.
Around May 1993, the U.S. Forest Service posted signs in the Rio Grande Forest at strategic road locations near the mine site to warn forest users not to drink river water because of heavy metals contamination (11). The Forest Service also formed a public information program to inform forest users of the Summitville Mine situation.
Numerous federal, state, and local government agencies and private companies have contributed to site maintenance; remedial actions; and characterization, research, and coordination efforts related to the Summitville Mine site. A collection of their studies efforts was presented in the Summitville Forum '95. Evaluations of possible damage to surface water, drinking water, crops, and livestock have come from various agencies and companies: the State of Colorado (particularly the Colorado Department of Public Health and Environment [CDPHE] and the Colorado Department of Natural Resources), the U.S. Geological Survey, the U.S. Fish and Wildlife Service, the U.S. Forest Service, the Colorado State University (CSU) Agronomy Department, the CSU Agricultural Extension Service, the Colorado Department of Agriculture, and others.
Numerous studies have been conducted and are in progress to address and characterize the environmental problems created by the Summitville Mine site. Some of the projects relevant to this health assessment are mentioned here. The U.S. Geological Survey and the U.S. Department of Agriculture are evaluating the Summitville Mine's downstream effects on agriculture and wildlife. The agricultural studies include soil pH and metals analyses in soils and crops (12). Water quality studies include well water sampling and evaluation of the water quality of the Wightman Fork, the mainstem of the Alamosa River, and Terrace Reservoir. Data collection also includes toxicity tests, invertebrate assessments, stream flow measurements, and an evaluation of sediments in Terrace Reservoir (8).
ATSDR visited the Summitville Mine site in 1993 and has visited the downstream areas twice, in 1993 and 1996. Laura Barr and John Crellin from ATSDR headquarters joined the Geologic Society of America Field Trip to the San Luis Valley in November 1996. They received information on the Summitville Mine and its downstream effects and visited downstream areas. Dr. Mark Rodriguez and Ms. Barr from ATSDR Headquarters and Susan Muza, ATSDR Region VIII representative, visited the Summitville Mine site October 19, 1993.
In 1993, EPA had converted some of the gold mining process equipment into treatment systems. The main treatment systems at Summitville then and now are a Cyanide Destruction Plant (CDP) and a Metals Recovery Plant (MRP) that remove various sources of metals and cyanide. ATSDR toured these treatment facilities in 1993. Although the mine site has no perimeter fencing, access roads to the site are guarded.
Since ATSDR's 1993 site visit, EPA has moved waste piles, capped the mine pits, and plugged mine adits. They have substantially reduced metal loading to Wightman Fork and the Alamosa River.
As part of our visits to the San Luis Valley in 1993 and 1996, the ATSDR staff members observed the Alamosa River drainage basin, some of which is experiencing effects of acid mine drainage from Summitville Mine. ATSDR staff observed the irrigation ditches in the Valley and the water in Terrace Reservoir. They also saw signs on some creeks warning "River Water Contaminated by Heavy Metals. Do Not Drink."
Summitville Mine is in southwestern Rio Grande County, Colorado. In 1990, Rio Grande County had a population of 10,770. Contamination from the mine transported by surface water, including that in irrigation laterals, affects portions of Rio Grande and Conejos Counties. Terrace Reservoir, approximately 17 miles downstream from the mine site, is located on the Alamosa River in Conejos County. There are only a few year-round residents above Terrace Reservoir (1). Residents of the San Luis Valley living downstream of Terrace Reservoir, who live approximately twenty-five miles downstream of the mine site, constitute the closest downstream population affected by the site [Figure 2]. The San Luis Valley is an arid basin about 150 miles long with a maximum width of 50 miles (13). Water from Terrace Reservoir irrigates a portion (approximately 45,000 acres) of the San Luis Valley. Alamosa River water affects approximately 140 wells that are downstream of the site and have permits for domestic use (14). The towns of Centro and Capulin lie near the Alamosa River. Two municipal wells and many domestic wells are used in Capulin, which has a population of approximately 400 (1). The population of Centro is not documented. Drainage from the mine site affects a population estimated at fewer than 1,100.
According to 1990 census data, the population in the area irrigated by Alamosa River water in the San Luis Valley (Figure 2) is 43% Hispanic (10). The non-Hispanic population includes Asians, Native American Indians, African-Americans, and Anglo-Americans. Approximately 25% to 35% of the population in Rio Grande and Conejos counties lives below the poverty line. There are also migrant farm workers in these counties.
The mine site's location in National Forest System lands makes it desirable for recreation such as snow skiing, hiking, camping, and hunting. The Alamosa River corridor downstream of the mine site receives heavy summer recreational use and is within a livestock grazing allotment (15). Cattle and sheep graze in the area during the summer.
There are no residences or schools within 2 miles of the site. Three summer cottages are located between 2- and 4-mile radii of the site. The nearest year-round downstream residents are in Jasper on the Alamosa River, approximately 7 miles downstream of the site. Although Stunner Campground is on the Alamosa, it is upstream of Wightman Fork and therefore is unaffected by contamination from the mine [Figure 1]. Phillips University Camp, approximately 13 miles downstream from the mine site, uses water from a well adjacent to the Alamosa River (1). Terrace Reservoir, approximately 17 miles downstream from the mine, is the source of water for irrigating approximately 45,000 acres of farmland (8) [Figure 2]. The Colorado Division of Wildlife stocked fish into Terrace Reservoir from the 1950s through 1990 (16).
The irrigated areas of the San Luis Valley receive both spray and ditch irrigation. The land adjoining the Alamosa River is primarily meadows and pasture land. Most farms have livestock that graze along the river and use the river for drinking water. Livestock include cattle, hogs, horse, and sheep (10). Dominant crops include potatoes, barley, wheat, and alfalfa.
Natural Resource Use
Summitville Mine lies in a highly mineralized region. Bedrock in the area of the site consists of quartz latite or andesite. The mineralized areas contain gold, silver, copper, and other metals. The mine workings lie in sulfide ores such as pyrite and marcasite (iron sulfides), covellite and chalcocite (copper sulfides), alunite (potassium aluminum sulfate), and jarosite (potassium iron sulfate) (8).
Cropsy Creek flows into Wightman Fork, which flows into the Alamosa River about 4 miles downstream. The Alamosa River empties into Terrace Reservoir and eventually empties into into the Rio Grande. Water from Terrace Reservoir irrigates a portion (approximately 45,000 acres) of the San Luis Valley. Irrigation is the principal means of watering crops in the San Luis Valley.
A portion of the Alamosa River downstream of the site supports six small wetlands comprising approximately 8 acres. Some of these wetlands are above Terrace Reservoir. The Alamosa National Wildlife Refuge is also downstream of the site and may have some hydrologic connection with Alamosa River water. Endangered migratory species such as the whooping crane, bald eagle, and peregrine falcon have been identified in these areas (8).
Because of acidic waters from naturally mineralized areas and mining, no fish have been found in Wightman Fork below the mine or in the Alamosa River above Terrace Reservoir since 1990 (2). Summitville Mine has affected surface water quality for more than 20 miles downstream of the site. The Terrace Reservoir presently contains no fish (15). Fish in some Colorado drainages include brook trout, brown trout, fathead minnow, rainbow trout, white sucker, and carp (17). If acid drainage from the mine site were eliminated, the other creeks (Iron, Alum, Bitter, and Jasper) would still contribute enough acid and metal loading to make it difficult to recolonize the Alamosa River immediately downstream of the confluence with Wightman Fork (18).
Where appropriate, ATSDR tries to identify whether there is more disease or higher levels of a site contaminant in residents' bodies in the population around the site than would be expected (19). To make such determinations, agency staff members evaluate health outcome databases such as cancer registries, birth defect registries, and death and birth certificates; epidemiological studies; medical records; and exposure studies (the level of a chemical in blood, urine, etc.).
The State of Colorado has birth and cancer registries and databases for death and birth certificates. For reasons that will be explained in the Health Outcome Data Evaluation Section, no health outcome data were evaluated for this public health assessment. The National Institute of Occupational Safety and Health (NIOSH) conducted a health hazard evaluation at Summitville. This will also be discussed in the Health Outcome Data Evaluation Section.
ATSDR held public availability sessions on October 18, 1993, but did not receive any reports of community health concerns. Community members had previously, reported some environmental concerns to EPA, particularly about contamination of their irrigation waters (10). The acid mine drainage from the Summitville Mine and other mine sites has raised environmental concerns because of the increased concentrations of metals and lower pH of the Alamosa River waters. There is community concern about effects from Alamosa River water on reestablishing fish in the Alamosa River and detrimental effects on crops, livestock, and wildlife habitats (20).