COPPER BASIN MINING DISTRICT, OPERABLE UNIT
COPPERHILL, POLK COUNTY, TENNESSEE
Elevated concentrations of lead, copper, and manganese were detected in waste sources, surface soil, and sediment. Prolonged human contact with this contamination could pose a public health hazard, particularly in young children who are more likely to ingest contaminants during hand-to-mouth activities. However, contamination was highest in industrialized or previously-mined areas, and children are not likely to access these areas under current conditions. If the land were converted to residential use, children could be exposed to contaminants at levels of health concern.
Lead concentrations in surface soil and sediment were generally less than 1,000 ppm; these levels would not be expected to pose a health hazard for adult workers. However, one waste sample collected near the Copperhill plant contained lead at 7,500 ppm. Exposure to this material could be of health concern. The risk posed by such contact would depend on the frequency of contact with the contamination, as well as the bioavailability of the lead in the waste material; neither of these variables is known.
Water samples from surface bodies of water in Operable Unit 5 contained concentrations of lead and manganese in excess of health-based guidelines for drinking water. Zinc was detected in water from Davis Mill Creek at concentrations as high as 92,000 ppm, which also exceeds an acceptable drinking water concentration. However, water from these creeks and ponds is not used for potable purposes. It is unlikely that anyone would swim or wade in these waters, since they are highly acidic, discolored, and aesthetically unappealing. Moreover, metals are poorly absorbed through intact skin, so even if dermal contact did occur, it would not pose a significant health hazard.
Mining and smelting over the past 100 or more years have released large quantities of sulfides and sulfur dioxide to the environment. This has contributed to acidic conditions in surface bodies of water. In lower North Potato Creek, the average pH of the water was 3 to 4, and a pH as low as 2.76 was measured.
The chemical form of acid in North Potato Creek was not identified, but it likely consists, in part, of sulfuric acid. Skin contact with strong mineral acids, such as sulfuric acid, can cause chemical burns. Factors that influence the severity of burn include the concentration of the acid and the ability of the acid anion to react with tissue components. The pH of the acid, by itself, is not the only determinant of effect; for example, lemon juice has a pH of 2 but is not irritating to the skin.
Moderate concentrations of mineral acids are surprisingly well tolerated on the skin . Controlled tests on persons with normal and abraded skin showed that irrigation of skin with 10% sulfuric acid was judged to cause minimal irritation. Therefore, even if casual dermal contact occurred with surface water in North Potato Creek, no adverse health effects would be expected.
The eyes are more sensitive than skin to contact with acid solutions. Eye contact with dilute mineral acids can cause immediate pain, conjunctivitis, and reversible injury to the cornea. However, as discussed above, such contact is unlikely to occur because of the unlikelihood of anyone swimming in the affected bodies of water.
Groundwater samples collected from two private wells did not contain contaminants at levels of health concern. One groundwater sample collected from a monitoring well located directly southeast of the BIT facility contained lead at a concentration of 72 ppb. This level exceeds the EPA recommended action level for lead in drinking water (15 ppb). Manganese was also detected in water from this well at a concentration of
670 ppb; this concentration exceeds EPA's Superfund Removal Action Level of 200 ppb. However, there is no known potable use of groundwater near the BIT.
The public water systems in the area obtain water from springs that are presumably free of contamination. However, if contaminated areas are developed for residential use in the future, private wells could be adversely impacted by site-related contamination.
There are several open mine shafts and pits in Operable Unit 5 that pose physical hazards. The largest of the mine pits is Boyd Mine, which is a open pit about 300 feet deep that is partially filled with water. The ground and portions of the fence around the mine have collapsed into the pit. Children, as well as adults, who walk around the pit could be injured or drowned if they fell into the pit.