ASARCO Hayden Plant

Superfund Alternative Site | ASARCO Hayden Plant

EPA #: AZD008397127

EPA Superfund Alternative Site Designation: The site is currently administered through an Administrative Settlement Agreement and Administrative Order on Consent (AOC) between the Environmental Protection Agency (EPA), ASARCO and ADEQ. Site contamination is caused by historical mining operations including smelting and ongoing processing operations.

Location: The ASARCO facility includes the smelter, concentrator, former Kennecott smelter and all associated tailings facilities. The facility is adjacent to the towns of Hayden and Winkelman, 100 miles southeast of Phoenix and about 50 miles northeast of Tucson. The project site is located in the area surrounding the confluence of the Gila and San Pedro Rivers.

Contaminants of Concern: Almost 100 years of smelting activities at this site has deposited lead, arsenic and copper across residential and industrial areas with the highest concentrations located on the north edge of town, near the old Kennecott smelter and on the east side near the concentrator and the No. 9 conveyor.

Arsenic soil concentrations in Hayden range from near background at 12.5 mg/kg to 540 mg/kg. Lead in Hayden ranges from near background (48 mg/kg) to 7,250 mg/kg. Copper varies from below a background of 1,270 mg/kg up to 39,700 mg/kg. In Winkelman, contamination is lower than Hayden and centered along the Highway 177 area and along the railroad tracks on the south side of town. Samples from the school complex on the north end of Winkelman indicate the school has relatively low soil concentrations with all concentrations below proposed remediation level.

Groundwater beneath the smelting and slag deposition areas of the site is impacted by selenium and molybdenum. Tailings impoundments along the Gila River, have caused elevated levels of contaminants to be discharged into surface and groundwater.

Despite the 1,000-foot-tall stack, air quality monitoring in the two towns measured elevated levels of arsenic, lead, copper, cadmium and chromium from site operations. Arsenic in Hayden air is approximately 60 times above expected in an area unaffected by smelting activities. In Winkelman, the average arsenic air concentration (0.00796 mg/m3) is 20 times higher than the Organ Pipe area and is likewise elevated when the wind direction is from the smelter. The high arsenic concentrations are not always associated with high dust levels.