ASARCO Hayden Plant

Superfund Alternative Site | ASARCO Hayden Plant

EPA Superfund Alternative Site Designation:

EPA #: AZD008397127
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.

Site 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.

The school complex on the north end of Winkelman indicate relatively low soil concentrations all below soil remediation levels.


The site is located within the Upper San Pedro groundwater basin. The major components of this system are the water-bearing sands and gravels of the Gila River and San Pedro River flood plains that are recharged from groundwater flows within smaller tributary stream alluvium. Ground water 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.

Regional groundwater flow direction within Hayden and Winkelman is in a southerly direction towards the Gila River/San Pedro River confluence.

The groundwater flow direction between the two tailings impoundments is generally in a northwesterly direction, consistent with the surface water flow direction of the Gila River.

Action Taken: 

Subsequent to an Arizona Department of Health Services 2002 health assessment, exposed residential yards and vacant lots with excess arsenic, copper and/or lead concentrations in soil were identified.  Between 2008 and 2009, the soil was excavated and replaced in about 250 properties in Hayden and Winkelman. The remainder of the homes did not require cleanup. In addition to residential yard cleanups, other areas such as vacant lots, businesses and dirt alleys were sampled and cleaned up.

In 2018 ASARCO completed installation of new process equipment and pollution control technology at the operations plant (smelter). In 2018 ASARCO was issued a renewal Title V Air Quality Permit issued by ADEQ.

In addition, ADEQ issued ASARCO an Aquifer Protection Permit (APP)  (the most recent permit amendment is P-100507). For more information on APP I Learn More >

In 2020, ASARCO completed closure of the Kennecott Avenue inactive tailings piles.

Work plans are in development for the closing of two (2) inactive tailings piles with work expected to begin in 2022.


The Site is currently in the Feasibility Study (FS) phase. The FS will focus on evaluating additional cleanup options for the site.