ASARCO Hayden Plant

Superfund Alternative Site | ASARCO Hayden Plant: Page 2 of 2

Public Health Concerns:

According to public health and ecological risk assessments conducted by the Arizona Department of Health Services, contamination at the site could pose risks if no cleanup actions are taken.

Environmental Challenges:

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.

Groundwater elevation measurements taken in February and October 2006 indicate that the regional groundwater flow direction within Hayden and Winkelman is in a southerly direction towards the Gila River/San Pedro River confluence. The groundwater flow gradient is relatively high in the Hayden area, and the gradient is considerably lower in the Gila River flood plain.

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. The tailings impoundments do not appear to be causing large mounding of the water table, but the relatively low gradient in the vicinity is likely the result of recharge from Gila River surface water losses and tailings impoundments drain down.

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.

Work plans are in development for the closing of three (3) inactive tailings piles with work expected to begin in 2019.


A Phase II Remedial Investigation (RI) report review is ongoing, supplementing prior studies. After the RI report and risk assessment review determine the nature and extent of contamination, a feasibility study (FS) will focus on developing additional cleanup options.

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Learn more about other agencies and groups performing independent studies by contacting the EPA.