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McKinley Mill Mine (Wetland Mine)


Bradshaw Mountains, approximately 8 miles southeast of Prescott, off Walker Road, Yavapai County

Date Discovered:

September 2000

Impaired Surface Waterbody:

Hassayampa River

Surface Water Quality Exceedances for Designated Uses:

  • Cadmium (aquatic and wildlife, coldwater)
  • Copper (aquatic and wildlife, coldwater)
  • Lead (aquatic and wildlife, coldwater and full body contact)
  • Zinc (aquatic and wildlife, coldwater)

Affected Media:

  • Soil
  • Surface Water

What Are My Health Risks?

For Surface Water | Surface water quality standards are established to provide protection for a waterbody’s designated use(s) | Learn more >

ADEQ and AZGFD jointly publish fish consumption advisories | Learn more >

For Soil | There is little to no health risk unless there is contact with skin or ingestion of contaminated soil

For Groundwater | If you are connected to a Public Water System (PWS) there is little to no risk of impact from exceedances because the water is filtered through the PWS for residential and business use | View Drinking Water Notices >

If you have a private well in the vicinity of the exceedance, we encourage you to test the well water. Not sure what to test for? | Learn More >

For Mining Adits/Shafts | If you encounter a mining adit or shaft, do not enter it. The Arizona State Mine Inspector conducts inspections of legacy mines and implements safety measures | Learn more >

Site Summary:

  • Site was mined intermittently in late 1800s
  • ADEQ completed water quality study (Total Maximum Daily Load) for Hassayampa River in 2002
  • ADEQ contractors conducted a site assessment and preliminary investigation in 2019
  • ADEQ conducted water quality sampling and remedial implementation in fall 2020
  • Initial soil XRF analysis completed on Oct. 9, 2020
  • Permit review process has been completed; project expected to start in September 2021
  • Private land access granted to ADEQ and contractors
  • Remediation design by Tetra Tech is completed and approved
  • Cultural resources surveys and biological evaluation completed
  • Clean Water Act 404 permit is approved by U.S. Corps of Engineers
  • Remediation to begin in September 2021 after threatened Mexican Spotted Owl breeding season is complete