Senator Mine, also known as 570 Adit Waste/Tailings Senator Highway, is a legacy mine site located approximately 11 miles south of Prescott in the Bradshaw Mountains and on the banks of the Hassayampa River. Features on legacy mine sites pre-date modern environmental regulations. Legacy mine features at the Senator Mine include an adit (horizontal opening in the mountain) and a tailings pile from previous mining activity that occurred between the late 1800s and early 1900s. 

No. The Senator Mine site is on private property. No one should trespass on the site. 

Features on legacy mine sites may not be well understood due to lack of historic documentation. Adits, shafts, tailings, and waste rock may be unstable. Never enter a mine opening and avoid contact with tailings and waste rock. The Arizona State Mine Inspector office investigates and closes legacy mine openings.

Arizona State Mine Inspector Abandoned Mines webpage | View > 

Water draining from the Senator Mine adit and stormwater or snowmelt over the tailings pile, as well as other legacy mine features in the area, are impacting water quality in the Hassayampa River. The river in this area is impaired for cadmium, copper, zinc, and pH. This means the water has high levels of these heavy metals and is acidic, which can negatively affect the health of wildlife (i.e., fish), food sources for wildlife (i.e., bugs), livestock and, if ingested over a long period of time, people. Drinking water from the river (both filtered and unfiltered) is not recommended.

EPA How’s My Waterway? Waterbody Report | View >

Mine drainage is discolored water — orange, brown or green —coming from mine sites, some of which predate modern environmental regulations, and can sometimes be seen in creeks and streams or from openings in the ground. Mine drainage may be acidic due to the natural geology of the area.

Legacy Mine Drainage Fact Sheet | View >

There are thousands of legacy mine sites in Arizona that predate modern environmental regulations. In cases where there is a responsible party, as with the Senator Mine site, ADEQ utilizes state and federal laws to hold the responsible party accountable to address the issue. 

The impacts of legacy mines are mitigated in a number of ways to minimize or eliminate impact to soil, groundwater, and surface water. Efforts may include consolidating and grading waste rock and tailings and capping with clean soil to reduce environmental exposure, plugging or sealing openings to underground mine workings, and routing stormwater flow around the site. Each legacy mine site is unique and requires extensive investigation to ensure the most effective remediation.

Surface Water Quality Remediation Sites webpage | View >

Videos of ADEQ legacy mine impacts | View Playlist >

An Arizona Pollutant Discharge Elimination System (AZPDES) permit is required for point sources discharging pollutants to regulated surface waters. For Senator Mine, the adit is considered a point source discharge and the property owner is responsible for meeting AZPDES permit conditions.

Permitting Unit webpage | View > 

AZPDES permit conditions are site-specific and include monitoring requirements, effluent limitations, assessment levels, and other permit conditions to ensure the receiving water and downstream waters are protected for its designated uses. These designated uses support aquatic life, wildlife and activities, such as providing public drinking water or recreation. Some waters may have multiple designated uses. As with the Senator Mine permit, AZPDES permits can require permittees to build facilities and install treatment systems to treat water to meet criteria protective of the designated use before it is discharged to a surface water. 

ADEQ ensures permittees comply with all AZPDES permit requirements by performing regular inspections of AZPDES-permitted facilities. ADEQ inspectors confirm that required information (discharge flow records, laboratory reports, discharge monitoring reports, etc.) have been submitted to ADEQ for review. Inspectors also verify that required documentation is present on site, including a copy of the permit and monitoring records. Inspectors visually inspect the treatment systems and outfalls to ensure they are well-maintained. ADEQ pursues enforcement to hold permittees accountable when there are deficiencies found. 

The State of Arizona Water Quality Assurance Revolving Fund (WQARF) managed by ADEQ was utilized for emergency remedial actions during the summer of 2024. ADEQ may seek reimbursement for this work as part of ongoing litigation or through the WQARF process. 

The remedial actions implemented in the summer of 2024 only addressed the immediate threat to the environment. ADEQ continues to evaluate the site and develop a long-term solution to address the ongoing discharges from the adit and tailings pile. ADEQ will seek to hold the property owners financially responsible for the long-term solution. 

ADEQ has the authority to revoke an environmental permit if the permittee is not meeting the permit conditions as defined in the Arizona Revised Statutes and Arizona Administrative Code. ADEQ may then seek a court injunction requiring the facility to cease operations until the violation has been corrected.

For the Senator Mine site, even if the permit were revoked, the adit discharge would continue. The discharge is from legacy mine workings and will require a long-term solution to protect water quality of the receiving water, the Hassayampa River. 

ADEQ does not regulate private groundwater wells. Testing of private groundwater wells is the responsibility of the landowner. Well testing information can be found at the Arizona Department of Health Services website | Learn More >

Currently, the headwaters segment of the Hassayampa River is impaired for pH for the designated use of full-body contact. Contact with surface water impaired for pH for full-body contact may result in irritation of skin, eyes, and nose. The natural geology of the area, as well as legacy mines, may be contributing to this impairment.

Please email ADEQ or call 602-771-1440 | Email >

ADEQ assesses the health of Arizona surface waters, including the Hassayampa River, utilizing current data and provides a publicly available interactive tool | Learn More > 

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