Pinyon Plain Mine (formerly Canyon Mine) | Permit of Interest | FAQs: Page 3 of 7

If the water is above drinking water standards, why is it being allowed to be stored in open impoundments where wildlife can come into contact with or drink it?

Water in the impoundment is not a source of drinking water. Drinking water standards are not used to evaluate wildlife protection, rather, they are allowable levels of certain compounds in water intended for human consumption.

In an effort to prevent larger animals from accessing the property, and to deter smaller animals, the facility is surrounded by a fence. Just as with any other type of impoundment located where wildlife live, such as wastewater treatment ponds and recreational swimming pools, while there is the potential for wildlife to access the impoundment, the probability is low, and even lower that any given animal would access the impoundment on a regular or frequent basis.

Potential impacts to wildlife from the mine area were analyzed by the USFS in its EIS when approving the facility Plan of Operations. Based on the results of its biological evaluation, USFS concluded that “[n]o adverse effects to threatened, endangered or sensitive wildlife species have been identified” (USFS EIS, p. 4.14).

What happens to the water in the impoundment?

The permitted, lined impoundment at the facility serves as a temporary storage area for water pumped from the lined mine shaft and stormwater runoff. Water in the impoundment slowly evaporates. When necessary, the facility encourages evaporation by employing a permitted evaporative spray system.

Is mist generated from the “water cannons” at the impoundment impacting public health or the environment?

ADEQ has determined that the evaporative spray system does not pose a concern for public health or the environment. 

The permitted, lined impoundment at the facility serves as a temporary storage area for water pumped from the lined mine shaft. Water in the impoundment slowly evaporates. When necessary, the facility uses a permitted down-draft evaporative mist system designed to increase the evaporation rate by using water from the impoundment to create a mist over the impoundment.

Using facility-specific data regarding uranium levels water pumped from the shaft and contained in the lined impoundment, ADEQ conducted modeling of the evaporative system to evaluate potential environmental impacts. This analysis indicated that the system complies with health-based state ambient air quality guidelines for uranium.

To ensure these particles in the mist and other windblown sources of dust are not impacting the environment, the state air quality permit for the facility requires soil sampling around the facility and testing for uranium and radium content.

Soil sampling and testing conducted to date for the air quality permit shows activities at the facility are not impacting surrounding soil.

The state air quality permit further requires monitoring for changes in gamma radiation levels around the facility. Results to date indicate that the facility is in compliance with permit conditions.

ADEQ conducts regular inspections of the facility to ensure permit conditions are being followed.

If the water is allowed to evaporate, wouldn’t that leave behind concentrated levels of uranium in the impoundment? How is this disposed of?

When the lined impoundment is closed, the General APP requires the facility to remove and properly dispose of all liquids and any solid residue [A.A.C. R18-9-D304.G.2.a]. Similar requirements will be included in the Individual APP

Will the mine contaminate groundwater?

Canyon Mine has been studied, scrutinized, and litigated for over 30 years, resulting in an extensive technical record. ADEQ reviewed this record and its findings and agrees with key conclusions that adverse impacts to groundwater from the facility are extremely unlikely.

ADEQ will review any new information and supporting application documents that may be presented during the application review process to inform permit conditions. More details on the available record for Canyon Mine follow:

  • The final USFS EIS and ROD for Canyon Mine were issued on September 29, 1986. USFS concluded that no measurable impacts are expected to groundwater. USFS also concluded that, with implementation of planned mitigation measures to seal the mine after operations are completed, the possibility for significant deterioration of water quality at any discharge is very small.
  • The Havasupai Tribe and others sued over this decision in the U.S. District Court for the District of Arizona. The District Court ruled for the USFS on all counts, and a subsequent appeal was filed with the U.S. Court of Appeals for the Ninth Circuit, which affirmed the District Court on August 16, 1991.
  • On June 25, 2012, the Kaibab National Forest completed a review of the Canyon Mine Plan of Operations and determined that no modification or amendment to the existing Plan of Operations was necessary.
  • ADEQ issued a Groundwater Quality Protection Permit (GWQPP) in May of 1988. GWQPPs are predecessor permits to APPs. The permit was appealed by the Havasupai Tribe and went to administrative hearing.  At the end of the hearing, the permit was affirmed in June of 1995. 
  • Expert hydrogeologic testimony was provided by the permittee during the administrative hearing. ADEQ re-examined this expert testimony and agrees with key findings, including the expert’s conclusion that it is virtually impossible for the mine to contaminate the Redwall-Muav Aquifer due to the impermeability and thickness of the rock layers between the bottom of the mine shaft and the Redwall-Muav Aquifer.

ADEQ has also reviewed more recent USGS hydrogeological information. ADEQ has determined that this newer information supports a conclusion of virtually no recent recharge occurring to the Redwall-Muav Aquifer or to the Coconino groundwater in the area of the mine. This information further supports the conclusion that intervening rock layers between the Coconino Formation and Redwall-Muav Aquifer are highly impermeable.