Pinyon Plain Mine (formerly Canyon Mine) | Permit of Interest | FAQs: Page 5 of 7

How could springs in the Grand Canyon be impacted? Is a tracer study needed?

ADEQ does not believe tracer studies or spring sampling are warranted:

  1. Impermeable rock layers between the bottom of the mine shaft and the top of the Redwall-Muav Aquifer serve as a natural protective barrier that prevents water in the shaft from reaching the Redwall-Muav Aquifer.
  2. Immediately beneath the Canyon Mine, the Redwall-Muav Aquifer flows to the south. Further downgradient it turns to the west and northwest. Therefore, springs in the Grand Canyon located due north of the mine cannot receive groundwater from the area beneath the mine due to the geological and hydrogeological conditions in the region.
  3. USGS data indicate that the age of Redwall-Muav groundwater beneath the mine and, more generally, within the interior of the Colorado Plateau, is older than 10,000 years. This means that groundwater in the area moves extremely slowly. Therefore, conducting tracer tests between the mine and springs located to the northwest of the mine in the Grand Canyon are not an effective tool to monitor for a connection between the mine and the springs.

Under the USFS ROD and USFS-approved facility Plan of Operations, groundwater monitoring is being conducted for a well in the Redwall-Muav Aquifer. The Individual APP will require EFRI to install additional groundwater monitoring wells in the Coconino Formation prior to beginning active mining. With these wells, ADEQ will be able to establish whether Coconino groundwater in the area is being captured by the mine shaft. The wells also will be used to determine groundwater flow direction beneath the facility and to monitor downgradient groundwater quality.

Why does the Canyon Mine have an air quality permit?

Mining operations are required to obtain and comply with an air quality permit prior to construction and operation per A.A.C. R18-2-302.B.3 and R18-2-302.01.D. The purpose of the air quality permit is to reduce airborne dust and ensure compliance with federal health-based, ambient air quality standards. As an added level of environmental protection, the facility’s air quality permit also requires EFRI to conduct soil sampling and testing to verify the effectiveness of air quality controls.

Issued in 2009, the air quality permit was reissued in 2016, and must be renewed in 2021.

In addition, radon emissions from the mine are regulated under an approval order issued by the EPA.

What are the results of the soil sampling at the Canyon Mine?

The air quality permit includes controls to reduce airborne dust, and, as an added level of environmental protection, EFRI is required to conduct soil sampling and testing to verify the effectiveness of the controls. Analytical results for soil samples collected to date as part of the required testing plan for soils surrounding the facility show that soils are not impacted | View Current Report >