DWQ-2024-008533

Joseph Beckstead
Mine Engineer
Redmond Minerals
2725 North 1000 West
P.O. Box 219
Redmond, UT 84652

Subject: GWPBR-24-004 - Renewal and Amended Ground Water Discharge Permit-By-Rule Determination for Ground Water Evaporation Ponds

Dear Mr. Beckstead:

The Division of Water Quality (DWQ) issued a Permit-By-Rule for a Ground Water Evaporation Pond (Pond 1) on August 22, 2018. On November 14, 2024 DWQ received documents requesting the
addition of a second smaller evaporation pond (Pond 2) northeast of the current pond. The second pond will provide as-needed capacity in the event of increased water in-flow due to
storm events. A bentonite pit will be converted to a pond and the pit as-is does not require any construction or work done to completely contain the additional water.

The project consists of an existing French drain that collects ground water before it can reach the active underground salt mining. The water is collected into two 2,500-gallon storage
tanks. The tanks are equipped with a float which controls a transfer pump. When the tanks are full, the pump turns on transferring the water to Pond 1. Water from Pond 1 could then
be pumped into Pond 2 to provide as-needed capacity in the event of increased flow during storm events.

During the warmer, drier months, to enhance the natural evaporation a misting sprayer is set-up to spray the water over Pond 1 increasing the evaporation rate. When needed water from
Pond 2 can be pumped back to Pond 1 for forced evaporation.

Below are the relevant factors evaluated in determining that the proposed operation qualifies for permit by rule and that the discharge will have a de minimis actual or potential effect
on ground water quality or beneficial uses of ground water resources.

The water being collected in the French drain is natural ground water with TDS of approximately 5600 mg/L. No outside contaminants or other mine facility processes will be mixed with
the ground water to create “contact” water.

The water will be discharged into abandoned bentonite clay pits with permeability no greater than 2.84x10-7 cm/sec as shown by samples collected from the walls and floor of the pit.
As a result, the water discharged into the pits will primarily dissipate through evaporation rather than infiltration.

The volume of the pond 1 is approximately 8-million gallons. The volume of pond 2 is approximately 3.8-million gallons.

Based on the factors described above, the proposed evaporation ponds should conform to the applicable class TDS standards and does not contain any contaminant that may present a threat
to human health or the environment and qualifies for permit-by-rule under UAC R317-6-6.2.A(1). If any of these factors change because of changes in your operation or from additional
knowledge of site conditions, this permit-by-rule determination may not apply and you should inform the DWQ. If future project knowledge or experience indicates that ground water quality
is threatened by this operation, the Director may require that you apply for a ground water discharge permit in accordance with UAC R317-6-6.2.C.

This permit-by-rule determination is effective for a period of 5 years from the date of this letter. Prior to the end of this 5-year period, Redmond Minerals shall submit laboratory
analysis from a recent ground water sample from the French drain and re-apply for a permit-by-rule determination so the Director may confirm site conditions have not changed.

If you have any questions about this letter, please contact Woodrow Campbell at [phone] or [e-mail].

Sincerely,

John K. Mackey, P.E.
Director

JKM/WWC/DJH/

cc: John Chartier, Central Utah District Engineer (via email)
Central Utah Public Health Department (via email)

Joseph Beckstead
Page 2

195 North 1950 West • Salt Lake City, UT
Mailing Address: P.O. Box 144870 • Salt Lake City, UT 84114-4870
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