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CIVIL RES'*URCES, LLC <br /> ENGINEERS & PLANNERS <br /> RECEIVED <br /> March 13,2024 <br /> MAR 212024 <br /> Colorado Division of Reclamation and Mining Safety OF RECLAMATION <br /> Mr. Rob Zuber pNIS1ON Np SAFTEY <br /> 1313 Sherman Street, Room 215 ►MINING A <br /> Denver, CO 80203 <br /> RE: Technical Revision 1 —Monarch DENM Mine(Permit M-2022-0009),Weld County,Colorado <br /> Dear Mr.Zuber: <br /> Monarch Mountain Minerals and Aggregates, LLC (MMMA) requests a Technical Revision 1 (TR-01)to Permit M-2022- <br /> 009 to revise the Groundwater Monitoring and Mitigation Plan to include baseline water quality analysis, submit the first <br /> round of analysis and the results of groundwater mounding and shadow model. <br /> Background <br /> The Monarch DENM Mine DRMS 112 permit application was approved by the Division of Reclamation, Mining, and <br /> Safety(the Division) on June 1, 2023. The mine subsequently applied for a Weld County Use by Special Review(USR) <br /> permit in July 2023. The USR was recorded by the Weld County Clerk and Recorder on December 15, 2023. The mine <br /> is currently in the process of constructing the plant and has excavated a freshwater and siltation pond above the <br /> groundwater table. At this point, groundwater has not been disturbed at the Site. Monarch expects to expose <br /> groundwater at the freshwater and siltation pond in April 2024, under an approved Substitute Water Supply Plan. MMMA <br /> plans on constructing the Cell 1 slurry wall in 2025. <br /> As a condition of the DRMS permit, Monarch committed to monthly groundwater elevation monitoring at their seven (7) <br /> piezometers. MMMA has been monitoring and recording groundwater elevation since November 2021. MMMA also <br /> committed to performing a groundwater mounding and shadow model and submitting the results as a TR to the Division <br /> prior to construction of the first slurry wall. <br /> Groundwater Analysis Plan <br /> This revision submits the attached"Groundwater Monitoring and Analysis Plan". In order to minimize confusion,this plan <br /> is meant to supersede the June 1st, 2022 letter titled "Monarch DENM Gravel Mine — Mitigation Plan for Potential <br /> Groundwater Impacts" which was submitted to the Division as a part of the adequacy review process, and any <br /> monitoring included in Exhibit G. <br /> The new "Groundwater Monitoring and Analysis Plan" includes the monthly groundwater elevation monitoring and <br /> mitigation that was a part of the previous plan and adds a requirement for five (5) quarters of baseline groundwater <br /> quality analysis at three (3)wells (PZ-04, PZ-09, and PZ-20), two (2) downgradient and one (10 upgradient of the Site. <br /> Initial sampling and lab analysis was conducted in January of this year and the initial results are attached. Each of the <br /> three wells had exceedances for Aluminum, Iron, and Manganese. PZ-4 and PZ-20 had an exceedance for Arsenic. <br /> PZ-15 and PZ-20 exceeded the standard for Uranium. At the conclusion of the five (5) quarters of baseline sampling <br /> MMMA will submit a report detailing the results and requesting variance values for analytes that exceed the regulatory <br /> limits set by the Water Quality Control Commission. <br /> 8308 COLORADO BLVD•SUITE 200•FIRESTONE, CO 80504• PHONE: 303.833.1416 <br />