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CIVIL REs'buRCEs, Lt_C <br /> ENGINEERS & PLANNERS <br /> RECEIVED <br /> December 3, 2025 <br /> DEC 0 4 2025 <br /> Colorado Division of Reclamation and Mining Safety <br /> Mr. Patrick Lennberg :olorado Division of Reclamation, <br /> 1313 Sherman Street, Room 215 Mining and Saftey <br /> Denver, CO 80203 <br /> RE: Technical Revision 4—Monarch DENM Mine (Permit M-2022-009),Weld County, Colorado <br /> Baseline Groundwater Monitoring Results <br /> Dear Mr. Lennberg: <br /> Monarch Mountain Minerals and Aggregates, LLC (MMMA) requests a Technical Revision 4 (TR-04) to Permit M-2022- <br /> 009 to present the baseline groundwater quality data collected for the Site. In addition to the baseline data, MMMA <br /> proposes to update the Groundwater Monitoring Plan to set revised analyte concentration limits for those exceeding the <br /> threshold and to reduce the number of analytes required for sampling. <br /> Background <br /> In Technical Revision 1 (TR1), MMMA developed and submitted to the Division of Reclamation, Mining, and Safety (the <br /> Division) a Groundwater Analysis Plan (Analysis Plan) in addition to the groundwater elevation monitoring plan that was <br /> already approved with the initial application. The Analysis Plan required MMMA to collect five (5) quarters of baseline <br /> water quality data and to submit this data to the Division through a Technical Revision (TR). MMMA started collecting <br /> water quality data in the first quarter of 2024 and TR1 was approved on May 24, 2024. Prior to the approval of the TR, <br /> the water quality samples that were collected in the first quarter(Q1)and the second quarter(Q2)of 2024 were analyzed <br /> for total metals instead of dissolved metals which is the standard. Starting in the third quarter (Q3) of 2024 the lab has <br /> been reporting dissolved metals according to the Regulation 41 standards. The Q1 and Q2 data is included with this <br /> report but not used in setting the baseline standards for the Site. <br /> The samples were collected using the methods outlined in the Groundwater Monitoring and Analysis Plan for the Site. <br /> The sampling started in the upgradient well PZ-20 and then progressed downgradient from PZ-15 to PZ-4 and PZ-1. Six <br /> (6) well volumes were purged during the initial sampling period in Q1 2024(and Q2 2024 for PZ-1) and three (3) well <br /> volumes were purged on subsequent events. <br /> Discussion of Baseline Data <br /> The baseline data collected demonstrates that the majority of the analytes sampled at the Site are below the regulatory <br /> threshold set in Regulation 41 with the exception of Uranium and Iron. See table below for the list of exceedances. <br /> Uranium and iron are both naturally occurring in the alluvial aquifer deposits and can leach into the groundwater through <br /> the weathering process. The elevated levels of uranium has not been consistent and has dropped below the regulatory <br /> limit on subsequent sampling periods. <br /> There has been one isolated exceedance for iron at an upgradient well (PZ-20) on the latest sampling event. The <br /> monitoring well location for the exceedance is directly adjacent to the Sweet Valley Mine Site which has just installed a <br /> slurry wall and discharge piping in close proximity to the well. In addition, an infiltration pond has been installed in the <br /> property to the south of the Site which could be having an effect. <br /> 8308 COLORADO BLVD• SUITE 200• FIRESTONE, CO 80504 • PHONE: 303.833.1416 <br />