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American Water Engineering Services, LLC <br /> February 21, 2023 <br /> Raptor Materials, LLC <br /> 8120 Gage Street <br /> Frederick, Colorado 80516 <br /> Attn: Garrett Varra <br /> RE: Comments on Analytical Parameters <br /> 112C Permit Application Adequacy Review <br /> DRMS Letter Date February 14, 2023 <br /> Dear Mr. Varra: <br /> This letter provides responses to a review of the Groundwater Monitoring Plan generated by <br /> American Water Engineering Services, LLC (AWES) for the Raptor Materials, LLC (Raptor) mine <br /> located near Evans, Colorado. This letter is intended to address the issues raised in the Division of <br /> Reclamation, Mining and Safety(DRMS) letter dated February 14, 2303. <br /> The following summarize DRMS comments by item. <br /> 1. Comment 16—Please amend section 2.2 of the plan to continue quarterly monitoring until <br /> the permit is terminated.The plan has been amended as recommended. <br /> 2. Comment 17 — Since the proposed operation clearly has the potential to impact <br /> groundwater, and groundwater at the site has not yet been classified, the Division will <br /> apply the Interim Narrative Standard from Reg. 41. At least one downgradient <br /> groundwater point of compliance will need to be established, where the standard will be <br /> applied. Typically the Division requires 5 quarters of water quality data prior to <br /> disturbance in order to establish baseline conditions, (without reliable baseline data the <br /> most restrictive parameter values from Tables 1-4 of Reg. 41 would apply). When <br /> evaluating a groundwater monitoring plan the Division typically looks for an analytical <br /> suite that includes the parameters from Tables 1-4, however the parameter list may be <br /> reduced if justification is provided. The parameters listed in Table 1 were based on a USGS <br /> study of the South Platte River basin which listed several trace metals detected in stream <br /> bed sediment and fish tissue. Those elements included As, Cd, Cr, Cu, Pb, Hg, Ni, Se and Zn. <br /> A comprehensive groundwater study was performed by the author and background levels of <br /> Mn, U, nitrate and sulfate exceeded current drinking water standards and those parameters <br /> were added to the list. I also included gross alpha particle activity due to the presence of <br /> uranium in groundwater and the high background levels of radon in the area. <br /> 3. Comment 18 — Please amend section 2.4 to specify that water monitoring data will be <br /> compiled into a report and submitted to the Division annually. Please also specify the <br /> date. The report should include the operator's analysis of the data, as well as the data <br /> itself.The plan has been amended to include recommended changes. <br /> /�w�S 48C9 Four Star Court, Fort Collins,CC SCJ24—91C-b9C-3SC1 <br />