2023-02-24_PERMIT FILE - M2022013 (3)

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months apart. The wells will be sampled for the laboratory parameters if there is an exceedance in the stormwater laboratory parameters. On an annual basis field parameters of pH, specific conductance and temperature will be measured in waters obtained from the selected wells after three well bore volumes have been evacuated." The only laboratory parameters proposed to be measured are Arsenic (total) and Selenium (dissolved). Item 17. The proposed water quality monitoring program described in section 2.3 needs further consideration. In addition to enforcing the requirements of the Mineral Rules and Regulations of the Colorado Mined Land Reclamation Board for the Extraction of Construction Materials ("Minerals Rules"), the Division is an implementing agency for Regulation No. 41 —The Basic Standards for Groundwater ("Reg. 41"), available from the Colorado Department of Public Health and the Environment website: https://cdphe.colorado.gov/water-quality-control-commission-regulations In order to better explain how the Division interprets its responsibilities under Reg. 41, a Groundwater Monitoring and Protection Technical Bulletin was produced in 2019 and is available on the DRMS website, or from the following link: https:Hdrive.google.com/file/d/121Uc KmuAx7xhc8heQcROPnK u-kcG-1/view?pli=1 Since the proposed operation clearly has the potential to impact groundwater, and groundwater at the site has not yet been classified, the Division will apply the Interim Narrative Standard from Reg. 41. At least one downgradient groundwater point of compliance will need to be established, where the standard will be applied. Typically the Division requires 5 quarters of water quality data prior to disturbance in order to establish baseline conditions, (without reliable baseline data the most restrictive parameter values from Tables 1-4 of Reg. 41 would apply). When evaluating a groundwater monitoring plan the Division typically looks for an analytical suite that includes the parameters from Tables 1-4, however the parameter list may be reduced if justification is provided. The parameters listed in Table 1 were based on a USGS study of the South Platte River basin which listed several trace metals detected in stream bed sediment and fish tissue. Those elements included As, Cd, Cr, Cu, Pb, Hg, Ni, Se and Zn. A comprehensive groundwater study was performed by Toby Adams, P.G., REM, author of the Groundwater Monitoring Plan prepared by AWES, LLC and background levels of Mn, U, nitrate and sulfate exceeded current drinking water standards and those parameters were added to the list. I also included gross alpha particle activity due to the presence of uranium in groundwater and the high background levels of radon in the area. Section 2.4 describes how water level data will be used for drawdown and mounding analyses. It states that "Variations in pre-mining water levels will be presented on a two dimensional contour map and will be compared to numerical predictions and will be provided to the Division upon request."