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Table G-1. Surface Water Discharge Monitoring Requirements in CDPHE Discharge <br /> Permit <br /> Parameter Monitoring Frequency Sample Type <br /> Flow Instantaneous,Monthly In-situ <br /> pH 2x/month Grab <br /> Total Suspended 2x/month Grab <br /> Solids <br /> Oil and Grease Visual 2x/month Visual <br /> Oil and Grease Contingent on visibility Grab <br /> of oil and grease <br /> Total Flow Instantaneous, Monthly Calculated <br /> Selenium,Potentially 2x/month Grab <br /> Dissolved <br /> Total Dissolved Solids Quarterly Grab <br /> Note: these are the anticipated analytes based on operator experience at similar sites. CDPHE <br /> may issue different sampling requirements with the permit. <br /> 3. Floodplain <br /> The site is completely outside the Yampa River Floodplain. <br /> 4. Wetlands <br /> The National Wetlands Inventory aerial-based mapping indicates no presence of wetlands <br /> within the permit area. The site was also inspected during the 110-permit process by the <br /> USACE. They inspected the ephemeral drainage and issued a letter clearing the site of <br /> wetlands. <br /> 5. Surface Water <br /> The mining operation will impact surface water in the area through stormwater runoff that enters <br /> the site. Map G-1 shows expected drainage patterns and how they are affected throughout the <br /> mine's life. The primary concern for surface water protection at the site is preventing the <br /> discharge of sediment, oil, and/or hydraulic fluids from operational areas. Oils and hydraulic <br /> fluids stored on site follow the standard best management practices. These practices include <br /> the use of secondary containment at fluid storage and transfer points, spill kits, and employee <br /> training regarding safe handling practices. Sediment is trapped onsite using physical controls <br /> and best management practices by directing and controlling surface water runoff that enters the <br /> disturbed areas. More information on sediment and surface water control is provided below. <br /> Yampa Valley Gravel Pit <br /> August 2025 G-2 101 I,cwicki& Associates <br />