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Table G-1. Surface Water Discharge Monitoring Requirements from Existing NPDES <br /> Discharge 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 /> Electrical Conductivity Quarterly Grab <br /> Arsenic,Total 2x/month Grab <br /> Recoverable <br /> 3. Floodplain <br /> The majority of the site is within the 100-year floodplain and floodway as reported by the <br /> Federal Emergency Management Agency. These boundaries are shown in the Exhibit C and F <br /> maps. The minimum distance maintained from the South Platte River to excavation activities is <br /> 100 feet. Additionally, no stockpiling or filling above the natural grade will occur in the floodway. <br /> Overall, the downstream flood impacts should remain the same or be reduced from activity at <br /> the site as the removal of material results in more storage space for flood water below the <br /> existing grade. A no-rise certification will be provided to Weld County as part of its floodplain <br /> development permit. <br /> In accordance with the Mile High Flood Control District technical guidelines, an inflow/outflow <br /> structure will be installed along the riverbank where mining reaches its closest point to the South <br /> Platte River to prevent erosion of the bank. Details of these designs can be seen on Map G-1. <br /> In the event of flooding at the site, equipment from the active mining floor will be removed and <br /> the pit will be allowed to fill with water. The flooded pit will be pumped only after the flood has <br /> subsided. All fuel will be stored at least one foot above the base flood elevation and in sufficient <br /> secondary containment with 110% carrying capacity. <br /> 4. Wetlands <br /> No wetlands exist on the site. <br /> 5. Aquifers <br /> The only identified aquifer located at the site is the shallow alluvial aquifer of the South Platte <br /> River. The depth to this aquifer varies throughout the year but is typically five feet below <br /> Evans Mining Resource <br /> October 2024 G-2 II1Lewicki&Associates <br />