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Table G-1. Surface Water Discharge Monitoring Requirements in NPDES Discharge <br /> Permit <br /> Parameter Monitoring Frequency Sample .- <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 may issue <br /> different sampling requirements with the permit. <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 /> or floodplain. All topsoil and overburden stockpiles will be placed on the upper terrace. Overall, <br /> the downstream flood impacts should remain the same or be reduced from activity at the site as <br /> the removal of material results in more storage space for flood water below the existing grade. A <br /> no-rise certification has been provided to the City of Fort Lupton as part of its floodplain <br /> development permit. <br /> In accordance with the Mile High Flood Control District technical guidelines, inflow/outflow <br /> structures will be installed along the river bank where mining pod 1 reaches its closest point to <br /> the South Platte River. Details of these designs can be seen on the Map G-1 — Drainage Map. <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 /> Ewing Gravel Pit <br /> �' <br /> August 2023 -2 Lewicki&Associates <br />