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Table G-1 —Surface Water Discharge Monitoring Requirements in NPDES 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 /> 3. Floodplain <br /> The majority of the site is within the 100-year floodplain while the northern portion of the site is <br /> within the floodway as reported by the Federal Emergency Management Agency. These <br /> boundaries are shown in the Exhibit C and F maps. The minimum distance maintained from the <br /> Gunnison River to excavation activities is 100 feet. Additionally, no excavation, construction, or <br /> other development will occur in the floodway. No permanent elevation of grades will take place <br /> within the 100-year floodplain. All topsoil and overburden stockpiles will be temporary during <br /> mining and will be removed during reclamation. Overall, the downstream flood impacts should <br /> remain the same or be reduced from activity at the site as the removal of material results in <br /> more storage space for flood water below the existing grade. <br /> In the event of flooding at the site, equipment from the active mining floor will be removed, and <br /> the pit pump will be disabled allowing the pit to fill with water. The flooded pit will be pumped <br /> only after the flood has subsided. All fuel will be stored at least one foot above the base flood <br /> elevation and in sufficient secondary containment with 110% carrying capacity. <br /> 4. Wetlands <br /> The National Wetlands Inventory aerial-based mapping indicates the presence of wetlands <br /> within the permit area. These wetlands are mostly associated with the vegetated banks in the <br /> north of the site and the various irrigation ditches crossing the property. The areas indicated in <br /> the north are likely to be actual wetlands based on previous permitting, however, no mining will <br /> take place in these potential wetland zones. Some potential wetlands crossing the mining area <br /> are those associated with the Relief Ditch and a historical irrigation ditch that has since been <br /> rerouted. Their locations crossing the mining area is the probable result of low GIS accuracy, as <br /> these areas are already disturbed with no vegetation with a small area of irrigated fields. <br /> Therefore, it is highly unlikely that the mining operation will disturb any wetlands. Nonetheless, <br /> Delta Paving Gravel Pit <br /> September 2022 G-2 Lewicki&Associates <br />