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4. SEDIMENT PONDS <br />A. NPDES Quarterly Reports <br />As required by the two NPDES permits, all sediment pond <br />discharges were appropriately sampled and the resulting quarterly <br />monitoring reports are contained in Exhibit 6. Note that since <br />the disturbed areas at the minesite have been stabilized through <br />reclamation, H-G Coal Company has amended the NPDES permit to <br />incorporate postmining effluent limitations for all discharge <br />points in Discharge Permit CO-0036447. There are no changes to <br />Discharge Permit CO-0038164 at the Loadout. <br />B. Quarterly Inspections <br />The Quarterly inspection reports are contained in Exhibit 7. No <br />significant problems with the structures were noted with any of <br />the structures. <br />Sediment Survey <br />During 1987, minimal amounts of sediment were generated from the <br />reclaimed areas at the mine and shop areas. Under Discharge <br />Permit C-0036441, all ponds at the minesite have additional <br />sediment storage capacity available. <br />Under Discharge Permit CO-0038164 at the loadout, the Railroad <br />• Loop Pond has additional sediment storage capacity available. <br />The Truck Loop Pond, however, has reached 66 percent of the <br />required sediment storage volume. Rather than dredge this <br />oversized pond, H-G Coal Company will submit a technical revision <br />that will propose to raise the outlet by adding a riser pipe to <br />the existing discharge pipe. In addition, a gate would be added <br />to the outlet structure to control the discharge. <br />A volumetric summary for sediment volumes for each pond is as <br />follows: <br />C~ <br />-13- <br />