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Pond 002 This pond is in the Little Grassy Creek watershed. It is the primary <br />stormwater retention structure for underground mining activities proposed at the <br />PSCM. This pond was constructed by not backfilling approximately 9 acres in the <br />downdip end of the Wadge Pit, and then allowing this area to fill with water. The pond <br />is completely incised and does not have an embankment. The pond has a combination <br />principal/emergency spillway that is an open-channel. The pond currently receives <br />surface runoff and spoil spring discharge from much of the reclaimed lands proposed <br />for transfer from the Seneca II Mine. The spoil spring inflow maintains a 23-acre-foot <br />permanent pool in the pond which causes perennial discharge from the pond. The pond <br />will receive surface runoff from PSCM portal and south ;Facilities areas, in addition to <br />the current runoff and spoil spring inflows. Underground mine water will be pumped <br />into the pond, if necessary. The expected maximum rate; of underground mine water <br />pumping is 75 gallons per minute. The drainage area of Pond 002 will be <br />approximately 3,028 acres, comprised of 177 acres in the PSCM portal/south surface <br />facilities area and the 2,851 acres of reclaimed lands transferred from the Seneca II <br />Mine. Calculated runoff from a 10-year, 24-hour design storm is 23 acre-feet. The <br />pond has total capacity (including sediment storage) of 2157 acre-feet. The analytical <br />sedimentology model in the permit application demonstrates the pond will effectively <br />control sediment from runoff and mine water pumping, and will meet the requirements <br />of Rule 4.05.6. As previously explained, the operator has applied for a CDPS permit <br />for the PSCM operation. <br />PeCoCo Impoundment This pond is in the Little Grassy Creek watershed, upstream <br />from Pond 002. The pond traps sediment prior to discharging water to Pond 002. This <br />pond was constructed by not backfilling approximately 2.6 acres in the downdip end of <br />the West Lennox area of the Wadge Pit, and then allowing this area to fill with water. <br />The pond has a low embankment that is about five feet long and a corrugated metal <br />pipe for a principal spillway and an open-channel emergency spillway. The pond <br />currently receives surface runoff and spoil spring discharge from 138 acres of <br />reclaimed lands proposed for transfer from the Seneca II Mine. The estimated average <br />spoil spring inflow is 40 gallons per minute, which maintains a permanent pool in the <br />pond. Total capacity of the pond is 19.7 acre-feet. PSCM proposes to route to the <br />PeCoCo pond the runoff from an additional 875 acres, composed of reclaimed and <br />undisturbed lands that are proposed for transfer to the PSCM from the Seneca II Mine. <br />This additional runoff will increase the estimated 10 .year storm inflow from the <br />existing 0.44 acre-feet to 3.2 acre-feet. To accommodate the additional inflow, SCCC <br />proposes to remove the existing pipe that is the principal spillway and reconstruct the <br />existing open-channel emergency spillway to serve as a combination <br />principal/emergency trapezoidal spillway. Discharge from the PeCoCo Impoundment <br />is not a CDPS outfall. <br />Pond 003 Pond 003 is in the Grassy Creek watershed. This pond receives runoff and <br />sediment from 30.1 acres that includes the existing shop area and warehouse/office <br />area that served the Seneca II Mine. These areas are proposed for transfer to the PSCM <br />and the approximate 17 acres of disturbance will not be changed. No changes to the <br />Peabody Sage Creek Mine 21 May 7, 2010