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Spill Control Pond #2 ie located is the NWS@lEH of Section 34, Township 6 North, Reage 87 • We9t. This pond wne constructed prior to 1977 end provides secondary containment for the three diesel Euel atorege tnnke located apyroximately 1800 Eeet eouthenst of the Seaece II shop Enci11t1ee. Tha location of Spill Control Pond #2 ie shown on Exhibit 7-7, Surface Hydrology DIaD• Tha pond hoe 4pproximnte dimensions of 120 feat long, 75 feet wide, sad n depth of 7 Eaet. This ia~pouadmeat does not act ae a sedimentation structure for nay df eturbed leads et the Seaece II Hiae. The design statistics and parameters for Spill Control Poad #2 ara contained is the Spill Prevention Control and Couatexmeeeure Plan (SPCC) for the Seneca Coa~lex. This plan ie oa file at the mine office and is available for inspection at any time. The two eectlona in the SPCC Plaa pertaining to Spill Control Poad #2 are included is this appendix Following the certification. ~A avmmary of the hydrologic design data ie included below. Pracipitati oa Amovat (100-year, 24-hour) = 2.4 inches Drainage Area = 1.84 nc res curve Number = 80 Time of Concentration = 0.187 hours This iayut data above provided the following SEDCAD+ output. Runoff Volume ~ = 0.13 acre-feet Peak Discharge - = 1.23 cfe Sediment Storage = 3.I tone = 0.002 acre-feet Therefore, the minimum ceDacity required to contain both the runoff and sediment would be 0.132 acre-feet, or 5750 cubic Eeet. The single largest tank that would drain to this pond is 10,000 gallons (1,340 cubic feet). Sc, a total required cnpac ity of 7,090 cubic feet plus freeboard is aeceeeery for Spill Control Poad #2. The SPCC P1 as eta tes that the overall cnpacity for this pond Se 0.459 acre-feet (20.000 cubic feet). The Division requeetefl as ae-built be provided confirming the storage capacity for Spill Control Poad #2. A pond survey was conducted on October 12, 1995 by the Seneca Coal Company survey crew. The survey provides the following elevatioa-caDacity table. 6610.0 0.03 ac rea 6612.0 0.06 acres 6614.0 0.10 acres 6616.0 0.17 acres The SEDCAD+ basin capncity utility cnlculated a totnl storage capacity of 0.51 acre-feet (22,200 cubic feet). This amount is slightly higher than the capacity stated in the SPCC Plan. However, it does provide morn thna sufficient capacity plus freeboard. Thin impoundment is included in the quarterly pond inspections done by SCC personnel . • APPROVED APR ~ :~ 1996 7-6h-1 Revised 03/29/96