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the larger[ foreseeable drainage area. this design acreage amounts to 0.50 acres or <br />an area approximately [SD feet by [50 feet. All other surface drainage into [he • <br />facility area in excess of the design acreage would be diverted away from the storage <br />site by dirt berms or diversion ditches in order to reduce the required containment <br />capacity at the catchment basin. This will also reduce the potential contamination <br />of adjacent rainfall runoff. Section E shows typical catchment basin designs. <br />There are two main catchment basins for the tanks at the Seneca Mine free Exhibit 1, Spill <br />Prevention Control). Spill Control Pond No. 1 is adjacent to the truck wash and has an <br />overall capacity of 0.197 acre-feet (8,600 cubic feet). This pond contains the secondary <br />containment for the 10,000-gallon (1,3L0 cubit feet) waste oil tank. Pond Mo. 1 has <br />virtually no surface drainage area- 0. "i" configuration on the spillway would prevent oil <br />from being discharged. In the event oil was discharged, it would enter a ditch which <br />leads to a sedimentation pond which employs a sorben[ boom in front of the discharge <br />culvert. This should prevent any oil from entering Grassy Creek, <br />Pond No. 2 provides secondary containment for the three diesel fuel storage tanks. The <br />overall capacity of this pond is 0.459 acre-feet (20,000 cubic fee[). Based on hydrologic <br />calculations presented in Section D for this pond, a minimum capacity of 7,000 cubic feet • <br />is required for direct rainfall and sediment storage. The SEDIMOT II computer model was <br />used to generate predicted flows and sediment delivery. The largest single tank that <br />would drain to this pond is 10,000 gallons (1,340 cubic feet) for a total required <br />Capacity of 8,3L0 Cubit fee[ plus freeboard. Therefore, the existing pond capacity i5 <br />more then sufficient. <br />(D) (1) Catchment basins will not be located in areas subject to periodic flooding, If <br />. needed, a diversion ditch or dirt berm will 6e placed upstream of all storage <br />facilities to limit the drainage area around the storage area and [he catchment <br />basin to less then 0.50 acres. Any water accumulations inside the diked area ar <br />catchment basin will 6e sampled by Environmental Affairs personnel before <br />devatering or discharging is allowed. Due to the small size of the drainage <br />area, most contained runoff will evaporate such that standing eater should not <br />become a problem at each site. <br />If [he water quality is within applicable limits as determined by Environmental <br />Affairs personnel, the water can then be pump[•d into sediment ponds located • <br />7-6h-4 Revised 03/29/96 <br />