2014-06-18_PERMIT FILE - C2009087A

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RULE 2 - PERMITS runoff to PECOCO. Discharge from PECOCO Pond flows through Channel SCM -2 to the Upper Sump and then through the drainage network to the Lower Sump and ultimately Pond 002. The PM- 3 /PM -5 channel system collects runoff from a 540 acre watershed; the runoff is routed through channels SCM -3 and SCM -4 to Pond 002. A series of new collection ditches will intercept disturbed area runoff from the South Facilities Area and route it through sumps located north of PECOCO pond and at the north end of the portal /coal handling facility. Discharge from the Lower Sump will flow to channel PM -1 and then into Pond 002. There are a series of existing diversion ditches constructed as part of the Seneca II Mine operations in the North Facilities Area. These ditches are included in the drainage and surface water control plan for PSCM. The Shop Diversion Ditch collects runoff from the Shop /Bathhouse area and conveys the runoff to Pond 003. The Old Boneyard Diversion Ditch, the Northwest Diversion Ditch and the Office Diversion Ditch collect runoff from an existing 5.4 acre small area exemption. A new small area exemption consists of 0.1 acres and is located outside the Shop Diversion Ditch. All diversion and collection ditches and postmine channels are designed to safely pass the peak runoff from the 10 -year, 24 -hour event, or if the drainage basin is greater than 640 acres, the 100 - year, 24 -hour design storm. PSCM has designed and sized culverts to convey runoff flows under or through active mine disturbance areas, including roads. Design information for ditches and culverts is provided in Exhibit 2.05.3 -E2, Drainage and Sediment Control Plan. The upper sump will have a minimum runoff storage capacity of 3.6 ac -ft. The lower sump will have a minimum runoff storage capacity of 6.0 ac -ft. Both sumps are designed with both principal and emergency spillway structures. Cleanout of sediment from the sumps will be conducted on an as needed basis; the required runoff water storage capacity will be maintained. The principal spillways are designed for the 10 -year, 24 -hour storm event; the emergency spillways are designed to pass the peak flows from the 25 -year, 24 -hour storm event with a minimum of one -foot of freeboard. Design information for the sumps, as well as, Ponds 002, 003, 004 and PECOCO Pond is present in Exhibit 2- 05.3 -E2, Drainage and Sediment Control Plan. Runoff and Stormwater Control and Discharge — PSCM has secured a Colorado Discharge Permit System (CDPS) permit for the PSCM Permit that includes a stormwater management component. A copy of the CDPS permit for the PSCM operations can be found in Exhibit 2.05.3 - E3, CDPS Permit. Pond 002 is the primary stormwater retention structure for the proposed south facilities area, as well as, existing Seneca II Mine areas, that have been successfully reclaimed and revegetated and, for which CDRMS has approved Phase I and Phase II Bond Release. Pond 003 is the stormwater retention structure for the north facilities area. Both of these ponds are permitted industrial stormwater discharge structures under the existing Seneca II Mine CDPS permit — the two structures are included in the PSCM CDPS permit as effluent outfalls and sample compliance points. Map 2.05.3 M4, Drainage and Sediment Control Plan, shows the location and flow relationships for all stonnwater control features and diversions. Additional information on stormwater conveyance structures is presented in Section 2.05.6 and in Exhibit 2.05.3 -E2, Drainage and Sediment Control Plan. MR -16 2.05 -28 Revision 11/2012