2008-05-29_ENFORCEMENT - C1994082

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e ENECA IM3 coal cornpEny Seneca Coal Company May 28, 2008 Mr. Daniel Mathews Division of Reclamation, Mining and Safety 101 South Td, Suite 301 Grand Junction, CO 81501 (970) 242-5025 RE: Seneca Yoast Mine (Permit C-94-082) NOV CV-2008-001 Abatement Step 1 Mr. Mathews, Mai ? V* po ision? ? ??y , Seneca Coal Company (SCC) is providing the mandated information required by Abatement Step 1, as stated in the "Attachment To NOV CV-2008-001". Step 1: No later than May 30, 2008, provide a P.E. certified report documenting the storage capacity in Pond 12, and demonstrating whether the pond capacity is adequate to treat the design storm event runoff in compliance with applicable requirements of 4.05.1, 4.05.2, and 4.05.6. If the certified report indicates that Pond 12 capacity is not adequate, the report will address measures to be implemented to ensure that adequate sediment controls are in place in the Pond 12 watershed, to ensure compliance with sedimentation effluent limits of 4.051, 4.50.2, and 4.05.6. Such measures may include clean out of Pond 12 and/or construction of Pond 12A and/or other measures as warranted. On May 17, 2008 SCC personnel conducted a physical survey of Pond 012 and determined that the current water capacity is 0.7 acre feet (as measured between the top of sediment and the invert of the principle spillway orifice). The SEDCAD calculated capacity required is 0.8 acre feet of water storage capacity. SCC has recorded nine (9) runoff events since September 2007 that have exceeded the expected runoff volume from a 10 year/24 hour precipitation event as calculated per TR-37. (see Appendix 13-12A-1-1.5). Pond 012 10 year/24 hour peak flow = 0.96 cfs 0.96 cfs = 0.345 depth of flow in the flume Seneca Coal Company • P.O. Box 670 • Hayden, Colorado 81639 Telephone (970) 276-3707 a FAX (970) 276-3014