2008-08-20_REVISION - C1980004 (2)

Home Browse Search

Mike Boulay -4- August 19, 2008 is required for the 10-year event demonstration to show compliance with 4.05.2(7). On revised Figure 2.2-3, the sediment storage level is given on Section A-A' at 5415.5 feet, which is equivalent to the primary spillway elevation. This appears to indicate that no treatment would be provided and there is no room for sediment storage (if the pond is passively discharged as indicated by the SEDCAD demonstration). If the pond is manually discharged, the outflow would have to be sampled every time to show compliance with water quality standards and effluent limitations. Rule 2.05.3(4) requires a detailed design plan be submitted for each sediment pond and more specifically 2.05.3(4)(a)(ii)(C) requires that the operation and maintenance of each structure be described. Please clarify the discrepancies described above and provide revised design information which clearly demonstrates how the pond will be operated in compliance with 4.05.2(7), 4.05.6, and 4.05.9. In accordance with 2.05.3(4) provide a description of the operation and maintenance of the new pond and incorporate this description into the permit document. CAM: The sediment pond is designed to contain the 10-year 24-hour event, page 2-48 is updated to reflect how pond will be operated and maintained. It will be manually discharged' and will be sampled every time, as is current practice with the existing sediment pond, in compliance with Rule 2.05.3(4). Discharge of the pond is done in compliance with Rule 4.05.2(7); an application for a minor permit modification to move outfall 001 to the location of the new sediment pond discharge point has been submitted to the Colorado Water Quality Control Division and will be supplied to the DRMS once it is granted. Per a conversation with Mike Boulay on July 28"', the Elevation-Capacity- Discharge table has been removed from the supplied data and replaced with an excel spreadsheet. The excel spreadsheet is used to show the designed capacity of the sediment pond, location of the spillways, and demonstrate that the pond will adequately contain the 10-year event. Please see Appendix M, page 24. (Note: In working with the excel spreadsheet, it was discovered that the bottom of the pond elevation 5412' was left off of the initial capacity calculations, and after correcting the error in the excel spreadsheet, the elevation of the primary spillway changed from 5515.5' down to 5414'). 20. through 23. Items Resolved. Rule 2.05.3(8) Coal Mine Waste and Non-Coal Processina Waste 24. DRMS: There are still some inconsistencies with the use of terminology for the "Coal Mine Waste Pile". Page 2-34 makes several references to "refuse pile" and the second full paragraph on page 2-27iii refers to the "waste rock disposal area". If appropriate please replace these references with "Coal Mine Waste Pile".