2010-08-04_GENERAL DOCUMENTS - C1994082

Home Browse Search

From: Karo, Roy [ mailto:RKaro @PeabodyEnergy.com] Sent: Tuesday, August 03, 2010 8:15 PM To: Mathews, Dan Cc: James, Jay Subject: RE: Diversion Ditch 14A Removal I love you man. I will get some more documentation, do you think we need a TR for this? Roy A. Karo, Manager Reclamation, Peabody Energy PO Box 670 37796 Rd. 53 Hayden, CO 81639 970 - 846 -3648 c 970 - 276 -5217 w 970 - 276 -5222 f 970 - 824 -4197 h From: Mathews, Dan [Daniel. Mathews @state.co.us] Sent: Tuesday, August 03, 2010 4:20 PM To: Karo, Roy Subject: Diversion Ditch 14A Removal Roy, I took a look at your letter dated August 2, 2010, which addresses hydrologic conditions associated with runoff and sedimentation into Diversion Ditch 14A, which reports to Sediment Pond 14 at Yoast. The letter was prompted by our conversation during my inspection last week, in which I indicated that required sedimentation demonstrations would have to be submitted before Ditch 14A could be reclaimed /eliminated, since it is currently a part of the approved sediment control system for the disturbed area at Yoast (certain reclaimed pit areas drain to the ditch, which reports to Pond 14). In the letter, you indicate that no runoff was ever expected from the watershed associated with Diversion Ditch 14, and you include SEDCAD documentation showing that the 32.5 acre sub - watershed SWS2 would not generate runoff or sedimentation as a result of a 10yr /24hr storm event. This is true, but it is not the whole story. See Map Exhibit 13 -12.1. Sub - watershed SWS2 is designated "UNDISTURBED ". The SEDCAD modeling indeed indicates that this 32.5 acre area of undisturbed aspen and mountain shrub would generate no runoff or sedimentation as a result of the design storm event. However, Exhibit 13 -12.1 also shows that 44.0 acres of disturbed land labeled Sub - watershed SWS1 ( "Pit /Pre- Strip ") drains into Ditch 14A. The Subwatershed Hydrology Detail on page 130 of Tab 13, Appendix 13- 12.1 shows that the design event was projected to generate a peak discharge of 26.37 cfs from the SWS1 Sub- watershed. The Subwatershed Sedimentology Detail on the same page indicates that the design storm was projected to generate a peak sediment concentration of 536,755 mg /l, with a peak settleable concentration of 217.44 ml /l. I have to conclude that the letter and documentation you provided does not demonstrate that "the ditch was not required during initial mining disturbance ". With the amount of flow and sediment projected from disturbed area Sub- watershed SWS1, the ditch would definitely have been required. The documentation you provided addressed only the undisturbed portion of the watershed tributary to Ditch 14A, not the disturbed portion of the watershed.