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VV VV ENGINEERING }}������++�/� <br />611 SKYLINE ROAD - LARAMIE, WY 82070 - (307) 742-0031 FAX (307) 721-2913 1r1L' Mu" <br />TO: MIKE BERDINE, MANAGER - TECHNICAL RESOURCES <br />TWENTYMILE COAL, LLC <br />FROM: JUSTIN TERFEHR, P.E. <br />SUBJECT: HYDROLOGIC/HYDRAULIC ANALYSIS FOR 9E UTILITY BOREHOLE PAD AND <br />ACCESS ROAD <br />DATE: MAY 6, 2016 <br />This Memo documents hydrologic and hydraulic evaluation of culverts and diversion <br />ditches for the 9E Utility Borehole Pad and Access Road to be constructed by Peabody <br />Energy, Twentymile Coal, LLC (Figure 1). The analysis modeled the upgradient <br />hydrology and sized the proposed culverts and diversion ditches utilizing SEDCAD. <br />Twentymile Coal uses 24 -inch diameter CMP culverts as a minimum for maintenance <br />and cleaning. The 24 -inch culvert is larger than what is required to pass the runoff from a <br />10 -year, 24-hour precipitation event for all four locations: 9E Culvert 1, 9E Culvert 2, 9E <br />Culvert 3 and 9E Culvert 4. The SEDCAD model was used to determine the diversion <br />ditch depths. Grades for each diversion ditch were determined from the existing site <br />topography. The diversion ditches shall be constructed as v -shaped ditches to a depth of <br />1.5 feet with 2:1 (horizontal: vertical) side slopes. <br />Watershed soil and cover information used for the SEDCAD modeling were taken from <br />the Topsoil Stockpiles Along 18 Right Shaft Access Road project (WET, Inc. 2005). <br />WET obtained the data from site photos and a soil investigation report (Habitat <br />Management, Inc. October, 2003. Fish Creek Shaft & Access Road Soil Investigation, <br />Routt County, Colorado, Twentymile Coal Company Permit #82056). All culverts and <br />diversion ditches were modeled for the 10 -year, 24-hour storm event with a precipitation <br />depth of 1.8 inches. <br />All SEDCAD modeling completed for this analysis are provided under Attachment 1. <br />1/1 <br />