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.: 4J CIVIL RES'~URCES,LLC ENGINEERS & PLANNERS June 9, 2003 RECE~VE~ Mr. Jeff Gregg MAY 12 2004 Hall-Irwin Corporation 3026 4r^ AVe. Division of Mirerais & Geology P.O. Box 2150 Greeley, CO 80631 RE: Hall•Irwin Corporation, File No. M-2002-120 Bernhardt Resource Storm Water Management Plan (SWMP). Dear Mr. Gregg Civil Resources, LLC has completed our preliminary engineering analyses of the drainage and erosion control issues at the Bemhardt Resources Gravel Mine located in Section 1, Township 4 North, Range 67 West of the 6'" P.M., refer to Figure 1. Drainage ditches, straw bales, berms, riprap and silt fences will be used in this plan to direct storm flows on the site. Description of Property The property is located in Weld County, Colorado along Weld County Road 48 approximately 1 mile Northeast of the Town of Milliken. The property is bordered on the east by Weld County Road 25 on the south by WCR 48, and by the Big Thompson River to the north and west. The runoff entering the site will primarily come from the west and the south. Refer to Figurel. The property is approximately 290 acres in size and was historically an irrigated farm. Hall-Irwin is leasing the property and proposes to mine it for sand and gravel in the near future. To the north the Big Thompson River has cut through a bluff with steep slopes. The site drains to the north and east towarl the river and . exhibits an average land slope of 0.004 fUft. According to the Soil Conservation Service report Soil Survey of Weld County, Colorado: Southern Part (Appendix A), the property soils are Aquolis and Aquents, Dacono clay loam, Kim loam, Nunn loam, Paoli loam, Tassel fine sandy loam, and Ustic Toniorthents, see Appendix A, Exhibit J. Drainage Analysis The site receives storm runoff from the north, west and south as seen on Figure 1. The design flow was 20 cubic feet per second (cfs) and was used to design the storm drainage channels throughout the property. Existing field drains and ditch laterals will be used in this plan. The drainage channels will have a minimum depth of 2 feet, have a 5 foot bottom width with 4 horizontal to 1 vertical side slopes. New channels will be designed with a 0.004 fUft slope and existing channels will be graded to the existing land and deepened if necessary. Ditches have been directed around existing wetlands, straw bales will be used as a filter and sediment trap. Riprap protection should be provided in areas of high velocity to prevent erosion. Refer to Figure 2 and Figure 3. 451 ^AK STREET. SUITE 209 ~ P.O. BOX 680 ~ FREDERICK, CO 80530 ~ 1303) 833-1 41 6 ~ (303) 833-2850 -FAX