Laserfiche WebLink
<br /> <br />INTRODUCTION <br />During August 1987, a joint inspection was conducted at the <br />Colorado Coal Mine No. 1. The purpose was to develop a strategy <br />to correct erosion problems associated with a subsoil stockpile <br />and Sedimentation Pond No. 1, to replace a culvert with a dry <br />crossing and to install check dams in a diversion ditch as <br />maintenance work (see Map 26). The correction of the erosion <br />problems abates NOVs C-87-033 and C-87-034. The installation of <br />the check dams on the diversion ditch enhances the siltation of <br />the ditch bottom, which is currently experiencing down cutting. <br />This work commenced on October 26, 1987 and will be completed <br />within the next 10 days. <br />This mining revision addresses the design criteria for the dry <br />crossing. Kaiser has received permission from the Huerfano <br />County Commissioners to remove the culvert and replace it with <br />the dry crossing. It is Raiser's understanding that Huerfano <br />County will maintain the culvert. <br />DESIGN CRITERIA <br />Design criteria for the dry crossing is based on a light road <br />use assumption and is in accordance with Section 4.03.3. <br />Specific design information is included on Map 25. The flow <br />calculations for the road crossing are based on the criteria for <br />Diversion Ditch 11 and are included on Table 1. <br />Raiser proposes to excavate the culvert and backfill the <br />excavation. The road surface will be a combination of fill <br />material and gravel. Excess fill material will be blended into <br />the side of the road and seeded. To maintain crossing integrity <br />and minimize downstream sedimentation, 6 inch riprap will be <br />installed on the upstream and downstream sides. The road <br />approaching at the bottom of the crossing is 4:1 slopes. <br />This modification is proposed to eliminate a high maintenance <br />culvert that silts-in annually. <br />