Laserfiche WebLink
<br />July 1996 CYVCC -Sediment Yicld Demonstration Rev.2 - Block C • 1 <br />1.0 INTRODUCTION <br />Cyprus Yampa Valley Coal Corporation (CYVCC) is in the process of requesting a Phase II and Phase <br />III bond release for Block C which is located in the Colorado Yampa Coal -Eckman Park Mine permit <br />azea approximately 25 miles west of Steamboat Springs, Colorado. As part of the request, CYVCC <br />contracted TerraMatrix Inc. to conduct a sediment yield demonstration for Block C. <br />Block C c~sists of four separate areas as shown on the Block C Bond Release Map. For this report the <br />areas are labeled 1 through 4. The size of each area and date of seeding are as follows: <br />Area Size Date Seeded <br />L 95.1 acres 10/80, 10/81, 8/82, 10/82 <br />2 39.3 acres 12/81, 8/82 <br />3 30.2 acres 12/81 <br />4 8.l acres l0/80 <br />According to Division of Minerals and Geology (DMG) Regulation 3.03.1(3)(6), no more than 60 percent <br />of the bond can be released until the applicant demonstrates that existing wnditions will result in <br />equivalent or lesser sediment contributions to surface runoff when compared with pre-disturbance <br />conditions or undisturbed areas. <br />CYVCC was granted a change in post-mining land use from rangeland to pasture by DMG for the area <br />containing Block C. The pre-mining vegetation cover type of rangeland (oak-aspen) varies significantly <br />from the vegetation cover type for the approved post-mining use of pastureland (herbaceous). Due to the <br />significant differences between these two vegetation cover types it would be difficult to develop a dircet <br />sediment yield comparison to satisfy DMG Regulation 3.03.1(3)(6). Given the change in post-mine land <br />use, TerraMatrix developed a model to compare the runoff from Block C to adjacent pasturelands. <br />To demonstrate that runoff from Block C will result in equivalent or lesser sediment contributions to <br />surface runoff when compared with adjacent pastureland conditions, TerraMatrix has developed a site <br />drainage and sedimentology model utilizing SEDCAI}+. $EDCAD+ is a computer soRware program <br />developed to assist in the evaluation of stormwater runoff, erosion, and sediment control management <br />techniques. <br />To develop an accurate model for the existing condition of Block C, TerraMatrix utilized the 1992 Block <br />C vegetation survey conducted by CYVCC and soil information from the existing permit document as <br />input to the SEDCAD+ program. <br />cwsieu~wr.raev <br />air. vve~~3ivm Ve TcrraAfalrix fnc ' ]65 South Union Boulevard Suite 400 • Lakewood, Colorado 80228 • (30J) 763-SIt0 <br />