Laserfiche WebLink
STORAGE AND TRAINING AREA (TRUDY'S CORNER) SAE AND ASC'S <br />Twentymile Coal Company (TCG) is requesting approval of a Small Area Exemption (SAE) for the Storage and <br />Training Area located at the Fordel Creek Mine as shown on Map 24, Surfaze Facilities. Drainage and sedimem <br />control for the Storage and Training Area is provided by the following Alternative Sediment Control (ASC) <br />measures: <br />An existing vegetated trapezoidal drainage ditch with rock check dams, Ckrannel TS, which transfers water <br />from the Storage and Training Area to the existing inlet for Pond A <br />A loaF gradient vegetated 'oiler to Pond A which serves as a natural vegetative fiber <br />As a relatively small area (approximately 0.78 acres), and given the effectiveness of the ASC measures identified <br />above in controlling both drainage and sediment from this area, the additional disturbance required to construct a <br />sediment pond or route drainage from this area to an existing sediment pond is not justified. Off-site sediment <br />contributions can be effectively controlled through the proposed ASC measures, consistent with applicable <br />provisions of Rule 4.05.2(3)(6). There will be no discharge or mixi ~ of site surface drainage with mine water. <br />Based on the accompanying SEDCAD4 modeling for this area, the peak flow and runoff for the Storage and <br />Training Area discharge {Channel TS) are 0.64 cfs and 0.05 af, respectively. The estimate peak settleable solids <br />concentration for the discharge is 0.03 mVL The natural vegetative filter is not considered in the modeling resuhs <br />and would provide an added measure of protection relative to effective control of off-site sedimern discharge. <br />The drainage configuration for the Storage and Training Area is shown by the accompanying Figure 2. Drainage <br />design documentation is provided by the accompanying SEDCAD4 computer modeling summaries. Designs for <br />the referenced d¢ch is summarized by the accompanying table, Channe] Design Schedule for Scoria Pile Area and <br />Trud}~s Corner. <br />Assumptions: <br />3) The Storage and Training Area location and configuration and layout of ASC drainage control measures are <br />as shown on Figure 2. <br />4) Hydrology and sedimentology inputs to the SEDCAD4 model are consistent with those utilized for <br />previouslysubmittedand approved drainage designs. <br />Design Parameters: <br />Watershed Area - 0.78 acres <br />10-year, 24hour storm - 1.8 inches (NRCS Type In <br />CN- 87 (herbaceous) <br />All other design parameters are as shown on the accompanying SEDCAD4 modeling summaries. <br />Design Results: <br />Peak flow- 0.64 cfs <br />Runoff Volume - 0.05 of <br />Settleable Solids Concentration - 0.03 ml/1 <br /> <br />