Laserfiche WebLink
By minimizing the extent of surface disturbance, EFCI effectively limited <br />potential changes in existing surface drainages. Because the Southfield <br />operation was an underground mine, associated surface disturbance is <br />limited relative to the total permit area. With a permit area of <br />approximately 2,800 acres including both mine and loadout areas and a <br />r <br />total surface disturbance of approximately 100 acres, surface disturbance <br />constitutes less than four (4) percent of the permitted area. <br />During mine development and facility installation, Dorchester constructed a <br />diversion to route the Magpie Creek drainage around the disturbance area. <br />This diversion is designed to minimize potential mining related impacts on <br />Magpie Creek and was designed and constructed as a permanent diversion to <br />minimize erosion and additional contributions of suspended solids to <br />drainage flows. While it was originally designed as a permanent structure, <br />the original design criteria for Magpie Creek only met subsequent <br />regulatory standards for temporary diversions. In order to comply with <br />regulatory provisions for permanent diversions, EFCI made appropriate <br />modifications to the Magpie Creek diversion in conjunction with site <br />reclamation. <br />Vegetation and topsoil was removed from all mine facilities areas prior to <br />disturbance. This practice, while necessary to preserve topsoil <br />resources, exposed underlying materials to potential erosion and <br />consequent material loss. In order to minimize erosion and prevent loss <br />of surficial materials, which can result in increases in TSS in the runoff <br />water, EFCI routed undisturbed drainage around disturbance areas, graded <br />disturbed areas to provide for effective drainage control, established a <br />drainage and sediment control network to collect and retain disturbed area <br />runoff, reclaimed disturbance areas as soon as operationally <br />practical, and utilized other specific localized drainage and erosion <br />control methods as necessary. <br />EFCI constructed and maintaind both temporary and permanent diversion <br />ditches to intercept and route drainage from disturbed areas around the <br />area of surface disturbance. Temporary diversions are designed to pass <br />peak flows resulting from at least a 10 -year, 24 -hour storm event with a <br />2.05.6 -16 Revised: 8/l/14 RN -06 <br />