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DM#1. East Collection Ditch midway along Bench 1, above the <br />temporary access road. Trapezoidal shape, 11' tw, 3' bw, 21" <br />d. 15% gradient, 12" riprap. Ditch capacity exceeds design <br />requirements, and SEDCAD evaluation indicates ditch adequate <br />for design flow. <br />DM#2. East Collection Ditch midway along Bench 2. <br />Trapezoidal shape, 10.5' tw, 4.5' bw, 18" d. 33% gradient, <br />12" riprap. Ditch capacity exceeds design requirements, and <br />SEDCAD evaluation indicates ditch adequate for design flow. <br />DM#3. East Collection Ditch midway along Bench 3. <br />Trapezoidal shape, 8.5' tw, 3.25' bw, 17" d. 21% gradient, <br />12" riprap. Ditch capacity exceeds design requirements, and <br />SEDCAD evaluation indicates ditch adequate for design flow. <br />DM#4. East Collection Ditch midway along base of bare refuse <br />Bench 4. Riprap has not yet been installed; to be completed <br />in conjunction with topsoiling of Bench 4. Trapezoidal shape, <br />8.5' tw, 3' bw, 16" d. 12% gradient. Ditch capacity exceeds <br />design requirements. SEDCAD evaluation indicates capacity <br />adequate for design flow, but riprap necessary based on flow <br />velocity. Note that subsequent to the special focus <br />inspection, ditch segment in this vicinity was filled in with <br />refuse sediment resulting from storm runoff which overtopped <br />the "roughed in" Terrace Drain #4, and eroded the bare refuse <br />outslope. The ditch breached as a result of the sediment <br />deposition. This location was included in NOV C-97-016, <br />issued October 3, 1997, for "Failure to ensure proper surface <br />drainage control on coal waste disposal areas..." <br />DM#5. West Collection Ditch at west end of Terrace Drain #3. <br />13' tw, 3.5' bw, 17"'d. 20% gradient, 12" riprap. Ditch <br />capacity exceeds design requirements, and SEDCAD evaluation <br />indicates ditch adequate for design flow. <br />DM#6. Lower section of West Collection Ditch adjacent to main <br />road. 13' tw, 3' bw, 17" d. 2% gradient, 30% vegetative <br />cover. The ditch segment meets permit depth specification and <br />exceeds top width specification for 3% slope, but SEDCAD <br />evaluation indicates ditch capacity would be insufficient for <br />100 year/24 hour design flow. Unless information documenting <br />that ditch capacity is adequate is submitted to the Division, <br />the permit designs will need to be amended and the ditch will <br />need to be modified as appropriate. An appropriate technical <br />revision application should be submitted to DISG by December 1, <br />1997. <br />4 <br />