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in 1981. After their completion 1n 1983, mine construction and coal extraction <br />will begin with the construction of mains radiating in a northeast and south- <br />west direction from the D-Portal (see Map 119 of the permit application). <br />Mains and submains will be constructed under the main channel of Red Wash be- <br />ginning in 1985. Longwall mining beneath Red Wash will occur during 1987-1990. <br />Mining under Scullion Gulch will commence with construction of mains in 1987 <br />and room and pillar extraction under the channel will begin in 1989. See the <br />Subsidence section of this TEA for further discussion of the mining oeration. <br />The proposed surface water control plan centers around provisions for the D- <br />Portal Area and Refuse Disposal Area, shown on Maps 24-27 and 76-80 of the per- <br />^/a ~ mit application. These two sites comprise almost all cerface distcrbance with- <br />/~I in the permit area, and sediment nnnds have been designed to control run-off in <br />(/'~~ these areas. Run-off from the coal transport and storage system is generally <br />S~ <br />V~~~ controlled by collector ditches and small ponds, which will serve as sediment <br />`"` traps. Where possible, runoff from undisturbed areas above the D-Portal and <br />Refuse Disposal sites has been routed around areas of surface disturbance. <br />The most dramatic example of this is the diversion of Scullion Gulch under the <br />D-Portal Area. Along haul and access roads which are not located in the <br />D-Portal or Refuse Disposal Areas run-off is routed through culverts and <br />ditches only. Erosion control in the ditches and discharge structures is <br />provided by riprap and revegetation. The applicant has also suggested that <br />check dams will be field located and used to control velocities in these <br />ditches (page IV-72). Run-off control in the Ventilation Entry area is limited <br />to that provided for roads (see Map 86 of the permit application and discussion <br />under part C of this review). <br />Diversions and Collector Ditches <br />Within the Refuse Disposal area, diversion ditches will be constructed to in- <br />tercept run-off from undisturbed areas and route it away fran disturbed sites <br />in order to prevent the erosion of refuse piles. Collector ditches will be <br />constructed to collect run-off from disturbed areas as each subarea is filled <br />with refuse from the mining operation. Flow from both types of ditches will be <br />routed into a sediment pond by perimeter diversion ditches. The ditches are <br />designed to carry the flow fran a 100 year-24 hour precipitation event, as cal- <br />culated and checked using the Soil Conservation Service Technical Paper 149. <br />6 <br />