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Exhibit 66. Documentation of specific parameters such as curve number, rainfall and time of <br />concentration are also found in Exhibit 66. This information for the RPE pond is located in Exhibit <br />70. <br />Miscellaneous Sediment Control Facilities <br />The raihoad loadout facility has been treated independently of the other surface facilities. The <br />loadout is located across the river from the other surface facilities and therefore must have its own <br />sediment control. The sediment control is a pond designed (sized) fora 25-yeaz, 24-hour storm <br />event and to accommodate wash-down water from the train load-out facility. Pond MB-4 was <br />relocated in 1998 from the east side of the train load-out to an azea west of the load-out between the <br />two sets of tracks. The relocated sediment pond is constructed with concrete and is preceded by an <br />oil skimmer and a sediment trap. The current design detail for this pond can be found in Exhibit <br />66. <br />The RPE area has also been treated independently of the other surface facilities. The RPE azea is <br />located to the east of the lower refuse disposal area and east of Sylvester Gulch. The sediment pond <br />has been designed to completely contain the runoff from a 100-yeaz, 24-hour storm event. The <br />design detail for this pond, the clean water diversion ditches and sediment ditches can be found in <br />Exhibit 70. <br />DCW-2, the ditch immediately south of the haul road above the Lower Refuse Pile, serves as the <br />clean water diversion ditch for the Lower Refuse Pile. It diverts undisturbed runoff from the Lower <br />Refuse disposal azea and is dischazged into sediment pond MB-2R. Runoff from the Lower Refuse <br />Pile is conveyed to sediment pond MB-2R via perimeter ditches D2R-1, D2R-la, and D2R-3, <br />which are all sized for the 100-yeaz, 24-hour storm event. <br />During construction of the West Elk Mine, a spring was located on the site where the substation <br />was to be built. In order to stabilize the substation pad, a french drain system and collection pipe <br />were constructed to dewater it. As shown in Exhibit 43 and on Map 54, a 6-inch PVC pipe collects <br />the water and drains it into Culvert C1-6A. MCC has designed and constructed several other french <br />drains azound the minesite, as approved by the CDMG, to improve stability. These french drains <br />are shown on Map 54. <br />2.05-30 Revised Jan 1996 RN03; Revised Nov. 1996 PR07; Revised Jan. 1997 TR79; Revised Jul. 1997 TR82; Revised Jun 1999 TR90 <br />