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D. T. Mathews - 2 - January 10, 2001 SurvCadd calculations are presented on Exhibit 8C. Strategically placed sections were developed for the North Portal to show the configuration of the reclaimed area. The sections are presented on Exhibit SC and 27. b) Regarding the new sediment pond for the North Portal presented on Exhibit SC, the DMG is concerned that the top of the sediment storage is only 0.20 feet below the primary spillway. The DMG is concerned that sediment laden water may be discharged during a significant storm event due to re-suspension of previously deposited sediment. The DMG recommends a minimum two foot elevation be maintained between the primary spillway and the top of the sediment storage area. PCC believes a 6-inch diameter normally closed dewatering pipe can function as a slow passive dewatering system. The valve can be adjusted to decant water at any flow rate. This sediment pond is designed to contain the discharge from a 10-year 24-hour precipitation event. Water accumulations in the pond will be held until adequate settling has occurred. Text in Tab Section 13 indicates that sediment ponds #4, #5, #6, #9, and #10 have a principal spillway consisting of a pipe installed just above the maximum sediment depth. The ponds are designed to prevent outflow through the emergency spillway during the containment of runoff resulting from a single 10-year, 24-hour precipitation event. Water accumulations in the pond above the maximum sediment level are held until adequate settling has occurred to meet discharge limits of Total Suspended Solids. Five sediment ponds with a dewatering device located just above the maximum sediment depth have been in existence at the Roadside Complex for almost 20 years. I do not believe there have been any problems with these five ponds and I do not believe there will be any problems with the new sediment pond as designed. Page 13-7 was amended to incorporate a brief discussion of the new pond (Pond 13) under the heading 2.05.3(4) Ponds, Impoundments and Diversions. Exhibit 8C was amended to show the 8.5H:1 V riprap channel extending into Coal Gulch. ( 3. ) The french drain system shown in plan view on Exhibit 6C has three branches. ~~ Two of the branches will intercept seepage from the portal seals. The third branch is designed to intercept water from the hillside southwest of the conveyor entry. This third leg extends above the level of the portal entries to intercept seepage noted along the existing slope. The french drain cross section on Exhibit 26 was labeled K-K to correspond to the section notation on Exhibit 6C.