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Permit Revision No. 7 -Responses Page 8 March 7, 199J 44. Page 2.05-29 has been revised to reference Table 42E of Exhibit 66 as the location of pond inflow and volume data. 45. MCC assumes that the Division's request that MCC consider the need for additional surface water monitoring locations as a result of the SGFA facilities, is referring to an additional NPDES discharge point. The Water Quality Control Division (WQCD) of the Colorado Department of Health and the Environment (CDPHE) has approved an additional NPDES discharge point for sediment pond SG-1. (Revised NPDES permit pages will be provided to CDMG in a separate revision.) As stated previously, it is anticipated that a maximum of 25 gpm or 0.055 cfs is expected to be contributed to SG-1 during construction of the shafts. MCC has no plans to pump mine water to SG-1 once the shafts are completed; therefore, Whole Effluent Toxicity (WET) testing will not be required for this pond. 46. All active and intermittent stream channel impacts (except for culverts) have been eliminated by redesign of embankments so that relocation of Sylvester Gulch is no longer necessary. Exhibit 69 has been revised to reflect this change. 47. The major Clearwater diversion ditches associated with the shaft site benches are not located within previously mapped landslide areas, nor have subsequent field investigations indicated that these areas show signs of current or past movement. The Clearwater ditches have also been redesigned and realigned to minimize placement on steep grades and minimize steep cut slopes along the south side of the shaft site. The Clearwater diversion for the south side of the shaft site has been redesigned to include, a new surge basin which will collect Clearwater runoff upstream of the shaft site and route it to a buried Clearwater diversion culvert (CCW-1B). The surge basin has been designed for the 250-year peak flow event. This new design also incorporates a concrete and steel grate overflow channel below the surge basin to provide a secondary inlet to the Clearwater culvert and provide additional assurance that water will not enter the shaft pads or sediment control ditch. Therefore, the south Clearwater ditch (DCW-6C) only collects localized Clearwater runoffto the south of the shafts site. This water flows into drop inlet structures and into CCW-1B. The design of the surge basin is shown on construction drawing E611303A. Some roadside ditches will pass through potentially unstable azeas. In these azeas, (station 17+00 to station 30+00 of the main hauUaccess road) french drains will be installed beneath the surface ditch to collect excess surface and ground water, thereby improving the stability of the road, ditch, and hillsides. 48. All culverts in natural drainages (i.e. Sylvester Gulch crossings) have been sized to convey the peak flow resulting from the ] 00-year, 24-hour storm event. 49. Table 44 on page 2.05-159 of the West Elk Mine permit lists three water rights in Sylvester Gulch that are entirely owned by MCC. The location of all sources associated with these rights are shown on Map 37, "Spring and Stock Pond Location Map" and are identified by decreed springs 1 through 1 ].