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Technical Revision No. 79 -PAR Responses Page 2 April 18, 1997 additional separation between the liner and groundwater beneath the lower portions of the RPE footprint. For these reasons MCC believes the configuration of the liner and rock drain to be prudent and conservative. MCC is amenable to the installation of additional piezometers after construction of Phase 1 of the RPE, as the Division has requested. However, we believe the Division and MCC aze in agreement that piezometers should not be installed in locations that would require penetration of the liner. MCC proposes that the location of future piezometers be determined in conjunction with the Division staff at a later date. Sand drains and rock drains have been sized for a minimum of 200 percent of the expected flow. As a contingency plan, should higher water volumes be encountered, a drain sizing matrix table has been prepazed to allow quick field modification of constructed drain sizes. Please also see response to question 22. Surveyed elevation data for LRP-1 and LRP-4 are now included on the water level data tables in Appendix I. Soils Resource Information 4. Topsoil will be stored on a stable surface where it will be protected from wind and water erosion. Figure 2.0, North Soil Storage Area shows that the northern edge of the disturbed azea is at an elevation of 6100 and the elevation of the river is approximately 6065 feet. In review of Map 39, Floodplain Delineation and Existing Conditions and Exhibit 21 Cross- Sections on the North Fork of the Gunnison River, which are both contained within MCC's permit, the elevation of the 100-year frequency flood at cross-section 160 (which is in the approximate area of the North Soil Storage Area) is approximately elevation 6077, well below the elevation of the North Soil Storage Area. MCC has provided the portion of Appendix M, "Soil descriptions and potentials" that was unreadable. Fish and Wildlife Resources Information 6. The Threatened and Endangered Species Survey for the Lower Refuse Pile Expansion report prepared by WESTEC has been revised to specifically identify those proposed or federally listed species which could potentially occur on the proposed disturbance or adjacent azeas. Included in the revised report is a letter from the U.S. Fish and Wildlife Service listing threatened and endangered species which may occur in the area and information concerning specific surveys for the habitats of those listed species. The surveys covered the habitats in the area of the proposed disturbance for the RPE. The report has also been revised to include a detailed discussion of the methods used to identify and survey