2007-07-30_GENERAL DOCUMENTS - C1981041

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reclaimed, and CRDA-I has been reclaimed with the exception of a segment oftemporary road up the side of the pile that has been left open to allow for disposal of coaly material during the course of reclamation operations. The slopes of the RSRDA have been fully reclaimed and revegetated. The flat top of the pile was approved as an equipment storage area during operations, and has not been revegetated. Refuse disposal within the Roadside Refuse Disposal Area (RSRDA) was completed in the early 1980's, and the slopes of the pile were temporarily stabilized. The flat top of the RSRDA is a permitted supply storage area. Final reclamation ofthe slopes ofthe RSRDA, including installation of approved terrace drains, was completed in the fall of 2002. A stability analysis for the RSRDA is provided in Appendix 13-4. Final grading is discussed in Tab 14. The reclamation plan for the top of the RSRDA will be modified by approval of PR-3, as the flat top of the waste pile is included within the designated alternative land use area (see Exhibits 6C and 6C-A). The top of the pile has been gravel surfaced, and under the PR-3 "industrial or Commercial" land use reclamation plan, the area will be left "as is" for use as a storage site for equipment and supplies associated with the commercial fruit operation. The area will not be topsoiled or revegetated. The 1~` Quarter 2007 refuse pile certification report documents that the required 18 inch minimum thickness of non-toxic cover material was placed over the coal waste material on the flat top of the pile. A short segment of existing Access Road 1 will be left in place for the postmining use. It will connect to the upper end of proposed Access Road 1 A, to provide access to the storage area on top of the RSRDA. The lower three benches of CRDA-1 and CRDA-2 were covered with the approved thickness of non- toxic cover, seeded, and mulched in the late summer/fall of 1994. Final reclamation of the upper benches was conducted in the spring of 2002. Geotechnical analyses for CRDA-1, and CRDA-2, are provided in Appendices 13-4 and 13-5 of the application. CRDA-1 has been constructed with three rock underdrains, and construction specifications include 2:1 slopes with 10' wide benches on 30' vertical intervals. The benches aze sloped to the inside and graded to drain to perimeter ditches along the sides of the pile. CRDA-2 specifications are similar, with the exception that pile design does not incorporate underdrains, and slope between benches is not to exceed 2.5:1. Stability concerns associated with higher than anticipated water levels in Piezometer CRDA-O1 resulted in suspension of waste disposal at the site in 1988, pending drainage modifications and stability re-evaluation. Between 1988 and 1993, the lower three benches were regraded to provide for better slope stability and drainage. Surface drainage was improved by the construction of diversion ditches that allow surface runoff to exit around the pile instead of contacting the face. A stability evaluation was performed in the spring of 1994 by Western Engineers, Inc. As a part ofthe study, pump testing was conducted in existing piezometers and 30 additional piezometers were installed to evaluate phreatic surfaces and pore pressures. The results of the study showed the pile to be stable as designed. Critical water levels were defined for each of the 30 new piezometers. Based on the study results, the operator was permitted to resume waste disposal at CRDA-I in 1994. The operator has committed within the permit to monitor the 30 piezometers quarterly, and if water level in any of the piezometers reaches critical target depth as listed on Table 18-4, stability ofthe pile will be reevaluated and corrective action taken if necessary. CRDA-l, and 2 will be monitored throughout construction. Monitoring will include: Permit Revision No. 3 Permit No. C-1981-041 July 30, 2007 Page 37