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2022-11-07_REVISION - C1981041 (2)
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2022-11-07_REVISION - C1981041 (2)
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Last modified
11/7/2022 1:11:41 PM
Creation date
11/7/2022 12:28:20 PM
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DRMS Permit Index
Permit No
C1981041
IBM Index Class Name
Revision
Doc Date
11/7/2022
Doc Name
Proposed Decision and Findings of Compliance
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DRMS
Type & Sequence
RN8
Email Name
CCW
THM
Media Type
D
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modified by approval of PR-3, as the flat top of the waste pile is included within the <br /> designated alternative land use area(see Exhibits 6C and 6C-A). The top of the pile <br /> has been gravel surfaced, and under the "Industrial or Commercial" land use <br /> reclamation plan approved by PR-3, the area will be left "as is" for use as a storage <br /> site for equipment and supplies associated with the commercial fruit operation. The <br /> area will not be topsoiled or revegetated. The 1 st Quarter 2007 refuse pile certification <br /> report documents that the required 18 inch minimum thickness of non-toxic cover <br /> material was placed over the coal waste material on the flat top of the pile. A short <br /> segment of existing Access Road 1 will be left in place for the postmining use. It will <br /> connect to the upper end of proposed Access Road IA,to provide access to the storage <br /> area on top of the RSRDA. <br /> The lower three benches of CRDA-1 and CRDA-2 were covered with the approved <br /> thickness of non-toxic cover, seeded, and mulched in the late summer/fall of 1994. <br /> Final reclamation of the upper benches was conducted in the spring of 2002. <br /> Geotechnical analyses for CRDA-1, and CRDA-2, are provided in Appendices 13-4 <br /> and 13-5 of the application. CRDA-1 has been constructed with three rock <br /> underdrains, and construction specifications include 2:1 slopes with 10'wide benches <br /> on 30' vertical intervals. The benches are sloped to the inside and graded to drain to <br /> perimeter ditches along the sides of the pile. CRDA-2 specifications are similar,with <br /> the exception that pile design does not incorporate underdrains, and slope between <br /> benches is not to exceed 2.5:1. <br /> Stability concerns associated with higher than anticipated water levels in Piezometer <br /> CRDA-01 resulted in suspension of waste disposal at the site in 1988, pending <br /> drainage modifications and stability re-evaluation. Between 1988 and 1993,the lower <br /> three benches were regraded to provide for better slope stability and drainage. Surface <br /> drainage was improved by the construction of diversion ditches that allow surface <br /> runoff to exit around the pile instead of contacting the face. <br /> A stability evaluation was performed in the spring of 1994 by Western Engineers,Inc. <br /> As a part of the study, pump testing was conducted in existing piezometers and 30 <br /> additional piezometers were installed to evaluate phreatic surfaces and pore pressures. <br /> The results of the study showed the pile to be stable as designed. Critical water levels <br /> were defined for each of the 30 new piezometers. Based on the study results, the <br /> operator was permitted to resume waste disposal at CRDA-1 in 1994. The operator <br /> has committed within the permit to monitor the 30 piezometers quarterly, and if water <br /> level in any of the piezometers reaches critical target depth as listed on Table 18-4, <br /> stability of the pile will be reevaluated and corrective action taken if necessary. <br /> CRDA-1, and 2 was monitored throughout construction. Monitoring included: <br /> 1. Piezometric monitoring of the coal processing waste embankment; <br /> 2. Monitoring of side slopes to maintain a maximum slope angle of 2:1 between <br /> benches on CRDA-I, and 2.5:1 on CRDA-2; <br /> 42 <br />
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