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be stable as designed. Critical water levels were defined for each of the 30 new piezometers. Based <br />on the study results, [he operator was permitted to resume waste disposal a[ CRDA-I in 1994. The <br />operator has committed within the permit to monitor the 30 piezometers quarterly, and if water level <br />in any of the piezometers reaches critical target depth as listed on Table 18-4, stability of the pile will <br />be reevaluated and corrective action taken if necessary. <br />CRDA-l, and 2 will be monitored throughout construction. Monitoring will include: <br />I. Piezometric monitoring of the coal processing waste embankment; <br />2. Monitoring of side slopes to maintain a maximum slope angle of 2:1 between benches on <br />CRDA-I, and 2.5:1 on CRDA-2; <br />3. Monitoring compaction of constructed lifts; and <br />4. Quarterly inspection for stability and compliance with approved plan by a registered <br />professional engineer. <br />Geotechnical analyses included in the permit application show that CRDA-I and CRDA ?are stable <br />at a minimum safety factor of I.S. The following specific findings apply to the approved refuse <br />disposal areas. <br />The disposal area will be inspected on a regular basis by a qualified professional specialist under <br />the direction of the professional engineer, experienced in construction of similar earth and waste <br />structures. Inspection by this person has been approved by the Division as appropriate <br />(4.10.2(1)). inspection shall occur quarterly and at critical construction periods. A copy of the <br />inspection report will be retained at the mine office and a copy will be forwarded to the Division. <br />2. An altemative subdrainage system for the coal mine waste area has been approved. The Division <br />finds that such an altemative will ensure the applicable static safety factor, stability of the fill, <br />and protection of the surface and groundwater (4.10.3(5)). No underdrains will be constructed <br />on Cameo Refuse Disposal Areas No. 2. The Roadside Refuse Disposal Area was also <br />constructed without an underdrain. <br />The pertnittee has demonstrated, based on physical and chemical analyses of refuse material and <br />cover soil, and vegetation field trials, that the revegetation requirements of 4.15 can be met with <br />less than four feet of cover on the coal processing waste bank (4.10.4(5)). This study which was <br />conducted over a span of 10 years was finalized during the summer of 1993. A determination <br />on the required cover depth was made by the Division pursuant to approval of Technical <br />Revision l6, in January, 1994. For further relevant discussion, see Section C.III of this <br />document. <br />Vll. Backfilling and Grading <br />Following removal of mine facilities, buildings, and asphalt, and sealing of underground mine <br />openings, all areas affected by surface operations will be backfilled and graded as necessary to <br />stabilize slopes and promote successful revegetation. The anticipated final surface configuration for <br />each affected surface area, as well as existing and proposed postmine cross-sections, are depicted in <br />Exhibits 6C through 12C, and Exhibits 26, 27 and 28 of the permit application. <br />39 <br />