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zone of the pile. During construction of the waste pile, topsoil stockpile SF-12 will be seeded with the topsoil <br />stabilization seed mixture at the first appropriate opportunity following stockpiling operations. <br />• Table 49A, Topsoil Stockpile Summary, has been revised to show the potential modification to the existing <br />stockpile SF-12 resulting from the construction of the refuse pile. Also, the table presents all the other topsoil <br />stockpiles located at Twentymile. The stockpile identification correlates with the stockpiles presented on Map 29. <br />Within 30 days of start-up of the preparation plant, a sample of the waste material generated from the preparation <br />plant will be obtained and analyzed to verify the assumptions used for the pile design presented in Exhibit 26A. <br />TCC will forward results of this analyses to the Division along with a certified statement from a registered P.E. <br />summarizing the results of the analyses as compared to the original design assumptions. If the results show the <br />properties of the wash plant materials are significantly different than the properties used in the design assumptions <br />for the waste pile, the waste pile design will be reviewed and modified accordingly. <br />Previously, during the evaluation of the waste pile permitted under TR I5, a chemical analysis of the processed <br />waste material was completed with the results presented as Table 20A, Waste Material Analysis. Based upon this <br />analyses, it appears the waste material will not pose toxicity or acid generating problems. The previously <br />referenced CTL/Tltompson report addressing the waste pile design and geotechnical evaluation includes a <br />conservative estimate of the maximum quantity of water projected [o drain from within [he pile (see Exhibit 26A. <br />page 17). The estimate is based upon the assumption that 3 inches of water infiltrates into and discltar_es from the <br />pile on an annual basis. The analysis further assumes that discharge from the pile occurs during a one month time <br />period. Under these conditions, the average calculated flow from the drain is 0? efs for the month draina_e <br />occurs. The discharge from the waste pile rock drain will be routed to Pond D. Given the minor magnitude of the <br />rock drain discharge relative to the surface water runoff contributions typically received by Pond D. ito adverse <br />water quality impacts are anticipated as a result of construction of the waste pile. Pond D will continue to be <br />monitored for the applicable NPDES discharge permit parameters as required. <br />Spoil /subsoil material will be used as the non-toxic material to be placed over the waste material. During the <br />development of the waste pile the spoil /subsoil material will be selectively removed from within the footprint of <br />the pile. The spoil /subsoil will be hauled directly to the site and spread over the waste material. After placement <br />of the spoil /subsoil material the area will be topsoiled as per the above. Redistributed topsoil will be seeded with <br />the pastureland seed mixture. <br />The permanent diversion ditches on and around the perimeter of the waste pile (see Map 24 and Exhibit 26A. <br />Appendix D) will be established prior to constructing the waste pile. However, the uppermost portion of the west <br />side diversion ditch segment RDA-Ib will temporarily be aligned slightly to the east of the location depicted oit <br />Map 24 in order to avoid the established topsoil stockpile (SF-6) in [Iris area (see Exhibit 26A, Figure ?). Topsoil <br />stockpile SF-G will remain in its current location and will be utilized as the initial topsoil source for reclamation of <br />the waste pile benches. In the event topsoil pile SF-6 Itas not been utilized [o the degree necessary to allow the <br />Fnal configuration of ditch RDA-I b once the pile is developed to this elevation, [he remainder of topsoil pile SF-G <br />conflicting with the tinal ditch alignment will be relocated and the permanent diversion ditch will be established <br />between the existing sections. TCC does not intend to riprap the temporarily located portion of ditch RDA-Ib <br />until the final alignment is established. <br />In order to facilitate the establishment of vegetation in permanent diversion ditch RDA-2, temporary rock check <br />dams wil, installed in selected segments of the ditch. The design of these rock check dams can be found in <br />Exhib' _ -a(I R ~ Pile. Rock Check Dam design. It should be noted [hat these dams will not exceed one foot <br />in I fight, and e.• nd acr ss the S' wide ditch bottom. The 13' rock dam will extend up the side slope of the flow <br />lin See insert. nsert: he rock check dam will be placed according to the following spacing interval: slope I% <br />or less - ver}~10 ee[, 2 slope -every 50 feet, 3% slope - 3 dams per 100 foot segment of ditch. 4% slope - 4 <br />~ ~ ~ AP~~?J~~ ~ << 2 ,s ?997 <br />c <br />MR 97-I~6 2.05-93/ Revised 12/24/97 <br />