2007-11-16_GENERAL DOCUMENTS - C1981041 (3)

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Sampled Area EC (avg.) SAR (avg.) CRDA-1 Cover Soil 11.0 11.72 Topsoil Pile 1 7.8 11.54 Topsoil Pile 2 13.3 18.01 Topsoil Pile 3 8.0 14.0 There would appear to have been no appreciable benefit gained from using some combination of available topsoil stockpiles for topdressing, as opposed to use of the CBA-2 borrow material. (Topsoil Pile 1 was marginally higher quality, but use of Topsoil Pile 1 would have "robbed" the material from the North Portal Reclamation project, and various other areas to be reclaimed). Original permit projections regarding the availability of sufficient material meeting "topsoil" criteria within approved stockpiles and designated borrow areas in the vicinity of the North Portal and CRDA refuse areas were apparently erroneous. RSRDA Roadside borrow area pre-salvage soils data indicated comparatively high quality soils, with all 16 sampled zones meeting subsoil quality criteria for both EC and SAR, and only 4 of the 16 marginally exceeding quality criteria for topsoil. Average values for EC and SAR were well below the permit specified criteria for topsoil. Re-spread sample data verify the generally high quality of the salvaged soils; EC and SAR levels were lower than the topsoil quality threshold in all 11 samples. Based on review of the information provided, the Division concludes that permit compliance was demonstrated for CRDA-2 subsoil quality, CRDA-1 subsoil quality, and RSRDA subsoil and topsoil quality. Quality of topdressing material was marginal on CRDA-2, and did not meet the suitability criteria on CRDA-1. Should observation and monitoring of vegetative development on the refuse piles indicate problems potentially attributable to high levels of salinity or sodium in the surface soils (e.g. significant bare areas or stunted vegetation out of character with the native environment), appropriate assessment and mitigative measures will be required. IV. Sealing, of Drilled Holes and Underground Openings The method for sealing portals is depicted in Permit Figure 14-2. The South Mine Portals have been sealed with a 24" thick concrete seal, and will be backfilled with approximately 100 feet of dirt backfill extending out from the concrete seals. An underdrain will be installed in conjunction with final backfilling to drain portal area seepage away from the portal backfill. Other mine area portal openings were backfilled with a minimum of 25 feet of incombustible backfill. Long term mine discharge (post reclamation) from the Roadside South Mine will be from a gravity discharge pipe installed by angled drilling in the vicinity of the North Decline area (Outfall 016); a back-up discharge system is provided by a portal drain installed in the seal of the reclaimed Northwest Intake Portal, which allows discharge through CDPS Outfall #002 via siphon tubes. Outfall 002 would only be used in the event of malfunction of Outfall 016. Due to the orientation of the North Mine workings, which slope away from the portal and river, and due to the elevation of the portal which is above the Permit Renewal No. 5 36 November 16, 2007