2015-02-06_REVISION - M2005059 (2)

Home Browse Search

SURETY INCREASE CLAY LINER/BACKFILL DESCRIPTION JANUARY 2015 Description All areas adjacent to oil and gas wells will be backfilled to a radial distance of 150ft following excavation. Reclamation will occur concurrently with mining following completion of gravel extraction in the western 1/3 of Cell A. Reclamation will backfill slopes to 3H:1V in the pit and the pit will be reclaimed as a water - storage reservoir. In addition, an area of approximately 5.5 acres in the northeast corner shall be backfilled to approximate historic grade. All affected areas above the normal pool elevation of the reservoir will have topsoil replacement and be re- vegetated with native vegetation followed by a weed control program. Exhibit F- Reclamation Plan Map shows final grading and topsoil/ re- vegetation areas. Reclamation Earthwork Reclamation earthwork will begin with backfilling areas adjacent to the oil and gas wells as shown in Exhibit F- Reclamation Map. These backfill areas will require approximately 115,000 yd of overburden of the 500,000 yd available. An area of approximately 5.5 acres in the north east corner of the pit will be backfilled to approximate historic grade which will require approximately 215,000 yd3 . This backfill will occur concurrently with striping of overburden. Following mining of the site, approximately 156,000 yd of weathered claystone shall be stripped from the pit floor and used to construct the clay liner as specified below. Approximately 170,000 yd of the remaining overburden will be used to backfill the slope to 3:1. General Clay Liner Construction Specification Weathered claystone shall be used exclusively as the borrow material for the compacted clay liner. This material shall undergo geotechnical testing including sieve analysis, Atterberg limits and standard proctor prior to construction. Moisture conditioning of the weathered claystone shall be conducted in place prior to striping. Moisture conditioning shall be performed to bring the moisture content of the borrow material to 0 - +3% of optimum moisture content as defined by standard proctor tests. Prior to constructing the compacted clay liner, a keyway shall be excavated as shown in the typical section (Exhibit F Reclamation Plan Map). Moisture conditioned clay liner borrow material shall then be compacted into the keyway to 95% of dry density as defined by the standard proctor test. It is important to keep the keyway and liner area dewatered during construction. The compacted clay liner will then be constructed to the general dimensional specification shown in the typical section (Exhibit F Reclamation Plan Map) by placing 8" lifts and compacting to 95% of maximum dry density as defined by the standard proctor test. Following construction of the clay liner, slope backfill material shall be placed as shown in the typical section. Topsoil Replacement Topsoil will be placed to a depth of 1 ft on all affected areas above the normal pool elevation of the reservoir. The total area to undergo topsoil replacement is 12.8 acres and the total topsoil replacement volume is approximately 20,651 yd