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Design and Operations Plan October 24, 2011 <br />Western Gravel E & P Waste Disposal Facility Page 22 of 51 <br />prevent leachate generation resulting from precipitation. Cell sidewalls will be excavated/constructed with 3 <br />(Horizontal) to 1 (Vertical) side slopes. The general configuration of future cells will be similar to Cell A. <br />Final size and orientation of cells will vary depending on site constraints, depth of bedrock, and <br />owner /operator's discretion based upon incoming waste volumes. The subgrade /top of liner contours for <br />future cells will be submitted to CDPHE for review and approval prior to construction. Subgrade /top of liner <br />contours for Cell A are shown on Figure 4. <br />The final quantity of cut and fills required for Cell A construction and the two future cells, located within the <br />Phase 1 mining footprint, will be variable and are to be determined following Phase 1 mining operations <br />completion. Based upon conceptual designs and proposed mining operations, it appears that the base /floors <br />of these cells, as well as the two cells located in the southern and western portions of the COD and outside of <br />Phase 1 gravel mining operations will be located approximately 10 feet to 25 feet below surrounding natural <br />ground surfaces. The cell base will be graded to follow bedrock bedding that dips away from the White <br />River and to the south. The leachate collection and leak detection systems will follow cell base grading and <br />drain to the south. <br />It is anticipated that the excavations of cell floors will be in bedrock and sidewalls will be constructed by <br />excavating into undisturbed overburden soils and underlying bedrock and/or by placement of embankment <br />fill materials over natural soils following topsoil and stockpiled materials removal. Embankment fills will <br />typically range from 1 foot to 10 feet in height in areas that will be mined Approximately 1 foot to 5 feet of <br />fill may also be required in order to bring cell floors to designed subgrade elevations in mined areas. A 12- <br />inch thick layer of clay fill will be placed at the base of all cells to allow for better grading and to help seal <br />bedrock materials exposed at the base of the excavations in order to provide an additional level of <br />environmental protection. <br />Fill materials placed in embankments will be constructed using on -site soils (clays, sands, and gravels or <br />bedrock materials). The fill materials placed in the base of the cells will consist of on -site clays classified as <br />CL or CH soils in accordance with USCS. Fill materials will be placed in 9 -inch maximum loose lifts and <br />compacted to at least 95% of the maximum standard Proctor density at -3 % to +3 % of the optimum <br />moisture content determined in accordance with ASTM D698. The fill materials placed in cells shall meet <br />properties listed in the Construction Quality Assurance /Quality Control Plan (CQA/QCP) provided in <br />Appendix H. Construction and testing procedures of these materials are provided in the CQA/QCP. <br />Excavation of bedrock materials will be conducted in a manner that minimizes fracturing of underlying <br />bedrock. Excavations into the underlying bedrock materials in Cell A has been limited to 5 feet in order to <br />allow removal of near surface bedrock materials using dozers equipped with ripper teeth. Prior to placement <br />of clay fill materials in cell floors, the base of the excavations will be inspected by the Construction Quality <br />Assurance Engineer (CQAE). Because blasting could potentially increase fracture and/or joint systems, <br />blasting will not be conducted in order to excavate landfill cells. <br />Prior to preparation of excavation, construction drawings of the two future cells to be located at the southern <br />and western ends of the COD and outside the Phase 1 mining area will be developed based upon additional <br />investigation activities. The investigations will be conducted in order to verify depth of overburden soils and <br />bedrock in these areas. <br />3.4.3 Soil Materials Management <br />In accordance with the mining plan and based upon classification, soils excavated from cells located within <br />Phase 1 are currently being separated as removed. Topsoil materials are stockpiled for reclamation purposes <br />and overburden clays are placed in separate stockpiles and sold as part of mining operations. Sands and <br />gravels are placed in separate stockpiles; however, these materials are being crushed and screened to produce <br />NWCC, Inc. <br />