2012-09-06_REVISION - M2008070 (18)

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Western Gravel E &P Waste Disposal Facility October 2011 CQA/QCP Page 17 of 19 LEACHATE COLLECTION AND RECOVERY SYSTEM PIPING This part of the CQA/QCP describes the piping materials used in the construction of the leachate collection and recovery system. Piping Perforated 12 -inch diameter HDPE collection piping will be placed at the bottom of the sump area. The perforated piping will be surrounded with clean leachate gravels as specified in the Earthen Materials section and shown on the Design and Construction Plans. A minimum of 2 inches of leachate collection gravels will be placed below the pipe and a 4 -inch thick layer of protective soil or a 16 -oz non woven geotextile fabric will be placed under the leachate gravels and over the primary liner. The slotted HDPE piping shall consist of SDR 17 pipe with % inch diameter perforations spaced 60 degrees radially and at 1 foot center. The collection pipe will connect to solid 12 inch diameter HDPE piping that will run up the sidewalls of the cell. The solid HDPE piping will extend beyond the finished soil cover /cap for the cell and be protected by a 24 -inch diameter galvanized CMP with a locking cap. Hydrated bentonite will be used to fill the annulus between the HDPE pipe and CMP. HDPE piping shall comply with ASTM D3035 and D3350. No specific testing of the piping is required; however all piping must be observed and accepted by the CQA Engineer during placement and prior to backfilling. SURVEY CONTROL This part of the CQA/QCP describes the survey control that will be required during the construction of the facilities. All surveying will be performed a Colorado licensed Professional Land surveyor. Surveys performed for inclusion in the CQAC Certification Reports shall include but not be necessarily be limited to: 1. As -built subgrade excavation contours and grades. 2. As -built anchor trench locations. 3. As -built top of primary liner. 4. As -built locations of the leak detection trenches, piping and manholes. 5. As -built locations of leachate collection system piping and gravels. 6. As -built locations, contours and grades of all engineered surface water diversion structures. 7. As -built locations, contours of final soil cover /landfill cap materials including contours and extent of GCL Excavation Surveying Grade staking will be performed by surveyor to establish required elevations for the excavation base facilities. Vertical elevations of excavation grades will be documented based on a grid spacing of 50 feet or less, and the axes of the tops and toes of slopes will be surveyed on a spacing of 50 feet or less. Vertical measurements shall be read to the nearest 0.01 foot to establish elevations at a minimum precision of 0.1 foot. Horizontal measurements shall be read to the nearest 0.1 foot to establish locations at a minimum precision of 0.5 foot. As -built measurements of the completed cell subgrade will be taken with the above requirements prior to placement of the secondary liner materials. Contour maps illustrating constructed grades and elevations for each of the cells shall be provided by the surveyor. NWCC INC.