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<br />P:\Projects\0106.069 CC&V 2024 CQA\J-REPORTS\2024 Phase 3B Subgrade and Leak Detection ROC Report <br /> Page 7 <br />2.2. Site Grading <br />Prior to construction a revised grading plan was submitted to and approved by the <br />Colorado Division of Reclamation, Mining and Safety. Approximately 1,335,622 cy of material was <br />removed from the Dump 1 facility. Material was cut and pushed by Holcim GPS dozers downslope <br />and stockpiled. CC&V mining operations loaded the cut material into 793 haul trucks and hauled <br />to VLF 2 Phase 2 and VLF 2 Phase 3 Stage A or to the ECOSA. <br />Approximately 109,776 cy of Structural Fill (SF) material was used for site grading. The Owner <br />Placed SF was placed in 5-foot loose lifts, moisture conditioned as required and compacted using <br />a loaded 793 haul truck. The Contractor Placed SF was placed in 2-foot loose lifts, moisture <br />conditioned as required and compacted using a CS-56 sheepsfoot vibratory compactor. The <br />entire surface of each lift was compacted with a minimum of two passes in accordance with the <br />developed method specification. The development of the method specification for Owner Placed <br />SF and Contractor Placed SF is described in Appendix D. <br />All subgrade preparation and SF placement associated with site grading was monitored by the <br />CQA Monitor to ensure that it was placed in acco rdance with the project technical specifications. <br />2.3. Leak Detection Trench <br /> 3,576 linear feet of leak detection trench was constructed within the VLF2 Phase 3 Stage B limits <br />in accordance with the project Technical Specifications. The Phase 3 Stage B section of leak <br />detection trenches were completed, as shown on Record Drawings No. 2 and No. 3. The Stage B <br />Leak Detection Trenches are designed to be extended and the sample access point relocated <br />during VLF2 Phase 3 Stage C construction. <br />Detail A on IFC Drawing A420 shows the typical leak detection trench section. A minimum one <br />foot by one foot trench was excavated and lined with 40 mil textured HDPE geomembrane. The <br />geomembrane was installed in long strips with a 5-foot overlap and was overlain by a 16 oz/yd2 <br />non-woven geotextile. A 4-inch diameter perforated corrugated polyethylene pipe (CPeP) was <br />then placed in the trench. The trench was backfilled with Leak Detection Fill (LDF) and the <br />geotextile was wrapped around the fill with a minimum 1-foot overlap. A minimum slope of <br />steeper than 2.0 percent and an average slope of 3.1 percent was maintained along the entire <br />length of both trenches. The CQA Monitor observed all leak detection trench installation. <br />The VLF 2 Phase 3 Stage B leak detection trench was constructed by installing approximately <br />18,000 square feet of 40 mil textured HDPE geomembrane, 18,000 square feet of 16 oz/yd2 non- <br />woven geotextile, 3,499 linear feet of 4-inch CPeP, 77 linear feet of solid 4-inch SDR 17 HDPE <br />pipe, two sample collection access points, and 137 cy of LDF.