2011-09-13_GENERAL DOCUMENTS - M2008070

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CD Application Technical Comments #1 September 9, 2011 Western Gravel Disposal Facility Page 4 not presented on any drawings inside the CD. Consider monitoring for explosive gases in any wet/dry wells installed. 31. 4.6 — Add bullets for the 5 -year third party cost estimate for financial assurance, quarterly HSRF fees and leachate management. Delete bullet #9 "records of all environmental controls ". 32. 4.7 — Consider revising this to a Contingency plan. Include actions proposed should run -off from the active cell enter a stormwater pond, if a wet/dry well becomes wet and if a new seepage is discovered on the steep north slope. 33. 5.0 — Closure plan needs more details including closure of ponds, roads, buildings, borrow areas and access control. Add there will be no nuisance conditions at the property boundary and no water pollution at POC. 34. 5.3 — For seeding, consider that root depths should not interfere with the intended function of the geocomposite clay (GCL). Consider an alternative cover design (maybe an Evapotranspiration / Water Balance cover). Note that the cover must perform better than the double liner as per Section 3.5.3 of the Regulations or you may need to ask for a waiver. The Division is working on a guidance document relative to water balance covers that (when finished) will assist applicants with their design. 35. 6.0 — In the Post Closure plan, inspect the pond and add the missing items identified in 3.6 of the Regulations. Add groundwater (or wet/dry) monitoring, leachate monitoring, leachate management/testing, and leak detection system monitoring. Figures 36. Figure 3 — Clarify if clean stormwater run -on controls will be north or south of the access road. Consider providing a figure that can present the stormwater controls at a larger scale than Figure 3 for Pond 1 contributions. 37. Figures 4, 5 and 6 — Finish the grading plan north of the cell where it ties into natural ground surface along cliff edge. Show fill plan within the arroyos north side of Cell A. Consider grading the base of the cells away from the steep north slope consistent with bedrock dip direction. Also move the LCRS and LDS to the south side of the cell if possible to be more protective of the White River and to improve wet/dry monitoring. Check the manhole top elevation in Detail 5D. 38. Figure 7 — For the closure grading plan, add the Cell A foot print and check if the final cover thickness at the inside top of slope (edge of waste) is a minimum of 3.5 feet. Finish the grading plan outside of the cell tying contours to natural ground elevations and including any stormwater controls. Some fill may be needed in the arroyos along north edge. Appendices 39. Appendix B — Conduct dynamic stability analysis using the maximum horizontal acceleration in lithified earth (3.1.4 of the Regulations). Add any new information regarding additional seep survey and fracture /joint survey on the steep north slope or additional stability information as identified previously. 40. Appendix C and/or Section 2.4.2 — Provide more complete description of the RQD results and what they mean relative to the overall weathering, stability of the bedrock and hence the facility. Consider writing a technical memo on the subject and then place it into Appendix C and summarize it in Section 2.4.2. 41. Appendix H CQA/CQC Plan (earthen materials) — Please compare the testing frequencies with the CQA Guidance Document (CDPHE, 2010) including the LCRS drain material. For earthen materials there is typically pre - construction and construction testing. Consider revising Table 3 adding these columns and testing frequencies. Provide a material specification for the embankments and add a one -point Proctor test during construction at one test per 10,000 cy. Provide an estimate of the volumes of materials to be placed or otherwise used in construction of Cell A and the stormwater pond. The Division will accept the minimal testing of the leak detection clays as proposed due to the small volume of this material and placement beneath 2 synthetic liners. 42. Appendix H CQA/QC Plan (synthetics) - For the synthetic liners add manufacturer's quality assurance (MQA) and CQA testing in accordance with the CDPHE guidance document. Add a statement that the synthetic liner installations will be in accordance with the manufacturer's recommendations. Check manufacturer's information and revise the HDPE liner specifications (Table 4 ?; note smooth 40 mil HDPE and textured 60 mil HDPE) and the geotextile specifications (Table 7 ?). For the GCL, add MQA and CQA