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Response to DBMS Comments <br />Environmental Protection Plan, <br />Denison Van 4 Mine <br />Response DRMS is correct that linear low density polyethylene (LLDPE) is an <br />appropriate liner material for ore pad construction. However, there are <br />several advantages for using polyvinyl chloride (PVC) liner at the Van 4 <br />Mine that will allow for easier construction while providing long-term <br />environmental protection: <br />¦ PVC will allow for a much simpler field installation with the liner <br />being completely fabricated by the manufacturer; no field seaming <br />will be required resulting in excellent quality control of the liner <br />seaming construction. In addition, the liner can be delivered and <br />installed almost the same day given the relatively small size of the ore <br />pads. <br />¦ PVC liners are relatively easy to repair in the field if damaged during <br />delivery or operational activities. The onsite engineer and installer <br />will be responsible for inspecting the liner for defective or damaged <br />seams and panels. All repairs will be made in accordance with the ore <br />storage pad specifications. <br />¦ Even though PVC is susceptible to damage from ultraviolet (UV) <br />radiation, in accordance with the technical specifications, the liner will <br />be managed such that it will be covered during on-site storage and <br />• will be installed as quickly as possible. Long term storage of exposed <br />PVC liner material at the mines will not be permitted; delivery of the <br />PVC liner material will be scheduled to minimize any on site storage. <br />The ore pad design includes 18 inches of cover material be placed on <br />top of the PVC liner for protection of the liner from surface <br />operations; this bedding thickness satisfies the manufacturer's <br />requirements for long-term protection of PVC liner from UV radiation <br />(Colorado Lining 2010). <br />¦ PVC liner material can be degraded by microorganisms using the <br />material plasticizer as a source of food. The ore pad subgrade and <br />bedding material (e.g., development rock) are expected to be <br />relatively inert and dry (based on data collected during the EPP). <br />Biological degradation of the PVC liner is not expected to be a <br />concern. <br />¦ LLDPE is more resistant than PVC to puncture from burrowing <br />animals; however, this should not be of concern due to the active <br />surface operations at the mine and the lack of vegetation within the <br />vicinity of the ore storage pad. <br />a Similar to LLDPE, PVC has high puncture strength and excellent <br />abrasion resistance (Colorado Lining 2010). <br />0 <br />Final Van 4 RTC v2 Letter.doc