2010-02-17_REVISION - M1977285 - Laserfiche WebLink

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The site maps depict acceptable liner locations. All are shown to be 100 ft x 100 ft, a standard size which comports with the written description. The exception is at the St. Jude Mine, as depicted in Figure 2-2, which shows a 50 ft x 200 ft liner. This does not match the 50 ft x 100 ft description included in the narrative. Please clarify. Geotextile Material: The Division and Denison agree that due to the inherent limitations of the onsite soil for use as a soil liner, an impermeable geo-membrane is required. Denison has proposed using a 30-mil PVC liner, but the Division recommends that PVC not be used, since there is evidence that can degrade fairly fast, even when covered. The Division suggests that an LLDPE membrane be used. Even when exposed to ultraviolet light, LLDPE has a functional life of about 12 years before it starts to degrade. Since the liner will be used in an area where ore is stored in piles less than 15 feet in height and which has low potential for runoff, a 30-mil LLDPE liner membrane represents the minimum acceptable thickness. Please forward the appropriate specifications for this different liner material. Installation: The Division generally accepts Denison's proposed plan. To clarify and/or reiterate, the following comments are included herein. Surface preparation prior to liner deployment will include the placement, grading and compaction of the soil substrate such that it produces a smooth surface on which to bed the liner. The soil substrate should be screened, placed, and compacted as proposed. The compaction of the soil substrate should be tested once for every ore pad liner installed to verify adequate compaction of material (per manufacturer's liner requirements). All bedding material will be visually inspected prior to liner deployment, and all particles larger than 3/8 inch, or other angular or protruding materials, must be removed to maintain integrity of the liner. The anchor trench along the perimeter of each geo-membrane must be a minimum of 1 foot deep and 1 foot wide; 2 feet deep and 2 feet wide is preferable. A perimeter berm must be included to prevent runoff and runon, yet must be traversable by equipment and not allow damage to the liner. The anchor trench should be located at least a foot outside the crest of the berm. Trench backfill materials must be adequately compacted. The liner cannot be deployed when temperatures are below 35 degrees F, or when there is precipitation (or per manufacturer's recommendations, whichever is more conservative). Liner material will be covered to a depth of at least 1 foot of clean and screened earthen fill, to be placed and spread as proposed. All preparation and installation must proceed according to the approved plan, and overseen and documented by qualified onsite QC monitor, who, per Hard Rock/Metals Rules, must be a Colorado registered PE. Testing and Certification: All liner deployment QA/QC will include trial seam testing, field seam testing (pressure testing), and destructive testing (at a location selected by the QC monitor). Destructive testing of the field seamed geo- membrane will be approximately 24 inches along the seam and 12 inches across the seam, one sample each day or every 500 feet along the seams. Agreement by Operator: After questions and issues have been addressed, written agreement to the final plan and design is required from the operator. Upon receiving the operator's agreement, the Division will prepare any final QC specifications and standards for uranium ore storage, in a formal memo to the operator. DRMS will also issue its written approval of the design and plan. Please respond to the above items within 30 days of the date of this letter, by sending two sets of response materials directly to me at the Division's Durango field office: 691 CR 233, Room A-2, Durango, CO 81301. If there are any questions you may send them to me at the same address. Sincerely, 6t 1Bob Oswald Environmental Protection Specialist Encl: memo