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<br />Letter to Kurt Nielsen 3 Mav 23, 1999 <br />still integral to the function of the pond because a homogeneous fill embankment is proposed. The DMG <br />has identified the following issues relative to the pond liner: <br />a. Section 4.0 of the specification states that seaming of joints shall be by the extrusion method. This <br />is not acceptable. The majority of the liner seaming should be by the hot shoe fusion or wedge <br />method. with only patching and detail work completed using extrusion welding. <br />b. A quality assurance plan for the liner installation must be provided. This would detail the type and <br />frequency of testing to be applied to seam integrity testing. Pages from a draft DMG guidance <br />document on liner design are enclosed and may assist American Soda in the development of a <br />quality assurance plan. <br />c. A liner installation report and certification will be a required component of the pond certification <br />discussed in item 4.c. above. <br />d. Page 8 of General Specification GC-18 provided to the Division is garbled and page 9 is missing. <br />Please provide five copies each of these pages. <br />11. Section 5.0 of [he Subsidence Monitoring Plan provided describes mitigation steps to be taken only <br />if subsidence is detected in [he vicinity of the dissolution surface. DMG will require submittal of a <br />mitigation or contingency plan to be implemented if the monitoring demonstrates subsidence or fracturing <br />:, the Mahogany Zone or indicates the potential for future fracturing of the zone. Potential fr•r commingling <br />~f the upa~r a::d lo~~~er aquifers and impacts to [he future minability of the Mahogany Zone are ::nacceptable <br />res~~;~s if caused by solution mining of nahcolite. Please provide triggering criteria and mitigation steps <br />relative to subsidence monitoring that will be protective of the Mahogany Zone. <br />12. Reference is made to the letter from General Chemical dated May l7, 1999, of which American <br />Soda was previously provided a copy. Four points for discussion are made in the General Chemical letter <br />under the heading "Subsidence Monitoring Recommendations." These four points are further discussed <br />here. <br />a. Please address General Chemica]'s recommendation to fix a survey point directly to well casings <br />and to increase the surface monument survey frequency to once every six months. <br />b. It is DMG's position that items 2 and 3 from the General Chemical letter will be addressed under the <br />requirements of section 3.3 from the Subsidence monitoring plan. It is'reiterated that provision and <br />DMG acceptance of a solution cavity characterization evaluation is a prerequisite for commercial <br />mining under a reclamation permit issued to American Soda. <br />c. Item 4 from the General Chemical letter addresses the duration of subsidence monitoring. The <br />DMG assumes that production well abandonment and reclamation procedures will not affect <br />American Soda's ability to continue with Time Domain Reflectometry monitoring. That being the <br />case, the DMG agrees that subsidence monitoring should continue beyond the proposed 5-year <br />timeframe until an adequate understanding of the data and the potential for subsidence is attained. <br />At that point, American Soda could apply to the DMG for modification or termination of the <br />monitoring requirements. <br />13. Reference is made to the letter from General Chemical dated May 12, 1999, of which American <br />Soda was previously provided a copy. Please address the feasibility and necessity sampling the liquid <br />