2001-06-08_REPORT - M1977378 (2)

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Annual Update Sunnyside Mine Bulkheads Page 4 Mine Pool: The American Tunnel bulkhead valve was closed in September 1996 and the Terry Tunnel bulkhead valve was closed in July 1996. Since September 1996 the mine pool has been allowed to rise towards physical equilibrium. As of the end of the report year (March 30, 2001), the mine pool had reached approximately 11,661 feet MSL. The rate of rise of the mine pool leveled off in November of 1999 and during the 2000 report year Sunnyside submitted monitoring data to DMG with the conclusion that physical equilibrium had been reached (DMG agreed) thereby starting the waiting period for final closure of the American Tunnel. Since physical equilibrium had occurred and further alkaline injection would not occur through the Terry Tunnel, Sunnyside submitted technical details to DMG for an additional near - surface bulkhead to be placed in the Terry Tunnel. This bulkhead's purpose was to stop flows to surface through the tunnel from seeps entering the Terry Tunnel downstream of the existing bulkhead. The submittal was approved and implemented during the 2000 report year. The Terry Tunnel surface disturbance was reclaimed during the report year although some finish work may need to be done during the 2001 report year. Included in Appendix B is monitoring data and a graph of the mine pool pressure readings through March 2001. Study Update: Attached in Appendix B is the data collected through March 2000 for the seep, spring, and flowing adit inventory and monitoring required by TR -14. During the report year no new monitoring sites were added and no sites were deleted. Sunnyside visited all identified sites twice during the report year, collected field data, and sampled for lab analysis more than the 20 percent of the sites the monitoring program (attached in Appendix B) requires. Data summary sheets are included in Appendix B.