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Annual Update <br />Sunnyside Mine Bulkheads <br />Page 3 <br />• Cement Creek Treatment <br />Diversion and treatment of Cement Creek was continuously active from June 1996 <br />through part of the 1999- report year. The entire stream was diverted and treated <br />during low flow conditions (August or September — April) and until June 1, 1999, the <br />quantity diverted and treated during high flow (April — August or September) was <br />regulated at the approximate capacity of the water treatment plant. On June 1, 1999 <br />Sunnyside discontinued treatment until November 22, 1999 when treatment was <br />restarted. From November 22, 1999 through March 31, 2001, Cement Creek diversion <br />and treatment was active. <br />This treatment is a temporary measure to offset or balance any short-term impacts that <br />may have resulted from implementation of the A List remediation projects or from <br />effects of the mine pool. This purpose, based on stream monitoring, had expired and <br />treatment was discontinued for part of the 1999 report year. When zinc levels in <br />Cement Creek above the American Tunnel treatment plant (CC -1) appeared to be <br />elevated from past monitoring results and during the fall seep, spring and flowing adit <br />monitoring session it was discovered that monitoring sites were flowing at above <br />normal quantities (most notably the Mogul Level #1 adit (M -1)), treatment was <br />restarted. This was a temporary measure taken to minimize any impacts on A -72 from <br />the increased flows. Potential causes of the increased flows could be; above normal <br />levels of precipitation; natural flow regimes being restored as the mine pool rises and <br />groundwater flows travel around the Sunnyside Mine workings instead of draining <br />through the American and Terry Tunnels; or a fracture connection exists between the <br />Mogul workings and the Sunnyside Mine workings. Because of continued uncertainty <br />over the reason for the increased flows, Sunnyside maintained the temporary diversion <br />and treatment of Cement Creek through the 2000 report year. <br />• Reporting <br />SGC is current on all Consent Decree monitoring and reporting requirements. <br />