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MAYFLOWER MILL AREA: <br /> (6) Mill Tailings Pond #4 Wells Figure 6 <br /> Some wells were destroyed in the reconstruction of Tailings <br /> Pond 4 berm in the summer 1989 . Section 22+00 wells are <br /> intact and levels show the expected decrease in water <br /> level-approximately 25' at well 13A86 . This line of wells <br /> plus the cluster wells ' shown on the area map will be <br /> monitored in the future. <br /> AMERICAN TUNNEL AREA <br /> (1) Cement Creek (CC-1 , CC-2) , Table 10 and Table 11 <br /> Typically the American Tunnel discharge AT004 is reflected <br /> in CC2 data . The improved quality of AT004 is seen in CC2 <br /> having higher ph, lower dissolved metals and lower TSS than <br /> CC1 above the mine. The degree of improvement is effected <br /> by what percentage of CC2 is made up by AT004. <br /> A bioassay of CC1 was done in spring of 1990 in conjunction <br /> with the first quarter Biomonitoring of AT004. The creek <br /> was determined to be toxic with Fathead Minnow LC50=33a and <br /> Ceriodaphnia dubia LC50=1o . This water was expected to be <br /> toxic above the mine as the ph is generally between 3 and 5 <br /> units and dissolved metals are high. Reconstituted lab <br /> water will be used as dilution water in all A`1'004 <br /> bioassay. CC1 will be sampled with each test to determine <br /> the hardness of the dilution water for the AT004 biotest. <br /> (2) American Tunnel Waste Pile Seeps (ATS-1 , ATS-2) Table 12 and <br /> Table 13 <br /> A slotted pipe drain was installed around the toe of the <br /> dump with a sample collection point located at ATS-2 in <br /> October 1989. Efforts will be made in the summer of 1990 <br /> and 1991 to estimate flows and to increase sampling to a <br /> monthly schedule. Samples taken in 1989 continue to show <br /> elevated TDS and dissolved metals . More data will be <br /> necessary to determine the best solution to this problem. <br /> Diversion to existing treatment ponds and wetland <br /> establishment are being considered . Sample sites were still <br /> under snow in May 1990 and so were sampled in June 1990 with I <br /> results pending. <br /> -9- <br />