1999-06-10_REPORT - M1977378 (2)

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Site Reclamation Activity April 1998 - March 1999 Page 8 MONITORING - Discussion of Water Quality Monitoring Results 1) Mayflower Millsite area The Animas River and Boulder Creek monitoring results continue to exhibit increased zinc and manganese concentrations between the upstream and downstream monitoring points during the spring sampling event although the differential was less for the spring, 1999 sample. Summer or fall sampling events have continued to show smaller or no significant change between these same points . As mentioned in previous reports, Sunnyside has sampled groundwater springs behind and above Pond No.4 and one surfacing in the vicinity of the Engineering Office Site buildings. These seeps indicate that background groundwater quality varies and can contain significant levels of Fe, Mn and Zn. Sunnyside will collect additional information on these sites in 1999. In addition, if upland groundwater is contacting tailings material in the spring, the projects planned for 1999 (TR-21)could have a beneficial effect on the spring monitoring differential. Other surface and groundwater sample results in the Mayflower Mill area (Pond No. 3 stream SCTP3-1 and SCTP3-2 and wells EOMW1 and EOMW2) were at or below levels of metals observed in the past. 2) American Tunnel area Cement Creek monitoring reflects some improvement due to stream treatment. Seeps entering the stream bed between CC1 and CC2 carry enough metals that CC2 quality is not the same as treated effluent from the American Tunnel treatment system even though basically all of the stream flow has been treated from August through the end of April, since 1996. The seep ATS2 , originally from the toe of the American Tunnel waste dump, has maintained the level of improvement first seen after completion of the waste dump reclamation. The seep ATS1 appears to have disappeared or relocated due to the reclamation of the waste dump. 3) Terry Tunnel/Lake Emma Eureka Creek monitoring above the Terry Tunnel continues to show the same level of improvement, as compared to previous years. 4) Mine Pool The Terry Tunnel and American Tunnel bulkhead mine pool water quality samples submitted with this report reflect the quality of water behind the bulkheads.