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Mayflower Mill - Tailings Pond No. 4 <br />Seepage Control Plan <br />Page 4 <br />1 <br />1. Water quality and phreatic monitoring well installation. The wells <br />installed in August of 1982 will be monitored on a regular basis to <br />determine the current status of seepage water quality and phreatic <br />levels within the pond embankment. Water quality will be monitored <br />for parameters contained in the NPDES permit issued for the tailings <br />pond outfalls. Once seepage water quality is known, then actual impa t <br />of the seepage on adjacent water courses can be determined. The pro- <br />posed monitoring program has already been initiated and sufficient <br />data should be compiled by July 1983. ,o <br />2. Modification of tailings depositional methods from modified downstream <br />to upstream. Tailings depositional methods have been shifted from the <br />modified downstream to the upstream method to increase the width of <br />the interior beach area (see Figure 3 ). This modification of the <br />tailings disposal method will place the ponding area further from the <br />outside embankment, permitting the toe drain more time and area for <br />drainage of phreatic water. Ultimately this will lower the phreatic <br />level in the embankment such that migrating water will not reach the <br />embankment toe. Tailings deposition in the upstream method has already <br />commenced and will continue until June 1983, at which time the effec- \boOd <br />tiveness of the tailings deposition modification will ha_known. <br />3. Installation of a bentonite seal at the abutment of the tailings em- <br />bankment and the old roadbed (see Figure 4 ). The old roadbed will' <br />be trenched and a bentonite seal placed at the point where the tailings <br />embankment abuts the roadbed. One of the major points of seepage is <br />occurring where the pond water is migrating around the tailings embank- <br />ment and through the relatively coarse roadfill material. Application <br />of the bentonite in the prescribed manner will hopefully eliminate <br />seepage at this point. This seepage control activity should be completed <br />by July 1983. <br />4. Installation of a drain and sump collection system around the embankment k`' <br />perimeter. If the preceding seepage control measures prove to be in- � % /1 <br />effective and the quality of seepage waters is such that Potential for <br />impacting adjacent water courses is possible, then plans for installation <br />of a drain and sump collection system at the toe of the tailings embank- <br />ment will be investigated. <br />I believe the preceding plans presented for controlling visual seepage noted <br />from Tailing Pond No. 4 sufficiently addresses requirements placed at <br />Part D of the mill discharge permit. A report detailing the status of the <br />control plans will be submitted at the interval required. <br />5 <br />