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5.3.1.4 No. 5 Dam (Mayflower Dam) Seepwater Pumpback Line <br />Description: Prior to construction of the extension of the Pumpback line in 1997, the <br />Mayflower Pumpback system intercepted Seepwater from the toe of the dam and pumped it over <br />the crest of No. 5 Dam to the north end of the impoundment, where it discharged in the general <br />vicinity of the decant risers. The 1997 extension of the lines consisted of burying 5900 feet of <br />14-inch SDR26 HDPE pipe and 3800 feet of 12-inch SDR21 HDPE pipe to deliver the collected <br />seepage to a lime mixing box at the south end of the impoundment. In addition, the extension <br />and use of the 14-inch line now allows for reverse flow to deliver water to Clinton cut-out, <br />located halfway between No. 5 Dam and the mixing box. With the option of delivering collected <br />seepage to the mixing box or the Clinton cut-out, better lime use can be achieved and introduced <br />more effectively to treat the water at more that one location within the Mayflower pond. <br />Location: The new 12-inch Seepwater Pumpback line connects with the existing 12-inch <br />delivery line at the north end of No. 5 Dam. The buried Pumpback line traverses the tailing pond <br />in a southwesterly direction for 3800 feet where it joins the buried 14-inch line for 5900 feet <br />trending in a more west-southwesterly direction to reach its final destination-lime mixing box. <br />Spill Potential: Rupture of either of the pipelines (12- or 14-inch) would result in water <br />reporting to the Mayflower tailing pond. In the unlikely event that such a situation existed, the <br />collected seepage water would be treated within the system in a manner that existed prior to the <br />construction of the extension lines. Therefore, potential adverse effects on the water quality <br />dischazge are minimal. <br />• Potential Volume Spilled: A major rupture in the line could result in the discharge of several <br />thousand gallons of collected Seepwater into the Mayflower tailing pond. <br />Prevention and Control: Periodic checking and maintenance of the pumps and lines aze the best <br />methods of ensuring against failure of the lines. <br />Countermeasures: Should either of the Pumpback lines rupture, the pumps delivering water to <br />the lines should be turned off, the lines repaired, re-tested for leakage, and then the system should <br />be re-started. As stated in the "Spill Potential" section above, any spill of collected Seepwater <br />within the Mayflower tailing pond would eventually be treated in a manner that existed prior to <br />construction of the Pumpback line extension. <br />Nearest Clean-up Equipment: Portable engine-driven pumps are located in the Open Pit <br />Wazehouse. Flexible plastic pipe and couplings aze also located in the Wazehouse. <br />Visual Inspections and Integrity Testing: Visual checks of the pump system and pipelines are <br />conducted daily. <br />Reporting: In the event of Pumpback line rupture, a "Spill and Release Information Sheet" <br />(Appendix 1) will be completed immediately and given to the Environmental DeparGnent. <br />• Conformance with Applicable Requirements: At the time of this writing (May 2004) the <br />Mayflower (No. 5 Dam) Seepwater Pumpback Line is in conformance with applicable regulatory <br />requirements. <br />50 <br />