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The flow from above the Longfellow mine will be routed around the waste rock <br /> pile and the constructed pond. A portion of this drainage will be piped to a <br /> large concrete box which will be filled with lime. The supernatant solution <br /> will then be injected into the constructed pond. Also, any drainage from the <br /> south will be ditched around the waste rock piles and constructed pond. Both <br /> draining adits will be excavated and filled with limestone. The drainage from <br /> the southern adit will be piped around the waste rock pile. <br /> The estimated cost for remediating the Longfellow-Koehler area is $272,000. <br /> The cost breakdown is as follows: <br /> 1) Ditching $ 2,000 <br /> 2) Pond Excavation 60,000 <br /> 3) Pond Lining 40,000 <br /> 4) Dam Construction 5,000 <br /> 5) Anoxic Limestone Drains <br /> Koehler Tunnel 35,000 <br /> Longfellow 37,000 <br /> 6) Cap Waste Rock 25,000 <br /> 7) Aqueous Lime Injection 45,000 <br /> 8) Organic Substrate 18,000 <br /> 9) Project Management and Development 35.000 <br /> TOTAL $272,000 <br /> Additional monitoring could be done at this site to determine the flow from <br /> the southern adit, the relative contribution of metals from each source, <br /> whether the water from the south portion of this area originates in the talus, <br /> and whether anoxic limestone drains are feasible. In order to determine the <br /> flow from the southern adit, the collapse material must be removed. This will <br /> also help to determine the source of the water in the south part of this area. <br /> Also, once that is done, each source can be monitored separately. In order to <br /> determine whether anoxic limestone drains are feasible, dissolved oxygen and <br /> EH measurements must be made at each adit. <br /> Carbon Lake Area (Main Stem) <br /> This site has three large waste rock piles and several small waste rock piles <br /> in or near the drainage above sampling site MC-3 (Figure 3) . A trans-basin <br /> diversion limits the amount of run-on water that comes in contact with the <br /> waste rock in most locations. There are several alternatives to reducing the <br /> metals from this site. The cheapest method will be to remove the lower-most <br /> waste pile adjacent to the stream channel and consolidate it with one of the <br /> relatively dry waste piles. The Lowermost waste pile is evidently located <br /> over a perennial spring. The water draining from this waste pile, in July, <br /> 1993, had a pH of 2.5 as compared to 5.5 above the pile. Below the confluence <br /> of the drainage from the lowest waste pile and the stream, the pH was measured <br /> at 3.3. To remove the lowest waste pile, construct run-off and run-on <br /> controls around the other waste piles and revegetate the barren areas would <br /> cost approximately $50,000. This cost does not include revegetation of the <br /> consolidated waste pile, which would add approximately $10,000 to the cost. <br /> -8- <br />