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Cheryl Linden, Esq. <br />July 1, 2010 <br />Page 2 <br />The fourth enclosure is the description of the remediation selected for the <br />Dinero Tunnel from the U.S. Bureau of Land Management ("BLM") web-site. <br />This remediation, selected with the participation of the Colorado Department of <br />Public Health and Environment and DRMS, included installation of a concrete <br />bulkhead, which would allow the mine workings to flood and create a mine <br />pool. According to this BLM description: <br />The bulkhead is a permanent acidic mine drainage fix or source <br />control method much preferable and lower cost than the long <br />term operation and maintenance commitment required for water <br />treatment alternatives. Properly designed and constructed, <br />bulkheads will last indefinitely, and allow groundwater to return <br />to its original condition prior to being disrupted by mining. <br />The description also stated that: <br />As the water backs up into the mine workings, the acidic mine <br />drainage discharging. from the tunnel will be reduced <br />considerably. However, groundwater may appear uphill where <br />former seeps and springs existed that dried up or partially dried <br />up after the tunnel was built. These renewed springs are <br />expected to have good water quality due to the following <br />factors: <br />• Mine pools becomes (sic) anoxic (oxygen deficient) <br />which removes the major component in the acidic mine <br />drainage chemical reaction. Simply stated, water no <br />longer flows through the mine workings at a rapid pace, <br />leaching out metals in an oxidizing environment. <br />• Metals generated in the upper portion of a mine pool <br />tend to migrate (through small differences in water <br />density) to the bottom. This mine pool "stratification" <br />results in settlement of the metals and helps to remove <br />acidic mine drainage from release. <br /> <br />#1481824 Q den