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stems/acre. The species diversity standard was developed from the baseline and <br />reference area data. These revegetation success standards are to be achieved <br />during the last two years of the liability period. <br />Final bond release requires a demonstration that the post mining land use has been <br />achieved. The post mining land uses at the Bourg Mine are rangeland and wildlife <br />habitat. <br />Lastly, for final bond release an evaluation of the surface and ground water <br />impacts relative to the statement of probable hydrologic consequences is <br />necessary. The analysis must show that onsite impacts have been minimized and <br />that offsite impacts have been prevented. Any observable hydrologic trends are to <br />be discussed. <br />III. OBSERVATIONS AND FINDINGS <br />A. PHASE II <br />Topsoil replacement at the Bourg Mine was completed in 1984 for the East Dump <br />and in 1988 for the remainder of the permit azea. In July 1989, the DMG measured <br />replaced soil depths. Nine holes were dug in the 1984 reclaimed area and nineteen <br />holes were dug in the 1988 reclaimed azea. In the 1984 area, topsoil depths ranged <br />from 9 inches to l7 inches and averaged 15 inches. In the 1988 area, topsoil depths <br />ranged from 11 inches to 32 inches and averaged 18 inches. The sampling indicated <br />that the site was in compliance with the approved plan for topsoil replacement. <br />An alternative sediment control system was approved in 1988. Terrace benches <br />were constructed to control erosion prior to revegetation establishment. The <br />benches in combination with the established vegetation are the only form of <br />sediment control left on the site as all sediment ponds were removed and <br />reclaimed. Flatiron Companies provided a site specific comparison of settable <br />solids for the reclaimed and undisturbed lands in their application for an altemative <br />sediment control system. The plan proposed to replace four sediment ponds at the <br />site with treatment facilities consisting of terrace benches constructed at two <br />hundred feet intervals. This proposal was accompanied by a SEDCAD (Sediment, <br />Erosion, Discharge by Computer Aided Design) to demonstrate that the reclaimed <br />area would produce less sediment loss than adjacent undisturbed areas. The plan <br />was approved by the DMG in 1988. The effectiveness of this treatment was <br />monitored by annual surveys of vegetative cover and rill and gully development. <br />During the spring of 1989, two gullies formed in the reclaimed area. It was <br />determined that reshaping the gullies into one permanent gully would create a stable <br />drainage and be consistent with the adjacent undisturbed lands. The permanent <br />gully was approved by the DMG in TR-5. It has been found to be stable and is <br />functioning as planned. No fiutlter rill and gully repairs were necessary. <br />Bourg Mine 4 Final Bond Release <br />Permit No. C-81-021 January 18, ?000 <br />