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13 ft throughout the reach containing these pits. Natural river processes have allowed mining- <br />induced incision to extend into areas that are located both upstream and downstream from the <br />pits, but incision depths in those areas are not as well known. <br />A detailed evaluation of mining impacts is beyond the-scope of this report, but they potentially <br />include increased bank erosion, lowering of the water table beneath the valley floor, loss of <br />riparian habitat, reduced averbank flood depths near the pits, and increased overbank flood <br />depths farther down-valley in areas that maybe considered for future development. <br />During the Animas River Stakeholders meeting on Apri129, 2003, it became clear that greater <br />efforts are needed to identify and implement sustainable mining practices. This process will <br />benefit immenselyfrom open cooperation among regulators, operators, consultants, and others. <br />Information sharing and dialogue will be critical, <br />This report (superceding drags provided on November 12 and 14} contributes to dialogue by <br />critically examining relevant documents and recent monitoring data. It fills a need because such <br />a broad review would be too costly for individual agencies or operators to conduct. The report is <br />based mainly on materials in USACE files, but also on examination of aerial photographs, very <br />limited field work, and other sources. Some of the information here is preliminary or <br />approximate, and relevant data unavailable during this analysis may exist elsewhere. I hope that <br />the report will be useful to others, and will stimulate continuing positive discussion and research. <br />Comments and corrections are welcome. <br />I thank Kara Hellige and Lesley Mc Whirter for access to USACE files though several FOIA <br />requests. <br />2.0 APPLICABLE SPECIAL CONDITIONS IN 199(r-1997 PERMITS <br />The existing permits were signed behveen December, 1996 and February, 1997 for an initial <br />three-year period, and later were extended twice until November 30, 2003. The following list <br />includes only those Special Conditions which are addressed in this report, These conditions <br />were initially uniform for all pits before individual modifications that are discussed below in the <br />sections concerning specific pits. <br />• Establish and survey topographic cross sections between upstream and downstream pit <br />boundaries at 5400 ft intervals. <br />~ Survey the cross sections approximately 30 days before and 30 days after mining, or in <br />August and March of non-operational years. [Note: in this report, a spring survey <br />preceding the annual high-flow period is considered to be apost-mining survey, showir <br />mined areas with relatively little naharal modification; conversely, a midsummer to ea*I <br />winter survey, performed after the spring runoff when natural channel modifications ~-: <br />occurring more slowly, is considered to be apre-mining survey.) I <br />Provide cross sections, streambed profiles, and a channel monitoring report twice <br />annually. <br />Gillam to Hellige, Nov. 28, 2003 page 2 <br />