2002-02-07_REVISION - M1976020 (7)

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Thomas pit is located between Miles 81.4 and 81.5 markers in the River. Six cross sections on this stretch of the river have been monitored since 1995. These are called 4+09, 9+93, 14+68, 17+39, 24+96, and 27+54. These cross sections are shown in plan view on Map Exhibit C-3. The cross-sec- tions are shown on Map C-3. These cross sections will be re-surveyed on a yearly basis and a report will be made of the results. The report will be submitted to both the US Army COE and the CDMG office in Durango. The current lease with the landowners lasts until March of 2021. River mining is planned until this date under the parameters described above. Since this is a highly aggrading area from a river leav- ing an extremely rugged mountain area, as demonstrated in the Wright McLaughlin study (1981), this area is actually more stable with carefully planned extraction. If extraction does not occur, de- position of large amounts of gravel will continue to build up and raise the level of the river above the surrounding floodplain. When a large flood occurs, it would cause more damage and could change the river location. 13y limited extraction to a stable grade, the river will stay within a much more limited area and will not threaten outside areas to the same degree during a flood. This was also the conclusion of the technical personnel who wrote the 1998 DMG study [itledIn-Stream Aggregate Extraction and Reclamation Guidance Document.This area and the OurayjRidgeway area on the Uncompaghre River are two prime examples of a highly aggrading river areas in Colo- rado that should be permitted to mine under controlled conditions. 2. To r~soil Handling for River Mining Approximately 4750 cubic yards of topsoil has been salvaged and stockpiled from a portion of the plant and yard area and is stored along the west boundary of the permit, adjacent to the irrigation ditch. Much of this yard area has little topsoil available. Certain substitute soils may exist below portions of the stockpile areas and can be used for reclamation. Also, since portions of these areas will remain for commercial use, less topsoil will be needed for reclamation. No topsoil or overbur- den is involved in the river harvesting, since all materials and sand and gravel alluvial material. No soil will be needed to reclaim the river channel itself. As explained in the reclamation plan, this top- soil will be used to restore part of the yard area to irrigated pasture use. Thomas Pit 2/02 9