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Identification of Alluvial Valley Floors <br />The general area in which the Bowie No. 1 Mine is situated contains several deposits of <br />alluvium. These alluvial deposits are derived from three sources: 1) Floodplain alluvium <br />(Qal) along the North Fork of the Gunnison River; 2) Valley fill deposits (Qvf) along a <br />portion of Steven's Gulch; and 3) Alluvial gravel (Qag). The valley fill deposits are located <br />along the North Fork Valley side slopes. <br />The applicant has identified alluvial/colluvial deposits in a second areathat islocatedalong <br />Steven's Gulch in the W'/2NW'/4 of Section 13, T 13S, R92W. As identified in the Phase 1 <br />AVF Study, the area is approximately 20 acres in size and is composed of valley fill <br />deposits (Qvf). The mine has a well in this deposit that can pump 30,000 GPD from the <br />alluvium/colluvium. Depth to water varies from about 7 feet in May to approximately 36 <br />feet in February. The area is high and isolated, but has been used for pasture -hay meadow <br />The area isnot flood irrigated, has not been flood irrigated, and is too high in elevation to <br />be flood irrigated (at this elevation, the growing season is too short for the normal flood <br />irrigated crops). Subirrigation is limited to areas along the stream channel itself. The area <br />is determined not to be an Alluvial Valley Floor based on its lack of flood irrigation <br />potential and lack of significant subirrigation. <br />An additional area along Steven's Gulch which lies within and to the south of the mine <br />permit area contains areas of alluvium. This area includes alluvial gravel deposits in <br />Sections 24 and25 (T 13S, R92W) andthe W'/2 of Section 30 (T 13 S, R91 W). Four separate <br />deposits have been identified within this area, as shown on Map No. 2-2 of the PAP. The <br />two larger deposits may meet the geomorphic criteria of Alluvial Valley Floors, but do not <br />meet the water availability criteria for either flood irrigation or subirrigation. Due to the <br />steep slopes, rocky surface, and lack of sufficient water, these areas cannot be flood <br />irrigated. Regarding subirrigation potential, the field investigation to detect subirrigated <br />species along Steven's Gulch did not identify any such species within these areas. <br />Vegetation suggests subirrigation does occur along portions of Steven's Gulch, but these <br />species are confined to the extreme channel bottom areas. Based upon this information, <br />these two areas are found not to meet the criteria for Alluvial Valley Floors. These are <br />older terraced deposits that have been dissected by stream channels, such that the channels <br />have completely cut through the deposit. T hese areas are found not to be Alluvial Valley <br />Floors. The larger of the two areas totals 11.5 acres, but the residential access road that <br />passes over the area reduces the acreage to below 10 acres. <br />A third area identified as having alluvial deposits is located along the North Fork of the <br />Gunnison River. These consist of floodplain and low terrace alluvial deposits and are <br />identified as (Al) on Plate No. 2 of the PAP. This area meets the geologic and hydrologic <br />criteria of an Alluvial Valley Floor in having unconsolidated streamlaid deposits with water <br />sufficient to sustain agriculture. Portions of the loadout facility and rail spur have been <br />part of the mine plan before August 3, 1977; therefore, their construction is grandfathered <br />(see Alluvial Valley Floor Findings that follow). <br />40 <br />