Laserfiche WebLink
not to meet the criteria for Alluvial Valley Floors. These are older <br />terraced deposits that have been dissected by stream channels, such <br />that the channels have completely cut through the deposit. These <br />areas are found not to be Alluvial Valley Floors. The larger of the <br />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 <br />the North Fork of the Gunnison River. These consist of floodplain and <br />low terrace alluvial deposits and are identified as (Al> on Plate <br />No. 2. This area meets the geologic and hydrologic criteria of an <br />Alluvial Valley Floor in having unconsolidated stream-laid deposits <br />with water sufficient to sustain agriculture. Portions of the loadout <br />facility and rail spur have been part of the mine plan before <br />August 3, 1977; therefore, their construction is grandfathered (see <br />Alluvial Valley floor Findings that follow). <br />Adjoining these deposits on both sides of the river are deposits of <br />course-grained outwash (pediment) labeled Qpc. Geomorphically the <br />deposits form lobes and undulating topography that extend down to the <br />low alluvial terrace deposits of the identified Alluvial Valley <br />Floor. These deposits are easily identified on Ma p.B-3 by the abrupt <br />change in slope as one leaves the flood-plain and terrace deposits <br />along the river. The slope outwash deposits are flood irrigated, <br />which meets the hydrologic criteria of an Alluvial Valley Floor, but <br />geologically they are mixtures Mancos shale and eroded alluvium that <br />were primarily deposited by gravity flow and sheet wash. As such, <br />they do not meet the criteria of being stream laid. During the <br />original review of the permit application, these deposits were <br />identified as part of the AVF. But further review and interpretation <br />of additional hydrologic and geologic information during the summer of <br />1991 indicated that the area did not meet the strict definition of an <br />Alluvial Valley Floor. Deposits at the mouth of Steven's Gulch mapped <br />as Qpc on Plates 1 and 2, of the Geo-Hydro AVF Phase I study (Volume <br />4) are identified as slope outwash deposits. As such, they also do <br />not meet the strict definition of undonsolidated stream-laid <br />deposits. The U.S. Soil Conservation Service has identified the Aqua <br />Fria soils in this area as "Farmland of Statewide Importance" and not <br />as prime farmland. Because much of the area is occupied by <br />flood-irrigated orchards, the Division feels these areas are worth <br />protecting for their agricultural contribution. Although these areas <br />are not AVF's, the Division will require that these areas be treated <br />as AVF's with respect to assuring that their essential hydrologic <br />functions be restored. On the basis of the information provided, the <br />North Fork of the Gunnison and its associated alluvium, identified as <br />(Al) on Plate No. 2 in those portions of Sections 29, 30 and 31 in <br />T135, R91W, and Section 36 in T13S, R92W, which lie roughly between <br />the Farmers Ditch and the North Fork of the Gunnison River, are <br />Alluvial Valley Floors. Slope outwash deposits and alluvial deposits <br />located upslope (northwest) of the Fire Mountain Canal did not meet <br />the geologic and water availability criteria, and were given no <br />further consideration. The Alluvial Valley Floor along the North Fork <br />continues downstream, as shown on Map 5-2. <br />_ qq_ <br />