Laserfiche WebLink
The subsidence portion of the application is in compliance with the <br />Regulations. <br />XVI. Concurrent Surface and Underground Mining <br />This section is not applicable to the Orchard Valley Mine. <br />XVII. Operations on Alluvial Valley Floors <br />The discussion of Alluvial Valley Floors can be found on pages 5-6, <br />Section 2.06 of Volume l; in the AVF Appendix A, Volume 4 and in the <br />Geo-Hydro Phase 2 studies. <br />Identification of Alluvial Vallev Floors <br />The general area in which the Orchard Valley Mine is situated contains <br />several deposits of alluvium. These alluvial deposits are derived <br />from three sources: 1) Flood-plain alluvium (Qal) along the North Fork <br />of the Gunnison River; 2) Valley-fill deposits (Qvf) along a portion <br />of Steven's Gulch; and 3) Alluvial gravel (Qag> divided into three (3> <br />age categories younger (Qagy), middle (Qagm) and older (Qago). The <br />valley fill deposits are located along the North Fork Valley side <br />slopes. <br />Cyprus has identified alluvial/colluvial deposits in a second area <br />that is located along Steven's Gulch in the W 1/2 NW 1/4 of Section <br />13, T13S, R92W. As identified in the Phase 1 AVF Study, the area is <br />approximately 20 acres in size and is composed of valley-fill deposits <br />(Qvf). The mine has a well in this deposit that can pump 30,000 GPD <br />from the alluvium/colluvium. Depth to water varies from about 7 feet <br />in May to approximately 36 feet in February. The area is high and <br />isolated, but has been used for pasture-hay meadow. The area is not <br />flood irrigated, has not been flood irrigated, and is too high in <br />elevation to be flood irrigated (at this elevation, the growing season <br />is too short for the normal flood.irrigated crops). Subirrigation is <br />limited to areas along the stream channel itself. The area is <br />determined not to be an Alluvial Valley Floor based on its lack of <br />flood irrigation potential and lack of significant Subirrigation. <br />An additional area along Steven's Gulch which lies within and to the <br />south of the mine permit area, contains areas of alluvium. This area <br />includes alluvial gravel deposits in Sections 24 and 25 (T13S, R92W) <br />and the W 1/2 of Section 30 (T13S, R91W). Four separate deposits have <br />been identified within this area, as shown on Map No. 2-2. The two <br />larger deposits, labeled Qagy and Qago, may meet the geomorphic <br />criteria of Alluvial Valley Floors, but do not meet the water <br />availability criteria for either flood irrigation or Subirrigation. <br />Due to the steep slopes, rocky surface, and lack of sufficient water, <br />these areas cannot be flood irrigated. Regarding Subirrigation <br />potential, the field investigation to detect subirrigated species <br />along Steven's Gulch did not identify any such species within these <br />areas. Vegetation suggests Subirrigation does occur along portions of <br />Steven's Gulch, but these species are confined to the extreme channel <br />bottom areas. Based upon this information, these two areas are found <br />-~3- <br />