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_17_ <br />Upland Terrace Deposits <br />The upland terrace deposits adjacent to and within the permit area of the mine <br />consist of unconsolidated stream laid deposits laid down by the Animas River <br />when it flowed 400 feet higher than its present level. However, there is <br />insufficient surface water to sustain irrigation of the terrace deposits. <br />Regionally, these types of terraces are not irrigated, and are primarily used <br />for the production of dryland wheat. The potential for flood irrigating these <br />upland terraces using Animas River water is not feasible, given the length of <br />the canal needed and the fact that a canal would have to flow through the city <br />of Durango, Colorado. The coarser gravels at the base of these deposits act <br />as an underdrain and prevent subirrigation. Since the terraces are not <br />capable of irrigation or subirrigation, the Division finds that the upland <br />terrace deposits do not constitute an AVF. <br />The Stream Valley in Carbon Junction Canyon <br />Much of the stream valley of Carbon Junction Canyon flows over sandstone <br />bedrock. Alluvial deposits in this canyon are less than 50 feet wide and 10 <br />acres in extent. Alluvial deposits of such limited extent are not considered <br />substantial enough to support agricultural activities. Therefore, the stream <br />valley in Carbon Junction Canyon does not contain an AVF. <br />The Animas River Valley Within Two Miles of the Mining Operation <br />The Division has determined that the alluvial deposits and terraces directly <br />adjacent to the Animas River constitute an alluvial valley floor. The <br />unconsolidated stream laid deposits have the potential for flood and <br />subirrigation. These alluvial deposits are flood irrigated south and north of <br />the confluence of Carbon Junction Canyon with the Animas River. The applicant <br />has given the Division little information on subirrigation of the alluvium and <br />lower terrace deposits, however the Division has made a worst case assumption <br />that the deposits are subirrigated and therefore consiitute an AVF. <br />Alluvial Valley Floor Findings <br />1. Rule 2.06.8(5)(a)(i)(A)(I) <br />The Carbon Junction Mine will not mine within the Animas River alluvial <br />valley floor or have surface mining facilities located on the alluvial <br />valley floor. Therefore, the mining operation will not interrupt, <br />discontinue, or preclude farming on the alluvial valley floor. <br />2. Rule 2.06.8(5)(a>(i)(A)(II) <br />The mining operation will impact the quantity and quality of water <br />tributary to the Animas River alluvial valley floor. However, the <br />impacts to the quality and quantity of water will be insignificant and <br />not cause material damage to the surface and ground water systems <br />supplying the alluvial valley floor. <br />