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Trout Creek <br />Alluvial deposits on Trout Creek meet alluvial valley floor criteria based on extensive acreage of flood <br />irrigated hayland, potential for flood irrigation and a presumed capability to support subirrigated <br />vegetation. The Division has determined that Trout Creek is an AVF as delineated on Map 15. <br />Twentymile Coal Company does not propose to undermine Trout Creek. <br />Foidel Creek/Middle Creek Confluence <br />The alluvial body at the confluence of Foidel Creek and Middle Creek, extending from the County Road <br />No. 33 crossing of Middle Creek, upstream on both Foidel and Middle Creeks, to the first Trout Creek <br />irrigation diversion ditch, does meet alluvial valley floor criteria based upon existing flood irrigation and a <br />presumed capability to support subirrigated vegetation. This area is also delineated on Map 15 of the <br />PAP. Permit Revision No. 5 approved undermining a portion of the Foidel Creek AVE <br />AVF Determination - Negative Determination <br />Foidel Creek <br />Previous to PR-03, an alluvial body along Foidel Creek in sections 28, 29, 31 and 32, T5N R86W, was <br />determined not to be an AVF based on a finding of insufficient water to support flood irrigation, and a <br />determination that subirrigated areas were less than 10 acres in extent and supported species which were not <br />agriculturally useful. <br />Due to the significant expansion of mining operations proposed in the LOM revision application <br />(PR-01), the potential impacts to identified alluvial valley floors were reevaluated. Areas previously <br />determined by the Division to not meet alluvial valley floor criteria were not reexamined. As a result of <br />additional vegetation data and land use information submitted by the applicant and site visits made by <br />Division staff, however, certain lands previously identified as alluvial valley floors were found not to meet <br />AVF criteria. <br />Based on the limited extent of arable land and relatively high percentage of non-agriculturally useful <br />species as documented by species composition data included in the September 22, 1986 submittal, the <br />Division concluded that the area of subirrigated alluvium on lower Foidel Creek denoted as "Pasture 19" <br />on supplemental Map No. 1 is not an alluvial valley floor. The extent of farmable acreage would be 10 <br />acres or less. The areas are not presently and have not historically been farmed and evidence presented <br />indicates that farming is not typically practiced on similar parcels in the region. <br />During PR03 review, the Division determined that areas upstream of the Leiske ditch crossing of Foidel <br />Creek as shown on Map 15 (Sections 14, 21, 22, 23, and 28, TSN, R86W) are not alluvial valley floors. <br />This determination was based on the lack of sufficient water for flood irrigation, the lack of flood <br />irrigation, the small size of the valley bottom and the narrow nature of the stream, and the lack of <br />meaningful production or cover differences between the creekside and upland vegetative communities. <br />Therefore, in summary, the Division fmds that all valley bottom areas along Foidel Creek upstream of the <br />County Road No. 33 crossing are not alluvial valley floors. <br />Middle Creek <br />Prior to PR-03, no previous AVF determination had been made for areas above the Foidel/Middle Creek <br />confluence AVF on Middle Creek as these areas were not proposed to be affected or impacted by the <br />27