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Map No. 1 is not an alluvial valley floor. (note 1) [A negative determination has also <br />been made for sub-irrigated portions of Middle Creek between the Foidel Creek <br />confluence and the first Trout Creek irrigation diversion in Section 12, TSN, R86W due <br />to [he limited extent of farmable acreage resulting from the narrow alluvial body <br />(averaging less than 500' in width) which is bisected by the meandering channel of <br />Middle Creek.] In both instances the extent of farmable acreage would be 10 acres or <br />less. The azeas are not presently and have not historically been farmed and evidence <br />presented indicates that farming is not typically practiced on similar parcels in the region. <br />Prior to the Division's finding made for Foidel Creek Mine PR-03 (Eastern Mining <br />District), an alluvial body in Sections 21, 22 and 28 (TSN, R86W) on Foidel Creek was <br />identified as an AVF. The applicant requested during Foidel Creek Mine's PR-03 review <br />process that azeas along Foidel Creek in sections 14, 21, 22, 23, and 28 TSN R86W not <br />be designated as alluvial valley floors. This information is contained in the Foidel Creek <br />Mine permit application (C-82-056), as Exhibit 42a and consists of vegetation sampling <br />data, valley floor cross-sections, and a transect location map. The applicant also refers to <br />the flow volume of Foidel Creek and its pre-mine intermittent nature. There is no <br />indication of past or current flood irrigation of these azeas along Foidel Creek. Based on <br />the lack of sufficient water for flood irrigation, the lack of flood irrigation, the small size <br />of the valley bottom and the narrow nature of the stream, and the lack of meaningful <br />production or cover differences between the creekside and upland vegetative <br />communities, the Division has determined [hat azeas above the Leiske ditch crossing of <br />Foidel Creek as shown on Foidel Creek Mine Map 15 aze not alluvial valley floors. <br />Therefore, in summary, the Division finds that all valley bottom areas along Foidel Creek <br />above the County Road No. 33 crossing are not alluvial valley floors. <br />Effects of Mining on Identified Alluvial Vallev Floors <br />Due to the development of relatively saline (2000-4000 umhos/cm) springs along the toe <br />of backfilled spoils at Mine 1, Eckman Park and Mine 2, [he potential for material <br />damage caused by salt loading was a major concern which had to be evaluated for each <br />of the alluvial valley floors. The concern was that increased salinity of the receiving <br />streams would lead to elevated soil and alluvial ground water salinity, with resulting <br />inhibitory effects on flood irrigated and sub-irrigated crops. <br />Material damage projections were calculated in both asub-irrigation and a flood <br />irrigation case analysis, using data obtained during low-flow-of-record years (see Table <br />17 contained in Section IX (CHIS) of this Findings Document). The sub-irrigation <br />scenario assumed that the stream would recharge the alluvial aquifer in the spring during <br />peak flows. The flood irrigation case utilized the period between June 1 and August 31. <br />Assumptions and equations used in projecting water quality impacts are set forth in detail <br />in the CHIS section of this Findings Document. Salt loading projections were an•ived at <br />29 <br />