Laserfiche WebLink
Foidel Creek mine operation. During the PR-03 review process, the applicant submitted information to <br />support that areas along the Middle Creek valley floor in sections 12, 23, and 26 T5N R86W are not <br />alluvial valley floors. Twentymile Coal Company provided information which is contained in the permit <br />application as Exhibit 42a and consists of vegetation sampling data, valley floor cross-sections, and a <br />transect location maps. The applicant also refers to the narrow and deeply incised nature of Middle <br />Creek. <br />There is no indication of past or current flood irrigation of these areas along Middle Creek and the <br />geomorphic characteristics of this area would not lend themselves to the development of an irrigation <br />system. Based on the lack of flood irrigation potential, the narrow and incised nature of the valley <br />bottom, and the lack of meaningful differences between the creekside and upland vegetative communities, <br />the Division has determined that areas upstream of the Connel ditch lateral crossing of Middle Creek, as <br />shown on Map 15, are not alluvial valley floors. In this case, 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. A previous negative <br />determination had already been made for those lands along Middle Creek downstream from the County <br />Road No. 33 in section 12 to the first irrigation ditch crossing (Connel ditch lateral). <br />Effects of Mining on Identified Alluvial Valley Floors <br />Due to elevated levels of salinity documented in current and future mine discharge water, and to potential <br />inhibitory effects of increased soil and alluvial ground water salinity on flood irrigated and subirrigated <br />crops, the potential for material damage caused by salt loading was a major concern which had to be <br />evaluated for each of the AVF's identified above. <br />Material damage projections were calculated in both a sub-irrigation and a flood irrigation case analysis, <br />using data obtained during low-flow-of-record years. The sub-irrigation scenario assumed that the stream <br />would recharge the alluvial aquifer in the spring during peak flows. The flood irrigation case utilized the <br />period between June 1 and August 31. Assumptions and equations used in projecting water quality <br />impacts are discussed in the Yampa River CHIA, which is on file at the Division office. Salt loading <br />projections were arrived at by stream flow modeling and analysis of past monitoring results and projected <br />dewatering activities. <br />In the supplemental information package dated September 22, 1986, the applicant submitted information <br />on vegetation cover and production by species for flood irrigated and sub-irrigated croplands on the <br />affected alluvial valley floors. Alluvial bodies, irrigated fields and vegetation sample locations are <br />depicted on supplemental Map No. 1 "Twentymile Park Salt Loading Study Land Use and Hydrologic - <br />Boundaries." This and other information was used by the Division to make the required findings with <br />regard to material damage. <br />Required findings for identified alluvial valley floors on Fish Creek, Trout Creek, and Foidel <br />Creek/Middle Creek confluence are presented separately below. <br />Fish Creek <br />1. The proposed mining operations will minimally interrupt, discontinue or preclude farming on a portion <br />of the alluvial valley floor. <br />28