GENERAL41728 - Laserfiche WebLink

Home Browse Search

peak flows. The flood irrigation case utilized the period between June 1 and August 31. Assumptions and equations used in projecting water quality impacts are set forth in detail in the CHIS section of this Findings Document. Salt loading projections were arrived at by addition of the projected impacts from spoils aquifers at surface mines in the drainage to predictions of peak discharges from the Foidel Creek Mine. In the supplemental information package dated September 22, 1986, the applicant submitted information on vegetation cover and production by species for flood irrigated and sub-irrigated croplands on the affected alluvial valley floors. Alluvial bodies, irrigated fields and vegetation sample locations are depicted on supplemental Map No. "Twentymile Park Salt Loading Study Land Use and Hydrologic - Boundaries." This information was used by the Division to make the required findings with regard to material damage. Required findings for identified alluvial valley floors on Trout Creek, Fish Creek, Foidel Creek/Middle Creek confluence and Foidel Creek are presented separately below. Trout Creek The boundaries of the Trout Creek alluvial valley floor which would potentially be affected by the proposed operation and to which these findings apply include irrigated pasture 8S which encompasses the Middle Creek, Trout Creek Confluence and all alluvial deposits downstream on Trout Creek to its confluence with the Yampa River as depicted on Supplemental Map No. 1. Alluvial deposits on Trout Creek meet alluvial valley floor criteria based on extensive acreage of flood irrigated hayland, potential for flood irrigation and a presumed capability to support subirrigated vegetation. Flood irrigated hayland and vegetation sample locations are depicted on supplemental Map No. 1. Irrigated hayland is the predominant land use on the Trout Creek AVF and the dominant species are Kentucky bluegrass, smooth brome and timothy. Based on the extent of existing flood irrigated farmland, and lack of specific information regarding extent or use of subirrigated alluvium, the Division finds that the Trout Creek alluvial valley floor is significant to farming. The required findings are set forth below. The proposed mining operations would not interrupt, discontinue or preclude farming on the alluvial valley floor. Mining activity would not directly impact any portion of the Trout Creek Alluvial Valley Floor. Any impacts would be indirect, as a result of discharge of affected water into Foidel Creek and Fish Creek. Fish Creek is tributary to Trout Creek and Foidel Creek is tributary to Middle Creek which is tributary to Trout Creek. Indirect impacts are addressed under Finding No. 2, below. The proposed mining operations would not cause material damage to the quantity or quality of surface and ground water that supply the alluvial valley Floor. The only potential for the diminution of the quantity of water supplied to the Trout Creek AVF would be as a result of undermining of Fish Creek, and Foidel Creek, which are tributary to Trout Creek. Dewatering of the streams as a result of undermining is not considered to be a possibility For reasons explained in the Fish Creek and Foidel Creek AVF Findings section of this document. 20