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A previous negative determination had already been made for those lands along Middle Creek <br />downstream from the County Road No. 33 in section 12 to the fast irrigation ditch crossing (Connel <br />ditch lateral). <br />Cow Camp and Bond Creeks <br />The Division considered the AVF potential of Cow Camp and Bond Creeks in a regional AVF study <br />conducted in 1986. The Division found that both creeks do not meet the criteria for AVF designation <br />because the meandering nature of their channels severely limits the farmable acreage within then <br />drainages. <br />Effects of Mining on Identified Alluvial Vallev Floors <br />Due to elevated levels of salinity documented in current and future mine dischazge water, and to <br />potential inhibitory effects of increased soil and alluvial ground water salinity on flood-irrigated and <br />subirrigated crops, the potential for material damage caused by salt loading was a major concern which <br />had to be evaluated for each of the AVFs identified above. <br />Material damage was projected for sub-irrigation and for flood irrigation, using data obtained during <br />low-flow-of-record years. The sub-irrigation scenazio assumed streamflow would recharge alluvium <br />during high springtime flows. The flood irrigation case utilized the period between June 1 and August <br />31. Assumptions and equations used in projecting water quality impacts aze discussed in the Yampa <br />River CHIA, which is on file at the Division office. Salt loading projections were arrived at by stream <br />flow modeling and analysis of past monitoring results and projected dewatering activities. <br />In the supplemental information package dated September 22, 1986, the applicant submitted <br />information on vegetation cover and production by species for flood irrigated and sub-irrigated <br />croplands on the affected alluvial valley floors. Alluvial bodies, irrigated fields and vegetation sample <br />locations are depicted on supplemental Map No. 1 "Twentymile Pazk Salt Loading Study Land Use and <br />Hydrologic -Boundaries." This and other information was used by the Division to make the required <br />findings with regazd to material damage. <br />Required findings for identified alluvial valley floors on Fish Creek, Trout Creek, and Foidel <br />CreeklMiddle Creek confluence are presented sepazately below. <br />Fish Creek <br />1. The proposed mining operations will not interrupt, discontinue, or preclude farming of the alluvial <br />floor. <br />The boundazies of the Fish Creek AVF aze shown on Map 15 of the permit application. The AVF <br />includes all alluvial deposits within and downstream from the permit azea as shown on supplemental <br />Map 1. Information discussed below has reaffirmed the Division's original determination that alluvial <br />deposits on Fish Creek meet AVF criteria based on exisfing flood irrigation, potential for flood <br />irrigation, and subirrigation. <br />Map 15 shows the following features in the Fish Creek AVF: azeas having potential for flood <br />irrigation, currently flood- irrigated fields, diversion structures, and irrigation ditches. <br />Several of the soils in the AVF exhibit late growing season ground water elevations within 6 feet of <br />t,'re surface (Exhibit 16, Soil Mapping Unit Descriptions and backhoe pit data provided on Page 2.06 <br />27 <br />