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in the Seneca II-W South Extension Area is projected to increase the salinity <br />levels in Hubberson Gulch. TDS concentration of the irrigation water used on <br />this field is estimated to be 1512 mg/I which equates to a specific conductance <br />of 2.0 millimhos/cm. In Tab 17, SCC presents an estimate of potential crop <br />reductions based on the increased salinity level of irrigation water in Hubberson <br />Gulch. SCC projects an estimated 1 percent yield reduction to the total <br />ranching operation. This is considered to be a negligible impact pursuant to the <br />Division's material damage guideline. <br />b. Due to the extremely limited acreage of proposed disturbance within the Sage <br />Creek watershed, and the fact that regional ground water flow is to the west, <br />the potential for material damage to the quality or quantity of water supplied to <br />the AVF is negligible. No measurable impacts to the quantity or quality of <br />water supplying the Sage Creek AVF are projected. <br />c. Background salinity levels in the lower segment of Dry Creek from the Yampa <br />River upstream to Section 28, Township 6 North, Range 88 West are high <br />enough that no degradation of water quality is anticipated due to mining. <br />Agricultural areas potentially impacted by increased salinity levels include two <br />small subirrigated grass hayfields in Section 9, TSN, R88W and flood irrigated <br />grass and alfalfa haylands in Section 28, T6N, R88W. <br />With respect to the flood irrigated fields in Section 28, the application indicates <br />and includes detailed mapping and aerial photographs which show that [he <br />subject fields are irrigated by water from J.C. Temple Reservoir Itl, not from <br />Dry Creek. Thus, water supplying the irrigated fields would not be affected <br />by the mining operation. <br />With respect to the subirrigated fields in Section 9, the applicant conducted a <br />detailed evaluation of the potential reduction in crop production resulting from <br />the projected increase in salinity of the alluvial water. The material damage <br />evaluation is presented on pages 47 and 48 of Tab 17. The evaluation projects <br />a potential production decline of 1.9%, which is considered to be a negligible <br />impact, pursuant to the Division's material damage guidelines. <br />There is no projected diminution of water quantity supplied to the Dry Creek <br />AVF. <br />3) Surface coal mining and reclamation operations will be conducted to preserve the <br />essential hydrologic functions of alluvial valley floors outside the permit area and <br />to reestablish the essential hydrologic functions of alluvial valley floors within the <br />affected area throughout the mining and reclamation process (4.24.2). <br />Seneca 1[-W Findings Document 43 June 15, 2001 <br />Permit Renewal Ho. 3 <br />