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• considered to be a conservative assumption may be less than 1.5:1). Data collected by 1986, showed root zone soil conductivity to Fiah Creek surface water conductivity. C~ (the actual relationship the Division on August 15, be slightly lower than The major portion of the Fish Creek Alluvial Valley Floor ie not flood irrigated but is assumed to be subirrigated based on vegetation types, alluvial water depths and late growing season color infrared photography. Material damage to subirrigated vegetation would not occur because the majority of discharge to the aquifer occurs during spring and early summer when mine discharge is diluted by high runoff volumes. Table 17 shows a predicted alluvial water quality on Fish Creek of approximately 1 mmhos/cm. Well 008-AU-3 on Fish Creek corresponds more closely with surface water quality and is thought to be a more representative site than 006-AW-2. Hosed on 008-AU-3, a measurable increase in salinity of alluvial aquifers is projected, but the predicted conductivity would be well below the 3 mmhoe/cm material damage suspect level for subirrigation. Water quality measured in well 006-AW-2 exceeds the suspect level in both the existing and predicted case, but mine discharge water would actually dilute the salinity of 006-AW-2 water, resulting in an improvement in water quality due to mining. Following mining and reclamation, the mine workings would fill with ground water and water passing through the mine workings would again discharge to the stream/alluvial aquifer system. This water would be expected to have a degraded water quality (3200 mg/1 TDS at the source), but concentrations would decrease as the affected water flows to the discharge area. The ground water discharge would be further diluted by flow in the stream/alluvial aquifer system. Because of the low flows involved (0.14 cfs), water quality degradation in the stream/alluvial aquifer system would not be sufficient to cause material damage to the waters which supply the alluvial valley floor. The proposed operation would preserve, throughout the mining operation, the essential hydrologic functions of the alluvial valley floor. The essential hydrologic functions of the Fish Creek alluvial valley floor have been identified ae the capacity to support subirrigated and flood irrigated agricultural activities. The proposed plan would result in a limited disturbance to the AVF due to subsidence. Mining beneath the AVF will be limited to panels 5, 6 and 7 and would not result in dewatering of the stream/alluvial system. Also, as discussed previously, no material damage would result from changes in the quality of surface and ground water that supply the alluvial valley flooz. Thus, the essential hydrologic functions of the alluvial valley floor would not be affected by the proposed operation. An adequate monitoring plan is in place to confirm the impacts (or lack of) to Fish Creek and should identify the development of impacts should they occur. Foidel Creek Map 5 (Surface Geology) and supplemental Map No. 1 identify several areas of unconsolidated streamlaid deposits along Foidel Creek. Some of these areas lie upstream of the proposed Foidel Creek Mine and would not be affected by the proposed mining operation. Therefore, no alluvial valley floor determination will be made for those areas that lie upstream of the USGS-WRD gaging station near Pinnacle Peak. Three other areas lie adjacent to or downstream from the proposed mining 24