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Significant increases in the salinity of alluvial ground water in the confluence area would not be anticipated since the majority of the recharge to the aquifer occurs during spring and early summer when Middle Creek and Foidel Creek Flows are highest and conductivity levels are lowest. Further dilution of alluvial waters would be provided by Trout Creek irrigation drainage water. Since Trout Creek irrigation water supports the critical function of the alluvial valley floor and the Trout Creek waters would not be affected by the proposed operatiuns, material damage to the quality of water supplying the AVF would not occur. 3. The proposed operation would preserve, throughout the mining operation, the essential hydrologic functions of the alluvial valley floor. The essential hydrologic functions of the confluence AVF are Flood irrigation primarily and, to a lesser extent, sub-irrigation, and both functions would be preserved. Flood irrigation on the AVF is by diversion of unaffected Trout Creek water. Sub-irrigation does not play a major role in maintaining the agricultural productivity of the AVF, but the quality of alluvial ground water would be maintained above the material damage suspect level of 3 mmhos/cm due to the fact that aquifer recharge occurs primarily in the spring and early summer when stream salinity levels are lowest, and the alluvial water would be further diluted by the low salinity Trout Creek irrigation drainage water. Alluvial Vallev Floor Monitorin Hydrologic monitoring as discussed in Section III. A and B of this document will be sufficient to verify projections and monitor effects of mining on the quality and quantity of water supplying the identified alluvial valley floors. Included in this monitoring plan is a monitoring schedule for the Fish Creek AVF to assess for impacu. A surface water and alluvial water site presently exists downstream of all Foidel Creek mining activities on Trout Creek (site 1005 and well 008-AT-I). Surface water monitoring and alluvial monitoring sites are located along both Foidel and Middle Creeks to assess possible impacts due to the undermining of these perennial streams. The Division finds that activities proposed by the applicant will not interrupt, discontinue, or preclude farming on the alluvial valley floors that are irrigated or naturally subirrigated (4.24.3(1)). The proposed activities will not materially damage the quantity or quality of water in the surface or ground water system described above (4.24.3(3) and 2.06.8(5)(a)(ii)). The proposed activities will comply with the requirements of the Act and the Regulations with respect to alluvial valley floors (2.06.8(Sxa)(iii)). Surface coal mining and reclamation operations will be conducted to preserve the essential hydrologic functions of alluvial valley floors outside the permit area and to reestablish the essential hydrologic functions of alluvial valley floors within the affected area throughout the mining and reclamation process (4.24.2). 1. An environmental monitoring system shall be installed, maintained, and operated by the permittee on all alluvial valley floors during surface coal mining and reclamation operations and continued until all bonds are released in accordance with Rule 3 (4.24.4). XIX. Operations on Prime Farmland C:UHB\C820561RN031RN03FIND.doc 36