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bank of the Trout Creek AVF were not affected, since the predicted lowering of the <br />alluvial water table was confined to the east side of Trout Creek. <br />Spoil I.eachate Impacts on AVF <br />Material damage to the AVF would be suspected if the specific conductivity of 'T'rout <br />Creek stream water or alluvial water significantly exceeded 2,300 mmhos/cm during the <br />July-August irrigation season. This material damage suspect level is based on Table 1 of <br />the Division's 1988 guideline, "A Description of the Material Damage Assessment <br />Process Pertaining [o Alluvial Valley Floors", assuming an orchazdgrass crop is grown <br />with calcium sulfate irrigation water. Edna's specific conductivity levels have not <br />approached the suspect level in more than 10 years of monitoring Trout Creek stream and <br />alluvial water, downgradient from the mine. The data indicate this vend can be expected <br />to continue. <br />A major discharge point for Edna's leachate is NPDES discharge outfall 007. Much of <br />this outfall's discharge comes from the Koll imgation ditch whose flow is largely <br />composed of leachate from Spoil Spring 1. That spoil spring's concentration of total <br />dissolved solids commonly exceeds 3000 mg/1, which equates to specific conductivity <br />greater than the material damage suspect level for Trout Creek stream and alluvial water; <br />therefore, the Division has imposed the following pernut stipulation: <br />WATER FROM NPDES POINT 007 WILL NOT BE USED AS SURFACE IRRIGATION <br />WATER UNLESS THE OPERATOR F/RST DEMONSTRATES AND THE D/V/SION FINDS <br />THAT IRR/GATlON W/TH THAT WATER WILL NOT RESULT IN MATERIAL DAMAGE. <br />AVF Findings <br />Based on the preceding discussions of impacts from leachate, physical disruption, and <br />dewa[ering, [he Division finds: <br />1. The activities proposed by the applicant will not interrupt, discontinue, or <br />preclude farming on the alluvial valley floors that are irrigated or naturally <br />subirrigated (4.24.3(1)). <br />2. The proposed activities will not materially damage the quantity or quality of <br />water in the surface or ground water system described above (4.24.3(3) and <br />2.06.8(5)(a)(ii)). <br />3. The proposed activities will comply with the requirements of the Act and the <br />Regulations with respect to alluvial valley floors (2.06.8(S)(a)(iii)). <br />4. Surface coal mining and reclamation operations will be conducted to preserve <br />the essential hydrologic functions of alluvial valley floors outside the permit <br />area and to reestablish the essential hydrologic functions of alluvial valley <br />Edna Mine 2B Permit Renewal No. 4 <br />