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SL4 Phase III bond release. Table 2.05.6(3)-Tl of PSC permit application contains a <br /> mass balance analysis that indicates that mixing of discharges from PSC ponds with <br /> stream waters will result in maximum TDS of 3,259 mg/lin the channel of the Grassy <br /> Creek AVE Although 3,259 mg/1 equates to 4,345 mmhos/cm,a value well above the <br /> 1,000 mmhos/cm material damage threshold, the high TDS is a result of Seneca II <br /> surface mining activities that, as previously explained, are exempt from AVF material <br /> damage rules 2.06.8(5)(a)(1) and (ii). Based on the limited effects of PSC discharges <br /> from underground mining activities on surface water quality in the Fish Creek, Grassy <br /> Creek, and Little Grassy Creek AVFs, alluvial ground water quality should not be <br /> significantly impaired. Subirrigation is expected to be less affected by mine discharge <br /> than by irrigation using surface waters. A conservative estimate of the expected effect <br /> of mining indicates that no material damage will result. <br /> In addition to water quality degradation, another type of material damage that can occur <br /> to an AVF is physical disruption of the AVF's capability for irrigation or subirrigation <br /> (the AVF's essential hydrologic function). PSC does not propose excavations in the <br /> Fish Creek, Grassy Creek, or Little Grassy Creek AVFs;therefore, the essential <br /> hydrologic functions of these AVFs will not be physically disrupted. PSC will monitor <br /> discharges to the Grassy Creek and Little Grassy Creek AVFs at pond 002 and will <br /> monitor discharges to the Fish Creek AVF at Pond 004 through their NPDES permit, <br /> though this pond is longer regulated by the Division. PSC will monitor alluvial ground <br /> water in the Grassy Creek AVF in well YSG5 and in the Little Grassy Creek AVF in <br /> well SGAL71. PSC will monitor surface water in the Fish Creek AVF at SSC10. <br /> The Division finds that activities proposed by the applicant will not interrupt, <br /> discontinue, or preclude farming on the alluvial valley floors that are irrigated or <br /> naturally subirrigated (4.24.3(1)). <br /> The proposed activities will not materially damage the quantity or quality of water in <br /> the surface or ground water system described above (4.24.3(3) and 2.06.8(5)(a)(11)). <br /> The proposed activities will comply with the requirements of the Act and the <br /> Regulations with respect to alluvial valley floors. (2.06.8 (5)(a)(110). An <br /> environmental monitoring system for alluvial valley floors has been installed, will be <br /> maintained and operated by the permittee during surface coal mining and reclamation <br /> operations, and will be continued until all bonds are released in accordance with Rule <br /> 3. (4.24.4). <br /> Those areas of the operation in the Grassy Creek or Little Grassy Creek watersheds <br /> where only surface coal mining activities were conducted produced coal in commercial <br /> quantities and were located within or adjacent to an alluvial valley floor prior to August <br /> 3, 1977 (4.24.3(4)(a) and 2.06.8(5)(b)(I)(A)). <br /> Page 26 of 27 <br />