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II. HYDROLOGIC BALANCE - Rule 4.05 <br />A. Water Quality Standards and Effluent Limitations <br />All surface drainage from the mine bench/face-up area is directed via the road <br />drainage ditch to a sedimentation pond, to ensure that all discharges meet effluent <br />limits specified in the CDPS discharge permit for the McClane Canyon Mine. <br />A storm water permit also dictates measures for ensuring that all surface runoff water <br />leaving the mine site meets applicable effluent limits. Three small disturbed areas; <br />the office area, topsoil stockpile, and construction dirt stockpile, are not routed to a <br />sediment pond, and are approved as small area exemptions (SAE's). In these areas, <br />sediment control is provided by diversion berms and silt fencing demonstrated to be <br />sufficient to ensure that runoff from the 10 year, 24-hour storm event will meet the <br />settleable solids discharge limit of 0.5 ml/1 (Appendix pages M-2 through M-4xxiii). <br />The silt fences were approved within TR-11 to replace total containment sumps that <br />had previously provided sediment control for the small areas. The silt fencing was <br />installed in 2002. <br />Mine water collected underground in sumps is authorized within the NPDES permit <br />to be pumped to the surface and directly discharged through a pipe to the McClane <br />Drainage without being routed through a sedimentation pond. Mine water <br />discharges have been necessary on occasion since resumption of operations in 2000, <br />and the discharges have been in compliance with applicable discharge permit <br />effluent limits. <br />Drainage and sediment control measures are addressed in Section 2.4.4 of the <br />application text, as well as various exhibits and appendices referenced in the text. <br />The following finding is made pursuant to the three small area exemptions <br />referenced above. <br />The Division proposes to grant small area exemptions (SAE's) from use of <br />sediment ponds for the office facility area (SAE-1, .78 acres), the topsoil <br />stockpile (SAE-2, .39 acres), and the construction dirt stockpile (SAE-3, .30 <br />acres) due to the limited size of the areas and due to the fact that the operator <br />has demonstrated that ponds and treatment facilities are not necessary for the <br />drainage to meet the effluent limitations of Rule 4.05.2 and applicable State and <br />Federal water quality standards for receiving streams, and also due to the fact <br />that no mixing of surface drainage with a discharge from underground workings <br />will occur (4.05.2(3)(b)(i). <br />B. Diversions, Conveyance of Overland Flow, and Stream Channel Diversions <br />The segment of McClane Canyon affected by mine surface facilities extends <br />approximately 3000 feet from a box canyon at its upper end to its junction with East <br />Salt Creek. Five tributary drainages come together at the upper end of the canyon to <br />form the main ephemeral drainage. The mine portal facilities are situated at this <br />15