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and the last valve set) is about 515 psi. At this pressure, the water level in the Northwest Mains Ventilation Shaft accumulator pipe is at about elevation 6,369 feet, or approximately 281 feet below ground surface. Responding directly to Parrs 3 and 4 of the NOV, given the pressure associated with a column of air in the accumulator pipe, coupled with the head necessary to raise water approximately 300 feet, an increase in water system pressure of roughly 160 psi would be necessary for mine water to discharge from the accumulator pipe. This pressure variance is outside of the maxuntun design operating limits for system pressure, as controlled bythe Roll-Seals. So long as one or both Roll-Seals are functioning properly, TCC would have no reason to anticipate that production water discharge from the accumulator pipe would ever occur. It is important to note that the dual Roll-Seal system is designed to provide back up pressure relief capabilities in the event a set of Roll-Seals fails. The unanncipated production mine water discharge experience on May 2/3 resulted from simultaneous or successive failure of both sets of Roll-Seals. Since discharge from the accumulator pipe was not reasonably anticipated, TCC did not plan for or pemut discharge, and did not provide documentation relative to water quality and companbiliry with effluent limitations. The unanticipated production mine water discharge resulted from a catastrophic failure of both sets of Roll-Seals and a consequent uncontrolled increase in system pressure. In order to prevent this from occurring again, TCC has installed new Roll-Seals and is working with the manufacturer to determine why they failed and how to prevent or effectively address the potential for any future failures. 2) Responding directly to Part 1 of the NOV, TCC submits that the NW Mains Ventilation Fan facility SAE is properly designed, and has been constructed and maintained consistent with the approved regulatory design basrs, ie: use of an approved surface runoff modeling program (SEDCAD) for a suitable design storm event (10-year, 24hour). The designed soil containment berms, soil runoff collection ditches, gravel filter, rock check dam, and vegetative filter were established during the early stages of site construction in late 2001 and early 2002. Since that time, they have functioned as designed to effectively control drainage and sediment from the site. Flooding of the low area on the south side of the access road, as noted during the inspection and addressed by the NOV, was directly related to the unanticipated and unforeseen production mine water discharge, and would not have occurred under the normal stormwater runoff conditions for which the SAE was designed. Given that; 1) The existing SAE treatment structures are properly designed to meet all applicable regulatory requirements and have functioned effectively to address nom~al site drainage and sediment control requirements; and 2) The production mine water discharge experienced on May 2/3 was unanticipated and the potential for any future production mine water discharge has been eliminated by placing a valve on the vent pipe; TCC submits that the SAE is properly designed and respectfully requests that Part 1 of the NOV be vacated 3) A grab sample of standing water resulting from the unanticipated production mine water discharge was collected, and full-state water quality analysis was completed to compare with applicable mine water effluent standards for Fish Creek Water quality analysis results for this sample are comparable to full-suite analysis results for previous mine water discharges from the 10-North Mains and Fish Creek Borehole CPDS discharge locations and do not exceed applicable effluent standards (water quality analysis results attached for reference). Given this consideration, the mine water treatment requirements under Rule 4.05.2(8) are not applicable, and consistent with the provisions of Rule NOV CV-2005-006 3 6/3/2005