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.1 Kathy Welt and Christine Johnston March 7, 1997 (DRAFT) Page 3 7. Establish whether surface water features aze hydraulically connected to the fault inflows and, in general, try to better understand the hydrogeology associated with the fault. 8. Develop the capability to store a substantial portion of the fault inflow underground, to minimize discharges to the North Fork and to keep the groundwater underground. 9. Evaluate the implications of storing large quantities of water underground, to ensure that no adverse hydrologic or water quality consequences occur. ]0. Implement an extensive monitoring program to assess surface water and groundwater quantity and quality impacts from water management activities. Include WET testing of the North Fork upstream and downstream of the mine (and for the mine outflows) to establish possible biological impacts. ] 1. Retain specialists, as necessary, to assist with the development and implementation of water quantity and quality management strategies, and to ensure that the key issues are addressed by MCC. Specific issues include: modifications to wastewater treatment practices to accommodate increased mine outflows; potential source(s) of the inflows; water rights implications; PHCs of the increased discharges to the North Fork; and PHCs of storing water in the sealed panels. 12. Continue to operate the mine so that any out-of-priority depletions to the North Fork are replaced, thereby protecting vested senior water rights. As a result of establishing these objectives for water management activities at the start of inflows from the B East Mains fault (in March 1996), and strictly adhering to them through late January 1997, the associated PHCs have been insignificant in most cases, and modest in others. In response to questions from CDMG staff about the PHCs associated with fault inflows, sump utilization, emergency discharges to the North Fork, treatability difficulties, etc., MCC retained Wright Water Engineers, Inc. (WWE) to evaluate the full range of PHCs that occurred in 1996. The text that follows summarizes W WE's findings. III. BEAST MAINS FAULT In March 1996, MCC intercepted a southwest to northeast-trending fault (B East Mains fault) between Cross-cuts #17 and #21 in the B East Mains (see Map 1). Initial contact with the fault zone (oriented in a N60°E direction) occurred while driving the #6 Entry between Cross-cuts #16 and #l7. At this location the mining encountered a series of small faults containing little water. The largest displacement was estimated to be approximately 2.5 feet with the upthrown side to the southeast. After mining the #16 and #17 Cross-cuts between the #5 and #6 Entries, mining was advanced in the #5 Entry into the fault between Cross-cuts #17 and #18. The fault displayed a similar N60°E orientation and had an apparent displacement of approximately 6 feet in one area. The fault dip angle was estimated to be 65° to the northwest again with the upthrown block to the southeast. Water was initially encountered on March 16, 1996 at an estimated rate of 350 gpm increasing to a maximum rate of approximately 800 gpm within 48 hours, primarily from the roof and floor. This inflow rate dropped to near 350 gpm by the end of March 1996 and dried up completely after the #4 Entry was advanced through the fault.