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Mine Dischar¢es The 1998 inflows and the estimated futwe mine inflows aze shown in Exhibit 49, Table E49-4. Projected mine discharges aze shown on Exhibit 49, Tables E49-6 through E49-8. The mining rate used in these projections was 8,000,000 tons per year. An increased mining rate will not effect the maximum flow rates but only move them forwazd in time. The mine groundwater inflow numbers are discussed above in the Ground Water Inflow to the Mine section. Much of the mine inflows will be dischazged and removed through the Fish Creek borehole. During periods when these pumps are not operating the sump below the borehole fills with mine inflow water. The present (1998/1999) pool volume is estimated to be 546,000,000 gallons (Ground Water Inflow to the Mine. Mine Water Balance) When both pumps at the borehole aze running it is capable of dischazging at approximately 850 gpm, although this rate may be increased to 1,200 gpm if warranted, however, the average annual futwe pumping rate is estimated to be 300 gpm At this rate, it is estimated that it will take 1.4 years to drop the pool elevation to the required operational level of 5,800 feet. At that time, the pumping rate will be maintained at a rate sufficient to maintain the water level by removing inflows from the WMD. This rate is estimated to be 55 gpm if no water is transferred from other parts of the mine. As of June 1999, the mine had completed a system to recycle some of the water that is produced underground. The average amount the system can recycle is over 175 gpm. The average annual recycling rate has been conservatively estimated to be 100 gpm. This will allow for the addition of some makeup water if needed to dilute any salt build- up. However, it does not take into account that additional water can be used to replace surface uses of water such as in the truck-wash, road watering, and the preparation plant, further decreasing the water dischazged from Site 109. Three cases are presented. In Case I (Exhibit 49, Table E49-6) all the water is pumped from Site 109 except the WMD inflow to the Fish Creek Borehole sump. In Case 2 (Exhibit 49, Table E49-7}, after the water level in the sump is lowered, 245 gpm of water is transferred into the sump from the eastern and northern parts of the mine. In Case 3 (Exhibit 49, Table E49-8), water is continuously diverted into the sump, and the dischazge rate from Site 1 15 increased, to compensate for the diversion. C The average water quality discharged from the Site 115 was estimated by incrementally averaging the average conductivity in the water in storage with the estimated conductivity of the WMD ground water inflow (See Tables E49-9 through 11 in Exhibit 49). This equation assumes that the present pool is homogeneous and that there will be instantaneous mixing of the two waters. In actuality, neither condition is met in the short ten-n, but for the long ten-n estimated of average discharge quality, it is appropriate. The Fish Creek Borehole is pumping from the bottom of the pool where the water has been standing the longest. Therefore, it will have the worst water quality. The mine inflow will only partially mix with the large pool of water, however, as the pool reduces in size mixing will occw more quickly. The results of this deviation from the equation's assumptions aze that the eazly time estimations aze low and the late time estimations are high. Because the inflow rate in the first 1.4 yeazs is much less than the outflow rate, and the pool is quite large, the under-estimation of the conductivity will be small. The average water quality discharged from the portal (Site 109), and other situations, was estimated using a simple flow weighted mass balance equation. The equation is of the form: Ce~~~ _ ((C~ * Q~) + (Cz * Qz) + •(C~ * Qa) / (Q~ + Qz +--Qa Where: C, =concentration from sowce I Q, =flow from sowce I C„ =concentration from sowce n Q~ =flow from sowce n Based upon the above inputs, in Case 1 (Exhibit 49, Table E49-6) the flow rate from Site ]09 will increase from 342 (0.76 cfs) to 612 gpm (1.36 cfs) at life-of--mine. The conductivity will decrease from 3,800 gmhos/cm to 3,100 µmhos/cm. The discharge from Site 115 will average 300 gpm for the fast 1.4 years and then 55 gpm for the remainder of the life of mine. In Case 2 the flow rate from Site 109 will peak at approximately 400 gpm (0.89 cfs) at the end of the fast 1.4 years and at the end of the life-of--mine. The conductivities in the Case 2 dischazges from the portal will be the same as Case 1. In Case 3, water is diverted from the EMD, North Mains and 6-Right azea TR07-60 2.05-152 05/01/07