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Similarly, review of TR-18 does not lcad to a conclusion that Battle Iv{ountain and <br />DMG anticipated the groundwater flow that occurred after backfilling the West Pit. In T2 u <br />actuality, as later confirmed in TR-26, the water elevation in the backfilled pit rose to an <br />elevation of approximately 8590 feet within one yeai~of the completion of backfilling. <br />TR-26 explains that the rapid refilling of the Rest Pit created a steep hydraulic gradient <br />between the water in the backfilled pit and the alluvial aquifer that, in part, led to the <br />violations at issue. ~2w~ <br />However, Exhibit G to TR-18 confirms that the original MLRB permit did not <br />anticipate hydrologic conditions which would lead to the open pit refilling wi°h <br />groundwater. Specifically, Exhibit G states that the original permit contemplated that any <br />seepage to the pit from either the Precambrian aquifer or the alluvial aquifer would be <br />"not significant" or "small." Exhibit G, p. G-2. TR-18 anticipated that the backfilled pit <br />would refill over an extended period of time (approximately 4 to 6 yeazs) to an elevation -T~tl2- <br />of 8570 feet See Exhibit G., p.G-3). Under this assumption, the potential flo~H rate <br />between the West Pit and the alluvial aquifer tivould have been substantially lower than <br />the flow rate that actually did manifest itself, because there would have been it lower <br />hydraulic gradient between the backfill material and the alluvial aquifer.~~r ' gni'~ ly;`~~`t'`~ <br />the projections in TR-18 indicate a relatively low risk of potential contamination of the <br />alluvial aquifer and the Rito Seco. <br />Based on the above evaluation, the Division believes that the rate of r.filling, the <br />final water elevation in the backfilled West Pit, and the potential for significant mixing <br />with the alluvial aquifer were not anticipated in TR-18.-1The Division has confirmed its <br />assessment of the record with DMG. ~ t~-Q. <br />16. CCCD and PASS questioned the Division's determination of no potential damage <br />to the classified uses of the Rito Seco and criticized the Division's reliance on limited <br />data supplied by Battle Mountain. Shalom Ranch expressed concern with the Division's <br />"no potential damage" conclusion in light of the lack of data collected downstream from <br />Battle Mountain's property. <br />The Division's determination of no potential damage to the classified uses of the <br />Rito Seco was based upon various sources of information provided by Battle Mountain <br />and DMG. The Division did rely, to some extent, on the risk assessment prepared by <br />Battle Mountain, although it was by no means the only information upon which the <br />Division based its detemvnation, as the Groups suggest. The Division also placed great <br />reliance on various sets of water qualiR~ data obtained from Battle Mountain r:nder its <br />monitoring programs with DMG and under Amendment No. 1 to the NOV-CI)O. <br />Studies conducted pursuant to TR-26 indicate that the "contaminant plume" that <br />is now confined to groundwater is at least 1.8 miles from reaching Battle Mor:atain's <br />downstream property boundary. The Division, therefore, believes that its reliance on in- <br />stream data from RS-5 at the downstream property boundary -which takes into <br />consideration discharges of pollutants into the Rito Seco via surface expressicns and <br />groundwater-is appropriate. The Division believes that the evidence in the record fully <br />60'd 8T:~T 00.6 6ny 855~998£0£:xe~ - - <br />