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George Patterson <br />July 19, 2013 <br />Page 3 <br />previously estimated that the mine would not fill entirely for approximately 285 years. <br />To determine the timing of mine filling at certain elevations, the Southfield Mine Permanent Closure <br />Map dated August 2001 was used to identify areas and volumes within the mine above and below <br />elevations of interest. Several refilling conceptual models were then considered, as described below <br />and summarized in Table 1. <br />Conceptual Model No. 1 — The entire mine is hydrogeologically connected and refills as a single <br />unit. <br />This conceptual model assumes that the workings of the mine are perfectly hydrogeologically <br />connected and the water level in the mine during refilling will be the same throughout the mine. <br />Based the South Field Mine Permanent Closure Map dated August 2001, approximately 3,125 acre - <br />feet of the total mine volume is lower in elevation than the 5860.5 -foot monitoring elevation for the <br />MW -NW well indicated by Janet Binns in the January 10, 2013 letter to George Patterson. <br />Based on the combined rate of estimated mine inflow of approximately 24.1 acre -feet per year, the <br />241.6 acre -feet that flowed into the mine between 1994 and 2000 and the volume of the mine <br />workings that will refill, the water level in the mine would not reach the identified monitoring <br />elevation for the MW -NW well for a total of approximately 120 years after the year 2000 or until the <br />year 2120. <br />Conceptual Model No. 2 — The seals in the 1 North, 1 '/2 North and 2 North areas hold and these <br />areas fill as a unit separate from the rest of the mine. <br />This conceptual model assumes that the seals in the 1 North, 1 '/2 North and 2 North areas hold <br />perfectly and that these areas fill separately from the rest of the mine with no seepage out of these <br />areas into other portions of the mine. <br />Based on the closure map, there is only approximately 121 acre -feet of the total mine volume area <br />below the monitoring elevation of 5860.5 feet and only approximately 160 acre -feet of the total mine <br />volume below the obstruction elevation in the MW -NW well of 5879.7 feet contained by the seals of <br />the 1 North, 1 '/2 North and 2 North areas. Based on the estimated inflow rate of 14 acre -feet per <br />year for this area, water would have been expected to reach the monitoring point elevation at the <br />MW -NW well location within approximately 8 years or by 2008 and the obstruction elevation in the <br />well within approximately 11 years or by 2011. Accordingly, we would already expect water to be <br />above the obstruction point in the MW -NW monitoring well if this conceptual model were valid. <br />The April 17, 2012 investigation proved that the well is in connection with the mine and the lack of <br />water within the well at this time indicates that this area is not refilling separately from the rest of <br />the mine as water would be observed in the well. Accordingly, this conceptual model is not valid, <br />the seals in the North area of the mine are not restricting flow of water through the mine and the <br />