2012-12-10_REVISION - M2004009 (9)

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Site Date Elevation Cell 2 A July Pond July 2012 4938.32 TH -39 Oct 1999 4937.5 Schell 108a Oct 2011 4938.51 TH -44 Oct 1999 4942.0 The observation well at 108A occurs at approximately the same up- gradient distance from the Schell house and therefore will serve as a good well to observe the influence of the clay backfill material on groundwater levels. It is estimated that the elevation of the lower footing at the Schell house is at 4944.0 ft. The threshold not to exceed groundwater elevation value at well 108A is therefore set at 4944.0 ft. The value of 4944.0 ft is 3.6 ft above the predicted seasonal high water table elevation at 108A. At a minimum, water levels at MW -1 and 108A shall be observed and recorded monthly for one year following the backfilling of Cell 1. A more detailed water level measurement schedule will be prepared and submitted to the DRMS before any more significant backfilling of Cell 2 occurs. If water levels are observed to exceed 4944.0 ft at 108A, then ASCI shall be required to design and build an engineered groundwater level mitigation system that will alleviate high groundwater levels on the Schell property to levels below 4944.0 ft at observation well 108A. Alternatively, ASCI will reserve the right to cause groundwater levels higher than 4944.0 ft on the condition that a signed notarized agreement between ASCI and Schell or Schell's successors that would allow them to do so. Table 1. Observed Groundwater Elevations In order to estimate the seasonal high groundwater elevation in the vicinity of the Timmreck house, the October 1999 observed water level at TH -44 is adjusted by 1.44 ft from 4942.0 ft to 4943.44. This adjustment is based on the predicted July elevation for TH -39 based on the discussion above. The distance from TH -44 to the Timmreck house is 493.52 ft. Multiplying that distance by a gradient of 0.0031 ft/ft (USGS OFR 02 -338) and adding to the adjusted TH -44 elevation yields a water level of 4944.96 ft. The finished floor elevation of the Timmreck house appears to be 4956.2 ft, which would put the bottom of the footing at approximately 4954.0 ft. The proposed observation well OW -1 occurs 146 ft down - gradient from the Timmreck house. Multiplying that distance by a gradient of 0.0031 ft/ft (USGS OFR 02 -338) and subtracting from 4954.0 ft elevation yields a water level of 4953.54 ft. The threshold not to exceed groundwater elevation value at well OW- 1 is therefore set at 4953.5 ft. This is approximately 8.5 ft above the predicted seasonal high groundwater elevation described above. At a minimum, water levels at OW -1 shall be observed and recorded monthly for one year following the backfilling of Cell 1. A more detailed water level measurement schedule will be prepared and submitted to the DRMS before any more significant backfilling Page 5 of 6