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6 Conclusions <br />Based upon the evaluation of groundwater conditions in the vicinity of the Stegner Farm gravel <br />mine, the following conclusions are provided. <br />• The results of this evaluation indicate that groundwater levels in the vicinity of the <br />Stegner Farm gravel mine have changed since the slurry wall was installed around <br />mining operation in April, 2000. These changes are the combined effects of local climatic <br />conditions (precipitation, temperature, and evapotranspiration), seepage from the Taylor <br />and Gill irrigation ditch, Local groundwater withdrawals, cessation of flood irrigation at <br />the Stegner Farm, and the slurry wall. <br />• Groundwater level increases ("mounding") have occurred along the north and west sides <br />of the slurry wall since it was installed. The highest groundwater levels typically occur at <br />well S-2 which is situated at the approximate center of the northern portion of the slurry <br />wall. The highest groundwater levels that occurred at the upgradient wells (S-1, S-2, S-3, <br />S-4, S-7, and S-8) during 2001 (Table 1) indicate that none of the wells have sustained a <br />groundwater level of two (2) feet or less below the natural ground surface for a period of <br />three weeks, which would require installation of a french drain as set forth in the mining <br />permit. <br />• Groundwater level decreases have occurred in the area of the Roe and Martin properties <br />resulting in a "groundwater depression" downgradient of the slung wall. The estimated <br />groundwater level decreases are approximately 1.8 feet beneath the Roe property and <br />approximately 1.4 feet beneath the Martin property in December 2001 compared to pre- <br />slurry wall groundwater levels in December 1999. The cause of these groundwater level <br />declines is the combined effect of the the slurry wall, local drought conditions, cessation <br />of imgation at the Stegner Farm, and local groundwater withdrawal near the Roe and <br />Martin properties. However, even considering all these effects together, the observed <br />groundwater level decrease is less than the 2-foot groundwater level decrease below <br />seasonal low water level incorporated in the Stegner Farm mining permit. <br />• Statistical analysis of groundwater levels at the Stegner and LaFarge monitoring wells <br />indicates that statistically significant groundwater level increases have occurred at wells <br />S-Z, S-3, and S-4 and a statistically significant groundwater level decrease has occurred <br />at well S-5 since the slurry wall was installed. None of the other wells analyzed (S-1, S-6, <br />S-7, S-8, L-1, L-2, L-3, and L-5) exhibited a statistically significant increase or decrease <br />since the slurry wall was installed. Therefore, for the monitoring wells analyzed, the most <br />16 <br />