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Evaluation of Potential Impacts <br />to Wetlands on the Sage Hill Farm from the <br />Proposed Nix Property <br />Sand and Gravel Operation <br />and the pond to the east on the Mayer property will sustain groundwater levels, and (4) <br />diversions and return flows in the laterals to the wetland will maintain groundwater levels. <br />The limited data collected show that the wetland currently experiences relatively large <br />fluctuations in groundwater levels and hydrologic conditions, and the vegetation in the wetland is <br />relatively tolerant to changes in moisture conditions. Slight changes in groundwater levels, <br />therefore, should not have a significant effect on the wetland. <br />The evaluation conducted by David Cooper in his letter of July 16, 2001 was based on dry <br />mining of the site with relatively Iazge reductions in the water table. The changes in the water <br />table from wet mining, as is now proposed, will be much smaller and would not result in large- <br />scale dewatering of the wetland. <br />RECOMMENDED MITIGATION MEASURES <br />The data collected and analysis conducted indicate that there could be small to moderate changes <br />in groundwater levels beneath the wetland from a wet mining alternative. However, the <br />magnitude of these changes will likely be within the range of existing groundwater fluctuations, <br />which appear to be 1 to 2 feet. However, to protect the wetland and insure no deleterious effect <br />on its hydro]ogic7egime, the following measures aze recommended: <br />1. Excavation of Area 3 should occur in two cells (3A and 3B on Figure 5). Area 3A should <br />be excavated first to the approximate limit ("new berm") shown on Figure 5. This will <br />create an upgradient lake with a lake surface elevation greater than that of the wetland. A <br />pipe/ditch should be constructed to deliver water from cell 3A to the wetland slough at <br />the most upgradient (highest) point possible. The slough is relatively flat. Maintenance <br />of the existing water level in the slough should stabilize hydrologic conditions in the <br />' 011-074.000 Wright Water Engineers, Inc. Page 8 <br />November 2001 <br />