Laserfiche WebLink
Evaluation of Potential Impacts <br />to Wetlands on the Sage Hill Farm from the <br />Proposed Nix Property <br />Sand and Gravel Operation <br />The easternmost lateral maintains surface water in the slough. Water from these laterals likely <br />extends the azea of saturated soils to the south and may result in a lazger wetland than that <br />sustained solely by groundwater. The slough acts as a buffer by controlling water levels in the <br />wetland. Excess water is dischazged from the wetland in the slough under County Road 28. <br />Evaluation of Potential Impacts from the Proposed Gravel Mine <br />The proposed mine plan is shown on Figure 5. As this figure shows, it is proposed to remove <br />aggregate by excavating (in the wet) a series of cells. <br />As described in detail in the well evaluation report by WWE, the effects of mining on <br />groundwater levels were evaluated by determining the change in groundwater as a result of the <br />proposed excavations. It was assumed that the water surface of an excavated lake on the Nix <br />property would equal the midpoint of the pre-existing groundwater surface across the lake. That <br />is, the lake level would be slightly higher than the existing groundwater surface on the <br />downgradient end of a lake, and slightly lower on the upgradient end. A schematic of this "lake <br />leveling" effect is shown on Figure 4. <br />Figure 5 shows the groundwater contours in the area, based on the September 14, 2001 <br />measurements, and the estimated maximum changes in groundwater levels along the south <br />boundary of the Nix property from the proposed mining. These changes would occur due to the <br />lake-leveling effect previously described. <br />It is difficult to estimate the exact effects of the changed groundwater levels on the subject <br />wetland. The changes in groundwater levels on the Nix property shown on Figure 5 represent <br />the theoretical maximum change as a result of lake leveling that could occur. However, it is <br />believed that the actual changes in groundwater levels beneath the wetland would be less <br />because: (1) the amount of the change will decrease with distance from a lake (Figure 4), (2) the <br />wetland is upgradient of the lakes, (3) seepage from the pond to the south on the Sage Hil] Farm <br />' 011-074.000 Wrighl Water Engineers, Inc. Page 7 <br />November 2001 <br />