2005-10-19_REPORT - M2003016 - Laserfiche WebLink

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Mr. Carl Mount September ; 4, 2005 P•t~e percent in the modeling versus 0.22 percent fi'an fire piezomerrie st!rf<ace contours), and the groundwater elevations for the non-growing season surface. The elevations from file monitorng data dining the growing season are around 1-foot lower than those in the modelir~ This canparison suggests that the steady-state modeling was reasonable in teens of predicting existing groundwater levels and piezometric surface shape. i'ossibie fu!p:tcrs. ~F'iggare 2 o;<tiae t9~iascE! in0®3 u~e~o-t). You indicated in your conversation witi~ Ms. Duncan tlrat you would like to understand what coutd'nappen with installation of the slurry wal' (e. g., basements flooded, cottonwood trees killed, etc.). The !nodeling showed that the magnitude of effects due to the Heit Pit will be relatively small (2-foot of n,otmdir_g and 3 feet of shadow effect). The eighteen mont;~s of nrotutorrng dats indicate that the predicted changes in ~-oundwater levels are elo,.~: to the range of nahual variation in eronrdrva.icr levels. hr ac~:~:i~n, '' - .-..~... . Koenig pit, whicl: is lined, has been in place imrnediately south of the proposed Heil Fit withouC any known negative unnacts on groundwater from this pit These 'Factors indicrr~. that at~y negative impacts will tike] ~ be small, and possibly difficult to detect. Additional id@toi'matloru oet n!iiigatiota rtaeasasres. The mitigation measures included in cur .luh• 2003 report included: © Pipeline to equalize groundwater. Deepening of existing wells. Drilling new we21s. Delivery ofwater f-om the Chambers Island Ditch. ® Relocation of wetland nursery stock (for Aquatic acrd Wetland Company nursery to the ^or[h). a Exca~~atien of area for nursery stock (for Aquatic and Wetland Company nursery to the rirr aU A Emergency pumping. A reassessrnei~+ of mitigation measures Ci~:r could be uses rca~irnrs tt.at these are appropriate mitigation measures. The specific measure used (if needed) will det~~:nd en the nature of any impact on groundwater levels. It is not possible to pre-determine the appropriate mitigation t e care. The mitigation measures have the potential to adjust ~nour:dwa~c,. Because ~ o!md,vater (low through the permit uea is d}ntamic, it is difficult `c calculate an exact rate and volume of v/atcr required to attain the required adjustment. The amorult will depend cn the specific location and nature ofthe impact.