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41° <br /> December 18, 2015 <br /> Mr. John S. Vazquez, P.E. <br /> Loloff Construction <br /> 801 8th Street, Suite 130 <br /> Greeley, CO 80631 <br /> RE: Loloff Construction, Inc. —Loloff Pit—Amendment, <br /> File No. M-1985-112, Adequacy Review Item 13— 6.4.7 Exhibit G— Water Information <br /> Dear Mr. Vazquez, <br /> We have reviewed the letter from DRMS dated October 14, 2015 regarding the request for <br /> additional information on a mitigation plan for the groundwater shadowing effects due to the <br /> proposed slurry wall. We are proposing similar trigger points for the shadowing effects that are <br /> proposed for the mounding effects. <br /> The mitigation measures would be utilizing a drain to take water from the up gradient side of the <br /> slurry wall (mounding location) and transfer it in the drain to the down gradient side of the slurry <br /> wall (shadow location) to recharge the aquifer and bring the water table to equilibrium if needed. <br /> The other mitigation measure would be to check wells that are within the affected area of the <br /> shadow from the slurry wall (based on Figure 2 page 8 of the McGrane Slurry Wall Assessment <br /> and Groundwater Modeling Report) and determine if the affected wells could be mitigated by <br /> lowering the existing pump location to maintain the current pumping capacity. <br /> The trigger points would be when water table depths of greater than 18 to 24 inches lower than <br /> the water depths measured prior to dewatering of the pit are seen in the adjacent down gradient <br /> Derr Pit monitoring wells once the slurry wall has been constructed. The wells down gradient of <br /> the slurry wall would then be checked to see if they are being impacted. If it is determined that <br /> the wells are being impacted then the mitigation measures would be looked at to determine <br /> which measure should be implemented to achieve mitigation of the impact to the down gradient <br /> wells. Please feel free to contact me with any questions or comments. <br /> Sincerely, <br /> e. <br /> J.C. York, P.E. <br /> J&T Consulting, Inc. <br /> V 305 Denver Avenue—Suite D• Fort Lupton CO 80621 •Ph: 303-857-6222•Fax: 303-857-6224 <br />