Laserfiche WebLink
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 />