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07 July 2009 <br />Pg. 2 <br />unrestricted into the pit, but would probably create a situation similar to the one existing <br />currently, which MDC believes has caused reduced flows in the ditch. A possible solution <br />might be to augment the ditch flows during mining using dewatering effluent. Post -mining <br />augmentation might consist of the scenario described in (1) above, i.e., diversion of a portion of <br />the impounded surface water to the ditch. <br />3) Relocate the ditch again so that its entire length is just outside of Bromley's slurry wall. This <br />appears to be in the plan for the amended area, but the entire ditch may have to be located east <br />of the slurry wall if it is not planned as such already. As we have seen at other sites, slurry walls <br />can cause mounding on the upgradient side of the slurry wall. If such a condition occurs, the <br />ditch may actually be supplied with more ground water than during pre -mine conditions and, if <br />properly lined with material of appropriate permeability, could act as a kind of French Drain <br />that could control ground water levels upgradient of the mine by intercepting ground water and <br />channeling it around the mine. This would serve the additional purpose of helping prevent <br />undesirable fluctuations in and around upgradient residents' property. This scenario would have <br />to include the provision that any backfill placed hydrologically upgradient of the slurry cannot <br />be of such low permeability that ground water flow to the ditch is restricted. <br />4) A combination of one or more of the above as needed. For instance, scenario 3 might work in <br />the short term but may require augmentation in the long term. <br />5) Mr. Spratlen implied in his letter of May 11, 2009 that if the Applicant can demonstrate that the <br />historic groundwater regime which is the water supply to the McCanne Ditch will not be <br />impaired by Ready Mixed mining activities, then MDC would withdraw their objection. The <br />various scenarios listed above, and perhaps others I have not thought of, could be evaluated <br />using a ground water model. The ground water model referenced in the Amendment <br />Application that was applied by Greystone Consulting could be modified to provide this <br />information.' <br />