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In response, the applicant has provided assurances that the slurry wall will be keyed into a <br />competent layer or cyuivalent using excavations and grouting if necessary, and indicates that a <br />gcotechnical engineer will be onsite to determine when adequate key material were penetrated. <br />Please commit to providing the Division with a copy of the QaQc Specifications for the Slurry <br />Wall Installation currently being prepared by Terracon. <br />.41so, there are certain locations of the slurry wall installation where underground utilities run <br />along or run perpendicular to the stony wall. Flas there been an analysis of what the impacts of <br />the slurry wall installation will have on these underground utilities'? Will the presence of the <br />utilities impact the structural integrity of the slurry wall? Arc there risks to the utilities during <br />the installation of the slung wall'? What steps will he taken to ensure problems fmm occurring. <br />Please respond. <br />3. Please address the following concerns with respect to the Groundwater Monitoring Plan <br />recommended by the Applegate Group. <br />a. Commitment - Catma has committed to implementation of a groundwater monitoring plan to <br />assess changes in water level elevations due to the slurry wall installation. At this time, Carma is <br />not yet the operator. Therefore, the current applicanUoperator (Sicgrist Constntetion Co.) will <br />need to provide a definite commitment that the operator of the site will implement the proposed <br />groundwater monitoring plan. <br />b. Revised Map -'T'he applicant will need to provide a revised copy of the Tab 1 d Nap ("Lake <br />Reclamation Exhibit") which shows the locations of proposed grotmdwater monitoring stations, <br />and the location(s) of where mitigation measures such as perimeter drains will be installed. <br />c. Baseline Data - lfie applicant has proposed to use the existing lake water levels as a baseline <br />water elevation. Please provide existing lake water surface data and a discussion of how the <br />applicant will collect a set of baseline water levels, prior to slurry wall installation, that are <br />representative of the existing groundwater levels in the area. Such dctennination will need to be <br />representative of either a "worst case" scenario or the full range of natural groundwater <br />fluctuations expected during the course of a 12 month period. <br />d. Trigger Criteria -The applicant has proposed a "trigger" of three (31 feet beyond natural <br />baseline elevations for determining when mitigation measures will be implemented. Please <br />discuss how this criteria was determined, and whether this criteria is adequate to ensure no <br />adverse impacts to structures to the west of the slurry wall, such as the CDOT hndge <br />foundations. (Ihe Division requests that the applicant use a trigger critena that provrdcs enough <br />sensitivity to dctemiine when adverse groundwater conditions may he occurring at or near a <br />nearby, permanent man-made structure). <br />c. Mitigation The proposed mitigation measures appear to he adequate to minimize impacts to <br />stnutures to the west and north of the slurry wall installation. <br />