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Mr. Robert Doss, P.E. <br /> November 25, 1991 <br /> Page 2 <br /> 3 . As indicated in our previous comments a second phase of the <br /> Remedial Investigation (RI) should be proposed in the <br /> schedule as a contingency measure to allow for further <br /> investigation, if necessary, without impacting the remainder <br /> of the schedule. As a response to our comment, PG&E has <br /> proposed a three month phase that has impacted the remainder <br /> of the project by postponing all remaining activities by <br /> three months. <br /> Most of the information required to begin preparation of the <br /> RI report will be gathered from the first RI phase. A <br /> second RI phase may be required just to confirm results or <br /> to collect additional information. Therefore, the <br /> Department recommends that preparation of the RI report <br /> begin during the second RI phase. Furthermore, the <br /> Feasibility Study (FS) is an interactive part of the <br /> investigation and thus should begin during the RI . A FS <br /> report should be submitted within 60 days from approval of <br /> the RI report, and a Remedial Action Plan must be submitted <br /> within 90 days from approval of the FS report. <br /> 4 . As indicated in our previous comments, the two soil samples <br /> proposed for Area III would not be sufficient to provide <br /> conclusive results. Therefore, an additional phase of <br /> investigation maybe required for this area. <br /> 5. The filter pack design for the proposed wells should not be <br /> based on the design of the existing wells. The existing <br /> wells ' filter packs are not properly engineered based on <br /> boring logs and seive analysis and as a result they yield <br /> highly turbid samples. As indicated in our previous <br /> comments, turbid samples may not provide reliable chemical <br /> data, and thus, would not be acceptable. Properly designed <br /> filter packs must be used to ensure reliable chemical data. <br /> In addition, the time required to take an accurate sample <br /> would be reduced and long term stability of the borehole is <br /> assured. <br /> 6. All water table monitoring wells must have at least 15-foot <br /> well screens so that five feet is above the water and 10 <br /> feet is below. This would allow for a more accurate <br /> representation of the hydraulic conductivity of the aquifer. <br />