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MEMORANDUM <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS: 8-495-5600 <br /> TO: A14TONIA K. J. VORSTER FROM: ROBERT L. NIBLACK <br /> Senior Engineer Engineering Geologist <br /> �CdDATE: 15 October 1987 SIGNATURE: ��k'� �GL , <br /> SUBJECT: COMMENTS ON WORKPLAN FOR LINCOLN CENTER GROUND WATER <br /> INVESTIGATION, SAN JOAQUIN COUNTY <br /> I have reviewed the workplan prepared by Leedshill-Herkenhoff, Inc. <br /> for the investigation of ground water pollution at Lincoln Village <br /> Center in Stockton. The proposed investigation is too limited in <br /> scope, does not propose a means to confirm contaminant sources, and <br /> lacks a rationale for the location of the monitoring wells. My <br /> specific comments follow: <br /> 1. The background section of the workplan states, "It is the <br /> RWQCB's opinion that the cleaning fluids leaked through joints <br /> and/or cracks in the sewer pipe, . . .and eventually migrated into <br /> the upper ground water aquifer. " This is not our opinion, but <br /> it is very likely considering the facts supplied by the <br /> extensive work performed by the San Joaquin County Department of <br /> Public Works. It is the most likely source identified at this <br /> time. Our opinion is that further source identification is <br /> necessary to aid in optimal well placement and plume definition <br /> tasks. <br /> 2 . The plan fails to propose any tasks for further source <br /> identification. The workplan proposes this work for phase II of <br /> the investigation, "if a phase II investigation is required. " <br /> It is necessary to perform task 1 of the Phase II investigation <br /> outlined in the workplan at this time as we indicated in the 1 <br /> July meeting and the memo of 22 July sent to Lincoln .Properties <br /> Limited. Further delay of source identification may aggravate <br /> the existing ground water problem. <br /> 3 . Rationale for selection of monitoring well locations is lacking. <br /> The proposed well locations appear appropriate for determining <br /> the ground water gradient, but have limited value in defining <br /> the extent of contamination. Since there is confirmed ground <br /> water contamination at Lincoln Village well No. 1, it would be <br /> useful to put a well cluster in this area. Several wells <br /> completed at different depth intervals in this location would <br /> help define the vertical extent of contamination. <br /> 4. The proposed wells are designed to be completed at a depth of 65 <br /> feet with a 15 foot screened interval. Final decisions on depth <br /> of completion and length of screened interval should be made <br /> based on the results of boring logs by the geologist at the <br />