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• MEMORANDUM • <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> Phone: (916) 255-3000 <br /> 3443 Routier Road, Suite A CALNET: 8-494-3000 <br /> Sacramento, CA 95827-3098 <br /> TO: Antonia K. J. Vorster FROM: James Taylor <br /> Senior WRC Engineer Engineering Geologist <br /> DATE: 19 February 1993 SIGNATURE: <br /> SUBJECT: REVIEW OF THE DRAFT FINAL PRE-DESIGN TECHNICAL S MM <br /> REPORT AND DRAFT <br /> FINAL REMEDIAL DESIGN <br /> SHAR , <br /> PLAN <br /> OPERABLECUNIT <br /> TY1, DEFENCE DISTRIBUTION <br /> REGION (DDRW <br /> I have reviewed the above referenced submittals received 15 January 1993. The Draft <br /> Final Reports were prepared by James M. Montgomery (JMM) for the U. S. Army Corps of <br /> Engineers (COE) . Overall , the reports contain the basic elements needed to proceed <br /> with the thirty percent design phase. My comments on the draft final submittals <br /> referenced above are listed below. <br /> Draft Final Pre-Design Technical Summary Report <br /> 1 . The Concentration Contour Map (Figure 2-2) appears to be in error in its <br /> depiction of Plume 6 TCE concentrations. Monitoring well 455-A is shown to <br /> contain concentrations of TCE at 12,000 ppb. The concentration contours in <br /> Figure 2-2 for Plume 6 are opposite of what the data indicates, and do not <br /> show enough contours to reflect the concentration found in monitoring well <br /> 455-A. <br /> 2. Page 3-2, Section 3. 1.2. 1; This section states that upgrades to the North and <br /> South Balloon extraction systems will be evaluated during the remedial design <br /> process. Clarification is needed on which contracting agency will be <br /> conducting these evaluations and at what point, during the remedial design, <br /> will these evaluations be conducted. At what frequency will these evaluations <br /> be conducted during the remedial design phase, and how will this be <br /> accomplished? Will separate workplans be prepared for these upgrades? <br /> 3. Page 3-3, Section 3. 1 .2.4; This section refers to the shallow groundwater <br /> remediation program including a groundwater monitoring program. This section <br /> states that the monitoring program will involve bi-annual groundwater sampling <br /> and a 5-year site review based on the SWDRs. This program must include <br /> quarterly groundwater monitoring which would include an annual groundwater <br /> monitoring evaluation report similar to the reports currently being prepared <br /> for monitoring the North and South Balloon treatment systems. Bi-annual <br /> monitoring is unacceptable. <br /> 4. Page 4-1, Section 4.1 .1 .1 and Section 4.1.2.1; We are pleased that the 3-D <br /> modeling is being used in the remedial design process. The quarterly <br /> groundwater monitoring should confirm 3-D modeling projections and will <br /> demonstrate whether the requirements of the SWDRs have been met. <br /> 5. Page 4-7, Section 4.3.2. 1, Page 4-8, Section 4.3.2.3, and Page 4-10, Section <br /> 4.3.2.11; These sections all refer to design and installation of the <br /> extraction wells. Which contracting agency will be conducting the design and <br /> installation of the extraction wells? Will separate work plans be prepared? <br />