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MEMORANDUM <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 <br /> TO: Antonia K. J. Vorster FROM: Camilla Williams <br /> Senior WRC Engineer Engineering Geologist <br /> DATE: 14 May 1991 SIGNATURE: 7.�[�yicl�CiU� LCC.lilrW� <br /> SUBJECT: REVIEN OF PHASE VI REPORT AND MINUTES OF THE 25 APRIL 1991 MEETING, NESTLE <br /> FOODS CORPORATION, SAN JOAQUIN COUNTY <br /> I have reviewed the Phase VI Report submitted by Camp, Dresser and McKee (CDM) for <br /> the Nestle Foods Corporation (Nestle) site. On 25 April 1991, a meeting was held to <br /> discuss the Phase VI Report and other issues involving the remediation at the site <br /> (Attachment 1) . The list of attendees is attached (Attachment 2) . <br /> PHASE VI REPORT <br /> Overall the Phase VI Report was comprehensive and concise and the graphics presented <br /> in the Report were above average. I concurred with the recommendations regarding <br /> the need for additional well installations, further calibration of the ground water <br /> model and completion of the Feasibility Study (FS) . <br /> At the meeting and during a telephone conversation with Ms. Sara Black of CDM on <br /> 2 May 1991, my major concerns with the remedial investigation were discussed and <br /> recommendations were made for additional work to be conducted. My major comments <br /> and concerns are listed below. <br /> WATER LEVEL AND WATER QUALITY DATA REVIEW <br /> 1 . Nestle should consider reducing the monthly ground water level monitoring in all <br /> of the wells to quarterly. Nestle has been collecting monthly ground water <br /> levels for over four years. Seasonal trends and regional and local impacts due <br /> to pumping centers should still be able to be defined with quarterly <br /> measurements. <br /> 2. Nestle should use the wealth of monthly ground water level measurements to <br /> prepare additional graphics to better define the characteristics of the <br /> aquifer's historical responses to stresses placed on the aquifer. I recommend <br /> that the monthly ground water elevations be use to construct the following <br /> graphics. These graphics, if constructed, may help to illuminate the reasons <br /> for historical changes in flow direction and plume movement and may aid model <br /> calibration. <br /> a. Hydrographs should be constructed for every well , particularly those wells <br /> with the longest historical records. Trends and patterns should be <br /> interpreted and may be compared to hydrographs of precipitation and trend <br /> (concentration versus time) graphs. <br /> b. Change maps may be informative and can be constructed from season to season <br /> or over a longer period of time (for a period of years) . The lateral <br /> distribution of major head changes may delineate those areas of the aquifer <br /> most responsive to hydraulic changes. Therefore, these maps may be useful <br />