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STATE OF CALIFORNIA- Environmental Protectiency • PETE WILSON Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road, Suite A Sacr$mento,CA 95827-3098 PHONE: (916) 255-3000 FAX: (916) 255.3015 94 APR 19 f pt}l G; 15 April 1994 Mr. Frank Zumstein Nestles Beverage Company 230 Industrial Ave. Ripon, CA 95366 SITE-WIDE COMPREHENSIVE GROUND WATER MONITORING PLAN AND 1993 ANNUAL REPORT, NESTLE BEVERAGE COMPANY, RIPON We have reviewed the Site-Wide Comprehensive Ground Water Monitoring Plan and the 1993 Annual Report, received on 30 December 1993 and I April 1994 respectively. Both reports are well written and data are presented in easily decernable format. These reports were submitted as part of the long-term ground water sampling program. The Plan, however, lacks a data management plan to handle the structure of reporting the data in this long-term program. Also the Plan has no mechanism for an annual evaluation to change or update the sampling plan, based on new data. Below are specific comments on the Site-Wide Comprehensive Ground Water Monitoring Plan: 1. A discussion is needed on the structure of the Annual Report and the format of data presentation. The present format of the Annual Report is acceptable. But, this general discussion is needed to keep a consistent format if a change in consultants should occur. 2. The sampling plan portion of the Monitoring Plan should be evaluated and updated annually and presented in the annual report. This would require a review of past years monitoring for each well and an evaluation of any needed changes. The update should: • propose the subsequent revised sampling Program using the decision process developed in the Monitoring Plan and • provide support for the adequacy of the proposed sampling or for any proposed changes. 3. Figure 2-1, Ground Water Monitoring Frequency Decision Tree we believe needs modified in the following areas: a) The decision to sample for wells within the plume should be based on consistency of data, not single detection. A well with inconsistent data should be sampled more often to develop a trend or a discussion on why the results are inconsistent. Just because a well has a one time level of nondetect should not in itself justify more or less sampling. A statistical method should be developed to determine if wells within the plume are giving consistent sampling results. If consistency is shown, the sampling maybe reduced.