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Mr. Mike Desso • - 2 - . 3 October 2006 i Regional Water Board Comments on Proposed Monitoring Wells Nestle proposes to install 16 groundwater monitoring wells within three aquifers. Six of the wells would be installed in the Upper Aquifer, defined as the water bearing soil between the water table at approximately 20 feet below the ground surface (bgs) and 120 feet bgs. Five wells would be installed in the Intermediate Aquifer, defined as the soil from 120 to 200 feet bgs. And five wells would be installed in the Lower Aquifer, defined as the soil from 200 to 390 feet bgs. There is significant hydraulic connection between the Upper and Intermediate Aquifers because the average hydraulic head measured in wells in both are approximately the same (within one tenth of a foot). However, the Lower Aquifer is not well connected to the Upper or Intermediate Aquifers because its average hydraulic head is approximately 5 feet lower. Regional Water Board staff has reviewed the draft Work Plan and have identified items that should be clarified, revised, or added in the final Work Plan. 1. Proposed well M-45A. It appears that this well will monitor northerly flow from the former facility in the direction of MW-13 as well as MW-5. Nestle should revise the Work Plan accordingly. 2. Concentrations of TCE and other contaminants identified in the report entitled "Initial Testing and Characterization Report, In Situ Groundwater Remediation Program", prepared by Geomatrix Consultants Inc. dated April 6, 2006. That report documented the drilling of 18 cone penetrometer test borings and the collecting of 51 discrete-depth groundwater samples in August and December 2005 from the Upper Aquifer at and immediately adjacent to the former facility. Laboratory chemical analyses indicated that concentrations of TCE were over 1,000 micrograms per liter in samples collected from six of the 18 borings. The final Work Plan should include a plan for monitoring this area of high contaminant concentrations in shallow zones of the Upper Aquifer. 3. Intermediate Aquifer plume west of the M-21 well nest. Starting in July 2003, concentrations of TCE and cis-1,2-DCE in well M-2101 have been reported during every quarter. Nestle should install a down-gradient monitoring well to the west of M- 21C1. 4. Text errors Page 6, second bullet item. This item indicates that monitoring well M27D only had detections of volatile organic compounds (VOCs) in May 2002. However, that monitoring well also had a detection of TCE in May 2005. Also, Nestle should indicate that the Ripon Christian School water supply wells are screened in the Intermediate Aquifer, not the Lower Aquifer. 5. City of Ripon municipal well MW-4. The Work Plan indicates that municipal well MW- 4 is now permanently non-operational. Nestle should explain what is meant by "permanently non-operational'. Has the well been disconnected or changed in some way that makes it impossible for the City of Ripon to use it in the future? 6. Fox River water supply well PW-8. The Work Plan indicates that Fox River Paper Company well PW-8 is only pumped minimally and produces very small to no apparent influence on the Lower Aquifer potentiometric surface. Nestle should include supporting data for this statement in the final Work Plan.