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Mr. Michael Desso • - 2 - 22 February 2005 Nestle USA, Inc. 3. Regional Board staff has found that many food-grade products that are used as substrate for enhancing bioremediation of CAHs contain relatively high concentrations of metals. The substrate should be tested for a full suite of metals and the results need to be provided to Regional Board staff for review prior to substrate injection. Although the matrix of molasses substrate may necessarily elevate the quantification limits of some metals, Nestl6 needs to instruct their contract laboratory to provide the lowest possible reporting limits. EPA Methods 1631 and 7199/1636 should be used for mercury and hexavalent chromium unless matrix problems prevent analysis using these methods. 4. Regional Board staff agrees that augmenting pump and treat actions in the Upper Aquifer with in situ carbohydrate-enhanced bioremediation is a worthwhile endeavor,but Nestle should consider conducting a pilot test in the Intermediate Aquifer too. Nestl6's plume in the Intermediate Aquifer is much larger and threatens many supply wells. Currently,Nestl6 has only one operating extraction well in the Intermediate Aquifer and addressing the hotspots in this aquifer now may significantly reduce the total cleanup time. Nestl6 should consider testing in situ carbohydrate-enhanced bioremediation for both the Upper and Intermediate Aquifers. 5. Only two groundwater samples from each CPT boring are proposed for delineating the treatment zone in the Draft Work Plan. The saturated interval in the Upper Aquifer is up to 95 feet thick beneath the Industrial Avenue property, so either explain how two samples will complete delineation of the Upper Aquifer or propose collection of additional depth-discrete groundwater samples. 6. The Draft Work Plan does not adequately address how Nestle will dispose of extracted groundwater containing substrate and sodium bromide. The existing on-site disposal options include discharge to the City of Ripon's sewer or non-potable water system. If Nestl6 is planning to use one of these options, the extracted groundwater must be treated for VOCs and any other constituents that the City of Ripon requires. The Final Work Plan should identify which disposal option will be used, provide confirmation that the City of Ripon will accept the discharge, and discuss what additional requirements (if any) the City is imposing on the discharge. 7. The Draft Work Plan does not discuss whether the short-term push-pull tests may result in incomplete reductive dechlorination and does not provide a contingency for creation of persistent vinyl chloride. The proposed test area is only equipped with a GAC treatment unit and GAC has proven to be a poor treatment method for vinyl chloride at the Nestle' site. Also, the injection of substrate may create other adverse breakdown products or mobilize some metals. Revise the Draft Work Plan to include adequate contingency plans for dealing with any potential adverse impacts caused by injection of the substrate. 8. Regional Board staff is concerned that groundwater extracted during the push-pull tests may contain excessive amounts of bacteria that could potentially foul the existing GAC treatment unit at the test area. The Final Work Plan should discuss whether disposal of the extracted groundwater could foul or reduce the effectiveness of the GAC, and if so, propose other treatment options. 9. The Draft Work Plan states one of the objectives of the push-pull tests is "assessing the potential for reducing conditions to mobilize trace metals that may be present in subsurface soils",but does not discuss how this will be accomplished. The proposed target analytes in Table 1 suggest that Nestl6