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• ........... - .................................................• .......... The Transmission Store -2- 23 February 2015 515 E. Charter Way, Stockton San Joaquin County at 16.53 grams H2O2 per gram of TPH) three times over a five week period (bi-weekly) to compensate for the competing reaction of the H2O2 with the natural organic content in the soil. AGE also included a figure showing the location of the injection well (no designation given), and identified background well (MW-2R), treatment zone well (MW-7S), transition zone well (B4R/VW-2D), and compliance well (MW-4R-S). Previously in the 12 December 2014 In-Situ Chemical Oxidation Pilot Test Work Plan—Addendum, AGE proposed a Contingency Plan that included cessation of injections and bulk groundwater extraction events until water quality is restored should potential adverse oxidation byproducts (e.g., mobilization of hexavalent chromium) be detected in groundwater. Groundwater monitoring was proposed to be increased to monthly during bulk groundwater extraction events to determine the effectiveness of the contingency action. Comments: 1. Background sampling for metals is necessary for establishing the trigger level for implementing a contingency plan if concentrations of metals in compliance zone wells exceed 20 % of background, not to exceed the water quality objective. Treatment zone and transition zone wells may temporarily exceed the trigger levels however, if the trigger level is exceeded in the compliance zone well MW- 4R-S, then the contingency plan will need to be implemented. Background cannot be established from analysis of groundwater in wells that have been impacted by petroleum pollution. Sampling from wells MW-4R-S, MW-7S and B4R/VW-2D to establish background, as proposed, is not needed. Please submit results of metal analysis from MR-2R by 15 April 2015. No injections may be implemented until background and trigger levels are established for this project. 2. AGE indicated it will quadruple the amount of hydrogen peroxide to compensate for organic carbon in the soils underlying your site. A site specific determination of the level of organic carbon should be developed. Soil samples may be collected during construction of the single injection well and analyzed for total organic carbon by EPA method 5310B. The analytical results should then be used to re-calculate the carbon load in the stoichiometric equation, to get a more representative amount of H2O2 solution needed to adequately promote remediation of the petroleum pollution. Please submit results of the total organic carbon content in soils from your site with any potential adjustments to the proposed peroxide solution concentration and volume by 30 June 2015. 3. Central Valley Water Board staff concur with the proposal to reduce the scope of this pilot study to a single injection well. The map figure submitted showing the locations of wells for monitoring up- gradient and down-gradient groundwater quality and designated as treatment zone, transition area and compliance wells is acceptable. Since the scope of this project has been reduced to address pollution in the shallow water table only, our request for analysis of metals in the intermediate water bearing zone is retracted. In summary, please submit the following: • Results of metals analysis from groundwater collected from well MR-2R in a letter report by 15 April 2015.