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RTCs on AASF Annual Report - 2 - 19 August 2014 <br /> Stockton CA ARNG <br /> A summary of findings of"Report on Groundwater Grab Sampling, Groundwater Monitoring Well <br /> Installation, and Soil Gas Investigation, California Army National Guard Army Aviation Support Facility, <br /> Stockton, California. September(SI Report, OTIE 2011b)"is provided below. <br /> . Impacts from petroleum hydrocarbons, related compounds, and select VOCs in excess of <br /> potentially applicable groundwater standards are confined primarily to the immediate vicinity of <br /> the former 20,000-gallon USTs and former wash rack. The noted exceedances were generally <br /> limited and minimal. <br /> • Site soil conditions (dominantly fine-grained soils to approximately 25 feet bgs, with interbedded <br /> sand zones and fine-grained soils below) appear to have limited to some degree the downward <br /> migration of petroleum hydrocarbons and related VOCs from the former 20,000-gallon USTs and <br /> former wash rack, based on the limited extent of these compounds detected in site groundwater. <br /> • A quarterly groundwater monitoring program implemented as part of this investigation, and <br /> including six wells, confirms that impacts to groundwater only occur in the immediate vicinity of <br /> the former 20,000-gallon USTs and former wash rack, and have not migrated appreciably away <br /> from that location. <br /> • Overall, results for groundwater, soil, and soil vapor indicate that impacts from petroleum <br /> hydrocarbons, related compounds, and VOCs are limited in extent and have not migrated <br /> appreciably away from the location of the former 20,000-gallon USTs and former wash rack. <br /> This response partially satisfies our comment. CA ARNG also needs to revise the <br /> Annual Report to clearly define the extent of the residual solvent contamination, identify <br /> the range of residual concentrations, and briefly compare them to applicable water <br /> quality objectives. CA ARNG should provide a new figure(s) that clearly shows the <br /> extent of residual solvents and the extent of residual petroleum hydrocarbons. <br /> Also, if CA ARNG considers tetrachloroethene, trichlorothene, and their degradation <br /> products to be constituents of"VOCs", then the definition of "VOCs" needs to be <br /> revised. Currently, the Annual Report defines "VOCs" as TPHg, naphthalene, and <br /> BTEX. <br /> Specific Comment 3: Page 5-1, Section 5.1, Site Background for Inorganics: Revise <br /> this section to explain why the highest concentration of each inorganic detected in site <br /> monitoring wells, prior to injection of the oxygen-release compound, was determined to <br /> be background. <br /> California Army National Guard Response: Page 5-1, Section 5.1, first paragraph, second <br /> last sentence is revised as below. <br /> "Site background values for inorganics were determined by the highest inorganic values in the <br /> groundwater of MW-1, MW-2, MW-3, MW-5, and MW-6, as sampled prior to the implementation of <br /> treatment activities, in compliance with the M&RP Order and California Code of Regulations (CCR) <br /> Section 20415(e) (10)." <br /> CA ARNG still needs to revise the Annual Report to briefly explain why selecting the <br /> highest inorganic concentrations from the background data set is appropriate for <br /> representing site background. Also, please remove the Feference to Title 27 as the AASF <br /> is not a waste management unit or waste disposal site. <br />