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Ms. Vera Fischer, P.G., RWQCB February 28, 2018 Work Plan for Additional Site Assessment Project No. 2154-1817-01 1817 South Fresno Avenue, Stockton, CA Page 2 the port of Stockton Turning Basin and 0.75 miles northeast of the San Joaquin River. The property is currently used as a truck, recreational vehicle, and boat parking area. The current configuration of the property is depicted on Figure 2. SITE HISTORY Petroleum hydrocarbon impact to the subsurface was discovered in 1992, at the time that two underground storage tanks (USTs) were removed from the subsurface. Beginning in 1997, subsurface investigation and sampling work was performed in order to assess conditions and levels of contaminants beneath the property. This work included the installation of 31 monitoring/remediation wells at the Site, advancement of at least 15 additional soil borings, and performance of groundwater monitoring and sampling for nearly 20 years. Table 1 provides a summary of information concerning the construction of the monitoring and remediation wells. The following presents a historical summary of conditions and events at the Barnes Trucking Facility, based largely on information provided from data and reports available on the State of California's GeoTracker website. Based on the available data, most of the petroleum hydrocarbon mass appears situated between about 15 and 30 feet below surface grade, although the extent of impact extends to over 60 feet bgs and is undefined. Groundwater monitoring and sampling beneath the property has been performed since September 1997, and is ongoing. Groundwater levels beneath the property have fluctuated between about 4 and 12 feet bgs between 1997 and March 2017. Groundwater flow beneath the property has been consistently to the southeast. Figures 5 and 6 illustrate the generalized extent of gasoline range organics (GRO) and benzene in shallow groundwater using Fall 2017 data (respectively). Groundwater samples are no longer tested for fuel oxygenates, including methyl tertiary butyl ether (MTBE), due to the absence of these analytes in historical samples. For approximately five years (beginning in 2004), a previous consultant (Clearwater Group) utilized an in-situ submerged oxygen curtain (iSOC) technology in an attempt to mitigate Site contaminants. Limited remedial progress appears to have resulted from use of the iSOC system, and given this condition, Clearwater Group prepared a Remedial Action Plan (RAP) in July 2010, that proposed to remediate Site contaminants using an alternate approach. The July 2010 document proposed to perform an in-situ chemical oxidation (ISCO) project that included addition of hydrogen peroxide and iron catalyst, with concurrent de-watering using large diameter (8-inch) wells. In August 2010, the previous regulatory agency for the Site (San Joaquin County Environmental KABames Trucking\Work Plans\bames trucking cpt work plan 2018.doc STRATUS