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River City Petroleum 2 - 29 January 2041 Connell Motor Lift Truck Stockton, San Joaquin County Since November 2004, the Soil Vapor Extraction (SVE) interim soil remediation in the USTs source area has removed approximately 3,630 gallons of petroleum hydrocarbons. In 2007, four Air Sparge (AS) wells were added in the shallow source area to the existing SVE system (Figure 12) for a 6-month SVE/AS pilot study. The CAP states the SVE/AS pilot study was effective in reducing petroleum hydrocarbon concentrations in shallow groundwater; however, the effectiveness of AS in deeper zones is questionable due to the prevalence of fine-grained sediments. Fine-grained sediments can significantly reduce the AS radius of influence or prevent the capture in the shallow SVE wells of the more volatile daughter constituents (gases chloroethane and vinyl chloride, enclosed Table 1.1 with Figure 1.41) of 1,2-DCA. Deeper AS may also cause the groundwater plume to migrate laterally beyond the existing monitoring well network through the preferential pathways under the fine-grained sediments. The CAP evaluated four additional remediation technologies for the deeper groundwater plume: including groundwater pump and treatment (GWP&T), monitored natural attenuation (MNA), insitu chemical reduction (ISCR), and insitu chemical oxidation (ISCO). With the exception of ISCR, feasibility tests have been conducted for the technologies listed above. 1 . A groundwater pump and treat pumping test in 2002 from extraction well EW-1 reported that the fine-grained units significantly slowed recovery rates, and that the approximately 17,0000,000 gallons of groundwater calculated as impacted by petroleum hydrocarbons would result in an unacceptable time to completion. The cost for GWP&T was estimated as up to $450,000. 2. MNA depends on chemical or biological processes to reduce concentrations of petroleum hydrocarbons. A laboratory bioenumeration study conducted in 2002 confirmed the presence of petroleum hydrocarbon degrading bacteria, however the bacteria counts were lower in the deeper zones, due to a lack of available nutrients. The dissolved oxygen levels in the deeper zones were also low. The MNA cost was not estimated due to the variability associated with long-term monitoring (up to decades), however the CAP stated that MNA may be required. 3. An ISCO bench scale test conducted in 2004 reportedly produced hexavalent chromium in water samples that did not degrade during the post-ozone injection testing phase. Due to secondary impacts to water quality, ISCO was not a recommended option. The ISCO cost was not estimated. 4. The ISCR injection technology promotes reductive (anaerobic) bioremediation. The recommended ISCR compound, trade named Hydrogen Release Compound (HRC TM) is a lactic acid that releases hydrogen ions as a nutrient for anaerobic bacteria, which consume and reduce the 1,2-DCA to ethane, ethene, and carbon dioxide. The CAP recommends conducting a pilot study for ISCR near monitoring wells MW-24 and MW-26, which are located inside of the warehouse. If the pilot study is successful, a full-scale injection plan described in the CAP (enclosed Figure 10 and Figure 11) expands the treated area to approximately 80 feet by 300 feet on a 20-foot by 20-foot grid, with first injected grid depths of 80 feet bgs to 100 feet bgs and second injected grid depths from 120 feet bgs to 150 feet bgs. The cost for ISCR is estimated as up to