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2905 West Benjamin Holt Drive, Stockton, California March 16, 1994 <br /> Chevron U.S.A. Products Company Page 10 <br /> plume does not migrate beyond the isolated area. It should be mentioned that further definition of <br /> hydrocarbon-impacted soil and groundwater on site would enhance the implementation of this <br /> alternative. <br /> 4.3 Bio-Sparging <br /> Bio-sparging involves the introduction of air through a short section of well screen into the saturated <br /> zone generally at a point 5 to 20 feet below the water table. Bio-sparging provides oxygen at a low rate <br /> to an oxygen deficient environment. The increased levels of oxygen then enhance the natural <br /> biodegradation of hydrocarbons. The low injection rate of oxygen is adjusted to sufficiently promote <br /> bacterial proliferation in the saturated and unsaturated zones and consequent oxidation of hydrocarbons <br /> to water and carbon dioxide. Hydrocarbon vapors are not emitted, and as a result, the process does <br /> not require vapor capture equipment or off-gas treatment. Lithologic data collected during preliminary <br /> investigations indicate that bio-sparging is a technically feasible alternative for hydrocarbon remediation <br /> at the site. Because hydrocarbon-utilizing bacteria are present throughout the subsurface, bio-sparging <br /> may remediate hydrocarbons in both the saturated and unsaturated zones. <br /> In order to implement this corrective action alternative, further assessment and continuation of the <br /> groundwater monitoring and sampling program would be required. Assessment would include further <br /> delineation of hydrocarbon-impacted soils, installation of a bio-sparge test well, and bio-sparge testing. <br /> A bio-sparge test well would be installed in the vicinity of the former UST pit where the highest dissolved <br /> hydrocarbon concentrations have been observed. A bio-sparge test would be conducted by injecting air <br /> at low flow rates and monitoring induced pressure, depth to water, dissolved oxygen and hydrocarbon <br /> vapor concentrations at the surrounding monitoring wells. Measurements obtained during testing would <br /> provide information regarding optimum injection rates and pressures for bio-sparging. <br /> Upon analysis of bio-sparge test results, a work plan detailing the steps required to install and implement <br /> a bio-sparge system would be submitted to SJCPHS and the CRWQCB-CVR for approval. <br /> 4.4 Soil Vapor Extraction <br /> Soil vapor extraction is a remediation technology proven to rapidly remove petroleum hydrocarbons <br /> from the subsurface. Soil vapor extraction is typically performed by applying a vacuum to vertical <br /> 5073PAR.RPT GROUNDWATER <br /> �I��. TECHNOLOGY <br />