ARCHIVED REPORTS XR0013077 - Laserfiche WebLink

Home Browse Search

2905 West Benjamin Holt Drive, Stockton, California March 16, 1994 Chevron U.S.A. Products Company Page 11 and/or horizontal vapor extraction wells screened in the zone of highest residual hydrocarbon concentration using a vacuum blower. The resulting air flow through the soil pores causes residual hydrocarbons to volatilize into the vapor phase. The pressure gradient in the subsurface induced by the vacuum blower captures hydrocarbon vapors through multiple extraction points. Extracted hydrocarbon vapors are then routed through an appropriate combustion/catalytic/adsorption device to destroy or remove hydrocarbons prior to release to the atmosphere. Groundwater is remediated indirectly by soil vapor extraction by removal of residual hydrocarbons in contact with groundwater, direct volatilization of hydrocarbons dissolved in groundwater and by enhanced biodegradation caused by increased oxygen in the subsurface. Lithologic data collected during preliminary investigation at the site suggest that vapor extraction is a technically feasible alternative for remediation of hydrocarbon-impacted material at the site, however, further testing would be required to verify this. A concurrent groundwater monitoring program would help evaluate the effectiveness of soil vapor extraction, In addition, further definition of hydrocarbon-impacted soil on site would enhance the implementation of this alternative. In order to Implement this corrective action alternative, further assessment would be required to evaluate the site specific feasibility of soil vapor extraction as a remediation technology. Assessment would +�.. require a soil vapor extraction test to determine the concentrations of BTEX and TPH-G in the extracted soil vapor, the radius of influence attainable through vapor extraction at the site and the flow rates allowed by subsurface material beneath the site. The test would be conducted using the existing vadose zone well and selected groundwater monitoring wells as extraction points and measuring the induced vacuum at the surrounding groundwater monitoring wells during extraction. Air samples would be collected to determine the concentration of BTEX and TPH-G in the extracted vapors. Extracted vapors would be controlled by an approved emission control method throughout the test. Data collected during the test would provide information necessary for remediation system design. Upon analysis of pilot test results, a work plan detailing the steps required to install and implement an effective soil vapor extraction system at the site would be submitted to SJCPHS and the CRWQCB-CVR for approval. 4.5 Air Sparging with Soil Vapor Extraction Air sparging involves forcing air under pressure through a short section of well screen into the saturated zone generally at a point 5 to 20 feet below the water table. Air sparging creates air-filled pores in the saturated zone which facilitates direct volatilization of hydrocarbons from unsaturated and saturated soil 5073PAR.RPT S GROUNDWATER:EE TECHNOLOGY