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ARCO Station 548 S EC R 1612 West Hammer Lane,Stockton Remedial Action Plan 'May 31,2006 i I - 6.2 Remedial Alternative Recommendation The magnitude of dissolved concentrations of dissolved petroleum hydrocarbons and MtBE beneath and downgradient of the site do not warrant the use of large scale conventional remediation systems. Based on the subsurface lithology and hydrology, location of UST and the successful use of air sparge to reduce dissolved petroleum hydrocarbons and MtBE concentrations at other sites, SECOR recommends remediation of the groundwater at the site using the existing AS system. AS will increase the aerobic biodegradation rate of petroleum hydrocarbons and oxygenates dissolved in groundwater. Air will be injected into the three .existing air sparge wells (AS-1 through AS-3). The injected volume and number of wells used will be adjusted to maintain the concentration of dissolved oxygen in the monitoring wells at or above 5 mg/kg. In order to determine the operational status of the existing system and the configuration of the system a feasibility test is proposed and the work plan for this test is included below. 6.3 Proposed Work Plan For AS Feasibility Testing The three AS wells are shown on Figure 2. The wells are located near and downgradient of the LISTS in areas of the maximum concentrations. The objective of the feasibility test is to measure the radius of influence of the sparging system and to determine the system operating parameters. The specific scope of work is discussed below: • Health and Safety Plan. A site-specific Health and Safety Plan (HASP) will be prepared as required by the Occupational Health and Safety Administration i (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120), and by California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192). Field staff and contractors will review the HASP before beginning field operations at the site. • Permitting and Utility Clearance. The applicable permits for well installation activities will be obtained prior to beginning work. • Baseline Data. To measure the radius of influence of the AS wells baseline data (DO concentrations, depth to water, pressure [inches of water], and wellhead organic vapor concentrations with a PID/FID) will be collected in all site wells prior to system start up. This information will be used to establish a background range for groundwater at this site. • Well Influence Test. All valves on the SVE system will be closed and the system will be restarted with 100% dilution air (so that the AS system will operate). Pressure gauges will be installed on the AS wells. Following system restart, a two-hour air sparge well influence test will be conducted on each of the AS wells. All site wells will be monitored at regular intervals during the test to determine the radius of influence of the AS wells. L� �,2 • Report. Following completion of test a report will be prepared documenting the field activities and the feasibility of using AS to remediate groundwater at this r site. The report will include field notes, system operation information, and f , analysis. U I:1BP-ARC0104 BP valley Portfolio15481Reports\RAP1548 RAP.doc