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Mr.Ron Rowe June 2, 1997 Page 4 3.3 Monitoring Well Development,Sampling and Surveying The cement grout surface seals will be allowed to set for a minimum of 48 hours prior to monitoring well development. Prior to well development,SECOR will measure depth-to-groundwater for the new and existing monitoring wells, including Texaco monitoring wells MW-6, MW-8 and MW-14. The new wells will be developed by alternately bailing and surging until the groundwater is reasonably free of sediment and at least 10 well casing volumes are removed. Monitoring well MW-I will also be purged of at least three well casing volumed by bailing. During well development and purging,measurements and observations of pH,electrical conductivity, temperature,color,and turbidity will be recorded. Following well development and purging, SECOR will collect groundwater samples from monitoring wells MW-1,MW-2,and MW-3 for chemical analysis. SECOR will attempt to coordinate sampling with the Texaco Service Station quarterly monitoring event in an effort to gather time correlative groundwater elevation and chemical data. Prior to sampling, wells will be allowed to recover to 80% of the initial water level prior to development. Groundwater samples will be collected using a disposable PVC bailer and decanted directly into laboratory-supplied sample containers. Each of the sample containers will be labeled, sealed in plastic bags, and placed in an ice-filled cooler. The samples will be submitted to a California state-certified analytical laboratory along with a completed chain-of-custody record. The newly-installed groundwater monitoring wells will be surveyed for top of casing elevation relative to mean sea level(msl)by a professional land surveyor and tied into existing Site elevation data. 3.4 Soil Vapor Extraction/Air Injection Pilot Test SECOR will perform a one day SVE/AI pilot test at vapor extraction well VE-1 to evaluate the feasibility of utilizing SVE/AI technology for remediation of petroleum hydrocarbon-impacted soil and groundwater beneath the former USTs. An 8-hour pilot test will be performed that will include approximately four hours of SVE operation followed by approximately four hours of combined SVE/AI operation. The pilot test will be conducted using a trailer-mounted VR Systems Internal Combustion (IC) engine and a 5.5-horsepower Speedaire air compressor. Extracted soil vapors will be discharged to the atmosphere in accordance with the requirements of the San Joaquin Valley Unified Air Pollution Control District. During the SVE/AI pilot test,SECOR will measure and monitor SVE and AI flow rates, vacuums,pressures and induced vacuums at 30 minute intervals. Monitoring well MW-I will be utilized as a monitoring point for evaluation of the SVE radius of influence. Influent and effluent volatile organic compound concentrations will be measured at approximately 30 minute intervals using a PID. During the pilot test, four influent and one effluent air samples will be collected in Tedlar sample bags. The air samples will be submitted to a state- certified analytical laboratory for chemical analysis under chain-of-custody documentation. H:\SFFB\STOCKTON\W PLN.RPT 50090-011-03,001