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^ ,1 20 December 2001 AGE-NC Project No 00-0769 Page 2 of 5 _ I TPH=g, BTEX and 1,2-DCA have been detected at conbentrations as high as 230,000 gg/1, 46,000 gg/l and 3,800 gg/l,respectively,in groundwater samples collected fromMW-1,MW-2A,MW-2B, MW-3A and MW-3B The highest concentrations of analytes have been detected in MW-1, the lateral and vertical extent of dissolved-phase hydrocarbons has not been defined by the current ground water monitoring network In August 2001, six cone penetrometer testing (CPT) borings were advanced at the site Ground water! samples were collected from each boring to depths as great as 173 feet bsg Petroleum I hydrocarbon-constituents were detected in 27 of the 29 `grab' ground water samples collected TPH-g, benzene and 1,2-DCA were detected at concentrations as high as 140,000 micrograms per liter(gg/l), 33,000 µg/l and 2,700 V.g/l,respectively Procedures and results of the August 2001 site subsurface investigation were presented in Cone Penetrometer Testing Site Investigation Report, ' dated 10'December 2001, prepared by AGE 3.0. PROCEDURES 4 • On 03 December 2001, ground water monitoring was performed at the site Field procedures were - performed in accordance with Central Vailey Regional Water Quality Control Board(CVRWQCB) and San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD) ' guidelines for subsurface investigations of underground storage tank (UST) sites and sampling ground water monitoring wells, respectively 3 1 WELL�MONITORING AND EVACUATION ' ` i ' On 03 December 2001, the depth to ground water was measured from the top of each well casing to the nearest 0 01-foot utilizing a Solmst water level meter Ground water elevations in each well were calculated by subtracting the measured depth to ground water from surveyed casing elevations ' (Table 1) During the December 2001 monitoring event, a two-stage pump was used to purge wells MW-2A ' and MW-3A of standing water following depth to water measurments,new disposable plastic bailers were used to purge wells MW 1, MW-2B and MW-3B Approximately 6 to 45 gallons of water (a I minimum of 3 casing-water volumes) were removed from each sampled well Ground water temperature,pH and conductivity were measured at regular intervals during purging using an Oakton water analyzer Field sheets and data from the December 2001 monitoring events are included in ' Appendix A Purged water was stored on-site in labeled, 55-gallon DOT-approved drums Advanced GeoEnvironmentai,Inc