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440 West Charter Way, Stockton, California September 16, 1992 • Texaco Environmental Services Page 3 throughout the life of the project Each extraction point consists of 4-inch diameter, 0 020- inch slot PVC well screen and blank PVC well casing A sand pack was placed around the screen and one to two feet above each section of screen using a number 2/12 Monterey sand or equivalent Each extraction point was sealed within the boring by placing a foot thick bentonite seal above the sand pack Construction details of the VE's are presented on the drill logs in Appendix A 3 2 Sod Vapor Extraction Pilot Test A sod vapor extraction (sod-vent) pilot test using the newly installed vapor extraction wells, was conducted on June 24, 1992 Permission was obtained from the San Joaquin County Air Pollution Control District prior to conducting the test The test was conducted to determine the radius of influence and the concentration of hydrocarbons in the soil vapor extracted from the VE's Vapors were drawn from each extraction well by a 1 5-hp regenerative blower Flow rate during the test was monitored with a Kurz model 441 air velocity meter, and was varied between 22 and 38 cubic feet per minute (cfm) Effluent from the blower was routed through a series of two 55-gallon drums of vapor phase granular activated carbon (GAC) Vapor emissions were controlled using GAC and the effluent air flow was monitored periodically throughout the test to ensure that hydrocarbons were being removed from the air flow prior to discharge During the test a sample from each extraction well was collected in a Tedlar bag and shipped with a chain-of-custody manifest to a Texaco approved laboratory for analysis for BTEX and TPH-G according to EPA methods 5030/8015/8020 4.0 SOIL VAPOR EXTRACTION TEST RESULTS The results of vacuum measurements taken during the soil vent pilot test are recorded in Table 1 , Both level A and level B wells required high vacuums ranging between 50 and 56 inches of water Within each individual extraction well the radii of influence generated in the A and B levels were similar However, the radii of influence determined for each nested well location varied from well to well Extraction well clusters located on the eastern side of the property (VE-3 and 4), recorded a greater air flow rate and induced a greater vacuum in observation wells; than those located adjacent to the Food Mart budding (VE-1 and 2) Vapor extraction 1701JI GROUNDWATER I'111--11 TECHNOLOGY