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2 3 2 Nested Air S ar e/Soil Val2or Extraction Well <br /> Woodward Drilling installed the air sparge and soil vapor extraction well nest to a total depth of <br /> approximately 55 feet The air sparge well was constructed with a 3-foot microporous bubbler <br /> (KVA spargepointTM) section, spanning from approximately 52 to 55 feet bgs, and one-inch PVC <br /> casing to the surface The soil vapor extraction well consisted of two-inch diameter PVC casing <br /> and (0 020-inch slot) PVC well screen, spanning from approximately 30 to 45 feet bgs <br /> Woodward Drilling placed a filter pack of Monterey#3 graded and washed sand around the <br /> sparge point and soil vapor extraction well screen intervals, and approximately two feet above the <br /> tops of the spargepoint and screen intervals Between the two filter packs, the driller installed a 5- <br /> foot thick layer of hydrated bentonite from approximately 45 to 50 feet bgs A four-foot thick <br /> hydrated bentonite seal was also placed over the top of the soil vapor extraction well filter pack <br /> Overlying this upper bentonite seal, the driller installed a surface seal of neat cement grout to the <br /> surface The well casings were secured with watertight locking caps, and the well nest was <br /> completed with an 18-inch diameter, traffic-rated, flush-mount street box <br /> 24 Soil Sampling and Analysis <br /> During drilling, soil samples were collected at five-foot intervals using a modified California split- <br /> spoon sampler lined with 2-inch diameter by 6-inch long stainless steel sleeves A Ramage <br /> Environmental field geologist logged each of the soil samples for geologic and hydrogeologic <br /> characteristics and screened each sample for organic vapors using a photoionization detector <br /> (PiD) The well logs are included as Appendix C <br /> To further evaluate the lateral extent of impacted soil west of MW-6, the soil samples collected at <br /> 50 and 55 feet bgs from the boring for MW-7 were submitted for laboratory analysis To update <br /> the soil sample analytical profile in the former UST source area, a total of 10 soil samples <br /> collected during the drilling of the remedial feasibility test wells were submitted for laboratory <br /> analysis These soil samples were sealed with Teflon film and plastic end caps, labeled, and <br /> transported in an iced cooler with chain-of-custody documentation to Excelchem Environmental <br /> Labs (Excelchem), a state of California certified hazardous waste testing laboratory (Certification <br /> #2119) Excelchem analyzed each of the soil samples for TPH-as-gasoline, BTEX, oxygenates <br /> (MTBE, DIPS, ETBE, TAME, TBA), and 1,2-dichloroethane (1,2-DCA) by EPA Method 8260B <br /> 8 <br />