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ATIAMMENT 2• INSTALLATION OF REMEDIATION WELLS A total of nine wells were installed by Westex Drilling Corporation Seven remediation ' wells were installed in November 1996 The two remaining remediation wells were installed in January 1997 due to station construction activities The borings were drilled to approximately ' 30 feet bgs During drilling, soil samples were collected at 5-foot intervals and retained for analysis Additional sampling was conducted for hthologic description ' Soil samples were collected by advancing a modified California split-spoon sampler, equipped with brass liners, into the undisturbed soil beyond the tip of the auger The split- spoon sampler was washed in a solution of nonphosphate detergent and potable water and triple rinsed in potable water prior to each use. Soil samples were described by a Geraghty & ' Miller representative using the Unified Soil Classification System Boring logs are presented in this attachment Soil samples to be analyzed were retained in the brass liners, sealed with ' TeflonTM tape and plastic end caps, placed on ice, and transported to Sequoia Analytical in Walnut Creek, California (Sequoia), along with appropriate chain-of-custody documentation The samples were analyzed for TPH as gasoline (USEPA Method 8015, modified) and BTEX with MTBE (USEPA Method 8020, modified) Soil sample analytical results are shown in Table 1 Analytical reports are included as Attachment 4 The soil generated during the field ' activities was placed in a stockpile onsite pending proper disposal Water generated during the field activities was placed in drums pending proper disposal The bongs were converted into double-completion remediation wells by installing two 2-inch diameter Schedule 40 PVC flush-threaded solid and screened casing into each boring ' through the hollow-stem augers The shallow completion (vadose zone) well will be used for SVE, and the deeper well will be used for biosparging The screened interval for the bio- nsparging wells, consisting of 0 02-inch slots, extends up from the bottom (at 27 to 30 feet bgs) of each boring approximately 2 to 3 feet A sand pack of#2112 Monterey sand was placed in ' the annular space surrounding the screened casing to a depth of approximately 1 foot above the screened interval. Coated bentonite pellets were used to create an effective seal between the wells The bentonite seal extends from above the sand pack for the biosparging well to approximately 18 feet bgs Between 5 and 8 feet of clay seal separate the biosparging well from the SVE well i GACNCHMOND DATA.CHEVRON CHEM N Z WRENJAM COM-ACT AUAh2 doc GERAGHTY&MILLER,INC %49