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F 03 March 1999 AGE-NC Project No 95-0142 ' Page 3 of 7 - 2 4 WELL COMPLETION ; s I Soil boring MW6 was completed as ground water monitoring well'MW6 at the northeast,edge of the _ ' former UST TK-90 The following is a summary of the exploration and construction details • The bonng for ground water monitoring well MW-6 was advanced to a total depth of 80 feet ' below surface grade (bsg) and completed with 0 02-inch slotted screen from depths of 70 to 80 feet bsg A filter pack was installed using#3 Lone'star sand from 70 to 80 feet Bentonite chips were used to make a 10-foot plug above the sand filter pack The remaining annular ' space was backf lied to the surface with,pord and cement A traffic-rated well box (8-inch diameter) was installed over the well, in accordance with San Joaquin County regulations ' As-built monitoring well specifications for monitoring well MW-6 are Included as Appendix A ' 2 5 MONITORING WELL PURGING PROCEDURES t x liet On i 1 December 1998,a Solinst water level meter was used to measure the depth to ground water in all monitoring wells (MW-1 through MW-6) and vapor wells screened in ground water (VW-1 through VW-4) at the site IAfter ground water depth measurements, a minimum of three well volumes of water was removed from each of wells MW-3, MW-4;MW-5 and MW-6 anI d VW-1 through VW-4 using a submersible ' pump Wells MW-I and MW-2 were not purged for sampling These wells have screen intervals , approximately 15 feet below the upper level of the water table ' Approximately 8 to 60 gallons of water were removed from each well, according to the purge- volume requirements Temperature, pH,and electrical conductivity were measured in purged water at regular purge-volume intervals using}an ICM water analyzer to monitor stabilization of these ' physical parameters Purge water stabilization field data sheets are included in Appendix A Purged = water was stored on-site in labeled DOT approved 55-gallon drums - 2 6 GROUND WATER SAMPLE COLLECTION ' Water samples were collected from each purged well (MW-3, MW-4, MW-5, MW-6, and VW-1 through VW-4)using new,clean,disposable-plastic bailers Immediately upon retrieval,the samples ' were transferred into EPA-approved 40-m1 VOA vials containing 0 5 milliliter hydrochloric acrd (18%) as a sample preservative The vials were then labeled and placed to a chilled container The samples were transported under chain-of-custody to McCampbell Analytical, Inc (MAI) a DHS- ' certified laboratory in Pacheco, California for analysis Ground water samples were analyzed in accordance for I ' ' Advanced GeoEnvsrenmental,Inc