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• REvISEO WORKPLAN FON7.41TIONAL INVESTIGATION. ACO PROPERTYSEPTEMBER 999 Workplan for Additional Investigation at Disco Property, Stockton, CA (Version 4) Introduction This workplan describes additional investigation activities to be undertaken at the Disco Property located at 110 North Filbert Street in Stockton,CA.The purpose of this workplan is to obtain additional data in the area of highest observed concentrations of petroleum constituents in order to evaluate future additional remedial activities. Background In February 1995 an air sparging/soil vapor extraction system(ASISVE) system was installed and operated at the Disco Property to reduce concentrations of gasoline constiments in the apparent core of the plume.The system consists of two sets of AS/SVE wells and two sets of nested piezometers and operated until November 1995, when rising groundwater Bevels submerged the SVE wells.An estimated 8,787 pounds of TPH-gasoline were removed during the Eystem operation,however elevated concentrations of gasoline constituents are still present in groundwater samples from this area. Scope of Work The work will involve CPT'logging,grab groundwater sampling, and soil sampling, all performed using the same sampling vehicle. . Prior to undertaking field work, utilities will be cleared and necessary permits obtained . A Health and Safety Plan which satisfies the requirements of 29 CFR 1910. will be prepared and implemented. . The location of exploratory holes will be documented by measuring the distance from two permanent structures or other suitably accurate methods. . Exploratory holes will be properly abandoned using a bentonite slurry or cement bentonite grout emplaced through a treinie pipe. Cone Penetrometer Logs. Five cone penetrometer(CPT) logs will be obtained to depths of 150 feet in the approximate locations shown on Figure 1 (SB-9 through SB-13).Specific activities include: . CPT logging will include measurements of cone beating,sleeve friction,dynamic pore water pressure, and bulk resistiviry. . if refusal is met during CPT logging prior to attaining the target depth, one additional attempt will be made at each location by moving a short distance from the original location and making one more attempt.If the second attempt fails, CPT logging in that location will be abandoned. Soil and Groundwater Sampling Near the same five locations where CPT logs were obtained, separate bore holes will be completed for collecting soil and/or grab groundwater samples using direct push methods that arc compatible with the CPT sampling vehicle capabilities as follows: olsw woRKF'LW v.a.00c OF2 09/29/98 TUE 13: 25 [TX/RX NO 75571