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S �l WESTERN Gt. OLOGIC RFsoupCf?S , INC , lPit``�r J.Randa11/14 November 1989 2 included the in':.dlation of ten on-site monitor wells,two off-site wells, and an on-site recovery well. About 600 gallons of liquid hydrocarbons were initially removed from the recovery well. Results of p groundwater sampling conducted by Emcon in October 1985;indicated that five of the wells contained liquid hydrocarbon. The remaining on-site and off-site wells contained dissolved gasoline up to 80,000 Parts-per-billion (ppb) and benzene up to Spo ppb. In ATM 1987, Western Geo-Engineers of Woodland,California,conducted a roil vapor survey. The results indicated that volatile hydrocarbons T were present in high concentrations,particularly on the south hof of the to a depth of about 10 ft. d In January 1988,Brown and Caldwell Consulting Engineers(B&Cl Z Sacrament-California iustailed Cour additional off-rile moniter.•ue1ls along Plymouth Rned,uad Benjamin Holt Drive. i!ie estimated direction of groundwater flow was to the northeast. Results of groundwater sampling conducte'i by B&C in November 19& indicated that benar:,_e was present in all but one well sampled,including wtfl PR- 1 at 6.4 ppb,located at the northeast"corner of Benjamin Holt Drive and Plymouth Road. Well<3HD- 1,located in the sidewalk along Benjamin Holt Drive and adjacent to the C1=crrou site,contained 1,870 ® ppb benzene,and wrll E-10,across the street on the Arco site,contained 2,780 ppb benzene. When the recovery well was operating at a rate of sbout 16 gpm,the northeast direction of groundwater flow on the north side of the site was reversed to a direction approximately to the southwest and southeast. The informarion concerning the Arco site was obtained from reports on file at the San Joaquin Local Health District. t --- In August 1988,Applied Geosystems conducted a subsurface:investigation at the Shell service -s Station to the west of the Chevron site. The results of the investigation were submitted to Shell Oil Company in a report dated 16 September 1988. Four monitor wells were installed. Fuel hydrocarbons were not detected in soil or groundwater samples. The estimated direction of groundwater flow was to the northeast. The site of Chevron Service Station#94275 is an active service station,remodeled in early I989, that retails regular,unleaded,and super-unleaded gasoline. The formes,location of the underground storage tanks was on the south side of the site near Benjamin Holt•Avcnue. The former waste oil tank was located on the northeast part of the sis.e. The new locatico O the underground storage tanks is on the north-central part of the site. The former underground st',rage tanks and the waste oil tank were removed by Blaine Tech Services(BTS)of San Jose,Califorria,between 6 and 19 January 1989. Results of the sod sampling conducted by BTS during the tank reasoval were reported to Chevron on 173,inuary 1989. Total petroleum hydrocarbons were detected in soils excavated from the tank pit. Oil and grease were detected in soil ext:avaied from the waste oil pit. A soil vapor survey(SVS)was conducted by WGR on 13 and 14 February 1989. Total volatile hydrocarbons were detected in vapor points sampled at about 15 ft below grade in the vicinity of the r former location of the underground storage tanks,along former product•linc Iocation%and adjacent to the former location of the pump islands. i"R2 tratiltio9