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w � "� �.. ' �� h � � , ^w � ,� � �'«• _� a _ #rye "�"�a�. '+n � STF. RN Git01.0 1c Rvs t' ltt:liti , [ NC . I Randall/15 Scpirmbcr 19E9 In May 1984,Arco reported a gasoline spill at thuir station across from the Chevron site. The release was estimated at between 2,000 gallons and 3,500 gallons. A subsurface investigation was conducted by Gettler-Ryan, Inc. of Hayward and Emcon Associates of San Jose, California, which s included the installation of ten onsite monitoring wells, 2 offsite wells, and an onsitc recovery well. About 600 gallons of liquid hydroczrbons were initially removed from the recovery well. Results of groundwater sampling conducted by Emcon in October 1985 indicated that five of the wells contained liquid hydrocarbon, The remaining onsitc and offsite wells contained dissolved gasoline up to 80,000 ppb and benzene up to 8,000 ppb. In April 1987, Western Geo-Engineers of Woodland, California, 71 conducted a soil vapor survey. The results indicated that volatile hydrocarbons were present in high concentrations,particularly on the south half of the site,to a depth of about 10 ft. In January 1988, Brown and Caldwell Consulting Engineers(B&C)of Sacramento,California installed 4 additional offsite monitoring wells along Plymouth ]toad and Benjamin Holt Drive. The estimated direction of groundwater flow was to the northeast. Results of groundwater sampling conducted by B&C in November 1988 indicated that benzene was present in all but one well sampled,including well PR-1 at s 6.4 ppb, located at the northeast corner of Benjamin Holt Drive and Plymouth Road. Well BHD-1 located in the sidewalk along Benjamin Moh Drive and adjacent to the Chevron site contained 1,870 ppb benzene, and well E-10 across the street on the Arco site contained 2,780 ppb benzene. When the recovrry well was operating at a rate of about 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 q information concerning the Arco situ was obtained from reports on file at the San Joaquin Local Health tr;.er District. In August 1988,Applied Gcosystems conductcd a subsurface investigation at the Shell service j station tc.the west of the Chevron site. The results of the investigation were submitted to Shell oil Company in a report dated ?6 September 1988. Four monitoring 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 SS#94275 is an acthe service station,remodeled in early 1989,that retails ® regular,unleaded,and super-unleaded gasoline. The former location of the underground storage tanks was on the south side of the site near Benjamin Holt Avenue. The former waste oil tank was located on the northeast part of the site. The new location,of the underground storage tanks is on the north- - - central part of the site.The former underground storage tanks ar,d the waste oil tank were removed by Blaine Tech Services(BTS)of San Jose,California,between 6 a'ii9 :n January 1989. Results of the soil ® sampling conducted by BTS during the tank removal were rep�ried to ChcvTon on 17 January 1989. Total petroleum hydrocarbons were detected in soils excavated from the tank pit. Oil and grenac were detected in soil excavated from the waste oil pit. .{ A soil vapor survey(SVS)was conducted by WG1? 13 and 14 Fel-ruary 1989. Total volatile hydrocarbons were detected in vapor points sampled at about 15 ft below grade in the vicinity;;f the iA former location of the underground storage tanks,along former product-line locations,and adjacent to `� 11}7R25ti'J 2