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WELL CONSTRUCTION REPORT USA STATION#110 - STOCKTON ' DECEMBER, 1995 Results from Parks work confirmed the presence of petroleum hydrocarbons in the soil and groundwater In late September, 1993, groundwater was calculated to be flowing south southeast, while in October, 1993 and January and February, 1994 it was flowing to the northeast During these penods groundwater was approximately 75-feet bgs For additional information the reader is referred to the following reports • Workplan dated October, 1994 • Groundwater Monitoring Report (GMR)dated October, 1994 • GMR dated January,July and October, 1995 ' 2.2 Area Background 1 Prior consultants have indicated that operating retail gasoline service stations have been previously located on all four corners at the intersection of East Mariposa Road and Farmington ' Road An assessment was performed at the abandoned Chevron service station on the northeast corner This property is fenced and has an open pit where underground tanks have been removed Work at that site has confirmed a TPH release(s) in the vicinity of the tanks A record review of County files indicated that there is an outstanding request for further characterization at this site The northwest corner is reported to be the site of a former Shell service station The property is ' presently an open field with no visual evidence of previous site use A review of County records did not produce any information about this property The underground storage tanks (USTs) and buildings were reportedly removed prior to implementation of UST requirements in 1985 rThe southwest corner is reported to be an abandoned Arco gasoline service station The property is fenced The service station building is still present on-site The location where a pump island was present is still visible from the pattern of concrete patches A review of agency files did not produce any information about this property A discussion with County staff yielded a recollection that the property owner had been queried about the presence of underground tanks and had informed the County that all tanks had been removed No verification was provided and no follow up was performed Apparently this site was also closed prior to UST requirements I3.0 Summary of Work Two borings were drilled on September 25 and 26, 1995 and completed as monitoring wells (MW-4-P and MW-6-P) MW-5-P was drilled and completed as a monitoring well on October 30, 1995 MW-4-P was originally planned to be located in front of the abandoned Arco service station on Mariposa Road Due to overhead utilities the well was relocated to a position southwest of the proposed position on the Arco site 2