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ALTON GEOSCIENCE <br /> Quarterly Progress Report Summary Sheet <br /> Second Quarter 1996 <br /> Former Mobil Station 04-343 San Joaquin County Site Code#: 1968 <br /> 500 East Grantline Road <br /> Tracy California <br /> Number of water zones: 1 This Page 1 <br /> FIELD ACTIVITY: Date Sampled: Apr.12,1996 <br /> Number of groundwater wells on-site: 8 Groundwater Wells monitored: I I <br /> Number of groundwater wells off-site: 4 Groundwater Wells sampled: 11 <br /> Groundwater Wells with Free Product: 0 <br /> Phase of Investigation:Vadose Zone: Characterization Groundwater Phase: Monitoring&Sampling <br /> SITE HYDROGEOLOGY: <br /> Approximate depth to groundwater below ground surface: l l <br /> Approximate elevation of potenliometric surface above Mean Sea Level: 20.5 <br /> Average Increase/Decrease in groundwater elevations since last sampling episode: no change <br /> Approximate flow direction and hydraulic gradient: North at 0.013 foot per foot <br /> GROUNDWATER CONTAMINATION(BENZENE MCL=1.0 ppb): <br /> Wells containing free product: 0 Range in Thicimcas of Free Product: NIA <br /> Number of wells with concentrations below MCL: 1 I Volume of Free Product Recovered This Period: NIA <br /> Number of wells with concentrations at or above MCL: 0 Volume of Free Product Reovercd To Date: NIA <br /> Range in Concentrations: Benzene:ND <br /> Nature of contamination: Diesel TPH-D: ND to 160 ppb <br /> ADDITIONAL INFORMATION: Closure activities arc currently being evaluated for this site_ An update will be provided <br /> m the forthcoming quarterly progress report. <br /> Prepared by: Lsa S Le May Alton Project No:30-0136 <br /> Geologist <br /> Approved by: Matthew W.Katen Submittal Date:Jun,30,1996 <br /> California RG#5 67 Senior Geologist <br /> ,•cp,ED G <br /> :lEp( <br /> m ..W434312.XLS W <br /> c� �r <br /> i <br />