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Wnght Enwo mental Sermces,Inc s 8.0 Conclusions and Recommendations Wright drilled three off-site cone penetrometer bonngs for further definition of the dissolved plume at the former Stefano's Gasoline site at 1419 Charter Way in Stockton, California The borings sampled discrete groundwater aquifer intervals for dissolved contaminant information Two aquifers are present the A-aquifer between roughly 45 to 60 feet with a related intebedded interval at about 70-75 feet The B-aquifer occurs below about 110 feet at roughly 115-120 feet Both aquifers display complex mterbedding and aquifer stratigraphy may be locally vertically and laterally variable Aquifer hydraulic conductivities are interpreted as moderately low TPHG and 1,2-DCA contaminants are present in the A-aquifer including a contributing up gradient off-site source This is significant to off site plume mapping since up to 90 ug/l TPHG and 21 ugh 1,2-DCA in the A-aquifer and 130 ug/l TPHG in B-aquifer are present Contaminants were not detected in the B-aquifer The very elevated concentrations of contaminants present in on-site wells MW-2 and MW-3 were not observed in the off-site CPT sampling The groundwater motion is east and southeast The furthest down gradient CPT-05 boring showed very low 1,2-DCA in the A-aquifer and no contaminants in the B-aquifer Gasoline volatile contaminants were not observed with the exception of one occurrence of TBA at the detection limit Wright interprets that this contaminant distribution indicates limited movement by the main dissolved plume mass Previous work by Ramage Environmental showed that no active water supply wells were near the site and a go-cart raceway and County fairgrounds are down gradient Work plans for interim site cleanup (sal vapor extraction and one-point ozone bubbler injection) have been submitted to SJC EHD for review On the basis of this work, Wright is recommending six additional monitoring wells The wells would be installed adjacent to the logged CPT borings and slotted at discrete aquifer depth intervals as follows (see Figures 4 and 5) New Well Location Aquifer Slotted depth_(feet_bgs CPT-01 B 114-119 CPT-04 A 50-60 CPT-04 A 70-75 CPT-04 B 115-120 CPT-05 A 47-57 CPT-05 B 115-120 Upon approval of the SJC EHD well installation permits, the wells will be installed and developed These wells will be added to the monitoring array and analyzed for the current contaminants in the quarterly monitoring Stefano's—CPT Report Page 8 of 11