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SITE CONCEPTUAL MODEL Former Shell Service Station 1267 Country Club Boulevard, Stockton, California " c- 2.8 2.8 Groundwater Flow Direction, Since 1998, depth to water has ranged:from 9.4 to 15.3 feet below Depth Trends and Gradient grade (fbg) in the monitoring-wells. ,D`uring 1995, depth to water in Trends soil borings ranged fro rri25 to 28 fb"'g`The groundwater flow direction is typically north tato north sae t and the gradient varies. 2.9 Stratigraphy and Hydrogeology The site is underlain by layers of clay(CL), silt(ML),clayey sand �`�� (SC), silty sand(SM), and sand (SP). Soil types vary from boring to yu,4, boring without a consistent stratagraphic order of soil types. The CPT borings encountered similar soil types to ose encountered in the soil borings,with silt being the predominant soil type to the total depth explored of 60 fbg. In both CPT borings, a silty sand to sand layer was encountered at approximate depths of 41 to 46 fbg. Boring logs are included in Attachment 3. 2.10 Preferential Pathways Analysis No analysis has been performed. 2.11 Other Pertinent Issues A geophysical survey indicated that the USTs were removed. W- Remediation Status W j�� . _. '.` i 3.1 Remedial Actions Taken None 3.2 Area Remediated NA 3.3 Remediation Effectiveness NA Well and Sensitive Receptor _ A - . Serve �. _:. 4.1 Designated Beneficial Water Existing and potential beneficial uses include municipal and Use domestic water supply, agricultural supply, industrial service supply, and industrial process supply(CVRWQCB Basin Plan). 4.2 Shallow Groundwater Use None identified. 4.3 Deep Groundwater Use None identified. 4.4 Well Survey Results A well survey conducted by Cambria in 2001 did not identify any existing water supply wells within a 2,000-ft radius of the site. ' 4.5 Likelihood of Impact to Wells NA; No wells identified. 4.6 Likelihood of Impact to Surface Unlikely because the only surface water body is the Smith Canal, Water located approximately 1,200 feet southeast(upgradient)of the site. ; flisk Assessmentt low quomm,-. , ,; .,,... 5.1 Site Conceptual Exposure The site is currently occupied by an office building (credit union). Model (current and future uses) The area surrounding the site is mixed commercial and residential. Future use of the parcel is assumed to be similar to current use. 5.2 Exposure Pathways Potential exposure pathways include onsite commercial occupant inhalation of vapors from impacted soil and groundwater, dermal exposure, particle inhalation,and ingestion of impacted soil by onsite construction workers, and ingestion of impacted groundwater offsite. 5.3 Risk Assessment Status No formal risk assessment has been performed for the site. 5.4 Identified Human Exceedances NA 5.5 Identified Ecological NA Exceedances l 0943 Page 2 of 3 Date Modified: 11/19/02 1