SITE INFORMATION AND CORRESPONDENCE

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(ABLE 1 -CHECKLIST OF REQUIRED DATA - FOR NO FURTHER ACTION REQUESTS'AT UNDERGROUND TANK SITES Site Name and Location: Former Shell Service Station; 1160 W. Yosemite Ave., Manteca, San Joaquin County(RB#390117) y 1. Distance to production wells for municipal, domestic, r A 2005 sensitive receptor survey reported one municipal agriculture, industry and other uses within 2000 feet of the site. Supply well and 12 domestic wells within 2,000'of the site. The nearest well is 1,270'to the northeast The wells are not threatened by the USTs release. # y 2. Site maps, to scale, of area impacted showing locations of In 1983, two 5,000-gallon, two 8,000-gallon and one any former and existing tank systems, excavation contours and 550-gallon unknown product USTs and associated piping sample locations, boring and monitoring well elevation were removed. contours, gradients, and nearby surface waters, buildings, streets, and subsurface utilities; Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of silt and sand to 85', the total depth!investigated. diagrams; N 4. Stockpiled soil remaining on-site or off-site disposal (quantity); The fate of the excavated soil is not discussed in the available reports. y 5. Monitoring wells remaining on-site, fate; Five(5)monitoring wells,(MW--1 through MW-5) will be properly abandoned. 6. Tabulated results of all groundwater Depth to groundwater varied from 13'bgs to 23'bgs. Groundwater elevations and depths to water; gradient varied from 0.001 ff/ft to 0.004 ft/ft. Groundwater flow direction' varied clockwise from northeast to northwest 7. Tabulated results of all sampling All data adequately tabularized in various reports, including closure report and analyses: FYI Detection limits for confirmation sampling 10 Lead analyses £ 8. Concentration contours of contaminants found and those remaining in soil and The extent of the identified groundwater, and both on-site and off-site: contamination is described in the available reports. # 0 Lateral and Vertical extent of soil contamination -� Lateral and MVertical extent of groundwater contamination HI9. Zone of influence calculated and assumptions'used for subsurface remediation An engineered remediation was not system and the zone of capture attained for the soil and groundwater remediation required by the regulatory agency. system; 77 10.Reports/information �Y Unauthorized Release Form �Y QMRs(22) 6/04 to 12-09. i i ❑Y Well and boring logs �y PAR FRP Other Soil Vapor Survey(8-11), Closure Report(3-10) Y 11.Best Available Technology (BAT) used or an explanation for not using USTs removal and natural attenuation. BAT; Ug 12. Reasons why background wasrs unattainable Minor residual soil and groundwater contamination remains' on-site. UBAT,' y 13.Mass balance calculation of substance treated Consultant estimates 156 lbs of TPN remain in soil,and 1.2406 lbs of i TPH remain in groundwater. versus that remaining; y 14. Assumptions, parameters, calculations and Soil concentrations did exceed Region 2 Environmental Screening 1 model used in risk assessments, and fate and Levels for TPHg gross contamination and direct contact at 15.5'bgs, transport modeling; which is below typical worker exposure depth. The consultant states . no significant risk exists from vapor intrusion to commercial buildin s. i y 15. Rationale why conditions remaining at site will Soil and groundwater contamination reportedly are limited in extent not adversely impact water quality, health, or other Land use(commercial)is not expected to change in the foreseeable beneficial uses;and future. TPH is estimated to reach WQGs in 2016. By: JLB �/,� Comments:In 1983, two 5,000-gallon, two 8,000-gallon and one 550-gallon unknown product USTs and associated piping were removed at the subject site. Minor residual soil and groundwater contamination t Date: remains on-site. Based upon the limited extent of contamination reported in soil and groundwater,a stable 11/23/2011 groundwater plume with declining concentrations, no foreseeable changes in future land use(commercial. and minimal risks from soil,soil vapor, and groundwater, Regional Board staff concur with San Joaquin County's Closure Recommendation.