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: Sutter Office Center, 242 N. Sutter St., Stockton, San Joaquin County(RB#1390910) Y1 1. Distance to production wells for municipal, A 2004 sensitive receptor survey reported six water supply wells domestic, agriculture, industry and other uses within 2,000'of the Site. The nearest well is 700'to the within 2000 feet of the site. southeast. None of the wells are threatened by the release. Y 2. Site maps, to scale, of area impacted showing In 2/60, four 550-gallon gasoline USTs were closed in place. In locations of any former and existing tank systems, 10/88, one 2,000-gallon unknown fuel, two 3,000-gallon unknown excavation contours and sample locations, boring fuel, two 4,000-gallon unknown fuel, and one 550-gallon waste and monitoring well elevation contours,gradients, oil USTs were removed. Site maps and figures showing tank and nearby surface waters, buildings, streets, and locations, excavations, building and residual pollutants were subsurface utilities; I provided in investigation reports. Y1 3. Figures depicting lithology(cross Site lithology consists of clay, silt, and sand to 170', the total depth investigated. section), treatments stem diagrams; Active remediation was not required by the regulatory agency. N 4. Stockpiled soil remaining on-site The amount and fate of the excavated soil is not provided in the available or off-site disposal(quantity); reports. Mass estimate for excavated soil was not reported by the consultant. }� 5. Monitoring wells remaining on-site, Eight(8)monitoring wells(MW-1 through MW-6, MW-1D and MW-6D) will be ate; properly destroyed prior to closure. 6. Tabulated results of all groundwater Tabulated data was provided in reports indicating depth to groundwater from elevations and depths to water; 20'bgs to 30'bgs. Groundwater flow direction from east-northeast to northeast. Groundwater gradient varied from 0.001 ft/ft to 0.011 ft/ft. 7. Tabulated results of all sampling All data was adequately tabulated in various reports, including waste oil analyses. and analyses: FYI Detection limits for confirmation sampling ❑Y Lead analyses 8. Concentration contours of contaminants found and those remaining in The horizontal and vertical extent of the soil and groundwater, and both on-site and off-site: petroleum pollution is confined to the property limits. ElLateral and FLYd Vertical extent of soil contamination Lateral and FiVertical extent of groundwater contamination 9. Zone of influence calculated and assumptions used for subsurface A treatment system was not installed. remediation system and the zone of capture attained for the soil and groundwater remediation system; 10.Reports/information❑Y Unauthorized Release Form QY QMRS(31)9-01 to 11-12 ❑Y Well and boring logs El PAR ❑N FRP FY Other Site Closure Report, 12-12;ME&TTRWQG, 8-13 Y 11.Best Available Technology(BAT) used or Leak was stopped by removing tanks and piping, over-excavation an explanation for not using BAT; removed additional soil pollution. Natural attenuation was chosen as the BAT. Y 12. Reasons why background was/is not Soil pollution presents a minimal threat to human health and finable using BAT groundwater ollution is predicted to be restored in 16 years. :YD 13.Mass balance calculation of substance Consultant estimated residual TPH mass is 400 lbs. (60.6 gal.)in soil. treated versus that remaining; Y 14. Assumptions, parameters, calculations Site does not meet the criteria in the LTCP for vapor intrusion (TPH>100 and model used in risk assessments, and fate mg/kg). Consultant states site does not represent a significant and transport modeling; environmental or health risk as current use is a paved parking lot. I, 15. Rationale why conditions remaining at Soil and groundwater pollution is reportedly confined to the property site will not adversely impact water quality, limits. Land use(commercial)is not expected to change in the health, or other beneficial uses;and foreseeable future. WQOs are predicted to be reached by 2084. Groundwater plume is stable and slow!y decreasing in concentration. By: JLB Comments:Multiple USTs were removed at the subject site. Based on the stable and declining concentrations in groundwater, no foreseeable changes in future land use(commercial), and minimal risks Date: from soil vapor and soil, Regional Board staff concur with San Joaquin County's Closure Recommendation. 10/23/2013