SITE INFORMATION AND CORRESPONDENCE

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1'W9LE 1 -CHECKLIST OF REQUIRED DATA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: 7 Eleven No. 17334,4501 N.Pershing Ave., Stockton,San Joaquin County(RB 11390521) :YD 1. Distance to production wells for municipal,domestic, A 1999 sensitive receptor survey reported two water supply agriculture, industry and other uses within 2000 feet of wells within 2,000'of the Site. The wells are 1,800 southeast the site. and 1,800 feet southwest,respectively. The supply wells are not threatened by the petroleum hydrocarbons release. Y 2.Site maps,to scale,of area impacted showing In 9/98, three 10,000-gallon gasoline USTs were removed. locations of any former and existing tank systems, Site maps and figures showing tank locations,area of excavation contours and sample locations, boring and excavations,buildings and residual pollutants were monitoring well elevation contours,gradients,and provided in investigation reports. nearby surface waters, buildings,streets,and subsurface utilities; 713. Figures depicting lithology(cross Site lithology consists of clay,silt,and sand to 50', the total depth investigated. section),treatments stem diagrams; All figures were provided in the investigation reports. Y 4.Stockpiled soil remaining on-site Approximately 8.3 tons of soil was excavated and transported to TPS or off-site disposal(quantity); Technologies,Inc.in Adelanto. Consultant did not estimate mass of TPH removed by excavation. Y 5. Monitoring wells remaining on-site, Seven(7)monitoring(MW-1 through MW-4,MW-1A,MW-5A and MW-5B)and two ate; I remediation(SPV-1 and SPV-2)wells will be properly destroyed prior to closure. 6.Tabulated results of all groundwater Tabulated data was provided in reports indicating depth to groundwater ranged elevations and depths to water; from 13'bgs to 20'bgs. Groundwater flow was towards the northeast. Groundwater gradient varied from 0.003 ft/ft to 0.004 ft(ft. 7.Tabulated results of all sampling All data was adequately tabulated in various reports. and analyses: Y❑ Detection limits for confirmation sampling ❑Y Lead analyses LyJ 8. Concentration contours of contaminants found and those remaining in The horizontal extent of the petroleum soil and groundwater,and both on-site and off-site: pollution extends approximately 50'offsite under N.Pershing Ave. Vertical extent was Lateral and Y❑Vertical extent of soil contamination delineated by non-detect results at MW-5B fo Lateral and FYI Vertical extent of groundwater contamination 9.Zone of influence calculated and assumptions used for subsurface Pilot study for SVE demonstrated a radius of remediation system and the zone of capture attained for the soil and influence at 30'.A full scale treatment system groundwater remediation system; was not required by the regulatory agency. YJ 10.Reports/information ❑Y Unauthorized Release Form ❑Y QMRs(59)12-97to 7-13 FY Well and boring logs 151PAR FRP FY Other Site Conceptual Model, 10-13;Site Closure Re uest, 10-13 Y I 11.Best Available Technology(BAT) used or Leak was stopped by removing tanks. Soil vapor extraction(pilot study) an explanation for not using BAT; and natural attenuation were implemented as the BAT. Y 12. Reasons why-.background.waslis not. Contaminant-concentrations-are declining-naturally and background is mable using BAT; predicted to be restored in 10 years. Y1 13.Mass balance calculation of substance Consultant did not provide estimates of mass in soil and groundwater. treated versus that remaining; Y 14. Assumptions, parameters, calculations Site is an active service station that is exempt from LTCP vapor and model used in risk assessments,and fate intrusion limits. Consultant states site does not represent a significant and transport modeling; environmental or health risk. _y] 15. Rationale why conditions remaining at Groundwater pollution is reportedly confined to within 50'of the site will not adversely impact water quality, property 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 2024. Groundwater plume is stable and slowly decreasing in concentration. By: JLB Comments: Three 10,000-gallon gasoline UST were removed at the subject site. Soil pollution presents a minimal threat to human health and groundwater pollution is predicted to be restored in 10 years.Based on Date: the stable and declining concentrations in groundwater,no foreseeable changes in future land use 3/17/2014 (commercial),and minimal risks from soil vapor and soil,Regional Board staff concur with San Joaquin County's Closure Recommendation.