SITE INFORMATION AND CORRESPONDENCE_CASE 1

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i TABLE 1 -CHECKLIST OF REQUIRED DASxe+ FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Five Star Marina(West), 345 N. Yosemite St., Stockton, San Joaquin County(RB(1391135) y 1. Distance to production wells for municipal, domestic, A 2009 sensitive receptor survey stated no municipal or agriculture, industry and other uses within 2000 feet of the site. private wells are located within 2,000'of the Site. y 2. Site maps, to scale, of area impacted showing locations of In May 1986, one 550-gallon gasoline UST was removed. any former and existing tank systems, excavation contours and sample locations, boring and monitoring well elevation contours, gradients, and nearby surface waters, buildings, streets, and subsurface utilities; Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of clay,silt,sand,and gravel to diagrams; 41', the total depth investigated. Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 363 tons of excavated soil was transported to Forward Landfill in Manteca. Y 5. Monitoring wells remaining on-site, fate; I Four monitoring wells(MW-1 through MW-4)will be properly abandoned. 6. Tabulated results of all groundwater Depth to groundwater varied from 5'to 9'bgs. Groundwater flow elevations and depths to water, direction varied from northwest to northeast. Groundwater gradient varied from 0.0008 to 0.027 ft(ft. . 7. Tabulated results of all sampling All data adequately tabularized in various reports,including closure report. and analyses: FYI Detection limits for confirmation sampling �N 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 shown in applicable reports. M Lateral and Y❑Vertical extent of soil contamination Lateral and Vertical extent of eroundwatercontamination 9. Zone of influence calculated and assumptions used for subsurface remediation Over-excavation of soil to 15'bgs(below system and the zone of capture attained for the soil and groundwater remediation water table) was the approved s stem; remediation. 10.Reports/information QY Unauthorized Release Form ❑Y QMRs 30 from 1/98 to 10/08 10 Well and boring logs 10 PAR � FRP 51 Other Closure Report(7/09) Y J 11.Best Available Technology(BAT)used or an explanation for not UST removal, over-excavation, and natural usi2q BA T- I attenuation. Uy 12. Reasons why background was<s Minor residual soil and groundwater contamination remain on-site. ttainable using BAT, y 13.Mass balance calculation of substance treated The consultant estimates 22.5 gallons of TPH remain in soil and versus-that remaining, 0.11 gallons of TPH remain in groundwater. Y 14. Assumptions, parameters, calculations and The consultant stated since residual petroleum hydrocarbons are model used in risk assessments, and fate and present in saturated soil below the water table at 15'bgs,and with low transport modeling; groundwater concentrations, conditions onsite do not pose a risk from vapor intrusion. TPHg exceeds gross contamination and direct exposure ESLs for soil at 15'bgs, which is below depths normally associated with direct contact. Y 15. Rationale why conditions remaining at site Soil and groundwater contamination reportedly are limited in extent. will not adversely impact water quality, health, or Land use(commercial)is not expected to change in the foreseeable other beneficial uses;and future. WQGs will be reached in 2 years. By: JLBj Comments:In May 1986, one 550-gallon gasoline UST was removed from the subject site.Based upon 30 quarters of groundwater monitoring showing a stable plume with declining concentrations, the limited Date: extent of contamination remaining in soil and groundwater, no foreseeable changes in land use,and minimal 5/27/2010 threats from soil vapor intrusion, direct contact,and gross contamination,Regional Board staff concur with San Joa uin County's Closure Recommendation.