SITE INFORMATION AND CORRESPONDENCE

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` -fABLE 1 -CHECKLIST OF REQUIRED DATA..t FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: City of Tracy Wastewater Treatment Plant, 3900 Holly Dr., Tracy, San Joaquin County(#391016) y 1. Distance to production wells for municipal,domestic, A 2010 sensitive receptor survey did not identify any agriculture, industry and other uses within 2000 feet of the site, water supply wells within 2,000 feet of the Site. y 2. Site maps, to scale, of area impacted showing locations of In January 1998, one 7,500-gallon diesel UST was any former and existing tank systems, excavation contours and removed. sample locations, boring and monitoring well elevation contours, gradients, and nearby surface waters, buildings, streets, and subsurface utilities; Y 3. Figures depicting litho/ogy(cross section), treatment system Site lithology consists of clay, silt, and sand to 25, the diagrams; total depth investigated. Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 40 yds of contaminated soil was returned to the tank pit. YJ 5. Monitoring wells remaining on-site, fate; One monitoring well(WESMW-1)will be properly abandoned. 6. Tabulated results of all groundwater Depth to groundwater was 8'bgs. Groundwater flow direction was elevations and depths to water; towards the northwest, and groundwater gradient was 0.0007 ft/ft (measured with adjacent existing shallow aquifer WWTP water quality monitoring wells). 7. Tabulated results of all sampling All data adequately tabularized in various reports,including closure report. and analyses: Y❑ Detection limits for confirmation sampling QN Lead analyses FV_T8. 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 shown in applicable reports. n Lateral and ElVertical extent of soil contamination Lateral and ny Vertical extent of groundwater contamination 9. Zone of influence calculated and assumptions used for subsurface remediation The regulatory agency did not require system and the zone of capture attained for the soil and groundwater remediation active remediation. system; 10.Reports/information FY-1 Unauthorized Release Form QY QMRs 2 from 10/09 to 9/10 FY] Well and boring logs 151PAR ❑N FRP Fy Other Closure Report(11/10) removal and natural attenuation. Y 11.Best Available Technology(BAT) used or an explanation for not UST usin BAT, Uy 12. Reasons why background was/is Minimal residual soil contamination remains on-site. ttainable using BAT; Y 13.Mass balance calculation of substance treated The consultant did not estimate mass removed in soil, and estimated versus that remaining; residual TPH as 2.4 gallons remain in soil and 0.0004 gallons remain in groundwater. 77 14. Assumptions, parameters, calculations and The regulatory agency did not require a soil vapor survey, due to low 7 model used in risk assessments, and fate and TPHd concentrations in soil. The Site(emergency generator)is transport modeling; surrounded by wastewater treatment ponds. 71 15. Rationale why conditions remaining at site Soil contamination reportedly is limited in extent.Land use will not adversely impact water quality, health, or (commercial)is not expected to change in the foreseeable future. Vapor other beneficial uses;and intrusion risk has been addressed.Soil contamination is no longer leaching to groundwater,since water quality goals have been reached. By: JLB . p Comments:In January 1998, one 7,500-gallon diesel UST was removed from the subject Site.Based upon 2 quarters of groundwater monitoring showing water quality goals have been met, the limited extent of Date: contamination remaining in soil, no foreseeable changes in land use, and limited threats from groundwater, 1/3/2011 soil, and soil vapor intrusion,Regional Board staff concur with San Joaquin County's Closure