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TABLE 1 - CHECKLIST OF REQUIREPDATA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Buffalo Tank, 5709 E. Fremont St. (AKA Hwy. 26 E.), Stockton, San Joaquin County(Case#390791) y 1. Distance to production wells for municipal, domestic, agriculture, A 2005 sensitive receptor survey identified industry and other uses within 2000 feet of the site. three supply well within 2,000';one onsite 60'north of the USTs and two wells approximately 250'northwest and southwest of the Site. None of the wells are threatened b the release. Y Site maps, to scale, of area impacted showing locations of any former and existing tank One 1,000-gallon UST and systems, excavation contours and sample locations, boring and monitoring well elevation one 2,000-gallon gasoline contours, gradients, and nearby surface waters, buildings, streets, and subsurface utilities; UST were removed 11189. Y 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of clay,silt, sand, and gravel to 85 feet, the total depth investigated. N 4. Stockpiled soil remaining on-site or off-site disposal(quantity). The fate of soil excavated during the tank removal is notdiscussed in the available reports. Y 5. Monitoring wells remaining on-site, fate; Three monitoring wells (MW1 through MW3) were properly destroyed on 10 November 2011. 6. Tabulated results of all groundwater Depth to groundwater varied from 57 to 73 feet below ground surface elevations and depths to water,- (bgs). The groundwater gradient varied from 0.001 to 0.006 ft/ft, and the downgradient direction was towards the northeast. 7. Tabulated results of all sampling and All data adequately tabularized in various reports, including closure analyses: report. Detection limits for confirmation sampling ❑Y Lead analyses 8. Concentration contours of contaminants found and those remaining in soil and The extent of contamination is groundwater, and both on-site and off-site. adequately defined by soil borings. Groundwater has reached WQGs. El Vertical extent of soil contamination El Lateral and © Lateral and © Vertical extent of groundwater contamination 9. Zone of influence calculated and assumptions used for subsurface remediation system Active remediation was not and the zone of capture attained for the soil and groundwater remediation system; required. 10.Reports/information FYI Unauthorized Release Form QY QMRs(6)4105 to 12/06 ❑Y Well and boring logs � PAR 0 FRP Other, Closure Summary Report(5-0)7 Y 11.Best Available Technology(BAT) used or an explanation for not using BAT; USTs removal and natural attenuation. HBAT; sidual soil contamination is not leaching to Y 12.Reasons why background was/is unattainable usingoundwater. Minor soil contamination remains. Y13.Mass balance calculation of substance treated versant estimates 260 gallons of TPHd and 96 gallons of that remaining; main in soil. Groundwater monitoring showed no impacts from petroleum hydrocarbons. Y 14. Assumptions, parameters, calculations and model used in A soil vapor risk assessment was not required, due to risk assessments, and fate and transport modeling; the depth of contaminants and distance to nearest building. Soil contamination is present below typical worker exposure depths. �, 15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent. Water quality impact water quality, health, or other beneficial uses;and goals(WQGs)have been reached. By. JLB r Comments: One 1,000-gallon UST and one 2,000-gallon gasoline UST were removed 11189 at the subject Site. Groundwater monitoring results were ND during the last 4 quarter of groundwater monitoring, confirming Date: petroleum hydrocarbons are not leaching to groundwater. Soil contamination is present from 20'bgs to 35' 11/22/2010 bgs and US Ts were approximately 40'from existing buildings; therefore, a soil vapor survey was not required. Based upon evidence that residual contamination is not leaching to groundwater from soil, groundwater having reached WQGs, minimal risk of vapor intrusion or direct contact exposure, and limited extent of contamination present in soil, Regional Board staff recommends closure for the Site.