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TABU,,., - CHECKLIST OF REQUIRED D*
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Largin Service Station,2235 Cherokee Road,Stockton,San Joaquin County
<br /> IV] 1.Distance to production wells for municipal, domestic,agriculture, A receptor survey was not completed. The County
<br /> industry and other uses within 2000 feet of the site; states that drinking water wells are not affected.
<br /> Ej2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Two 6,000-gallon gasoline
<br /> excavation contours and sample locations, boring and monitoring well elevation contours, USTs were removed in
<br /> gradients, and nearby surface waters, buildings, streets, and subsurface utilities; December 1989. Site maps
<br /> are provided.
<br /> E3. Figures depicting lithology(cross section),treatment system diagrams; Solis encountered during tank removal show
<br /> clay and silt to 16 feet
<br /> FN--1 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Excavated soils were stockpiled and sampled, then
<br /> returned to the tank pit excavation at a later date.
<br /> r= 5.Monitoring wells remaining on-site, fate; Groundwater was not sampled, and monitoring wells were not installed.
<br /> 6. Tabulated results of all groundwater elevations and depths to water,- -DePh-tO—Wa-ter is es ima d-d aT45-to`Str r#-eT-n�-- -
<br /> groundwater flow direction is unknown.
<br /> 0 7.Tabulated results of all sampling and analyses: Maximum tank pit excavation samples In mg/kg collected at 15 feet
<br /> Detection limits for confirmation sampling show TPHg at 20,benzene at 0.012, toluene at 0.040, ethyl benzene at
<br /> 0.024,xylenes at 0.37,MtBE at<0.005. Maximum lead was identified in
<br /> Lead analyses one soil pile composite sample at 30 mg/kg.
<br /> Y 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater,and both on-site and off-site: The lateral and vertical extent of soil
<br /> © Lateral andY❑ Vertical extent of soil contamination contamination Is defined. Groundwater was
<br /> Lateral and a Vertical extent of groundwater contamination not encountered at a total depth of 16 feet.
<br /> 9.Zone of influence calculated and assumptions used for subsurface A remediation system was not operated at
<br /> Qremediation system and the zone of capture attained for the soil and this site.
<br /> groundwater remediation system;
<br /> 10.Reports/information 9 Unauthorized Release Form ❑ QMRs
<br /> N1 Boring logs N� PAR D FRP 0 Other(Site Assessment Report)
<br /> Ya 11.Best Available Technology(BAT) used or an explanation for not using BA T* Remove USTs,natural attenuation.
<br /> 12.Reasons why background wasCs
<br /> unattainable using BAT, Petroleum hydrocarbons remain in on-site soils near the former UST.
<br /> 0 13.Mass balance calculation of substance
<br /> treated versus that remaining; A mass balance was not completed.
<br /> N❑ 14.Assumptions,parameters, calculations and model used in risk
<br /> assessments,and fate and transport modeling, A risk assessment was not completed.
<br /> 1 15. Rationale why conditions remaining at site will not adversely Contamination is limited to soil at the former UST.
<br /> impact water quality, health,or other beneficial uses;and Contamination will naturally attenuate.
<br /> By: Comments: The site was a former service station,and the current site status is unknown. Two 6,000-gallon gasoline
<br /> USTs were removed from the site in December 1989, and tank pit samples showed soil contamination at one end of one
<br /> of the USTs. In March 1996, the tank pits were overexcavated to a total depth of 16 feet, and soil samples collected at
<br /> this depth were non-defect for all constituents including MtBE. Due to no staining, odor, or detectable concentrations in
<br /> D e: soils sampled at 16 feet, a groundwater investigation was not required. The County states that the minimum depth to
<br /> groundwater is 45 feet. Based on the limited contamination identified in soil and the reported depth to groundwater, Board
<br /> D) staff concur with San Joaquin County's closure recommendation.
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