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TA
<br /> TA16 ,E 1 - CHECKLIST OF R UNDERGROUND TANK SITES
<br /> FOR NO FURTHER ACTION REQUESTS
<br /> Site Name and Location: McDowell &Davis Towing,1360 Escalon Avenue, Escaton,San Joaquin County
<br /> ::�
<br /> A sensitive receptor survey conducted in 2002
<br /> 1.Distance to production wells for municipal,domestic,agriculture,
<br /> Y reported one public supply well located 1000'SSW,
<br /> industry and other uses within 2000 feet of the site; and one private well located 750'NE of the site.
<br /> One 7,500-gallon regular and
<br /> a2. Site maps, to scale, of area impacted showing locations of former and existing tank d
<br /> systems, excavation contours and sample locations, boring and monitoring well elevation two 5,000-gallon ungasoline, and one 250-gaion
<br /> contours,gradients, and nearby surface waters,buildings, streets, and subsurface utilities; waste oil USTs were removed In
<br /> 3/99.
<br /> Site ilthology consists of sand,slit and clay,.
<br /> 3. Figures depicting lithology(cross section), treatment system diagrams; The total depth investigated was 70 feet.
<br /> Na 4. Stockpiled soil disposed off-site (quantify); An unspecified amount of soil was excavated.
<br /> 5. Monitoring wells remaining on-site, fate;
<br /> Three monitoring wells,installed for this Investigation, will be properly
<br /> abandoned. -
<br /> - The depth to water/s 65 feet The groundwater flow
<br /> 6. Tabulated results of all groundwater.elevations and depths to water,• direction is to the west
<br /> abulated results of all sampling and analyses: Maximum soil boring results In 2000 reported TPHg(2,600 mg/kg),
<br /> benzene(0.86 mg/kg),and MtBE(87 mg/kg). In 8/03,additional soil
<br /> Y Detection limits for confirmation sampling analyses reported TPHg(M mg/kg),benzene(<0,005 mg/kg),and MfBE
<br /> ©Lead analyses (<0.1 mg/kg). Groundwater maximum sample from 6/01 reported TPHg
<br /> (2,400 pg/L),benzene(110 pg/L), and MtBE(77 pg/L). In 12/03,
<br /> groundwater samples reported TPHg(500 pg/L), benzene(0.3 pg/L),
<br /> and MtBE(<0.5 pg/L).
<br /> ED 8. Concentration contours of contaminants found and those remaining in soil The extent of contamination is defined by
<br /> and groundwater, both on-site and off-site: soil borings and groundwater monitoring
<br /> Lateral and Vertical extent of soil contamination wells.
<br /> Lateral and Vertical extent of groundwater contamination
<br /> Q9.Zone of influence calculated and assumptions used for subsurface Based on the limited extent of soil and
<br /> remediation system and the zone of capture attained for the soil and groundwater contamination,an engineered
<br /> groundwater remediation system; remedlation system was not required at
<br /> this site.
<br /> 0 10,Reports/information F1 Unauthorized Release Form 0 QMRs, 11/00 to 12/03
<br /> 0 Boring logs a 0 PAR El FRP Other (Risk Assessments/Conceptual Site Models))
<br /> 0 11.Best Available Technology(BAT) used or an explanation for not using BAT, Remove UST,natural attenuation.
<br /> 12.Reasons why background wasris
<br /> unattainable using BAT, Minor soli and groundwater contamination remains on-site.
<br /> 13.Mass balance calculation of substance Mass balance was estimated for soil, TPHg(2 gal), and MISE(<.0.1 gal).
<br /> treated versus that remaining;
<br /> EEI 14.Assumptions,parameters, calculations and model used in risk
<br /> assessments, and fate and transport modeling,and A risk assessment,while not required, was submitted.
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<br /> 15.Rationale why conditions remaining at site will not adversely Soy contamination is limited in extent, and based on
<br /> impact water quality, health, or other beneficial uses. twelve quarterly sampling events, contamination is not
<br /> continuing to leach to groundwater. Groundwater
<br /> -monitoring shows a decreasing trend In concentrations.
<br /> By: Comments: One 7,500-gallon regular and two 5,000-gallon unleaded gasoline, and one 250-gallon waste oil USTs were
<br /> R,B removed from the subject site in 3199. Multiple borings were completed in 2000 and 2003, to delineate contamination at
<br /> this site. Maximum soil boring results in 2000 reported TPHg(2,600 mg/kg), benzene(0.86 mg/kg), and MtBE(87 mg/kg).
<br /> Date: in 8103, additional soil boring resmits reported TPHg(<1 mg/kg), benzene(<0.005 mg/kg), and MtBE(<O.1 mg/kg).
<br /> Groundwater maximum results from 6101 reported TPHg(2,400 pg/L), benzene(110 pg/L), and MtBE(77 pg/L). In 12/03,
<br /> 3/1/04 groundwater samples reported TPHg(500 pg/L),benzene(0.3 pg/L), and MTBE(<0.5 pg/L). Based on the limited extent
<br /> of soil and groundwater contamination and twelve quarters of groundwater analysis, which show a decreasing trend in
<br /> concentrations, Board staff concur with San Joaquin County's Closure Recommendation.
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