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f~' TABU - CHECKLIST OF REQUIRED D TA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Beacon#27 (Cardlock 610), 3300 Waterloo Road,'Stockton,San Joaquin County
<br /> A well survey in 2002 shows two domestic water
<br /> FT1 1. Distance to production wells for municipal, domestic, agriculture, su 1 wells located approximately 325 feet south and
<br /> industry and other uses within 2000 feet of the site; pp Y.,
<br /> 1200 feet southwest of the site.
<br /> 0 2. Site maps, to scale, of area impacted showing locations of former and existing tank One lian waste oil UST was
<br /> systems, excavation contours and sample locations, boring and monitoring well removveded in June 1957. Two
<br /> elevation contours, gradients, and nearby surface waters, buildings, streets, and 10,000-gallon gasoline, and one
<br /> subsurface utilities; IM 10,000-gallon diesel USTs were
<br /> removed in October 1993.
<br /> I I 3. Figures depicting lithology(cross section), treatment system diagrams; Site lith,ology consists of clay,silt,sand and
<br /> gravel to 90 feet, the total depth investigated. A
<br /> higher permeability zone lies between 55 and 65
<br /> feet below ground surface.
<br /> EJY p• p (q y), Approximately 900 cubic,yards.of excavated soil was transported by
<br /> 4. Stockpiled soil disposed off-site uantif
<br /> _..._-- , W Sen.-s._Truck.6_Equip._lnc._to_RedDluff_foraerationand.disposal.
<br /> 0 5. Monitoring wells remaining on-site, fate; Seven monitoring wefts(MW- through MW 7)and three vapor extraction
<br /> wells(VE-1 through VE-3)have been'Linstalled for this investigation. The
<br /> wells will be property destroyed pending site closure.
<br /> { ❑Y 6. Tabulated results of all groundwater elevations and depths to water, The depth oto water varied from 35 to 75 feet, and
<br /> I the'groundwater flow direction varied from south
<br /> (1987) to northwest(1999).
<br /> 0 7. Tabulated results of all sampling and analyses: Groundwater monitoring results in 9199 were: 66 erg/L for TPHd,
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<br /> <50 lig/L for TPHg, X0.5 pg/L for benzene,and<0.5 Ng/L for MtBE.Detection limits for confirmation sampling Lead in soil was 12 mg/kg In 10193.
<br /> Y Lead analyses
<br /> {' 0 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater, both on-site and off-site: Th'e extent of contamination is defined by
<br /> ®Y Lateral and Y Vertical extent of soil contamination art-site soil borings and monitoring wells.
<br /> Lateral and ® Vertical extent of groundwater contamination
<br /> ETI 9. Zone of influence calculated and assumptions used for subsurface Based on the limited extent of soil
<br /> remediation system and the zone of capture attained for the soil and contamination,an engineered remediation
<br /> groundwater remediation system; ; sy�tem was not required at this site.
<br /> ' 10.Reports/information 19 Unauthorized Release Form � QMRs(3187 to 41187, 10194 to 12/95, 3199 and 9199)
<br /> Boring logs El PAR N❑ FRP (No Further Actilon Request Reports, 1195 and 8102) j
<br /> 11.Best Available Technology(BAT) used or an explanation for not using BAT" Remove USTs and natural attenuation.
<br /> 012,Reasons why background wasrs Decreasing concentrations have been attained at all monitoring wells as a
<br /> unattainable using=BAT;— `- result of excavation__Minor.soil contamination remain_s on-site..
<br /> Y !n 1195, the consultant estimated that 5 gallons of TPHg and 46 gallons of TPHd
<br /> 13.Mass balance calculation of substance m
<br /> treated versus that remaining; remain in shallow soils. Mass balance was not calculated for groundwater.
<br /> 14. Assumptions,parameters, calculations and model used in risk 'IF
<br /> assessments, and fate and transport modeling;and A risk assessment was not required.
<br /> y 15. Rationale why conditions remaining at site will not adversely Sol/contamination is limited in extent, and based on
<br /> impact water quality, health, or other beneficial uses, nine sampling events, contamination is not continuing to
<br /> { leach to groundwater. Groundwater monitoring shows a
<br /> decreasirr trend in concentrations for all constituents.
<br /> By: Comments: Two 10,000-gallon gasoline and one 10,000-gallon dieser USTs were removed from the subject site in 1199.
<br /> ' JLB One 550-gallon waste oil tank was removed in 6187. Soil contamination was identified at the gasoline/diesel USTs area.
<br /> Multiple borings and seven monitoring wells were completed to delineate and monitor contamination at this site. UST
<br /> monitoring wells MW-1 through MW-4 were sampled from 3187 to 9199! MW-5 through MW-7 were sampled from 4193 to
<br /> Date: 9199. In 9199, maximum groundwater contaminant concentrations had I declined to 66 pg/L for TPHd, X50 ug/L for TPHg,
<br /> X0.5 pg1L for benzene, and X0.5 pg/L for MtBE. After testing in 10/01, results'showed that the nearest domestic supply
<br /> 3120103 well was not impacted by contaminants. Based on the minor soil contamination and the low level of TPHd in
<br /> groundwater, Regional Board staff concur with San Joaquin County's Closure'Recommendation.
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