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TA1 - CHECKLIST OF REQUIRED TA
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<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
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<br /> Site Name and Location: Hammer Lane Shell, 7910 Lower,Sacramento Road,-Stockton,San Joaquin County
<br /> Eighteen private wells are located within 2000 feet. All
<br /> 1. Distance to production wells for municipal, domestic, agriculture,
<br /> 18 wells and Fivemile Creek,�located approximately
<br /> industry and other uses within 2000 feet of the site;
<br /> 200 feet away,are upgradient of the site.
<br /> Two 5,000-gallon and two 8,000-
<br /> 2. Site maps, to scale, of area impacted showing iocations of former.and existing tank gallon gasoline USTs were
<br /> systems, excavation contours and sample locations, boring and monitoring well removed 12/88. Soil
<br /> elevation contours, gradients, and nearby surface waters, buildings, streets, and contamination was reported under
<br /> subsurface utilities; the north dispenser island. i
<br /> Site lithology consists of clay,silt clay and silty
<br /> 3. Figures depicting lithology(cross section), treatment system diagrams; sand to 42 feet, the total depth investigated.
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<br /> 0 4. Stockpiled soil disposed off-site{quantity); Approximately 160 cubic yards of soil was excavated and disposed at
<br /> Forward Landfill in Manteca..
<br /> 0 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1 through MW-3)were installed.
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<br /> -°6. Tabulate d,results-of a!l-groundwater elevations anddepths-towater The depth to water varied from 30 to 60 feet
<br /> EE bulated results of all sampling and analyses: in 12/88, confirmation soil analyses reported TP14g(4,880 mg/kg),
<br /> benzene(27.7 mg/kg), toluene(32.1 mg/kg), ethylbenzene(33.9 mg/kg)
<br /> Detection limits limits for confirmation sampling and xylenes(988 mg/kg). Soil borings in 1997 reported TPHg
<br /> ®Lead analyses (0.3 mg/kg); benzene(0.005 mg/kg),and toluene(0.011 mg/kg).
<br /> Maximum groundwater monitoring results in 8/89 were benzene
<br /> (0.5 Ng/L)and toluene(11 pg/L). In 11/03, maximum groundwater
<br /> results were xylenes(2. 3 pg/L),and,MtBE(2.3 pg/L).
<br /> 8. Concentration contours of contaminants found and those remaining in soil F
<br /> and groundwater, both on-site and off-site: The soil borings and'monitoring wells
<br /> ®Y Lateral and Vertical extent of soil contamination define the extent of contamination.
<br /> Lateral and• Vertical extent of groundwater contamination
<br /> EYD 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; system was not requited at this site.
<br />+ Q 10,Reports 1 information 0 Unauthorized Release Form. 0 55 QMRs (8189 to 2104)
<br /> Y❑ Boring logs El PAR 0 FRP El Other Site investigation Report and.Request for Closure
<br /> Q 11.Best Available Technology(BAT) used or an explanation for not using BAT, . Soil Excavation with Offsite Disposal,
<br /> Natural Attenuation.
<br /> -�WYY 12.Reasons'why background wasrs
<br /> --,:-unattainable:using.BAT; ry„ Minor soil contamination remains on-site.
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<br /> 0 13.Mass balance calculation of substance
<br /> treated versus that remaining; Mass balance was not calculated for soil or groundwater.
<br /> 14.Assumptions,parameters, calculations and model used in risk
<br /> A risk assessment was not required
<br /> assessments, and fate and transport modeling;and
<br /> 15. Rationale why conditions remaining at site will not adversely .. Soil contamination is limited in extent,and after 55
<br /> impact water quality, health, or other beneficial uses. quarterly sampling events, contamination is not leaching
<br /> E into groundwater.
<br /> By: Comments: Two 5,000-gallon and two 8,000-gallon gasoline US Ts were removed at the subject site in 12/88. Soil
<br /> JLB contamination was reported under the north dispenser island. In 12/88, confirmation soil analyses reported TPHg
<br /> (4,880 mg/kg), benzene(27.7 mg/kg), toluene(32.1 mg/kg), ethylbenzene(33.9 mg/kg)and xylenes(188 mg/kg). Soil
<br /> Date: 9 Y A
<br /> boring analyses in 1997 reported TPHg(0.3 mg/kg), benzene(0.005 mg/kg), and toluene(0.011 mg/kg). Maximum
<br /> 4/30103 groundwater monitoring results in 8189 were benzene(0.5 Ng/L)and toluene(11 pg/L). In 11103, maximum
<br /> groundwater results were xylenes(2. 3 pg/L)and MtBE.(2.3 pg/L). Based on the minor soil contamination and
<br />' declining groundwater concentrations, Regional Board staff concur with San Joaquin County's Closure
<br /> Recommendation.
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