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TABLE -1 -CHECKLIST OF REQUIRED DA v A
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: City of Escalon/Former ARCO station, 1305 Escalon Ave., Escalon,San Joaquin County
<br /> 1.Distance to production wells for municipal, domestic, agriculture, A well survey in 2400 shows two public water supply
<br /> industry and other uses within 2000 feet of the site; wells are located approximately 1600 feet north and
<br /> 9800 feet southwest of the site. One irrigation well is
<br /> located approximately 750 feetto the northeast.
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank One 8,000-gallon and two
<br /> systems, excavation contours and sample locations, baring and monitoring well 10,000-gallon gasoline USTs were
<br /> elevation contours, gradients, and nearby surface waters, buildings, streets, and removed in 9198.
<br /> subsurface utilities;
<br /> 2] 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of sand,silt and Gay to
<br /> 115 feet, the total depth investigated.
<br /> M4. Stockpiled soil disposed off-site(quantity); The fate of approximately 100 cubic yards of contaminated excavated
<br /> soil was not reported.
<br /> 5. Monitoring wells remaining on-site, fate; Six monitoring wells(MW--1 through MW-5,and MW-101), installed for this
<br /> investigation, will be properly destroyed.
<br /> Y 6. Tabulated results of all groundwater elevations and depths to water, The depth to water varied from 61 feet(2000) to
<br /> 65 feet(2005). The groundwater flow direction
<br /> varied from west to northwest.
<br /> 7.Tabulated results of all sampling and analyses: Confirmation soil results in 11198 were 6,200 mg/kg, TPHg;2.64 mg/kg,
<br /> ®Y benzene;220 mg/kg, toluene;140 mg/kg, ethylbenzene;730 mglkg,
<br /> Detection limits for confirmation sampling xylenes,and 8 mg/kg,MtBE. After Soil Vapor Extraction(SVE)in 9103,
<br /> Lead analyses soil results were 3,130 mg/kg, TPHg; 1.9 mglkg, toluene;30.4 mglkg,
<br /> ethylbenzene;and 194 mg/kg,xylenes. Groundwater monitoring
<br /> results on 4100 were 516 pg/L, TPHg;621tg1L,,benzene,42 Pg/L,
<br /> toluene;10 pg/L,ethylbenzene;57 yg/L,xylenes;and 220 pg1L, MtBE.
<br /> In 5105, groundwater monitoring results were all ND.
<br /> 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater; both on- and off-site; The extent of contamination is defined by
<br /> Y Lateral and Y Vertical extent of soil contamination on-site soil borings and monitoring welts.
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 9. zone of influence calculated and assumptions used for subsurface
<br /> remediation system and the zone of capture attained for the soil and SVE, the engineered remediation system,
<br /> groundwaterremediation system; rem o ved approximately 1,013 gallons of
<br /> gasoline from soil at this site.
<br /> 10.Reports/informafion Unauthorized Release FormQMR5 22 QliriRs from 4/00 to 5/05.
<br /> Boring logs El PAR 0 FRP Q Other Site Closure Report
<br /> L_ 1 11,Best Available Technology(BAT) used or an explanation fornot using BAT Remove USTs,SVE and natural attenuation.
<br /> Q12.Reasons why background wasps
<br /> unattainable using BAT; Groundwater contamination is no longer present. Minor soil contamination
<br /> remains on-site.
<br /> 0 13.Mass balance calculation of substance
<br /> treated versus that remaining; Approximately 56 gallons of gasoline remain in soil onsite.
<br /> M14. Assumptions.parameters, calculations and model used in risk A limited risk assessment was conducted in the Site
<br /> assessments, and fate and transport modeling;and Closure Report.
<br /> Y 15, Rationale why conditions remaining at site will not adversely Although minor soil contamination is present onsite,
<br /> impac€water quality, health, or other beneficial uses. based on 22 groundwater sampling events,petroleum
<br /> hydrocarbons are not continuing to leach to
<br /> groundwater.
<br /> By: Comments: One 8,000-gallon and two 10,000-gallon gasoline USTs were removed from the subject site in 9198.
<br /> JLB Confirmation sail results in 11198 were 6,200 mg/kg, TPHg;2.64 mg/kg, benzene:220 mglkg, toluene; 140 mg/kg,
<br /> ethylbenzene; 730 mg/kg, xylenes, and 8 mg/kg, MtBE. After Soil Vapor Extraction(SVE)in 9/03, soil results were
<br /> Date.. 3,130 mglkg, TPHg; 1.9 mg/kg, toluene;30.4 mglkg, ethylbenzene;and 194 mglkg, xylenes. Groundwater monitoring
<br /> results on 4100 were 516 yg1L, TPHg; 62 pglL, benzene;42 pglL, toluene; 10 pglL, ethylbenzene;57 pg/L, xylenes;and
<br /> 7127105 220 pgA.., MtBE. In 5105, groundwater monitoring results were all ND. Based on the low levels of residual soil
<br /> contamination and no petroleum hydrocarbons leaching into groundwater, Regional Board staff concur with San Joaquin
<br /> ntv's Closure Recommendation.
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