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TABM 1 - CHECKLIST OF REQUIRED Dri l A
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: City of EscaionlFormer ARCO station, 1305 Escalon Ave., Escafon, San Joaquin County
<br /> 0 1. Distance to production wells for municipal, domestic, agriculture, A well survey in 2000 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 /> 4800 feet southwest of the site. One irrigation well is
<br /> located approximately 750 feet to 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, boring and monitoring well 10,000-gallon gasoline USTs were
<br /> elevation contours, gradients, and nearby surface waters, buildings, streets, and removed 7n 9198,
<br /> subsurface utilities:
<br /> 3. Figures depicting lithalogy(cross section), treatment system diagrams; Site lithoiogy consists of sand, silt and clay to
<br /> 115 feet, the totsl depth investigated.
<br /> 4. 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 rernairring on-site, fate; Six monitoring wells(MW-1 through MW-5, and MW-101), installed for this
<br /> investigation, will be properly destroyed.
<br /> FYI 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 /> 0 7. 'Tabulated results of all sampling and analyses: Confirmation soil results in 11198 were 6,200 mg/kg, TPHg;Z 64 mg/kg,
<br /> Y benzene;220 mg/kg, toluene; 140 mg/kg, ethylbenzene; 730 mg/kg,
<br /> N Detection limits for confirmation sampling xylenes,and 8 mg/kg, MtBE. After Soil Vapor Extraction (SVP) in 9/03,
<br /> Lead analyses soil results were 3,130 mg/kg, TPHg; 1.9 mg/kg, toluene;30.4 mg/kg,
<br /> ethylbenzene;and 194 mg/kg,xylenes. Groundwater monitoring
<br /> u results on 4/00 were 516 pg/L, TPHg; 62 yg/L, benzene;42 pg/L,
<br /> toluene; 10 pg/L, ethylbenzene;57 pglL, xylenes;and 220 pg/L, 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 /> Hateral
<br /> ateral and Y Vertical extent of soil contamination on-site soil borings and monitoring wells.
<br /> and Y vertical extent ofgroundwatercontamination
<br /> 0 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 /> groundwater remediation system; removed approximately 1,013 gallons of
<br /> gasoline from soil at this site.
<br /> 10.Reports/information Unauthorized Release Form QMRs 22 QMRs from 4/00 to 5/05.
<br /> 19 Boring logs PAR LJ FRP Other Site Closure Report
<br /> 11.Best Available Technology(BAT) used or an explanation for not using SAT Remove USTs, SVE and natural attenuation,
<br /> 12.Reasons why background waslis
<br /> unattainable using SAT; Groundwatercontaminatlan is no longer present. Minor soil contamination
<br /> remains on-site.
<br /> 13.Mass balance calculation of substance
<br /> treated versus that remaining; Approximately 56 gallons of gasoline remain in soil onsite.
<br /> FE14. 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 /> FTJ 15, Rationale why conditions remaining at site will not adversely Although minor soil contamination is present onsite,
<br /> impact 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 /> Bv: Comments: One 8,000-galion and two 10,000-gallon gasoline USTs were removed from the subject site in 9/98.
<br /> 3LT3 Confirmation soil results in 11/98 were 6,200 mg/kg, TPHg; 2.64 mg/kg, benzene;220 mg/kg, 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 rngfkg, TPHg; 1.9 mg/kg, toluene;30.4 mg/kg, ethylbenzene;and 194 mg/kg, xylenes. Groundwater monitoring
<br /> results on 4/00 were 516 pg/L, TPHg; 62 pg/L, benzene;42 pg/L, toluene; 10 pg/L, ethylbenzene; 57 pg/L, xylenes;and
<br /> r 220 pg,'L, MtBE. In 5/05, groundwater monitoring results were all ND. Based on the low levels of residual soil
<br /> 2 7,105 contamination and no petroleum hydrocarbons leaching into groundwater; Regional Board staff concur with San Joaquin
<br /> Counfv's Closure Recommendation.
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