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BILE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: El Dorado Apartments Development, 2450 S. El Dorado St.,Stockton, San Joaquin County
<br /> (RB#3900015)
<br /> y 1. Distance to production wells for municipal,domestic, A sensitive receptor survey was not completed;however
<br /> agriculture, industry and other uses within 2000 feet of the site: Geo Tracker lists three municipal supply wells(two at
<br /> 1,100'north and one 1400'north) within 2,000'of the Site.
<br /> y 2. Site maps, to scale, of area impacted showing locations of Two 20,000-gallon heating oil USTs constructed of
<br /> any former and existing tank systems, excavation contours and redwood with steel banding and associated brick debris'
<br /> sample locations, boring and monitoring well elevation were removed 11/02.
<br /> contours; gradients, and nearby surface waters, buildings,
<br /> streets, and subsurface utilities;
<br /> Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of clay, silt and sand to 45',.the
<br /> diagrams; total depth investigated.
<br /> Y 4. Stockpiled soil remaining on-site or In 11/02, 2,000 cu.yds. of soil and debris was over-excavated and segregated into
<br /> off-site disposal(quantity); stockpiles. 372 tons of contaminated soil and construction debris were disposed
<br /> at Forward Landfill in Manteca. The remaining excavated soil was spread onsite,
<br /> and stockpiled soil from other locations onsite was used to backfill the pit.
<br /> 5. Monitoring wells remaining on-site, fate; Three lost monitoring wells(MW-1, MW-2, and MW-3) will be located and
<br /> - _-�:YD.- .. _ ro _erl abandoned:before-a-NFARJetter_iS ran.ted. .._ -�,
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 34'to 36'bgs. Groundwater flow
<br /> elevations.and depths to water, direction was towards the southeast,gradient varied from 0.01 to 0.003 ft/ft.
<br /> 7. Tabulated results of all sampling ' In 11/02, the maximum confirmation soil concentrations were TPHg, 87 mg/kg;and
<br /> and analyses: TPHd, 28,000 mg/kg. In 2/03, maximum soil boring results(MW-1) were TPHd, 130
<br /> mg/kg. In 7/02, maximum grab groundwater results(source area) were TPHg ,270
<br /> Y❑ Detection limits for conflrmation mg/kg;toluene, 2.6 mg/kg;ethylbenzene, 2.3 mg/kg;and xylenes, 27.6 mg/kg.
<br /> sampling Four quarters(2/03 to 1/04) of groundwater monitoring results were all ND.
<br /> �Y Lead analyses
<br /> 8. Concentration contours of contaminants found and those remaining in soil and The extent of the identified
<br /> groundwater, and both on-site an&off--site: contamination is described in the
<br /> reports.
<br /> Y❑Lateral and �Vertical extent of soil contamination
<br /> Lateral and ryl Vertical.extent of groundwatercontamination
<br /> 9. Zone of influence calculated and:assumptions used for subsurface remediation Over-excavation of soil was required by
<br /> system and the zone of capture attained.for the soil and groundwater remediation the lead agency.
<br /> system,
<br /> i 10.Reports l information ❑Y Unauthorized Release Form FY QMRs 4 from 2/03 to 1/04
<br /> FYI Well and boring logs [0 PAR ❑N FRP Other Closure Report(9/04) '
<br /> Yj 11.Best Available Technology(BAT) used or an explanation for not using USTs removal,soil over-excavation,and
<br /> BAT, natural attenuation.
<br /> Y — .- easons why background was�unaftaina-bie—-iV norresidua!soil-contamination-remains=on-site - "
<br /> BAT;
<br /> Y 13.Mass balance calculation of substance treated In 9/04, the consultant estimated that 1,781 gallons of TPHd remain in
<br /> soil. No estimate was provided for contaminant mass removed.
<br /> versus that remaining;
<br /> Y 14. Assumptions, parameters, calculations and Region 2ESLs were exceeded for gross contamination and direct
<br /> model used in risk assessments, and fate and exposure at 20'bgs. The site is a large vacant lot for proposed
<br /> transport modeling, a artments in a-mixed residential/commercial area of Stockton.
<br /> Y 15. Rationale why conditions remaining at site willSoil contamination reportedly is limited in extent. Land use
<br /> not adversely impact water quality, health, or other' (residential/commercial)is not expected to change in the foreseeable
<br /> beneficial uses;and future.
<br /> By: JLB Comments: Two 20,000-gallon heating oil USTs constructed of redwood with steel banding were removed
<br /> 11/2002. In 11/02, the maximum confirmation soil concentrations were TPHg, 87 mglkg;and,TPHd, .�
<br /> Date: .28,000 mg/kg. In'2/03, maximum soil boring results(MW-1) were TPHd, 130 mg%kg. In 7/02, maximum grab
<br /> 5/113//2009 ' groundwater results(source area) were TPHg, 270 mg/kg; toluene, 2.6 mg/kg;ethylbenzene, 2.3 mg/kg;and
<br /> xylenes, 27.6 mg/kg.:,Four quarters(2/03 to 1/04) of groundwater monitoring results were all ND. Based 5
<br /> upon ND results of groundwater monitoring, the limited extent of contamination remaining in soil,gross
<br /> contamination and direct exposure ESLs exceeded at a depth(20) where worker exposure is unlikely, and
<br /> with the assurance that San Joaquin County will enforce their well regulations(monitoring wells will be
<br /> f found and properly abandoned priorto issuance of the NFAR letter), Regional Board staff concur with Sari
<br /> Joaquin County's Closure Recommendation once wells are located and abandoned.
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