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<br /> \_413LE 1 -CHECKLIST OF REQUIRED DA1-,-,,"
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Fmr. Nelson Ready Mix, 2059 Navy Dr., Stockton,San Joaquin County, LUSTIS#390887
<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, A well survey on 2/06 identified one onsite supply
<br /> industry and other uses within 2000 feet of the site; well located 100 feet west(crossgradient)of the
<br /> site.
<br /> Y
<br /> 2. Site maps, to scale, of area impacted showing locations of former One 4,000-gallon diesel UST was removed 2/95.
<br /> and existing tank systems, excavation contours and sample locations, An over-excavation of the tank pit occurred 2/04.
<br /> boring and monitoring well elevation contours, gradients, and nearby Approximate 36,000 gallons of water from the
<br /> surface waters, buildings, streets, and subsurface utilities; excavation was disposed at/nstrat, Inc. of Davis.
<br /> Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of sand,silt, and clay to 20
<br /> diagrams; feet, the total depth investigated.
<br /> 4. Stockpiled soil disposed off-site(quantity); Of the total 700 cu.yards excavated, approximately 300 cu.yds. of soil
<br /> were impacted b TPHd, bioremediated aerated ands read onsite.
<br /> Y 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1 through MW-3)installed for this investigation
<br /> will be abandoned.
<br /> Y 6. Tabulated results of all groundwater elevations and depths to The depth to water varied from 7 to 9 feet. The direction
<br /> water, - of-groundwater varied from south to southwest from
<br /> 0.0018 to 0.004 ft/ft.
<br /> Y 7. Tabulated results of all sampling and In 10/95, the maximum confirmation soil results were TPHd,
<br /> analyses: 13,000 mg/kg;toluene(T), 0.097 mg/kg;ethy/benzene, (E) 0.47 mg/kg;
<br /> and xylenes(X), 0.2 mg/kg. In 11/05 after over-excavation, the maximum
<br /> Y Detection limits for confirmation sampling petroleum hydrocarbons soil boring result was TPHd, 150 mg/kg. The
<br /> El
<br /> N Lead analyses maximum petroleum hydrocarbons grab groundwater results in 11/05
<br /> were TPHd, 19,000 ug/L; TPHg, 64 ug/L;and D/PE, 54 ug/L. T E X were
<br /> not detected in soil or groundwater after 1995. In 6/06 and 2/07,all
<br /> groundwater monito ng results were ND.
<br /> Y 8. Concentration contours of contaminants found and those remaining The extent of contamination was defined by soil
<br /> soil and groundwater, both on-site and off-site: borings,grab groundwater samples,and
<br /> PY Lateral and Y Vertical extent of soil contamination monitoring wells.
<br /> Y Lateral and P1 Vertical extent of groundwater contamination
<br /> Y 9. zone of influence calculated and assumptions used for subsurface 1 An engineered remediation system was not
<br /> remediation system and the zone of capture attained for the soil and required by the lead agency.
<br /> groundwater remediation system;
<br /> 10.Reports/information 0 Unauthorized Release Form a 2 QMRs(6/06 and 2/07)
<br /> ElBoring logs 0 PAR F FRP ❑Y Other: Site Conceptual Model(Closure Report)
<br /> Y 11.Best Available Technology(BAT) used or an explanation for not Remove USTs, over-excavation, bioremediation of
<br /> using BAT, I excavated soil, and natural attenuation.
<br /> Y 12.Reasons why background was/is unattainable using BA T; Minor soil contamination remains on-site. `
<br /> Y 13.Mass balance calculation of substance treated versus that The consultant estimated remaining mass in soil(TPHd,
<br /> remainin ; 178 lbs).
<br /> 14.Assumptions, parameters, calculations and model The 11/05 soil boring results(TPHd, 150 mg/kg) exceed Region 2
<br /> used in risk assessments, and fate and transport ESLs(100 mg/kg) for gross contamination. Groundwater
<br /> modeling;and monitoring well results were ND in 6/06 and 2/07.
<br /> 15. Rationale why conditions remaining at site will not Soil contamination is limited in extent. Two monitoring events
<br /> adversely impact water quality, health, or other show no petroleum hydrocarbons remaining in groundwater.
<br /> beneficial uses.
<br /> By: Comments: One 4,000-gallon diesel UST was removed 2/95 from the subject site. A 300-cubic yard over-
<br /> JLB excavation of the tank pit occurred 2/04. Stockpile excavation soil was bio-remediated and spread onsite.
<br /> Approximately 36,000 gallons of pit water was tested(TPHd, 900 ug/L) and received proper disposal. Minor soil
<br /> contamination and no groundwater pollution remain onsite. The 11/05 soil boring results(150 mg/kg) exceed
<br /> Date: Region 2 ESLs(100 mg/kg) for gross contamination. Groundwater monitoring well sample results were ND in
<br /> 6/06 and 2/07. Site is zoned commercial and reportedly will be redeveloped as an auto recycling facility. Based
<br /> 10/4/07 on adequate definition of extent of contamination in soil, and declining TPHd concentrations to ND in
<br /> groundwater, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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