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,,ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location7 The Auto Factory, 5942 S. Hwy 99, Stockton, San Joaquin County(RB#f391092)
<br /> 7Y 1. Distance to production wells for municipal, domestic, The onsite supply well has been sampled quarterly by
<br /> agriculture, industry and other uses within 2000 feet of the site. ARCO#595 since 2002. All sample results were ND.
<br /> Y1 2. Site maps, to scale, of area impacted showing locations of Three 8,000-gallon gasoline USTs and associated piping
<br /> any former and existing tank systems, excavation contours and were removed 12/80. In 10/99, Caltrans advanced three
<br /> sample locations, boring and monitoring well elevation borings onsite in the tank pit for the Hwy 99 Hammer
<br /> contours, gradients, and nearby surface waters, buildings, Lane interchange project, and detected TPHg and TPHd
<br /> streets, and subsurface utilities; in soil and in a grab groundwater sample.
<br /> Y1 3. Figures depicting lithology(cross section), treatment system Site lithology consists of silt and sand. The total depth
<br /> diagrams, investigated was approximately 70 feet. Depth to water
<br /> was 56 feet.
<br /> Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); The fate of the USTs soil excavated is not addressed in
<br /> the reports.
<br /> 5. Monitoring wells remaining on-site, fate; One monitoring well(MW-1) was installed 6/00 and sampled once for this
<br /> Ix 1r— Iinvesti ation. The well was subsequently abandoned duringconstruction.
<br /> 6. Tabulated results of all groundwater Depth to groundwater was reported from approximately 38 feet(8199,
<br /> elevations and depths to water, possibly perched)to 60 feet(1/08)below ground surface(bgs). The
<br /> reported regional groundwater flow direction is towards the south.
<br /> 7. Tabulated results of all sampling In 10/99, the before maximum soil boring results were TPHg, 2,390 mg/kg; TPHd,
<br /> and analyses: 573 mg/kg;toluene, 25.6 mg/kg;ethy/benzene, 41.2 mg/kg;and xylenes,
<br /> 239 mg/kg. The after soil borings concentration in 6/00 was TPHd, 2.9 mg/kg. In
<br /> Detection limits for confirmation 10/99, one grab groundwater sample result was TPHd, 173 ug/L. In 6/00 the single
<br /> sampling groundwater monitoring event result was NO for all constituents.
<br /> QN Lead analyses
<br /> LyJ 8. Concentration contours of contaminants found and those remaining in soil and The extent of the identified
<br /> groundwater, and both on-site and off-site: contamination is described in applicable
<br /> reports.
<br /> 0 Lateral and ElVertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation An engineered remediation was not
<br /> system and the zone of capture attained for the soil and groundwater remediation required by the lead agency.
<br /> system;
<br /> 10.Reports/information [Y Unauthorized Release Form QN QMRS one event in 6/00
<br /> Well and boring logs QY PAR FN-] FRP 0 Other
<br /> 1 11
<br /> Y I 11.Best Available Technology(BAT) used or an explanation for not using Removal of UST and piping, natural
<br /> BAT; attenuation.
<br /> Y 12. Reasons why background washis unattainable Minor residual soil contamination remains on-site.
<br /> BAT,
<br /> Initial mass and treated mass were not calculated by the consultant.
<br /> Y 13.Mass balance calculation of substance treated
<br /> versus that remaining;
<br /> Y 14. Assumptions, parameters, calculations and After soil sample results show no Region 2 ESLs were exceeded and
<br /> model used in risk assessments, and fate and after groundwater sample results show WQGs were not exceeded in
<br /> transport modeling; groundwater. The onsite supply well has been sampled by ARCO
<br /> since 2002 and results have been NO.
<br /> _y] 15. Rationale why conditions remaining at site will Soil contamination is limited in extent and not leaching to
<br /> not adversely impact water quality, health, or other groundwater. Land use(car lot)is not expected to change in the
<br /> be ficial uses; and foreseeable future.
<br /> By: JL Comments Three 8,000-gallon gasoline USTs and associated piping were removed 12/80. In 10199 Caltrans
<br /> advanced three borings onsite in the tank pit for the Hwy 99 Hammer Lane interchange project, and detected
<br /> Date: TPHg and TPHd in soil and in a grab groundwater sample. One monitoring well(MW-1) was installed 6/00
<br /> 1/23/2009 and sampled once for this investigation;the groundwater monitoring results were NO for all constituents.
<br /> The monitoring well was subsequently abandoned during construction. The onsite supply well has been
<br /> sampled quarterly by ARCO#595 since 2002 and sample results have been ND. Minor residual soil
<br /> contamination remains on-site. Based upon the limited extent of contamination present in soil, no evidence
<br /> of leaching to groundwater, no ESLs exceeded,and the lack of a threat to from soil vapor intrusion in the car
<br /> lot, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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