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<br /> TABLE I -CHECKLIST OF REQUIRED DATA ., f
<br /> FOR NO FURTF;�.- 'ACTION REQUESTS AT UNDERGROUND SITES
<br /> 1
<br /> Site Name and Location: Valley Water Treatment, 612 N. Buena Vista Ave., Stockton,San Joaquin County(RB Case 391177)
<br /> - Y Distance to production wells for municipal, domestic, A 2008 well survey reported two supply wells within 2000'of
<br /> culture, industry and other uses within 2000 feet of the site. the site, 1500'south and 700'northeast of the site.
<br /> Y 2. Site maps, to scale, of area impacted showing locations One 1,000-gallon gasoline UST was removed 2187. TPHg,
<br /> of any former and existing tank systems, excavation toluene, ethylbenzene, and xylenes were detected in soil
<br /> contours and sample locations, boring and monitoring well beneath the UST. No new USTs were installed.
<br /> elevation contours, gradients, and nearby surface waters,
<br /> buildings, streets, and subsurface utilities; •i
<br /> 1 Y 3. Figures depicting lithology(cross section), treatment Site lithology consists of clay,silt,and sand to 20 feet, the
<br /> system diagrams; focal depth ir:vestrgated.
<br /> 1
<br /> y Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); in 6107; approximately 65 cubic yards of soil wasexcavated to 14'bgs and transported to Forward
<br /> Landfill. i�
<br /> :Y:1 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1,MW72, and MW-4)remaining on-site will be
<br /> properlyabandoned.
<br /> 6. Tabulated results of all groundwater
<br /> Depth to groundwater varied from 5 to 8 feet below ground surface(bgs),
<br /> elevations and depths to water, The groundwater gradient varied from 0.0025 to 0.006. The
<br /> downgradient groundwater flow direction varied from northwest to
<br /> northeast. f
<br /> 7. Tabulated results of all sampling Maximum soil boring concentrations(5/05) were TPHg, 1500 mglkg;toluene,
<br /> and analyses: 1.1 mg/kg;ethylbenzene, 33 mg/kg;and xylenes, 170 mglkg(MTBE was not
<br /> analyzed). In 6107, confirmation soil after results were TPHg, 5.2 mg/kg;
<br /> VI Detection limits for confirmation ethylbenzene,0.52 mg/kg;and xylenes, 13 mg/kg. Maximum grab groundwater
<br /> sampling concentrations(5/05) were TPHg,;11300 u`g/L;benzene, 2.8 ug/L;toluene, 6.3 ug/L;
<br /> ethylbenzene,12 ug/L;and xylenes, 48 ug/L. In 4108,groundwater monitoring
<br />{ �Y Lead analyses concentrations were NO(MTBE was not,
<br /> 'detected).
<br /> 8. Concentration contour's of contaminants found and those remaining in soil and The extent of the identified
<br /> groundwater, and both on-site and off-site: contamination shown in applicable
<br /> reports.
<br /> Latera!and Y❑Vertical extent of soil contamination
<br /> �J
<br /> Lateral and 10 Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation A limited sail over-excavation and
<br /> system and the zone of capture attained for the soil and groundwater remediation natural attenuation were the
<br /> s stem; ;3 required engineered remediation.
<br /> 10.Reports/information ❑Y Unauthorized Release Form ❑Y QMRs(9 from 1106 to 4108)
<br /> Well and boring logs � PAR � FRP � Other; Closure Report 6/08
<br /> �7:1 11.Best Available Technology(SAT) used or an explanation for not using BAT. Removal of UST, over-excavation to
<br /> If 14'b s, and natural attenuation.
<br /> 12. Reasons why background was/is unattainable using BAT; Limited soil contamination remains on-site.
<br /> Y
<br /> 13.Mass balance calculation of substance treated versus that The consultant estimated 0.16 pounds of gasoline
<br /> contamination:'remain in soil.
<br /> remaining;
<br /> 7Y 14. Assumptions, parameters, calculations and model used in No soil 'vapor commercial ESLs were exceeded during
<br /> risk assessments, and fate and transport modeling; the soil;vapor analyses.
<br /> Y 15. Rationale why conditions remaining at site will not adversely Soil corrtamina',tion is limited in extent and not leaching to
<br /> impact water quality, health, or other beneficial uses;and groundwater. Results of 9 quarters of groundwater
<br /> monitorin show WQGs have been reached.
<br /> BY: JLComments: One 1,000-gallon gasoline UST was removed 2187. TPHg, toluene, ethylbenzene,and xylenes were
<br /> 1. 41 detected in soil beneath the UST. No new USTs were install6ii. In 6107, approximately 65 cubic yards of soil
<br /> Date: was excavated to 14'bgs and transported offsite. Maximum soil boring concentrations(5105) were TPHg,
<br /> 12117/2008 1500 mg/kg;toluene, 1.1 mg/kg;ethylbenzene,33 mg/kg;and,xylenes, 170 mg/kg(MTBE was not analyzed).,.In
<br /> 6/07, confirmation soil after results were TPHg, 5.2 mg/kg;ethylbenzene, 0.52 mg/kg;and xylenes, 13 mg/kg.
<br /> Maximum grab groundwater concentrations(5/05)were TPHg, 1300'ug/L;benzene, 2.8 ug/L;toluene, 6.3 ug/L;
<br /> ethylbenzene,12 ug/L;and xylenes, 48 ug/L. In 4108,groundwater monitoring concentrations were NA(MTBE
<br /> was not detected). Based upon 9 quarters of declining groundwater,`concentrations to NO, no reported threat
<br /> from vapor intrusion, no anticipated threats to sensitive receptors,and the limited extent of contamination
<br /> present in soil, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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