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kW4L'E 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Former Mobile Oil Corporation#10-NPA,2375 Tracy Boulevard, Tracy, San Joaquin County
<br /> (RB#390017)
<br /> Y 1. Distance to production wells for municipal,domestic, The 1986, 2001, 2005, and 2007 sensitive receptor
<br /> agriculture, industry and other uses within 2400 feet of the site. surveys reported two domestic, two irrigation, and one
<br /> municipal supply wells within 2,000'of the site. None of
<br /> the wells are threatened by the release.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of Two 10,000-gallon and one 5,000-gallon gasoline USTs,
<br /> any former and existing tank systems, excavation contours and and one 280-gallon waste oil UST were removed 8/86. The
<br /> sample locations, boring and monitoring well elevation product lines and dispensers were removed 6195.
<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 off-site disposal (quantity); Approximately 600 y of excavated soil was
<br /> trans orted in 1986 to 11689 Clover Rd.in Trac .
<br /> Y 5. Monitoring wells remaining on-site, fate; Fifteen(15)monitoring wells(AMW-1 through AMW-6,and MW-1 through
<br /> MW-9)will be properly abandoned.
<br /> 6.-Tabulated results of all groundwater _ _ Depth to groundwater varied from 4'bgs to 8'bgs. Groundwater flow
<br /> elevations and- to water; -direction-varied•from-non'h-to-northvrest at a-gradient-varying-from
<br /> 0.004 ft/ft to 0.033 ft/ft.
<br /> 7. Tabulated iesults of all sampling All data adequately tabularized in various reports, including closure report.
<br /> and analyses:
<br /> Y❑ Detection limits for confirmation
<br /> sampling
<br /> 10 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 and off-site: contamination is described in the
<br /> available reports.
<br /> 0 Lateral and Y❑Vertical extent of soil contamination
<br /> FYI Lateral and Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Over-excavation of soil,groundwater
<br /> system and the zone of capture attained for the soil and groundwater remediation pump and treatment,and batch
<br /> system; groundwater extraction were the
<br /> engineered remediation.
<br /> 10.Reports 1 information 1Y Unauthorized Release Form � QMRs 4-90 to 4-11
<br /> Well and boring logs CY PAR ❑Y FRP EY1 Other Closure Report(6-11)
<br /> :7:1 11.Best Available Technology(BAT) used or an explanation for not using UST removal, over-excavation,groundwater
<br /> BAT; pump and treat, batch groundwater
<br /> extraction and natural attenuation.
<br /> -12.—Reasons-why-background-waslis-unattainable—-Minor-residual-soil and-groundwater-contominationfemains-on-site:---
<br /> -6 BA T,-
<br /> Y 1 13.Mass balance calculation of substance treated Consultant estimates 163 lbs of TPHg removed from groundwater by
<br /> versus that remainin ; batch extraction.
<br /> Y 14. Assumptions, parameters, calculations and Pre-excavation soil concentrations did exceed Region 2
<br /> model used in risk assessments,-and fate and Environmental Screening Levels for direct contact and gross
<br /> transport modeling; contamination. Confirmation soil samples were not taken. Consultant
<br /> states no significant risk exists after remediation. The store is
<br /> approximately 30'from the former USTs and dispensers, and is not
<br /> threatened by soil vapor intrusion.
<br /> :Y:1 15. Rationale why conditions remaining at site will Soil and groundwater contamination reportedly are limited in extent
<br /> not adversely impact water quality, health, or other Land use(commercial)is not expected to change in the foreseeable
<br /> beneficial uses;and future. TPHg estimated to reach WQGs in 2048.
<br /> By: JLB I� Comments Two 10,000-gallon and one 5,000-gallon gasoline USTs,and one 280-gallon waste oil UST were
<br /> caJ removed 8/86. The product lines and dispensers were removed 6195 at the subject site. Minor residual soil
<br /> Date: and groundwater contamination remains on-site.Based upon the limited extent of contamination reported in
<br /> 9/8/2011 soil and groundwater,no foreseeable changes in future land use(commercial),and minimal risks from soil,'
<br /> soil vapor, and groundwater,Regional Board staff concur with San Joaquin County's Closure
<br /> Recommendation.
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<br /> 9" S
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