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<br /> TABLE 1 -CHECKLIST OF REQUIRED�DATA��`'
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> i,
<br /> Site Name and Location; Tuff Boy Trailers, 5151 Almondwood Drive, Manteca,San Joaquin County (Lustis#391052)
<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, I A well survey in 2000 showed at least 24wells
<br /> industry and other uses within 2000 feet of the site; �1: (22 domestic and 2 irrigation) within 2000 feet
<br /> j of the site. Three of the wells located within
<br /> 500 feet of the UST were NO for gasoline.
<br /> Y Site maps, to scale, of area impacted showing locations of any former I One;11,100-gallon gasoline UST was removed in
<br /> and existing tank systems, excavation contours and sample locations, 2/99:
<br /> boring and monitoring well elevation contours, gradients, and nearby i;
<br /> surface waters, buildings, streets, and subsurface utilities; IE 1 1[
<br /> Y 3. Figures depicting lithology(cross section), treatment system diagrams; .1. Site lithology consists of clay,silt and
<br /> sand to 38 feet, the total depth
<br /> I€
<br /> investigated.
<br /> Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 30 yards of over-excavated soil was
<br /> I from the tank pit,sam led, ands read onsite.
<br /> Y 5. Monitoring wells remaining on-site, fate; Eleven monitoring wells(MW-1 through MW-11D)remaining on-site will be
<br /> pMerly abandoned. 11
<br /> 6.`Tabulati=d re"sui[s of afl groundwater°` Depth to-groundwater-varied from 44o 7-feet-below ground surface{bgs):--
<br /> elevations and depths to water;
<br /> The groundwater gradient varied from 0.001 to 0.00085 ft/ft,and the
<br /> downgradient direction varied from North to West.
<br /> 7. Tabulated results of al/sampling and In 2/99, maximum soil concentrations were: TPHg, 630 mg/kg;benzene,
<br /> analyses: 1.4 mg/kg, toluene; 1.3 mg/kg, ethylbenzene;2.9 mg/kg,and xylenes; 13 mg/kg.
<br /> In 1/04, maximum soil boring concentrations were: TPHg, 24 mglkg;and xylenes;
<br /> Detection limits for confirmation 0.2 mg/kg. Maximum groundwater concentrations in 1/01 were: TPHg, 8,000 pg/L;
<br /> sampling benzene, 13 pg/L;ethylbenzene, 64 pg/L;xylenes, 200 yg/L;and MtBE, 16,ug/L.
<br /> i In 11/05,maximum groundwater concentrations were: TPHg, 64 pg/L;and MtBE,
<br /> ❑N Lead analyses 5.3pg/L. '
<br /> yJ 8. Concentration contours of contaminants found and those remaining in soft and The extent of contamination is
<br /> ndwater, and both on-snd off--site: ; adequately defined by soil borings
<br /> Y Lateral and ly I Vertical extent of soil contamination I s and monitoring wells. i
<br /> ©Lateral d anercaextentogroundwater contamination
<br /> waer conaa©Vertical ii
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation An engineered remediation was
<br />`` system and the zone of capture attained for the soil and groundwater remediation ^ not required by the lead agency.
<br /> system; Il.
<br /> 10.Reports/information �Y Unauthorized Release Form FY QMRs(317 from'2001 —2005)
<br /> �y Other;Additional Investigation and Closure Summary Reports
<br /> FY] Well and boring logs PAR FRP
<br /> YJ 11.Best Available Technology(BAT)used or an explanation for not using BAT,• Removal of US Ts, minor over-excavation
<br /> k y and natural attenuation.
<br /> Y 12.Reasons why.background wasfis unattainable using BAT Limited soil contamination and groundwater pollution
<br /> remainson-site.
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<br /> Y 13.Mass balance calculation of substance treated versus that An engineered remediation was not required. In 2002,
<br /> remaining; the residual contamination was estimated at 33 gallons
<br /> of TP,g in soil and x0.001 lbs of TPHg in groundwater.
<br /> Y
<br /> 14. Assumptions, parameters, calculations and model used in Soil ESLs are not exceeded. Secondary MCL Water
<br /> risk assessments, and fate and transport modeling; Quality Goals(WQGs) are exceeded for TPHg and MtBE.
<br /> Y 15. Rationale why conditions remaining at site'will not adversely Soil contamination is limited in extent. Results of
<br /> impact water quality, health, or other beneficial uses;and 17 quarters of groundwater monitoring show a
<br /> decreasing trend in concentrations. WQGs will be
<br /> reached in less than two years.
<br /> By. JLB Comments: One 1,100-gallon gasoline UST was removed in 2199 from'subject site. Site is a large fenced trailer
<br /> manufacturing facility, so threats from vapor intrusion are minim al. Based upon 17 quarters of declining groundwater
<br /> Date: concentrations, and the limited extent of contamination present'in soil, 'Regional Board staff concur with San Joaquin
<br /> 4/18/2006 County's Closure Recommendation. li
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