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i ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Pombo Rank Property, 24100 Lammers Rd.,Tracy, San Joaquin County (Lustis Case 11391027)
<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, Well surveys in 2000 and 2003 showed three
<br /> industry and other uses within 2000 feet of the site; domestic wells located 50 feet west, 220 feet
<br /> southwest and 450 feet west of the site.
<br /> Y Site maps, to scale, of area impacted showing locations of any former One 5,000-gallon gasoline UST was removed
<br /> and existing tank systems, excavation contours and sample loca ions, 3/88, and one 10,000-gallon diesel UST was
<br /> boring and monitoring well elevation contours, gradients, and nearby removed 6/83.
<br /> surface waters, buildings, streets, and subsurface utilities;
<br /> Y 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of sand, silt, and
<br /> clay to 40 feet, the total depth
<br /> investigated.
<br /> :Y] 4. Stockpiled soil remaining on-site or off-site disposal(quantity); approximately 1,524 tons of over-excavated soil was
<br /> removed in 3/05 and transported to Forward Landfill in
<br /> Manteca.
<br /> Y 5. Monitoring wells remaining on-site, fate; Six monitoring well (MW-1 through MW-5 and MW-105)remaining on-site
<br /> will be propeLly ab ndoned.
<br /> - ' -6-Tabuleted-resutts-of-all-9rouf4dwa#er Depth to groundwater varied from-9.to 13 feet below ground surface
<br /> elevations and depths to water, (bgs). The gro n wa er gradin vane rom O.-004-M-t O.V)9 ff/ft157W the downgradient direction was reported as consistently to the Northeast.
<br /> 7. Tabulated results of all sampling and In 9/98, maximum Geop obe soil concentrations were: TPHg, 480 mg/kg; TPHd,
<br /> analyses: 140 mg/kg;benzene, 1 r ig/kg;toluene, 3 mg/kg; ethylbenzene, 9.2 mg/kg;xylenes
<br /> FYI26 mg/kg, and MtBE 2.3 mg/kg. In 3/05 after over-excavation, maximum soil
<br /> Detection limits for confirmation confirmation concentra ion were: TPHd, 37 mg/kg;ethylbenzene, 0.67 mg/kg;and
<br /> sampling xylenes, 1.3 mg/kg. Ma imum grab groundwater concentrations in 9/98 were:
<br /> TPHg, 56,000 fag/L;ben;-ene 3,700 fag/L;toluene, 1,200Irg/L; ethylbenzene, 2,400
<br /> ❑Y Lead analyses ug/L;xylenes, 4,000 fag/ and MtBE, 3,400 pg/L. in 4/06, maximum groundwater
<br /> concentrations were: TJ 114g, 60 /L;and MtBE, 6.6 /L.
<br /> 8. Concentration contours of contaminants found and those remaii7ing in soil and The extent of contamination is
<br /> groundwater, and both on-site and off-site: adequately defined by soil borings
<br /> Y Lateral and y Vertical extent of soil contaminatior and monitoring wells.
<br /> Lateral and e Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Over-excavation was the required
<br /> system and the zone of capture attained for the soil and groundwater remediation remediation. A groundwater
<br /> system; remediation system was not
<br /> required by the lead agency,
<br /> 10.Reports/information Unauthorized Release Form FY QMRs (14 from 1999-2006)
<br /> FY] Well and boring logs PAR FRP FY] Other, Site Closure Report
<br /> 1?.Best Available Technology(8A T) used or an explanation far not using BAT, BAT was over-excavation and natural
<br /> attenuation...
<br /> Y1 12.Reasons why background waslis unattainable using BAT Limited soil contamination and groundwaterpollutidin
<br /> remains on-site.
<br /> Y 13.Mass balance calculation of substance treated versus that In 6/06, the consultant estimated the residual mass in
<br /> soil as benzene, 0.012 lbs; toluene, 0.016 lbs;
<br /> remaining; ethylbenzene, 0.021 lbs;and xylenes, 0.041 lbs. The
<br /> estimated residual mass in groundwater is 0.05 lbs. of
<br /> TPHg and 0.01 lbs. of MtBE.
<br /> Y 14. Assumptions, parameters, calculations and model used in A risk assessment was not required. Soil ESLs are not
<br /> risk assessments, and fate and transport modeling; exceeded. Water Quality Goals are excee�(or TPHg
<br /> 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, orother beneficial uses; and 14 quarters of groundwater monitoring show a
<br /> decreasing trend in concentrations, which are estimated
<br /> to decline to WQGs in two ears.
<br /> By: JLB Comments: One 5,000-gallon gasoline UST was removed 3/88, and one 10,000-gallon diesel UST was removed
<br /> 6/83 from the subject site. Site is a farm surrounded by the City of Tracy. Soil concentrations are below residential
<br /> Date: ESLs, so threats from vapor intrusion and direct exposure are minimal. San Joaquin County staff has stated they are
<br /> 716112006 in compliance with public participation requirements. Based upon 14 quarters of declining groundwater
<br /> concentrations, and the limited extent of contamination present in soil and gropundwater, Regional Board staff
<br /> concur with San Joaquin County's Closure Recommendation.
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