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TA 1 -CHECKLIST OF REQUIREDTA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES .
<br /> Site Name and Location: Grantline Gas and Food,2420 Grant Line Road, Tracy,San Joaquin County
<br /> 1. Distance to production wells for municipal, domestic, agriculture, Four private welts are located within 2,000 feet of the !
<br /> industry and other uses within 2000 feet of the site; site. The wells are 50 feet south(ND in 1/02}300 feet
<br /> southwest, 1,600 feet east and 1,700 feet east.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of former and existing tank Two 7,500-gallon and one
<br /> systems, excavation contours and sample locations, boring and monitoring well elevation 5,000-gallon gasoline USTs
<br /> contours,gradients, and nearby surface waters, buildings, streets, and subsurface utilities, were removed in 6/93.
<br /> 0 3. Figures depicting lithology(cross section), treatment system diagrams; - She lithologY consists of gravel, clay and sand.
<br /> The total depth investigated was 20 feetEq .
<br /> 4. Stockpiled soil disposed p off-site(quantify); The amount and fate of soil removed was not reported. I,
<br /> 5. Monitoring wells remaining on-site, fate;
<br /> Eight monitoring wells(MW-1 to MW-8) were Installed for this investigation.
<br /> LY-1 6. Tabulated results of all groundwater elevations and depths to wafer; The depth to wafer varied from 6 to 10 feet onsite,
<br /> and 10 to 15 feet offsite. The groundwater flow i
<br /> _direction is to the north, at a gradient of 0.008 ft/ft.
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<br /> 7.Tabulated results of all sampling and analyses: In 6193, conprmation soli afratyses reported TPHg(360 mglkg),benzene
<br /> Y Defection limits for confirmation sampling (0.077 mg/kg), toluene(0.18 mg/kg),ethylbenzene(0.25 mg/kg)and
<br /> xylenes(0.74 mg/kg). Soil borings reported TPHg(150 mg/kg), .
<br /> Lead analyses benzene(0.13 mg/kg), toluene(0.10 mg/kg), ethylbenzene(0.15 mg/kg)
<br /> and xylenes(0.22 mg/kg). Maximum groundwater monitoring results
<br /> in 1994-95 were TPHg(1,000 pg/L), TPHd(3,400,000 pg/L),benzene
<br /> (77 ug/L), toluene(1 80pg/L), ethylbenzene(110 pg/L),and xylenes
<br /> (360 pg/L). In 6103, maximum groundwater results were TPHd
<br /> (990 pg/L),and MtBE(310 lig/L).
<br /> 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater, both on-site and off-site: The extent of contamination is defined by
<br /> ®Y Lateral and Y Vertical extent of soil contamination soll borings and monitoring wells. y
<br /> Lateral and ® Vertical extent of groundwater contamination If
<br /> 0 9. Zone of influence calculated and assumptions used for subsurface Based on the limited extent of j
<br /> remediation system and the zone of capture attained for the soil and contamination,an engineered remedlation
<br /> groundwater remediation system, system was not required at this site.
<br /> 0 10.Reports/information E] Unauthorized Release Form [71 thirty two QMRs(1/91 to 8/03)
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<br /> El Boring logs fl PAR FRP 0 Other Closure Summary Report 10103
<br /> 11.Best Available Technology(BAT) used or an explanation for not using BAT; Remove USTs and natural attenuation.
<br /> 0 12.Reasons why background waslis Decreasing concentrations have been attained at an monitoring wells, with the
<br /> unattainable using BAT exception of increasing MtBE coming from an offsite source. Minor soil x3
<br /> contamination remains on-site.
<br /> `Q"13.-Mass balance"calculation of substance- ,The.consultant estimated remaining soil contamination is 24 gallons of TPHg
<br /> treated versus that remaining; and 400 gallons of TPHd in 7,453 cubic yards of impacted'soils left onsite. =1
<br /> 0 14.Assumptions,parameters, calculations and model used in risk A.risk assessment was not required.
<br /> assessments, and fate and transport modeling;and
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<br /> 15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent,and based on
<br /> impact water quality, health, or other beneficial uses. 33 quarters of sampling, contamination is not continuing
<br /> to leach to groundwater. Groundwater monitoring"
<br /> shows a decreasing trend in concentrations.
<br /> By: Comments: Two 7,500-gallon and one 5,000-gallon gasoline USTs were removed from the subject site in 6193. Multiple
<br /> ]LB borings and eight monitoring wells(MW-1 to MW-8) were completed to delineate and monitor contamination at this site.
<br /> In 6193, confirmation soil analyses reported TPHg(360 mg/kg), benzene(0.077 mg/kg), toluene (0.18 mg/kg),
<br /> Date: ethylbenzene(0.25 mg/kg)and xylenes(0.74 mg/kg). Additional soil borings analyses reported TPHg(150 mg/kg),
<br /> benzene(0.13 mg/kg), toluene(0.10 mg/kg), ethylbenzene(0.15 mg/kg)and xylenes(0.22 mg/kg). Maximum
<br /> k
<br /> 5/21104 groundwater monitoring results in 1994-95 were TPHg(1,000 pg/L), TPHd(3,400,000 pg/L), benzene(77 pg1L), toluene
<br /> (180 pg/L), ethylbenzene(110 pg/L), and xylenes(360 pg/L). In 6103, groundwater results were TPHd(990 ug/L),and
<br /> MtBE(310 pg/L). Groundwater flow direction was reported to the north, with a gradient of 0.008 ft/ft. MtBE from a new
<br /> release is under investigation at an adjacent site and is now detected in offsite cross-gradient wells. Based on the limited
<br /> extent of soil contamination and decreasing onsite contaminant concentrations in groundwater, Board staff concur with I
<br /> San Joaquin County's Closure Recommendation.
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