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OLE 1 - CHECKLIST OF REQUIRED DA0
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Shell #204-7524-4404, 3011 W. Benjamin Holt Drive, Stockton, San Joaquin County,
<br /> LUSTIS#390557
<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, Two irrigation wells are located 900 feet east
<br /> industry and other uses within 2000 feet of the site; (cross-gradient) of the site.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of former One 550-gallon waste oil UST was removed 6/87.
<br /> and existing tank systems, excavation contours and sample One 10,000-gallon and two 8,000-gallon gasoline
<br /> locations, boring and monitoring well elevation contours, gradients, USTs were removed 10-96. Two 15,000-gallon
<br /> and nearby surface waters, buildings, streets, and subsurface gasoline and one 550-gallon waste oil USTs were
<br /> utilities; removed 11-04.
<br /> Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of sand, silt, and clay. The
<br /> diagrams; total depth investigated was 120 feet.
<br /> N 4. Stockpiled soil disposed off-site (quantit The consultant did not address the fate and amount of 1996 excavated
<br /> y), soil excavated. Approximately 298 tons of soil and pea gravel was
<br /> excavated and trans o ted to Forward Landfill in Manteca in 2004.
<br /> 5. Monitoring wells remaining on-site, fate, Seventeen monitoring wells (MW-1 through MW-13, MW-1-49, MW-1-88,
<br /> MW-2-50, and MW-2-82) were abandoned 6 Aug 2009.
<br /> Y 6. Tabulated results of all groundwater elevations and depths to The depth to water varied from 4 to 18 feet. The
<br /> water, direction of groundwater flow was towards the
<br /> northeast.
<br /> Y 7. Tabulated results o/all sampling and In 1/90 and 8/98, maximum soil boring results were TPHd, 1,200 pg/kg;
<br /> analyses: toluene, 160 pg/kg; ethylbenzene, 19 pg/kg;xylenes, 71 pg/kg;and MtBE,
<br /> e Detection limits for confirmation sampling 2,200 pg/kg. In 11/04, all soil confirmation results were ND. Maximum
<br /> groundwater monitoring result in 6/97 was MtBE,29,000 pg/L. In 12/07,
<br /> Lead anal ses maximum roundwater result was MtBE, 24 /L.
<br /> 71 8. Concentration contours of contaminants found and those remaining The extent of contamination was defined by soil
<br /> soil and grounter, both on-site and off-site: borings, and grab groundwater samples.
<br /> �IL�JI Lateral and Vertical extent of soil contamination Monitoring wells in the downgradient direction
<br /> Lateral and Vertical extent of groundwater contamination show that the plume is moving under Interstate 5.
<br /> N 9. Zone of influence calculated and assumptions used for subsurface An engineered remediation system was not
<br /> remediation system and the zone of capture attained for the soil and required by SJCEHO.
<br /> roundwaterremediation system,
<br /> Y 10.Reports/information Y❑ Unauthorized Release Form Y❑ 55 QMRs(2/94 to 4'/06)
<br /> El Boring logs O PAR N❑ FRP Y❑ Other: Closure Report, Vapor Intrusion Analysis, F& T Model
<br /> Y 11,Best Available Technology(BAT) used or an explanation/or not Remove USTs and natural attenuation.
<br /> usin BAT,
<br /> Y 12.Reasons why background wash"s unattainable using BAT; Soil contamination remains on-site and leaching to
<br /> groundwater is still occurring, though at a much-reduced
<br /> rate nine ears after the eak of MtBE concentrations.
<br /> 13.Mass balance calculation of substance treated versus that The consultant estimated remaining mass in groundwater
<br /> remaining; as 0.29 lbs. Of MtBE.
<br /> Y 14. Assumptions, parameters, calculations and model The consultant compared the 11/04 soil confirmation results(ND)
<br /> used in risk assessments, and fate and transport to Region 2 ESLs for vapor intrusion for residential use and
<br /> modeling;and passed. Groundwater exceeds WQOs (5 ug/L) for MtBE. Fate B
<br /> Transport Model predicts 100+years to reach WQOs.
<br /> 15. Rationale why conditions remaining at site will not Soil contamination is limited in extent. Since 1994, 55 quarters of
<br /> adversely impact water quality, health, orother groundwater monitoring data show a decline in concentrations
<br /> beneficial uses. (3 orders of magnitude) for MtBE.
<br /> By: Comments: One 550-gallon-waste UST was removed 6/87,-one and two 8,000-gallon gasoline USTs
<br /> JLB were removed 10/96;and two 15,000-gallon gasoline and one 550-gallon waste oil US Ts were removed 11/04 from the
<br /> subject site. No remediation was conducted at the site. The consultant compared the 11/04 soil confirmation results
<br /> (ND) to Region 2 ESLs for vapor intrusion for residential use. Groundwater exceeds WQOs (5 ug/L) for MtBE. The
<br /> Date, consultant claims the MtBE has attenuated in groundwater, although the adjacent Interstate 5 complicates further
<br /> groundwaterinvestigation by requiring an investigation over 1,000 feet to the northeast. Although F&T Model predicts
<br /> 9130/2009 WQGs won't be reached for 100+years, no wells are threatened as plume remains under freeway. Land use for
<br /> freeway is unlikely to change be/ore WQGs are reached. There/ore, Regional Board staff requests a No Further Action
<br /> Required determination.
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