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T - CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location. Shell tl204-7524-4404, 3011 W. Benjamin Holt Drive, Stockton, San Joaquin County,
<br /> LUSTIS It 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.Sile 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 lilhology (cross section), treatment system Site lithology consists of sand, silt, and clay. The
<br /> diagramstotal depth investigated was 120 feet.
<br /> N 4. Stockpiled soil disposed off-sife The consultant did not address the fate and amount of 1996 excavated
<br /> P P (quantity),
<br /> soil excavated. Approximately 298 tons of soil and pea gravel was
<br /> excavated and trans orted 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)'installed for this investigation will be abandoned.
<br /> Y 6. Tabulated results of all groundwater elevations and depths to The depth to water varied from 4 to 18 feet. The
<br /> wafer principal down-gradient direction of groundwater was
<br /> towards the northeast.
<br /> y 7 Tabulated results of all sampling and In 1/90 and 8/98,maximum soil boring results were: TPHd, 1,200 p
<br /> analyses: toluene, 160 pglkg; ethylbenzene, 19 pg/kg;xylenes, 71 pg/kg; and MTBE,
<br /> y 2,200 pg1kg. In 11/04, all soil confirmation results were ND. Maximum
<br /> Detection limits for confirmation sampling groundwater result in 6/97 was:MtBE(29,000 pg/L). In 4/06, maximum
<br /> 1 Lead analyses groundwater result was: MtBE(86 1!9LLJ.
<br /> Y 8. Concentration contours of contaminants round and those remaining The extent of contamination was defined by soil
<br /> Ysoil and groun y fee. both on-site and off-site' borings, and grab groundwater samples.
<br /> 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 /> remedrafion system and the zone of capture attained for the soil and required by SJCEHD.
<br /> groundwater remediation system,
<br /> y 10.Reports/infomation Unauthorized Release Form F] 50 OMRs (2194 to 4106)
<br /> ElBoring logs y❑ PAR N❑ FRP y❑ Other Closure Report. Vapor Intrusion Analysis
<br /> N 11.Best Available Technology(BAT) used or an explanation for not Remove USTs and natural attenuation.
<br /> using BAT;
<br /> N 12.Reasons why background was/is unattainable using BAT, Soil contamination remains on-site and leaching to
<br /> groundwater is still occurring, though at a much-reduced
<br /> rate nine years after the peak of Mf9E 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 11104 soil confirmation results (ND)
<br /> used in risk assessments and late 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.
<br /> y 15. Rationale why conditions remaining at site will not Soil contamination is limited in extent. Since 1994, 50 quarters of
<br /> adversely impact water quality, health. of other groundwater monitoring data show a decline in concentrations
<br /> beneficial uses, (3 orders of magnitude)for MTBE(except MW-11. which rose from
<br /> 19 to 86 ppb between March and April 2006).
<br /> By CommentsOne 550-gallon waste oil UST was removed 6/87. one 10,000-gallon 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 USTs 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 /> Dale consultant claims the MTBE has attenuated in groundwater although the adjacent Interstate 5 complicates furlher
<br /> groundwater investigation by requiring an investigation over 1,000 feet to the northeast, which SJCEHD does nor
<br /> 11/27/06 support. Based on the fact that the lateral extent of the groundwater plume was not delineated. and there are fluctuating
<br /> MIBE concentrations in donwgradient groundwater monitoring wells. Regional Board staff does not concur with San
<br /> Joaquin County 5 No Further Action Required determination
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