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ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Former Unocal#6981,4707 Pacific Ave., Stockton, San Joaquin County(RB#39020 4)
<br /> Y 1. Distance to production wells for municipal, A 1992(updated 2009)sensitive receptor survey reported 1 municipal
<br /> domestic, agriculture, industry and other uses and 1 domestic water supply wells within 2,000'of the Site. The
<br /> nearest well is 1,500'to the south. The wells are not threatened by the
<br /> within 2000 feet of the site. release.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of any former and In 6/88, three 10,000-gallon gasoline USTs
<br /> existing tank systems, excavation contours and sample locations, boring were removed. In 3/00, two 12,000-gallon
<br /> and monitoring well elevation contours, gradients, and nearby surface gasoline i were removed.
<br /> waters, buildin s, streets, and subsurface utilities,
<br /> Y 3. Figures depicting lithology(cross Site lithology consists of clay, silt, and sand to 86', the total depth investigated.
<br /> section, treatments stem dia rams;
<br /> remaining on-site Approximately 1,600 y excavated soil was transported to an unknown location
<br /> Y 4. Stockpiled soil
<br /> or off-site disposal (quantityoffsite in 6/88. In 4/00, approximately 200 yd' excavated soil was transported to
<br /> Forward Landfill and 100 yd'excavated soil was transported to Ecology Control
<br /> Industry in Richmond. Approximately 20 yd'excavated soil was transported to
<br /> Keller Can on Landfill in Pittsbur it 8/10.
<br /> Ii throu h -9, 1111
<br /> -14
<br /> Y 5. Monitoring wells through MW-hteen )16, VW-1 through remaining monitoring wells VW 7Ma d PTi and thirteen(1)remediation wells s(S P-1
<br /> remaining on-site, fate; throw h SP-13 will be ro erl destro ed prior to closure.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 24'bgs to 57'bgs. Groundwater flow
<br /> elevations and depths to water,' direction was towards the northeast. Groundwater gradient varied from 0.002
<br /> to 0.004 ff/ft.
<br /> 7. Tabulated results of all sampling All data adequately tabularized in various reports.
<br /> and analyses:
<br /> Detection limits for confirmation
<br /> sampling
<br /> QY Lead analyses
<br /> 8. Concentration contours of contaminants found and those remaining in The extent of the identified contamination is
<br /> soil and groundwater, and both on-site and off-site: described in the available reports.
<br /> Y❑Lateral and Y❑Vertical extent of soil contamination
<br /> Lateral and FYI Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface Soil vapor extraction (SVE) with air sparging
<br /> remediation system and the zone of capture attained for the soil and (AS)and ozone sparging(OS) were the
<br /> roundwater remediation s stem;
<br /> engineered remediation.
<br /> 10.Reports/information QY Unauthorized Release Form QY QMRs(83) 10-90 to 5-12
<br /> ❑Y Well and boring logs QY PAR ❑Y FRP QY Other Hydrogeologic Modeling 7/11;Hydrogeologic
<br /> Modelin U date, 12/11; Closure Re ort,4/12
<br /> USTs removal, over-excavation, SVE/AS, OS, and natural
<br /> Y 11.Best Available Technology (BAT) used or an explanation attenuation.
<br /> for not usin BAT;
<br /> Y 12. Reasons why background waslis Residual soil and groundwater contamination remains.
<br /> ffainable usin BAT;
<br /> SVE removed approximately 14,977 lbs. TPH from soil. Consultant did not
<br /> y 13.Mass balance calculation : substance estimate residual mass in soil or groundwater.
<br /> treated versus that parameters,
<br /> ;
<br /> 14. Assumptions, parameters, A soil vapor survey passed the Region 2 ESLs except for TPHg. Soil met
<br /> Y calculations and model used in risk S WRCB low risk closure policy for commercial use. Site is a paved parking lot
<br /> assessments, and fate and transport for a shopping mall. Consultant states site does not represent a significant
<br /> delin risk.A fate and trans ort mode Drovided estimates for time to reach WQGs.
<br /> Y 15. Rationale why conditions remaining at Soil and groundwater contamination reportedly are limited in extent. Land use
<br /> site will not adversely impact water quality, (commercial)is not expected to change in the foreseeable future. Consultant-
<br /> health, or other beneficial uses;and estimated WQGs will be reached by 2035. Groundwater plume is stable and
<br /> nd in 3100, two 12,000-gallon declinin .
<br /> By JLB USTs were removed at the sub"e�site. Residual soil and groundwatee
<br /> contaminat on remains. Based upon
<br /> Date: the limited extent of contamination reported in soil and groundwater, a stable and declining concentration
<br /> 4/23/2013 plumeno foreseeable changes in future land use(commercial), and minimal risks from groundwater, soil
<br /> ,
<br /> vapor and soil, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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