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TABLE 1 CHECKLIST OF REQUIRED DAT)
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Slame and Location: US Postal Service,3131 Arch Road,Stockton,San Joaquin County
<br /> 1.Distance to production wells for municipal, domestic,agriculture, A receptor survey was not completed. County
<br /> industry,and other uses within 2000 feet of the site; reported the nearest well,a City of Stockton municipal
<br /> well,at 800 feet northwest of the site.
<br /> 1, 2.Site maps,to scale, of area Impacted showing locations of former and existing tank systems, Two USTs removed In May
<br /> 0 excavation contours and sample locations, boring and monitoring well elevation contours, 1998,and two USTs,
<br /> gradients, and nearby surface waters, buildings, streets,and subsurface utl#tles; removed to July 1999. Site
<br /> maps provided
<br /> 0 3.Figures depicting lithology(cross section), treatment system diagrams; Boring logs show silty clay to 30-feet
<br /> rwi 4. Stockpiled soil remaining on-site or off-site disposal(quantify); Excavated soil was backfilled Into the tank pit
<br /> tnot lnstalied
<br /> LIE
<br /> ❑N
<br /> 6. Tabulated results of all groundwater elevations and depths to water; Depth to water Is estimated at 70 feet with an
<br /> ypasterly flow. Groundwater was not encountered.
<br /> 7.Tabulated results of all sampling and analyses: Maximum soll results In mg/kg show TPHg at 0, TPHd at 817,benzene
<br /> at<0.005, toluene at<0,005,ethyl benzene at<0.005,xylenes at<0.005,
<br /> F1 Detection limits for confirmation sampling and lead at 5.9: MtBE was Identified In one soil sample at 0.34 mg/kg.
<br /> Lead analyses All other oxygenates were less than reporting limits by 8260B method.
<br /> 8. Concentration contours of contaminants found and those remaining in soil Lateral and vertical extent of soil
<br /> 0 and groundwater, and both on-site and off-site: contamination Is defined. Groundwater
<br /> © Lateral and 0 Vertical extent of soil contamination water was not encountered
<br /> aLateral and Vertical extent of groundwater contamination
<br /> 9.Zone of influence calculated and assumptions used for subsurface A remediation system was not operated at
<br /> 0 remediation system and the zone of capture attained for the soil and this site.
<br /> groundwater remediation system;
<br /> 10.Reports/information F1
<br /> Unauthorized Release Form ❑ QMRs
<br /> F1 soft fogs � PAR � FRP � Other(Soil Quality Evaluation,June 2000)
<br /> Y
<br /> 11.Best Available Technology(BAT)used or an explanation for not using BAT; Remove USTs,natural attenuation.
<br /> why background was/fs TPHd and MTBE constituents remain In shallow on-slte soils.
<br /> Y❑ unattainable using BAT;
<br /> 13.Mass balance calculation of substance
<br /> treated versus that remaining; Amass balance was not presented.
<br /> 14.Assumptions,parameters,calculations and model used In risk A risk assessment was not completed.
<br /> ❑ assessments,and fate and transport modeling,
<br /> 15 Rationale why conditions remaining at site will not adversely Remaining contamination Is limited'to shallow on-site
<br /> impact water quality,health,or other beneficial uses;and soils. Contamination will naturally attenuate.
<br /> By: Comments: Two USTs(one 12,000-gallon gasoline and one 12,000-gallon diesel)were removed from the site in
<br /> 14, May 1998, and two USTs(one 1,000-gallon new oil, and one 1,000-gallon waste oil) were removed In July 1999. TPHd
<br /> was idehtifred below the diesel tank, and MtBE was identified in one soil sample beneath the conveyance piping at three
<br /> feet. In April 2000, five borings were completed to 30 feet below the former diesel UST and the conveyance piping where
<br /> Date: contamination was identified. TPHd was identified at 4.8 mg/kg in one soil sample collected at four feet All other
<br /> samples were non-detect for all constituents including MTBE and other oxygenates using EPA Method 82600. The site,is
<br /> r� lpp covered with concrete, which should limit the leaching of contaminants. Based on the limited extent of site contamination,
<br /> Board staff concurs with San Joaquin County's closure recommendation. ,
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