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<br /> -1BLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FUR 'R ACTION REQUESTS AT UNDERGROUNC NK SITES i
<br /> Site Name and Location: San Joaquin Co Ag Commission, 503 E. 10th St.,Tracy, San Joaquin County(Case 390321)
<br /> Y Distance to production wells for municipal, domestic, A 1997 well survey reported no supply wells within 2000'of
<br /> -dgficulture, industry and other uses within 2000 feet of the site. the site. Four private wells were reported 8/08 within 2000'of
<br /> the site:2 at 1800'southeast, 1 at 1200'southwest and 1 at
<br /> 100'to 400'northeast(McArthur Dr. and old Hwy 120 AKA
<br /> 11 rrr St. The Countyreported 6 rivate wells in their letter.
<br /> Y1 2. Site maps, to scale, of area impacted showing locations Two 1,000-gallon weed oil and one 1;000-gallon gasoline
<br /> of any fomrer and existing tank systems, excavation USTs and associated piping were removed 10/86. TPHg,
<br /> contours and sample locations, boring and monitoring well TPHd,benzene, toluene,ethylbenzene, and xylenes were
<br /> elevation contours, gradients, and nearby surface waters, detected in soil beneath the UST. No new USTs were
<br /> buildings, streets, and subsurface utilities; installed.
<br /> Y1 3. Figures depicting lithology(cross section), treatment Site lithology consists of clay, silt and sand to
<br /> system diagrams; 20 feet, the total depth investigated.
<br /> NI 4. Stockpiled soil remaining on-site or off-site disposal(quantity); The fate of the excavated soil is not discussed in the
<br /> reports. 11
<br /> :YD 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1 through MW-3)remaining.on-site will be
<br /> ro
<br /> erly abandoned.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 6 to 9 feet below ground surface(bgs).
<br /> The groundwater gradient varied from 0.0022 to 0.0029. The
<br /> elevations and depths to water, ,;
<br /> downgradient groundwater flow direction varied from west to northeast.
<br /> 7. Tabulated results of all sampling Maximum confirmation soil concentrations(10/88) were TPHg, 760 mg/kg; TPHd,
<br /> and analyses: 4,800 mg/kg;benzene, 27 Ing/kg;toluene, 210 mg/kg;ethylbenzene, 96 mg/kg;and
<br /> xylenes, 340 mg/kg(MTBE was not analyzed). In 12/97, soil boring after results'
<br /> Detection limits for confirmation were TPHg,400 mg/kg; TPHO, 1,800 mg/kg;benzene, 5.4 mg/kg;toluene,
<br /> sampling 16 mg/kg;ethylbenzene, 10 mg/kg;and xylenes, 39 mg/kg. Maximum grab
<br /> groundwater concentrations(10/97)were TPHg, 140 ug/L; TPHd, 1,300 ug/L;
<br /> FY Lead analyses benzene;11 ug/L;toluene, 18 ug/L;ethylbenzene,3.6 ug/L;xylenes, 18 ug/L;and
<br /> MTBE;.,0.4 ug/L. In 6/08, maximum groundwater monitoring concentration was
<br /> TPHd, 68 ug/L.
<br /> LyJ8. Concentration contours of contaminants found and those remaining in soil and The extent of the identified
<br /> groundwater, and both on-site and off-site., contamination shown in applicable
<br /> reports. a
<br /> Y❑Lateral and Vertical extent of soil contamination
<br /> FYI Lateral and vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation The regulatory agency did not
<br /> system and the zone of capture attained for the soil and groundwater remediation require an.engineered remediation.
<br /> system;
<br /> 10.Reports/information FY Unauthorized Release Form fY QMRs(12 from 11!98 to 6108)
<br /> ❑Y Well and boring logs ❑Y PAR FRP ❑Y Other;Soil Vapor Sampling and Human Health Risk Assessment
<br /> and Sensitive Receptor Survey), 8/08
<br /> Y 11.Best Available Technology(BAT) used or an,explanation for not using BAT; Removal of USTs and natural attenuation.
<br /> 12. Reasons why background wasps unattainable using BAT Limited soil contamination remains on-site. +
<br /> y 13.Mass balance calculation of substance treated versus that The consultant did not estimate contamination remain in
<br /> soil.
<br /> remaining;
<br /> I, 14. Assumptions, parameters, calculations and,model used in No soil vapor ESLs were exceeded during the soil vapor
<br /> risk assessments, and fate and transport modeling, analyses.
<br /> Y 15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent and not leaching.to
<br /> impact water quality, health, or other beneficial uses;and groundwater. Results of 12 quarters of groundwater
<br /> monitorin .show a decreasing trend in concentrations.
<br /> By.' Comments: Two 1,000-gallon weed oil and one 1,000-gallon gasoline USTs and associated piping were
<br /> ftL removed 10/88 at the subject site. Maximum confirmation soil concentrations(10/88)were TPHg, 760 mg/kg;
<br /> Dad TPHd,4,800 mg/kg;benzene, 27 mg/kg;toluene, 210 mg/kg;ethylbenzene,96 mg/kg;and xylenes, 340 mg/kg
<br /> 9/2312008 (MTBE was not analyzed). In 12/97,soil boring after results were TPHg,400 mg/kg; TPHd, 1,800 mg/kg;
<br /> benzene, 5.4 mg/kg;toluene, 16 mg/kg;ethylbenzene, 10 mg/kg;and xylenes, 39 mg/kg.'Maximum grab
<br /> groundwater concentrations(10197) were TPHg, 140 ug/L; TPHd, 1,300 ug/L;benzene,J1 ug/L;toluene,
<br /> 18 ug/L;ethylbenzene,3.6 ug/L;xylenes, 18 ug1L;and MTBE;0.4 ug/L. In 6/08, maximum groundwater
<br /> monitoring concentration was TPHd, 68 ug/L. Based upon 12 quarters of declining groundwater
<br /> concentrations, no reported threat from vapor intrusion,no anticipated threats to sensitive receptors, and the
<br /> limited extent of contamination present in soil,Regional Board staff concur with San Joaquin County's
<br /> Closure Recommendation.
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