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TABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> 3 FOR NO FURTHUCTION REQUESTS AT-UNDERGROUND T/"W SITES 1
<br /> mmission, 503 E. 10'"St.,Tracy, San Joaquin County(Case 390321)
<br /> Site Name and Location: San Joaquin Co Ag Co
<br /> Y Distance to production wells for municipal, domestic, A 1997 well survey reported no supply wells within 2000'of
<br /> culture, 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 1.20 AKA
<br /> Iite St. The County reported 6 private wells in their letter.
<br /> 2. Site maps, to scale, of area impacted showing locations Two 1,000-gallon weed oil and one 1,000-gallon gasoline
<br /> Y of any former and existing tank systems, excavation USTs and associated piping were removed 10/88. TPHg,
<br /> I r. 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;
<br /> installed.
<br /> Site
<br /> Y
<br /> Site lithalogy consists of clay, silt, and sand to
<br /> Y 3. Figures depicting lithology(cross section), treatment 20 feet, the total depth investigated.
<br /> system diagrams;
<br /> The fate of the excavated soil is not discussed in the
<br /> 4. Stockpiled soil remaining ori-site or off-site disposal(quantity); reports. ,
<br /> ti Y 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1 through M.W-3)remaining on-site will be
<br /> ro eri abandoned.
<br /> fi. Tabulated results of all groundwater Depth to groundwater varied from 6 to 9 feet below ground surface(bgs).
<br /> elevations and depths to wafer, The groundwater gradient varied from 0.0022 to 0.0029. The
<br /> down radient roundwater 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 mg/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 /> 0 Detection limits for confirmation were TPHg, 400 mg/kg; TPHd, 1,800 mg/kg;benzene, 5.4 mglkg; toluene,
<br /> 16 mg/kg;ethylbenzene, 10 ing/kg;and xylenes, 39 mg/kg. Maximum grab
<br /> sampling groundwater concentrations(10197) were TPHg, 140 ug/L; TPHd, 1,300 ug/L;
<br /> PY Lead analyses benzene;11 ug/L;toluene, 18 ug/L;ethytbenzene,3.6 ug/L;xylenes, 18 ug/L;and,
<br /> MTBE;0:4 ug/L. In 6/08, maximum groundwater monitoring concentration was
<br /> TPHg, 68 upIL,
<br /> 8. Concentration contours of contaminants found and these remaining in soil and The extent of the identified
<br /> groundwater, and both on-site and off-site: f contamination shown in applicable
<br /> reports. '
<br /> 4 Lateral and Y vertical extent of soil contamination g
<br /> FYI Lateral and vertical extent of roundwatercontamination
<br /> .r9. ,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 /> s -Stem;
<br /> 10.Reports l information FYI Unauthorized Release Form FY-1 QMRs(12 from 11198 to 6108) '
<br /> Well and boring logs ❑Y . PAR n FRP Other-, Soil Vapor Sampling and Human Hearth Risk Assessment
<br /> f ,
<br /> and Sensitive Receptor Survey), 6/06
<br /> Y 1 11,Best Available Technology(BAT) used or an explanation for not using BAT; Removal of USTs and natural attenuation.
<br /> 12. Reasons wh back round waslrs unattainable usln BAT; Limited soil contamination remains on-site.
<br /> Y The consultant did not estimate contamination remain in
<br /> 13.Mass balance calculation of substance treated versus that Y
<br /> soil. �. ,..
<br /> remaining; x,
<br /> Y 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; m. analyses.
<br /> �, 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 decreasin trend in concentrations.
<br /> By: Comments: Two 1,000-gallon weed oil and one 1,000-gallon gasoline USTs and associated piping were
<br /> removed 10/88 at the subject site. Maximum confirmation soil concentrations(10188)were TPHg, 760 mg/kg;
<br /> k and x lanes, 340 mg/kg
<br /> Da TPHd, 4,800 mg/kg;benzene, 27 mg/kg;toluene, 210 mg/kg;ethylbenzene, 96 m g/ g; Y
<br /> 9123!2.008 (MTBE`was not analyzed). In 12197,"soil boring after results were TPHg, 400 mg/kg; TPHd, 1;800 mglkg;
<br /> benzene, 5.4 mg/kg; toluene, 16 mg/kg;ethylbenzene, 10 mg/kg;and xylenes, 39 mgJkg.' Maximum grab
<br /> groundwater concentrations(10/97)'were TPHg, 140 ug/L; TPHd, 1,300 ug/L;benzene, 11 ug/L;toluene,
<br /> 18 ug/L; ethylbenzene, 3.6 ug/L;xylenes, 18 ug/L;and MTBE;0.4 ug/L. In 6/08, maximum groundwater
<br /> monitoring concentration was TPHd, 68 ug/L. Based upon 12 quarters af;decJining 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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