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"'BLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FUR1�2 ACTION REQUESTS AT UNDERGROUNG,_-,NK SITES
<br /> Site Name and Location: Boyett Petroleum,419 S.Main St., Manteca,San Joaquin County(Case 390972)
<br /> Y
<br /> Distance to production wells for municipal, domestic, The 2000 and 2002 well surveys reported no supply within
<br /> —agnculture, industry and other uses within 2000 feet of the site. 1500'of the site,and at least 7 private wells within 500'of the
<br /> site. One p 'vate well sampled was ND.
<br /> Ir 12. Site maps, to scale, of area impacted showing locations Three 10,000-gallon gasoline USTs were instal/ed10/85. When
<br /> of any former and existing tank systems, excavation the associated piping was removed and replaced 11/96,
<br /> contours and sample locations, boring and monitoring well toluene, ethylbenzene,xylenes,and MTBE were detected in
<br /> elevation contours, gradients, and nearby surface waters, soil beneath the old piping. The site is an active station.
<br /> buildings, streets, and subsurface utilities;
<br /> Y 3. Figures depicting lithology(cross section), treatment Site lithology consists of clay,silt,and sand to
<br /> system diagrams; 125 feet, the total depth investigated.
<br /> Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); The fate of excavated soil was not discussed in the
<br /> available reports.
<br /> Y 5. Monitoring wells remaining on-site, fate; Ten monitoring wells(MW-1R, MW-2 through MW-4, MW-6 through MW-11,
<br /> and EW-1 remaining on-site will be properly abandoned.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 14 to 24 feet below ground surface(bgs).
<br /> elevations and depths to water,' The groundwater gradient varied from 0.00089 to 0.00014. The downgradient
<br /> groundwater flow direction varied from northwest to northeast.
<br /> 7. Tabulated results of all sampling Maximum confirmation soil concentrations(10197) were toluene,0.0086 mg/kg;
<br /> and analyses: _ ethylbenzene,0.025 mg/kg;xylenes, 0.43 mg/kg, and MTBE, 4.7 mg/kg. In 10103,
<br /> soil boring after result was MTBE, 0.053 mg/kg. Maximum groundwater monitoring
<br /> QDetection limits for confirmation concentrations(9/01) were TPHg, 0.63 ug/L;benzene,37 ug/L;toluene, 19 ug/L;
<br /> sampling ethylbenzene, 90ug/L;xylenes, 1,200 ug/L;and MTBE;27,000 Pg/L. In 11108 after
<br /> limited remediation,groundwater monitoring concentration was MTBE, 1.4 ug/L,
<br /> ❑Y Lead analyses only.
<br /> 8. 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.
<br /> Lateral and 0 Vertical extent of soil contamination
<br /> FYI Lateral and 171 Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Limited groundwater extraction
<br /> system and the zone of capture attained for the soil and groundwater remediation (GWE pump test) was the required
<br /> system; engineered remediation.
<br /> 10.Reports/information ❑Y Unauthorized Release Form ❑Y QMRs(40 from 9/99 to 11/08)
<br /> ❑Y Well and boring logs ❑Y PAR FRP ❑Y Other;Soil Vapor Intrusion, Risk Assessment and No Further Action
<br /> Re ort, 11108
<br /> Y I 11.Best Available Technology(BAT) used or an explanation for not using BAT, Removal of USTs, GWE, and natural
<br /> attenuation.
<br /> 7Y 12. Reasons why background was/is unattainable using BAT,- Limited soil and groundwater contamination remains on-
<br /> site.
<br /> Y1 13.Mass balance calculation of substance treated versus that The consultant did not estimate contamination treated
<br /> remaining; and contamination remaining in soil.
<br /> 14. 4ssumptions-paran%-ters-calculations-and-model-used in -No Region 2-ESLs were exceeded for-soil vapor—
<br /> samples-risk assessments, and fate and transport modeling;
<br /> Y 15. Rationale why conditions remaining at site will not adversely Soil and groundwater contamination is limited in extent.
<br /> impact water quality, health, or other beneficial uses;and Results of 40 quarters of groundwater monitoring show a
<br /> decreasing trend in concentrations.
<br /> By: B Comments: Three 10,000-gallon gasoline USTs were instal/ed10/85. When the associated piping was removed
<br /> and replaced 11196, toluene, ethylbenzene,xylenes,and MTBE were detected in soil beneath the old piping.
<br /> Dat : The site is an active station. Maximum confirmation soil concentrations(10/97) were toluene,0.0086 mg/kg;
<br /> 12 31/2008 ethylbenzene, 0.025 mg/kg;xylenes, 0.43 mg/kg, and MTBE,4.7 mg/kg. In 10103,soil boring after result was
<br /> MTBE, 0.053 mg/kg. Maximum groundwater monitoring concentrations(9/01) were TPHg, 0.63 ug/L;benzene,
<br /> 37 ug/L;toluene, 19 ug/L;ethylbenzene, 90ug/L;xylenes, 1,200 ug/L;and MTBE;27,000/ug/L. In 11108 after
<br /> limited remediation,groundwater monitoring concentration was MTBE, 1.4 ug/L. Based upon 40 quarters of
<br /> declining groundwater concentrations, no reported threat from vapor intrusion,no anticipated threats to
<br /> sensitive receptors,and the limited extent of contamination present in soil and groundwater, Regional Board
<br /> staff concur with San Joaquin County's Closure Recommendation.
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