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I
<br /> "FABLE 1 -CHECKLIST OF REQUIRED DATAv
<br /> II FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Former Thiemann's Service Station, 106 W. Second St., Ripon, San Joaquin County(RB#390726)
<br /> yl Distance to production wells for municipal, domestic, A 2006 sensitive receptor survey reported one active
<br /> agriculture, industry and other uses within 2000 feet of the site. municipal supply well(1,125'southwest)and one
<br /> irrigation well(2,000'northwest)within 2,000'of the site.
<br /> The wells are not threatened by the USTs release.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of In 3-91, two 4,000-gallon gasoline, one 10,000-gallon
<br /> any former and existing tank systems, excavation contours and gasoline, and one 400-gallon waste oil USTs were
<br /> sample locations, boring and monitoring well elevation removed.
<br /> contours, gradients, and nearby surface waters, buildings, E
<br /> streets, and subsurface utilities;
<br /> Y 3. Figures depicting lithology(cross section), treatment system Site lithology consists of clay, silt, and sand to 50', the
<br /> diagrams; total depth investigated.
<br /> The fate of the excavated soil was not discussed in the
<br /> N 4. Stockpiled soil remaining on-site or off-site disposal (quantity); available rep
<br /> e orfs.
<br /> Y: 5. Monitoring wells remaining on-site, (ate; Six,(6)monitoring wells(MW-1 through MW-6)will be properly destroyed.
<br /> Yj 6. Tabulated results of all groundwater Depth to groundwater varied from 18'bgs to 29'bgs. Groundwater flow
<br /> elevations and depths to water, direction varied from northeast to southeast. Groundwater gradient
<br /> I varied from 0.0007 ft/ft to 0.02 ft/ft.
<br /> 7. Tabulated results of all sampling All data adequately tabularized in various reports, including closure report.
<br /> and analyses: -
<br /> I
<br /> ElDetection limits for confirmation
<br /> sampling
<br /> QY Lead analyses
<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 is described in the
<br /> available reports.
<br /> - - E]Lateral;and >.. --❑Y-Vertical-extent-of-soil-contamination-. _ _ o - -
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation An engineered remediation was not
<br /> system and the zone of capture attained for the soil and groundwater remediation required by the regulatory agency.
<br /> system;
<br /> 10.Reports/information MY Unauthorized Release Form QMRs(56) 8-93 to 4-10
<br /> FY] Well and boring logs ❑y PAR FRP Other Soil Vapor Report(5-08), Closure Reports(12-10&
<br /> 11-11 -
<br /> Y 11.Best Available Technology(BAT) used or an explanation for not using USTs removal and natural attenuation.
<br /> BAT; ..,.
<br /> Ir 12. Reasons why background wads unattainable Minor residual soil and groundwater contamination remains on-site.
<br /> BA T;
<br /> y 13.Mass balance calculation of substance treated Consultant estimated total soil mass from data collected through 1998
<br /> versus that remaining; as 1,243 lbs of TPH;9.9 lbs of TPHg remain in groundwater.
<br /> Y 14. Assumptions,parameters, calculations and Soil concentrations did exceed Region 2 Environmental Screening
<br /> model used in risk assessments, and fate and Levels(ESLs)for commercial use at depths of 10'bgs or more, below
<br /> transport modeling, typical direct contact depth.A J&E model also exceeded the risk
<br /> levels in soil.A soil vapor survey did not exceed the ESLs. Consultant
<br /> states site does not represent a significant risk.
<br /> I, 15. Rationale why conditions remaining at site will Soil and groundwater contamination reportedly are limited in extent.
<br /> not adversely impact water quality, health, or other Land use(commercial)is not expected to change in the foreseeable
<br /> beneficial as;and iL future. TPHg is estimated to reach WQGs in 2024.
<br /> By: JL�BJL D Comments In 3-91, two 4,000-gallon gasoline, one 10,000-gallon gasoline, and one 400-gallon waste oil USTs
<br /> were removed at the subjectsite. Minor residual soil and groundwater contamination remains on-site.Based
<br /> Date: upon the limited extent of contamination reported in soil and groundwater, a stable groundwater plume with
<br /> 12/15/2011 declining concentrations, no foreseeable changes in future land use(commercial), and minimal risks from
<br /> soil,soil vapor, and groundwater, Regional Board staff concur with San Joaquin County's Closure
<br /> Recommendation.
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