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"ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FUR1,�.R ACTION REQUESTS AT UNDERGROUNL,_,CNK SITES
<br /> Site Name and Location: Chevron#9-1452,334 E.Main St., Ripon,San Joaquin County(Lustis Case 390716)
<br /> y 1. Distance to production wells for municipal, A 2004 well survey reported 2 public,5 private, and 8 domestic
<br /> domestic, agriculture, industry and other uses within wells exist within 2000'of the site. One public well is located 1500'
<br /> 2000 feet of the site. to east,and two domestic wells are 1500'to north and 1900'to
<br /> northwest.
<br /> y 2. Site maps, to scale, of area impacted showing One 5,000-gallon and two 10,000-gallon gasoline,and one
<br /> locations of any former and existing tank systems, 1,000-gallon waste oil USTs, dispensers,and piping were removed
<br /> excavation contours and sample locations, boring 9/95 during station upgrades. Subsequently two of the three
<br /> and monitoring well elevation contours, gradients, 12,000-gallon gasoline replacement USTs failed a leak detection
<br /> and nearby surface waters, buildings, streets, and test in 9/01 for uncalibrated detection meters(over 3 gallons per
<br /> subsurface utilities; hour). The meters were recalibrated and no leaks were detected.
<br /> Y 3. Figures depicting lithology(cross section), Site lithology consists of clay,silt and sand to
<br /> treatment system diagrams; 120 feet, the total depth investigated.
<br /> Y1 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 315 yards of over-excavated soil was
<br /> removed and transported to BFI Landfill 10/95
<br /> Y 5. Monitoring wells remaining on-site, fate; Ten monitoring wells(MW-1 through MW-4, MW-5S,MW-5D,MW-6S, MW-6D,
<br /> MW-7D, MW-8)remaining on-site will be properly abandoned.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 20 to 35 feet below ground surface
<br /> elevations and depths to water; (bgs). The groundwater gradient varied from 0.001 to 0.009 ft/ft,and the
<br /> downgradient direction varied from southwest to southeast.
<br /> 7. Tabulated results of all sampling Maximum tank pit confirmation(9/95-10/95)and boring(1/96)sample soil
<br /> and analyses: concentrations were TPHg,260 mg/kg; TPHd, 1.3 mg/kg;benzene,0.03 mg/kg;
<br /> toluene;0.037 mg/kg;ethylbenzene, 0.014 mg/kg;xylenes, 2.4 mg/kg;MtBE,
<br /> FYIDetection limits for confirmation 2.4 mg/kg;and methanol(1/02),3.6 mg/kg. Soil after results(1/02) were MtBE,
<br /> sampling 0.002 mg/kg and methanol,2.5 mg/kg. In 5/04,maximum groundwater
<br /> concentrations were TPHg,4,100 ug/L;MtBE; 76,000 ug/L; TBA, 2,800 ug/L;and
<br /> ❑Y Lead analyses TAME, 3,800 ug/L. In 11/07,all groundwater sample results were non-detect.
<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 /> Y❑Lateral and �Vertical extent of soil contamination
<br /> Lateral and 10 Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation The engineered remediation was
<br /> system and the zone of capture attained for the soil and groundwater remediation periodic batch groundwater extraction
<br /> system; with offsite disposal by tank truck.
<br /> Unauthorized Release Form ❑Y QMRS(30 from 2/96 to 11/07)
<br /> 10.Reports/information FY,
<br /> 0 Welland boring logs [5] PAR FRP 0 Other-NFAR,7/07; Soil Vapor Investigation Report, 2/08
<br /> Y J 11.Best Available Technology(BAT)used or an explanation for not using Removal of USTs, over-excavation,periodic
<br /> BAT; groundwater batch extraction(11/03 to 5/05)
<br /> and natural attenuation.
<br /> U12. Reasons why background wasps unattainable Limited soil contamination remains on-site.
<br /> ng BAT
<br /> Periodic groundwater batch extractions removed 3.8 lbs of MtBE. The
<br /> y 13.Mass balance calculation of substance treated
<br /> versus that remaining; residual contamination was estimated as petroleum hydrocarbons,
<br /> 0.5 lbs.in soil in 1997 Case Closure Report.
<br /> Y 14. Assumptions, parameters, calculations and No soil vapor ESLs were exceeded during the soil gas survey.
<br /> 7
<br /> model used in risk assessments, and fate and Further,site will remain an active service station for the foreseeable
<br /> transport modeling; L future.
<br /> Y 1
<br /> 15. Rationale why conditions remaining at site will Soil contamination is limited in extent. Results of 30 quarters of
<br /> not adversely impact water quality, health, or other groundwater monitoring show a decreasing trend in concentrations to
<br /> beneficial uses;and non-detect. WQOs have been reached.
<br /> By: L Comments:One 5,000-gallon and two 10,000-gallon gasoline, and one 1,000-gallon waste oil USTs, dispensers,_
<br /> and piping were removed 9/95 during station upgrades at the subject site. Subsequently two of the three
<br /> Date: 12,000-gallon gasoline replacement USTs failed a leak detection test in 9/01 for improperly calibrated detection
<br /> 5/8/2008 meters(over 3 gallons per hour). The meters were recalibrated and no leaks were detected. A closure request
<br /> in 1997 was denied due to a lack of downgradient monitoring wells at the site. Subsequent investigations
<br /> starting in 2001 revealed groundwater pollution,and batch water extraction was conducted from 11/03 to 5/05.
<br /> Based upon 30 quarters of declining groundwater concentrations to ND, no exceedence of ESLs for vapor
<br /> intrusion,and the limited extent of contamination present in soil, Regional Board staff concur with San
<br /> Joaquin County's Closure Recommendation.
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