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TABLE 1 -CHECKLIST OF REQUIRED DATA v
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> a
<br /> Site Name and Location: Chevron#9-1452, 334 E. Main St., Ripon, San Joaquin County(Lustis Case 390716
<br /> _Y] i. 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 /> to east,and two domestic wells are 1500'to north and 1900'to
<br /> 2000 feet of the site. 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 defected.
<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 /> Approximately 315 yards of over-excavated soil was
<br /> Y 4. Stockpiled soil remaining on-site or off site disposal(quantity); 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 /> down radient 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; ethy/benzene, 0.014 mg/kg;xylenes, 2.4 mg/kg;MtBE,
<br /> Lid FyDetection limits for confirmation 2.4 mg/kg;and methanol(1/02), 3.6 mg/kg. Soil after results (1/02) were MtBE,
<br /> 0.002 mg/kg and methanol, 2.5 mg/kg. In 5/04, maximum groundwater
<br /> sampling 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 /> Lateral and 0 Vertical extent of soil contamination
<br /> Latera!and 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 /> 10.Reports/information
<br /> DY Unauthorized Release Form �Y QMRs(30 from 2196 to 11107)
<br /> Y Well and boring logs � PAR o FRP � Other, NFAR,7/07; Soil Vapor Investigation Report, 2108
<br /> Y Removal of USTs, over-excavation,periodic 11.8est Available Technology{BAT)used or an explanation for not using groundwater batch extraction(11/03 to 5/05)
<br /> BAT; and natural attenuation.
<br /> Z12. Reasons why background wesrs 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 /> residual contamination was estimated as petroleum hydrocarbons,
<br /> versus that remaining; 0.5 tbs.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 /> model used in risk assessments, and fate and Further, site will remain an active service station for the foreseeable
<br /> transport modeling; future.
<br /> �, 15. Rationale why conditions remaining at site will Soil contamination is limited in extent. Results of 30 quavers 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:,,'4Lf3 Comments: One 5,000-gallon and two 10,000-gallon gasoline, and one 1,000-gallon waste oil USTs, dispensers, _
<br /> tt 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 /> 5/812008 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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