|
BLE 14°CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> 'f
<br /> Site Name and Location: Dick's Exxon,2360 East St.,.,Tracy, San Joaquin County(RB#390629) 9
<br /> y 1. Distance to production wells for municipal, domestid, A 2009 sensitive receptor survey identified two municipal
<br /> agriculture, indust and other uses within 2606 feet of the site. supply wells, 1,100'east and 1,300'southeast of the site.
<br /> y 2- Site maps, to scale, of area impacted showing locations of Two 5,500-gallon gasoline, one 5,500-gallon diesel and
<br /> any former and existing tank systems, excavation contours and one 500-gallon waste oil USTs and associated piping were
<br /> sample locations, boring and monitoring well,elevation removed 4191 from the site.
<br /> contour's, gradients, and nearby surface waters, buildings,
<br /> streets, and subsurface utilities, k
<br /> :Y0 3. Figures depicting lithology(cross section), tieatmenfaystem Site lithology consists of clay,silt, and sand to 83', the'
<br /> diagrams; total depth investigated.
<br /> ,i
<br /> Y1 4. Stockpiled soil remaining on-site or off-site disposal(quantity)' The fate of soil over-excavated during the USTs #
<br /> I 'rh removal was not discussed in the available reports.
<br /> YD 5. Monitoring wells remaining on-site, fate; ' .Five m#itoring wells(MW-1 through MW-5)will be properly abandoned.
<br /> p
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 6'to 13'bgs. Groundwater flow
<br /> elevations and depths to water direction varied from northeast to northwest. Groundwater gradient t
<br /> r varied from 0.006 to 0.020 ft/ft.
<br /> 7. Tabula ted.results of all sampling Maximum confirmation soil concentrations on 4/91 were TPHg, 1300 mg/kg; TPHd, '
<br /> and analyses: -'-220'irig/kg;bemene;9.6 mg7kg;toluene;''66 mg7kg;,ethylbeiFzene,'25 mg/kg;and-
<br /> xylenes, 150 Ing/kg. In 12/91,soil boring results were ND(MTBE wa`s ND on 7/97).
<br /> ❑ Detection limits for confirmation In 12191, maximum groundwater monitoring concentrations were TPHg,
<br /> sampling 1.2,006 ug/L; TPHd, 7,200 ug/L;benzene, 200 ug/L;toluene, 84 ug/L;;iethylbenzene,
<br /> 130 ugnes, 360 ug/L;and MTBE, 28 ug/L. In 9/08, maximum g
<br /> /L;xylenes, N
<br /> ❑Y Lead analyses monitoring results were TPHg, 370 ug/L;benzene,3.7 ug/L;toluene; 17 ug/L;
<br /> eth lbenzenel 34 ug/L;xylenes, 1.9 u /L;and naphthalene, 0.8 ug/L.
<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 y
<br /> A❑ : � reports. � #Lateral and 0 Vertical extent,of soil contamination
<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 lead agency.
<br /> Ms-tem; +
<br /> 10.Reports/information ❑Y Unauthorized Release!~orm ❑Y QMRs 26 from 12/91 to 12/08
<br /> ❑ Well and boring lags ❑ PAR FRP YOther Soil Vapor Rpt.,4/09;NFAR Rpt. (8/09)
<br /> Al11.Best Available Technology(BAT) used or an explanation for not using USTs removal, over-excavation of
<br /> BAT, contaminated soil, and natural attenuation,
<br /> 12. Reasons why background wads unattainable Minor residual soil and groundwater contamination remains on-site.'
<br /> Y
<br /> BAT; rI
<br /> FY 13.Mass balance calculation of substance treated The consultant estimated remaining soil contaminant mass as TPHg,
<br /> versus that remaining; a 140 pounds and TPHd, 0.5 pounds;and in groundwater, TPHg, E
<br /> _0.1 pounds.
<br /> 14. Assumptions, parameters, calculations and Region 2 ESLs were exceeded for TPHg and benzene for vapor
<br /> Y model used in risk assessments, and fate and intrusion;however a Tier 2 J&E model did exceed 1X10'6 for cancer,`
<br /> transport modeling; h risk for benzene soil gas in one sample near Grant Line Road. The ,s
<br /> site is located in a commercial area of Tracy. p F
<br /> Y 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 Lund use(commercial)is not expected to change in the foreseeable
<br /> beneficial uses;and future.
<br /> By: JLW Comments: Two 5,500-gallon'gasoline, one 5,500-gallon diesel and one 500-gallonwaste oil USTs and
<br /> associated piping were removed 4/91 from the subject site. Based upon 26 quarters of groundwater
<br /> Date: monitoring showing a stable plume with declining concentrations, the limited extent of contamination
<br /> 10/1212009 remaining in soil and groundwaterno foreseeable changes in land use(commercial), and the`sixty plus feet
<br /> to the building from the soil vapor benzene result with 2.73x1018 cancer risk, with a non-detect for benzene
<br /> soil vapor result next to the building, Regional Board staff concur with San Joaquin County's'Closure 'I
<br /> gegoMMendation.
<br /> s r
<br /> I
<br />
|