SITE INFORMATION AND CORRESPONDENCE_CASE 1

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TABLE ' - CHECKLIST OF REQUIRED DP-'\ FOR NO FURTHER AW17ION REQUESTS AT UNDERGRO"�JD TANK SITES Site Name and Location: PG&E Stockton Service Center,4040 West Lane, Stockton, San Joaquin County 0 1. Distance to production wells for municipal, domestic, agriculture, Based on the limited contamination identified in soll, a industry and other uses within 2000 feet of the site; receptor survey was not required. 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Piping and soil removal in Yaexcavation contours and sample locations, boring and monitoring well elevation contours, December 2000. site maps gradients, and nearby surface waters, buildings, streets, and subsurface utilities; are provided. 3. Figures depicting lithology(cross section), treatment system diagrams; Soil was excavated to a maximum depth of 7 feet. No additional treatment was warranted. PTI 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 245 cubic yards of excavated soil and pea gravel was disposed at Forward Landfill. N 5. Monitoring wells remaining on-site, fate; Contamination was limited to sell. Monitoring wells were not required. FN 1 6. Tabulated results of all groundwater elevations and depths to water,• Groundwater was not encountered during the soil investigation. Depth to water is estimated at 40 feet 7. Tabulated results of all sampling and analyses: Maximum concentrations of soil samples after excavation activities show TPHg at 1.6 mg/kg and TPHd at 77 mg/kg. BTEX and MtBE were Detection limits for confirmation sampling non-defect at X0.005 mg/kg. Lead analysis was not required. Lead analyses 8. Concentration contours of contaminants found and those remaining in soil The lateral extent of soil contamination was and groundwater, and both on-site and off-site: excavated and removed. The vertical extent Lateral and Vertical extent of soil contamination of soil contamination was identified to 7 feet. Lateral and 19 Vertical extent of groundwater contamination Groundwater was not encountered at a total 19 depth of 7 feet. 9. Zone of influence calculated and assumptions used for subsurface A remediation system was not required at Qremediation system and the zone of capture attained for the soil and this site. Contaminated soils were groundwater remediation system; excavated and disposed off-site. 0 10.Reports/information 0 Unauthorized Release Form F1 QMRs El Boring logs N❑ PAR Iq FRP Iq Other(Site Assessment Report) 11.Best Available Technology(BAT)used or an explanation for not using BAT; Excavate contaminated soils, and dispose Off-site. FTI 12.Reasons why background was/is Minor contamination remains in on-site soils. Further excavation or unattainable using BAT; remediation is not cost effective. The remaining concentrations do not present a significant threat to water quality. 13.Mass balance calculation of substance treated versus that remaining, Based on the limited contamination identified in soil, a mass balance was not required. EiTJ14.Assumptions,parameters, calculations and model used in risk Based on the limited contamination identified in soil,a assessments, and fate and transport modeling; risk assessment was not required. FE 15. Rationale why conditions remaining at site will not adversely Contamination is limited to soil below the former impact water qualify, health, or other beneficial uses;and dispensers. Contamination will naturally attenuate. By: Comments: The site is an active PG&E refueling facility. Dispenser piping was removed in December 2000, and soil contamination was identified in soil samples collected at 3 feet. Approximately 245 cubic yards of soil and pea gravel was excavated to remove contaminated soil down to a total depth of 7 feet. Soil samples collected following excavation activities only showed TPHg and TPHd at 1.6 mg/kg and 77 mg/kg, respectively. Groundwater was not encountered at Date: 7 feet, and a groundwater investigation was not required. The depth to groundwater is estimated at 40 feet. The site has been covered with asphalt and concrete that should limit infiltration and leaching of contaminants. Based on the limited contamination identified in soil and the reported depth to groundwater, Board staff concur with San Joaquin County's closure recommendation.