SITE INFORMATION AND CORRESPONDENCE_CASE 2

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i TABL 1 - CHECKLIST OF REQUIRED DATA { FOR hNO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES ► I� Site Name and Location: Conti Trucking, 2660 Loomis Road, Stockton, San Joaquin County A receptor survey was not completed. The nearest 1. Distance to production wells for municipal, domestic, agriculture, industry and other uses within 2000 feet of the site; well is an an-site domestic well approximately 750 feet � northeast of the former USTs. 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Two diesel USTs removed in 0 excavation.contours and sample locations, boring and monitoring well elevation contours, September 7999. Site maps provided. gradients, and nearby, surface waters, buildings,streets, and subsurface utilities; y❑ 3. Figures depicting lithology(cross section), treatment system diagrams; Boring logs show predominantly sand and sift. a 4. Stockpiled soil remainingon-site or off-site disposal(quantity)" Approximately 150 cubic yards of stockpiled soil 0 p p remains on-site. Soil will be backfilled following County approval. 0- 5. Monitoring.welts remaining on-site, -- fate; �•Monftorfnqwells were not installed.- - - 0 6. Tabulated results of all groundwater elevations and depths to water, Depth to water is estimated at 60 feet with an easterly flow. Groundwater was not encountered. 0 7.Tabulated results of all sampling and analyses: Maximum soil results in mg/kg show TPHd at 13,000,and toluene at 0.005 at the tank pit. Results of three soil borings in mg/kg show non a Detection limits for confirmation sampling detect for all constituents except toluene at 0.070, and xylenes at N Lead analyses 0.026. MtBE was reported at c0.05 mg/kg by 8020. ❑ M FTI8. Concentration.)contours of contaminants found and those remaining in soil Lateral and vertical extent of contamination and groundwater, and both on-site and off-site: is defined. Lateral and Vertical extent of soil contamination ❑ Lateral and ❑ Vertical extent of groundwater contamination k 9.Zone of influence calculated and assumptions used for subsurface A remediation system was not operated at remediation system and the zone of capture attained for the soil and this site. groundwater remediation system; Y10.Reports/information Unauthorized Release Form N❑ QMRs Boring logs PAR FRP Other(PIER, March 2000) y11.Best Available Technology(SAT)used or an explanation for not using BAT,• Remove USTs,natural atternowion. w _ `_.-12.ReaBons wliy'tiackground was is 3 , unattainable using BAT; TPHd and BTEX constituents remain in on-site soils. -- 4i 13.Mass balancedcalculation of substance treated versus that remaining; Amass balance was not presented. , 0 14.Assumptions,parameters, calculations and model used in risk A risk assessment was not completed. --1 assessments, and fate and transport modeling; 15. Rationale why conditions remaining at site will not adversely Remaining contamination is limited to the tank pit area. t Y� impact water quality, health, or other beneficial uses;and Contamination will naturally attenuate. { By; Comments: Two diesel USTs were removed from the site in September 1999. Tank pit samples show soil t contamination. Three geoprobe borings were completed to 30 feet bgs in February 2000, and only low concentrations of toluene and xylenes were identified in soils. MtBE analyzed by 8020 was not identified at this site. An on-site water supply well is located northeast of the former USTs, and sample results were not provided for this well. Although Date:, i groundwater is estimated at 60 feet, it is in the best interest of Conti Trucking to sample their well for petroleum ,.J i.��r;' hydrocarbons. Based on the limited extent of site contamination, and the absence of fuel oxygenates, Board staff `7 „ concurs",with San Joaquin County's closure recommendation.