SITE INFORMATION AND CORRESPONDENCE

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TABLE 1 - CHECKLIST OF REQUIRED DATA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Paige's Towing Services, 1807 Douglas Road,Stockton, San Joaquin County IE1. Distance to production wells for municipal, domestic, agriculture, A receptor survey completed in June 2000 did not industry and other uses within 2000 feet of the site; identify any water supply wells within 2,000 feet of the site. E2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Two 10,000-gallon USTs excavation contours and sample locations, boring and monitoring well elevation contours, were removed in 1199. Site gradients, and nearby surface waters, buildings, streets, and subsurface utilities; maps are provided. 0 3. Figures depicting lithology(cross section), treatment system diagrams; Boring logs and cross-sections show silty clay to 10 feet, and sand to silty sand to 45 feet FN7 4. Stockpiled soil remaining on-site or off-site disposal(quantity), Excavated soil was backfilled into the tank pit along with pea gravel. 5. Monitoring wells remaining on-site, fate; Four monitoring wells currently exist on-site. The wells will be properly destroyed following site closure. 6. Tabulated results of all groundwater elevations and depths to water; Groundwater levels varied from 13 to 15 feet below ground surface, and flow is to the northeast. 7. Tabulated results of all sampling and analyses: Maximum groundwater monitoring results for September 2000 in pg1l ©Detection limits for confirmation sampling show TPHg at 330, TPHd at 450, all BTEX constituents at<0.5, and MtBE at 1.T. Other oxygenates are non-detect by 8260B analysis. ELead analyses Maximum lead in soil,analyzed during UST removal, is 2.85 mg/kg_ FE 8. Concentration contours of contaminants found and those remaining in soil The lateral and vertical extent of soil and and groundwater, and both on-site and off-site: groundwater contamination has been © Lateral and 0 Vertical extent of soil contamination defined. 0 Lateral and 0 Vertical extent of groundwater contamination 0 9. Zone of influence calculated and assumptions used for subsurface A remediation system was not required at remediation system and the zone of capture attained for the soil and this site. groundwater remediation system; 71 10.Reports/information E] Unauthorized Release Form 0 QMRs(2°d Qtr 1999 to 3`d Qtr 2000) Y❑ Boring logs N❑ PAR F FRP El Other(Additional Site Assessment Report 5/00) 11.Best Available Technology(BAT) used or an explanation for not using BAT, Remove USTs, natural attenuation of contaminants. 12.Reasons why background wasrs Contamination remains in shallow on-site soil and groundwater. Further unattainable using BAT,• remediation is not cost effective. The groundwater contamination is limited in extent,and remaining concentrations do not present a significant threat to water quality. 13.Mass balance calculation of substance The consultant estimates that approximately 14 pounds of TPHd remain in treated versus that remaining; vadose zone soils near the former USTs. N❑ 14.Assumptions,parameters, calculations and model used in risk Based on the limited extent of groundwater assessments, and fate and transport modeling; contamination,a risk assessment was not required. FTJ 15. Rationale why conditions remaining at site will not adversely Remaining contamination is limited in extent impact water quality, health, or other beneficial uses;and Contamination will naturally degrade. By: Comments: Two 10,000-gallon gasoline USTs were removed from the site in January 1999. Soil contamination was identified, soil borings and monitoring wells were installed, and groundwater monitoring has been conducted from 4199 to 9/00. MtBE was identified in one monitoring well of a maximum of 45 p9/1 in 7/99, but has decreased to <1.0 Ng/l in 9100. All other fuel oxygenates are non-detect at appropriate defection limits. The site is covered with asphalt, which should limit Date: further leaching of contaminants into groundwater. Based on the investigation completed to date, Board staff concur with vL lj Q San Joaquin County's closure recommendation.