SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

TABLE 1 - CHECKLIST OF REQUIRED eTA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Former Town and Country Chevron, 13336 East Highway 88, Lockeford,San Joaquin County 0 1. Distance to production wells for municipal, domestic, agriculture, Four water supply wells were identified within industry and other uses within 2000 feet of the site, 2,000 feet of the site. The nearest downgradient well is 1,900 feet south of the site. 2. Site maps,to scale, of area impacted showing locations of former and existing tank systems, Four USTs(one waste oil Y excavation contours and sample locations, boring and monitoring well elevation contours, and three gasoline)were gradients, and nearby surface waters, buildings, streets, and subsurface utilities, removed in July 1991. Y� 3. Figures depicting lithology(cross section), treatment system diagrams; Boring logs show sand and silt to 90 feet,and clayey sand and silt to 120 feet. 0 4. Stockpiled soil disposed off-site(quantity); Erickson Hauling reportedly transported approximately 100 cubic yards of soil off-site for disposal. 5. Monitoring wells remaining on-site, fate; Three monitoring wells remain on-site. The wells will be property destroyed EDpending site closure. ❑Y 6. Tabulated results of all groundwater elevations and depths to water, Groundwater levels varied from 80 to 81 feet below ground surface(bgs), and flow is to the south. FY-1 7. Tabulated results of all sampling and analyses: Monitoring results for the 2"d Quarter 2001 is 5 pg/1 for toluene,and for the 3`d Quarter 2001 is 1.0 pg/1 for 1,2-DCA with a detection limit of Detection limits for confirmation sampling 1.0 pg/1. All other constituents and fuel oxygenates including MtBE are Lead analyses non-detect during the two quarters of sampling. Soil samples collected during UST removal reported maximum lead at 10 mg/kg. Y 8. Concentration contours of contaminants found and those remaining in soil and groundwater, and both on-site and off-site: The lateral and vertical extent of soil and Latera!and Vertical extent of soil contamination groundwater contamination has been Lateral and Vertical extent of groundwater contamination defined. 9.Zone of influence calculated and assumptions used for subsurface Based on the limited groundwater Qremediation system and the zone of capture attained for the soil and contamination,site remediation beyond groundwater remediation system; overexcavation of contaminated soils was not required. y❑ 10.Reports/information yl Unauthorized Release Form 9 QMRs(3101 to 7/01) Y❑ Boring logs N❑ PAR N❑ FRP 171 Other(Well Installation Report, 5/01) YE11.Best Available Technology(BAT)used or an explanation for not using BAT, The USTs and contaminated soils were removed. 12.Reasons why background wasps TFHg and BTEX contamination remains in soil surrounding and underlying the unattainable using BAT,. tank pit area. Minor groundwater contamination identified. The remaining contamination does not present a significant threat to water quality. Y� 13.Mass balance calculation of substance The mass balance calculations show that approximately 1,186 pounds of treated versus that remaining; TPHg,and 33 pounds of benzene remain in site soils. Maximum soil contamination was identified from 20 to 40 feet bgs at the tank pit 14.Assumptions,parameters, calculations and model used in risk Fate and transport modeling concluded that 4.3 pg/l assessments, and fate and transport modeling; benzene from one groundwater grab sample would not impact groundwater at adjacent water supply wells. 15. Rationale why conditions remaining at site will not adversely Petroleum hydrocarbon contamination is limited to soil impact water quality, health, or other beneficial uses;and 20 to 40 feet above first groundwater. Contamination will naturally degrade. 16.WET or TCLP results. TCLP leachability testing identified that benzene in soil at 20 to 60 feet will not contaminate underlying groundwater. By: Comments: The site is currently a used car lot. Four USTs were removed in July 1991, and soil contamination was I identified in tank pit soils. Multiple soil borings were completed, and three monitoring wells were installed. TPHg and BTEX contamination was identified in soil from 20 to 60 feet bgs, and traces of toluene and 1,2-dichloroethane were identified in monitoring wells 30 to 40 feet from the tank pit area. Fuel oxygenates including MtBE were non-detect in soil Date: and groundwater samples. The site is covered with asphalt, which should limit further leaching of contaminants. Based 9112101 on the investigation completed to date and the minor groundwater contamination, Board staff concur with San Joaquin County's closure recommendation.