SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Sent By: RWaCB; 2553439; Sep-21 -11' 8:04; Page 313 TABLE 9 .:CHECKLIST OF REQUIRED DATA 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 thQ Site; 2,000 feet of the site. The nearest downgradient well is 1,900 Beet south of the site. 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Four LISTS(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, s#reels, and subsurface utilities; removed in July 1991. ED 3. Figures depicting lithology(Cross section),;treatment system diagrams; Boring logs show sand and sift to 90 feet and clayey sand and silt to 120 feet 4_ Slockpilgd soil disposed off-silo(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-sine. The wells will be properly destroyed Y :pending site closure. 0 6. Tabulated results of all groundwater elevatlons and depths to water; Groundwater levais varied from 80 to 87 Beet below ground surface(bps),and flow is to the south- y 7.Tabulated results of all sampling and analyses: Monitoring results for the 2"d Quarter 2001 is 5 Ng#for toluene,and for the 3'd Quarter 2001 is IX pg/l for 1,2-DCA with a detection limit of F1Detection limits for confirmation sampling 1.0 p911. All other constituents and/tool oxygenates Including MtBE are F 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 ofoontaminants foynd and those remaining in soil and groundwater,and both on-site and off-site: The lateral and vertical extent of soil and © Lateraf 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 0 remediation system and the zone of capture Attained for the soil and contamination,site remedlation beyond groundwater remediation system; overexcavation of Contaminated soils was not required. E1 10,Reports/information © Unauthorized Release Form Y❑ QMRs(3/01 to 7/01) Y Boring logs Nl PAR E] FRP a Other(Well installation Report,W i) 11.Best Available Technology(BAT)used or an explanation for not using BAT, The LISTS and contaminated soils were removed. 12.Reasons why background was/is TPHg and BTEX contamination remains in soil surrounding and underlying the unattainable using BAT; tank pit area, Minor groundwater contamination identified. The remaining Fontaminatlon does not present.?significant threat to water quality. TI 13-Mass balance calculation of substance the mass balance calculations show that appr�oximStely 1,186 pounds of treated versus that remaining; tPHg,and 33 pounds of benzene remain In site soils. Maximum soil tDniamination was Idandfiad from 20 to 40 feet bgs at the tank pit 0 14_Assumptions,parameters,calculations and model used in risk Fad and transport modeling concluded that 4.3 PO4 assessments, and fate and transport modeling; benzene from one groundwater grab sample would not impact groundwater at adjacent water supply walls. LE] 15. Rationale why conditions remaining at site will not adversely Petroleum hydrocarbon contamination Is limited to soli --o impact water quality,health,or other beneficial uses;and .20 to 40 fleet above first geoulidwater. Contaminatlon will naturally degrade. TCLP leachability testing identified that benzene In soil at 20 to 90 feet will not y� 16.WI=T or TCLP results. contaminate underlying groundwater. By: Comments: The site is currently a us0d car lot_ Four USTs were removed in July 1991,and$oli Contamination was NIH identified in tank pit soils. Multiple soU borings were completed,and three monitoring wells were installed. TPHg and BTEX contamination was identified lir:soil from 20 to 60 feet bgs,and traces of toluene and 1,2-dichloroethane were identified in monitoring wells 30 to 407feet from the tank pit area. Fuel oxygenates including MWE were►ton-detect in soil Date: and gmundwarer samples_ The site ii;covered with asphalt, which should limit further leaching of contaminants. Based 8!12101 on the Investigation completed to dot*and the minor groundwater contamination, Board staff concur with Sen Joaquin County's closure recommendation.