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Additional Subsurface Investigation And Well Installation Report 7 The Southland Corpmatlon,Store#19976 1399 N Main St Manteca California November 15 1998 hydrocarbon concentrations appears confined to a limited area beneath the former UST pit and pump island Copies of the analytical results and chairs-of-custody documents are included in Appendix D 4.3 Results of Groundwater Monitoring/Analyses Groundwater monitoring and analytical data from the three wells are presented in Table 2 During the monitoring and sampling on September 16, 1998,the equilibrated depth to water was approximately 14 feet BGS Figure 3 shows the lateral distribution of dissolved hydrocarbons(benzene, TPH-g) and MTBE in groundwater samples collected on September 16, 1998 Benzene ranged from below method detection limit In wells MWA and MW-3 to 245 micrograms per liter (pg/L) in well MW-2 TPH-G ranged from 185 pg/L in well MWA to 2,430 pg/L in well MW-2 MTBE ranged from below method detection limit in wells MWA and MW-3 to 449 pg/L in well MW-2 TBA and TAME were detected in well MW-2 at 75 pg/L and 114 pg/L, respectively TBA, DIPE, ETBE, and TAME were not detected in any of the other wells sampled Well MWAA which is screened deeper,45 to 50 feet BGS,than the other wells contained higher concentrations of TPH-G, MTBE, and benzene than MWA which is screened from 10 to 30 feet BGS The lateral extent of dissolved hydrocarbons has been delineated crossgradient(south) of the former tank pit area based on non-detectable to low BTEX,TPH- G and MTBE concentrations in the groundwater samples collected from monitoring well MW-3 Non- detectable to low hydrocarbon concentrations were detected in downgradlent well, MWA which is located near the former UST pit and pump island (source area) Copies of the analytical reports and chain-of-custody forms are included in Appendix D I50 WELL SEARCH During the third quarter 1998, Fluor Daniel GTI personnel conducted a well search of the site vicinity in order to determine risk to any local domestic or municipal groundwater supply wells Information was gathered from the California Department of Water Resources (CDWR) and from the City of Manteca In a telephone conversation the City of Manteca indicated that there are no municipal supply wells within a 2,000 foot radius of the site (Figua 6) From CDWR well drillers reports fifteen domesbatpublic wells ' were located within an approxima:half-mile radius of the site The nearest wells are approximately 1,000 feet to the south and southst,on Joseph Road and Main Street Eleven of the fifteen well t reports contained perforation data, all eleven wells are screened starting at 99 feet BGS or deeper, q r' indicating that they are not in hydraulic communication with groundwater at the subject site (Table 3) 6- 19070aar rpt FLUOR DANIEL GTI