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13 MTBE concentrations appear to be increasing in monitoring wells MW-3A, 3D, and 1 I and fluctuating in monitoring wells MW-3 and MW-13 1,2-DCA concentrations have only been I detected in monitoring well MW-11, located off-site This constituent has not been detected in wells located in the UST release area or immediately downgradient of the release area and may not be related to the release at the Canteen Facility site IConcentrations of dissolved-phase hydrocarbons in the groundwater exceed the CAMCL for benzene (1 0 ug/l), toluene (150 ug/1), ethylbenzene (700 ug/1), xylenes (1,750 ug/1), MTBE (13 ug/1), and 1,2-DCA(0 5 ug/1) TPH-G concentrations ranged from<50 to 220,000 ug/1) The majority of the groundwater impacts are centered on the MW-3 and MW-13 series wells Concentrations of 1,2-DCA has only been detected in off-site monitoring well MW-11 and may not be related to the UST release Historical groundwater analytical results are summarized in Table 3 Graphical presentation of the data is included in Appendix B Isoconcentration maps showing the horizontal extent of the dissolved-phase hydrocarbons are presented in Appendix C Accordingto the San Joaquin Count Flood Control District map, no water wells are located q Y P within one half mile of the site The Flood Control District water well location map is included as Figure 7 The groundwater gradient is consistently towards the south based on 18 monitoring events The closest down gradient water well is located over one mile from the site Available . records indicate that most water wells are completed below 125 feet due to seasonal water fluctuations and the lack of sufficient aquifers above that depth ' 4.0 REMEDIATON TECHNOLOGIES EVALUATION One of the objectives of the PAR is to assess various remediation technologies for applicability to the specific site conditions at the Canteen Facility Based on the site assessment results, remediation of both soils and groundwater is required Residual soil impacts were identified in the former UST tank pit excavation area The extent of the groundwater impact is generally on-site The groundwater plume extends from the former UST tank pit area (MW-13 well series) to dust downgradient of the MW-3 well series I The remediation options listed below were evaluated according to their performance, reliability, and applicability to the site-specific conditions Excavation The source of the release was a 10,000-gallon UST, removed in March of 1992 Impacted soils were excavated to a depth of 19 5 feet and properly transported and disposed of off-site in November 1992 Approximately 36 cubic yards of soil were transported to Forward Inc Landfill The former tank hold was backfilled with clean imported fill Further excavation of the site is not 5 I