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' 9110 Thornton Road, Stockton, California April 27, 1994 The Southland Corporation Page 6 The results of the sod vapor extraction test conducted at this site indicate that hydrocarbons are present in the vadose zone sod or in the capillary fringe at this site, however, based on the laboratory analytical results of air sampling, the estimated quantity is small GROUNDWATER MONITORING AND SAMPLING As agreed upon during the December 15, 1993 closure issues meeting, groundwater sampling and monitoring was conducted at this site on January 24 and January 26, 1994 The CRWQCB-CVR and SJCPHS were notified prior to conducting groundwater sampling As agreed between Southland ' and the CRWQCB-CVR, the CRWQCB-CVR's representative collected groundwater samples from the same wells that were sampled by Groundwater Technology during the sampling event ' Groundwater Monitoring ' On January 26, 1994, all site-related accessible groundwater monitoring wells were gauged to determine depth to groundwater (DTW) and depth to SP, if present, using an ORS Environmental Equipment INTERFACE PROBETAd well monitoring system The January 26, 1994 groundwater monitoring data are presented in Table 6 A potentiometric surface map (Figure 11), generated based on the monitoring data collected on ' January 26, 1994 indicates groundwater Sow is to the east Groundwater Sampling and Results On January 24, 1994, groundwater samples were collected from monitoring wells MW-1, MW-9, ' MW-11 and MW-14, and domestic wells 9156 Connie Avenue and 9172 Thornton Road by Groundwater Technology and the CRWQCB-CVR's representative Prior to groundwater sampling, Groundwater Technology purged each well of at least four well-casing volumes The groundwater samples were collected by Groundwater Technology using a Teflon sampler, then placed in 40-milliliter glass vials, which were acidified with hydrochloric acid to preserve the samples The ' samples were sealed using Teflon septum caps, labeled with the job identification number, the sample number, date, time and type of laboratory analysis required The samples were stored on ice and transported with a chain-of-custody mandest to GTEL Environmental Laboratories, Inc in Concord, California Groundwater sampling methodology and procedures used by the CRWQCB-CVR's representative were similar to those previously mentioned ' The groundwater samples were analyzed for BTEX and TPH-G, using EPA methods 5030, 8020 and modified 8015 Laboratory results of the groundwater samples collected on January 24, 1994 are summarized in Table 7 BTEX and TPN-G concentrations were below the MDLs in samples collected i ..1LJ11 GROUNDWATER Lit ii TECHNOLOGY