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1 PHONIE 285 24CO CABLE ADDRESS ThvOIL SEATTLE T (FAX) 206 283 8036 TACOMA e" PORTLAND STOCKTON li? � To ICHMOND RENO LOS ANGELES za "E TIME ® ■®! L o x 7 7 2737 WEST COMMODORE WAY SEATTLE WA 98199 1233 PRODUCTSP O BOX 24447 SEATTLE WA 98124-0447 TIME TESTEb 1ME February 5, 2004 Mr Harlin Knoll San Joaquin County Public Health Services MDEC HWED Environmental Health Division W�C 1"l P 4 Box 2009 Stockton, California 95201 FEB 12 2004 RE Submittal of"Quarterly Monitoring Report, October- December 2003"for ENVIRONMENT HEALTH Jackpot Food Mart, 14000 E Highway 88, !_ockeford, California (Property No 04-049) PERMIT/SERVICES Dear Mr Knott, An environmental investigation was implemented at the subject site in December 1994 to evaluate the extent of hydrocarbon-impacted soils and to determine whether or not groundwater had been impacted Four monitoring wells were installed during this investigation (MW-1 through MW-4) In July 1996, six additional monitoring wells were installed on and off of the subject site to assist in defining the extent of groundwater impacts (MW-5 through MW-10), and quarterly monitoring was implemented In August and September 1999, SECOR installed a vapor extraction/air sparging system at the subject site to remediate hydrocarbon- impacted soils and groundwater System operation began December 13, 1999 Please find enclosed SECOR's "Quarterly Monitoring Report, October - December 2003" dated February 4, 2004 This document presents analytical results and field observations collected during Fourth Quarter 2003 groundwater sampling, and discusses the efficiency of the remediation system currently in operation Fourth Quarter 2003 Groundwater Sampling Results On October 23, 2003, a representative of SECOR attempted to collect groundwater samples from each of the monitoring wells (MW-1 through MW-10) at the subject site Prior to purging, the depth to water in each well was measured to evaluate elevation, flow direction, and gradient As noted in the attached report, groundwater with a south-southwesterly flow direction and a gradient of 0 06 ft/ft was encountered in the wells at depths of 71 98 feet to 93 11 feet below ground surface A small amount of free product was observed in MW-1 (0 01 feet) The locations of the wells are identified on Figure 2 of the attached report Since the July 2003 sampling event, groundwater elevation increased in MW-2 by 0 21 feet, while it decreased by 0 2 feet to 1 06 feet in the remaining wells These changes resulted in an overall average decrease in groundwater elevation of 0 48 feet across the site Changes in groundwater elevation are most likely a result of seasonal variation Groundwater gradient and flow direction remained consistent with previously collected data Table 1 in the attached report summarizes historical groundwater elevation data TPH-g and BTEX were not identified in the groundwater samples submitted from MW-2, MW-3, MW-4, MW- 6, MW-7, MW-8, and MW-9 Analyses Identified low concentrations of MTBE in the sample collected from MW-9 (1 5 ug/1), however, none of the other samples contained detectable concentrations of MTBE Other fuel oxygenates (TBA, DIPE, ETBE, and TAME) were not present at detectable concentrations in any of the samples No sample was submitted from MW-1, as it contained a trace amount of free product Samples were not submitted from MW-5 and MW-10 because they were dry or contained too little water to sample Table 2, Table 3, and Figure 3 in the attached report summarize groundwater analytical data and laboratory reports are included as Attachment 2 The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW- 1) When compared to the July 2003 sampling data, hydrocarbon concentrations Increased in MW-1 (as shown by a reoccurrence of free product) while they remained essentially unchanged in the remainder of the wells Since the initiation of remediation efforts, hydrocarbon concentrations across the site have substantially decreased