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WASHINGTON Te OREGON PHONE (206)285-2400 CALIFORNIA T FAX(206)283-8036 IDAHNEVADO W12 ETIME OIL co . T5 2737 WEST COMMODORE WAY SEATTLE WA 98199 1233 PR90UCT5 T,. PO BOX 24447 SEATTLE,WA 98124-0447 TIME TESTED e February 2, 2001 Mr Harlin Knoll , San Joaquin County Public Health Services Environmental Health Division P O Box 2009 Stockton, California 95201 RE Submittal of"Quarterly Monitoring Report, October--December 2000'for Jackpot Food Mart, 14000 E Highway 88, Lockeford, California (Property No 04-049) Dear Mr Knoll, At the request of the San Joaquin County Public Health Services Environmental Health Division (PHSIEHD), 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 A total of four monitoring wells were installed during this investigation 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 and quarterly monitoring was implemented In August and September 1999, SECOR installed a vapor extractiontair 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 2000" dated February 1, 2001 This document presents analytical results and field observations collected during Fourth Quarter 2000 groundwater sampling, and discusses the efficiency of the remediation system currently in operation Fourth 2000 Groundwater Sampling Results On November 4, 2000, samples were collected from each of the groundwater monitoring wells (MW-1 through MW-10) at the subject site by a representative of SECOR 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 southwesterly flow direction and a gradient of 0 08 ft/ft was encountered in the wells at depths of 67 07 feet to 75 14 feet below ground surface Free product was encountered in MW-1 (0 75 feet) The locations of the wells are identified on Figure 2 of the attached report Since the August 2000 sampling event, groundwater elevation increased in some wells by up to 5 53 feet and decreased in some wells by up to 1 10 feet These changes resulted in an overall average increase in groundwater elevation of 0 83 feet across the site Changes in groundwater elevation are most likely a result of seasonal variation and operation of the remediation system Groundwater gradient and flow direction remained consistent with previously collected data Table 1 in the attached report summarizes groundwater elevation data collected to date Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-4 (277 ppb TPH-g, 24 9 ppb benzene, 1 1 ppb toluene, 18 9 ppb ethylbenzene, and 12 ppb xylenes) and MW-5 (97 9 • ppb TPH-g, 10 6 ppb benzene, 9 1 ppb toluene, 16 ppb ethylbenzene, and 10 ppb xylenes) Lower concentrations of hydrocarbons were found in the sample collected from MW-9 (53 9 ppb TPH-g and 16 ppb benzene) Hydrocarbons were not identified in the samples collected from MW-2, MW-3, MW-6, MW-7, MW- 8, or MW-10 Low concentrations of MTBE were identified in the groundwater samples collected from MW-2 (0 8 ppb), MW-3 (0 9 ppb), MW-5 (2 2 ppb) and MW-6 (0 5 ppb) MTBE was not Identified in the samples