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i =WASHINGTON TE PHONE(206)285-2400
<br /> I OREGON " r`i �1ftTiii f t�}' j.r F ,(206)283-8036
<br /> CALIFORNIA T 1� � j
<br /> 121
<br /> NEVADA .
<br /> IDAHO 2 TIME OIL CCS .
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<br /> 7TESTED 4 2737 WEST COMMODORE WAY SEATTLE,WA 98199�i. P.O.BOX 24447 SEATTLE,WA 98124-0447
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<br /> _ = February 28, 2000
<br /> f
<br /> Mr.'Harlin Knoll `
<br /> i San Joaquin County'Public Health Services
<br /> l � .
<br /> Environmental Health Division
<br /> P.O. Box 2009
<br /> Stockton, California 95201
<br /> RE: Submittal of Fourth Quarter 1999 Groundwater Monitoring Report for
<br /> Jackpot food Mart, 14000 E. Highway 88, Lockeford, California (Property No. 04-049)
<br /> v ,
<br /> Dear Mr. Knoll,
<br /> t
<br /> At the request of the San"Joaquin County Public Health Services Environmental Health Division (PHSIEHD),
<br /> an additional environmental investigation was implemented at the subject site in December 1994 to evaluate
<br /> 'the extent of hydrocarbon-impacted soils and to determine whether or not.groundwater had been impacted.
<br /> A total of four groundwater monitoring wells 4wer6 installed during this investigation. 'In July 1996, six
<br /> additional groundwater monitoring wells were installed on and off of.the subject site to assist in defining the
<br /> extent of groundwater impacts. Based on the results of the investigations, Time Oil implemented
<br /> groundwater monitoring."
<br /> Please find enclosed Science & Engineering Analysis Corporation's (SECOR's)"Quarterly Monitoring Report,
<br /> October — December 1999" dated February 25, 2000. This document presents analytical results and field
<br /> observations collected during Fourth Quarter 1999 groundwater sampling.
<br /> Fourth Quarter 1999 Groundwater Sampling Results -
<br /> On November 24, 1999; samples were collected from each of the groundwater monitoring wells (MW-1
<br /> through MW-10) at the subject site by a representative of SECOR. Prior,to purging, the depth to water in
<br /> each well was measured to evaluate elevation, flow direction, and gradient. As noted in the attached report,
<br /> groundwater with a south-southwesterly flow direction and a-gradient of 0.03 ft./ft. was encountered in the
<br /> r wells at depths of 66.80 feet to 80.35,feet below ground surface. Free product was not encountered in any of
<br /> the wells. The locations of the wells are identified on Figure 2 of the attached report.
<br /> Since the July 1999 sampling event, groundwater elevation decreased in each well by 0:63 feet to 2.01 feet,
<br /> s resulting in an overall average decrease in groundwater elevation of 1.15 feet across the site. Changes in
<br /> { groundwater elevation are most likely a result of seasonal variation. Groundwater gradient and flow direction
<br /> i remained consistent with previously collected data. Table 1 -in the attached report summarizes groundwater
<br /> elevation data collected to date.
<br /> Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (6,320 ppb
<br /> TPH-g, 2.4 ppb toluene, 425 ppb ethylbenzene, and 654 ppb xylenes), MW-2 (505 ppb TPH-g, 5.7 ppb
<br /> r benzene, 1.2 ppb toluene, and 24.5 ppb xylenes), MW-3 (1,010.p-pb TPH-g, 55.3.ppb benzene, 60.6 ppb
<br /> toluene, 32.2 ppb ethylbenzene; and 147 ppb-xylenes), and MIN-4 (886,ppb TPH-g, 193 ppb benzene, 6,6
<br /> ppb toluene, 103 ppb ethylbenzene, and 17.4 ppb xylenes). Lower concentrations of Hydrocarbons were
<br /> found.in the samples collected from MW-5 (146 ppb TPH-g, 3.2 ppb benzene, 1.2 ppb toluene, 0.7 ppb
<br /> ethylberizene, 146 ppb xylenes); MW-6 (0.5 ppb benzene and 1.0 ppb ethylbenzene), MW-7 (0.5 ppb
<br /> benzene), and MW-9 (1.3 ppb benzene). Hydrocarbons were not detected in the samples collected from
<br /> MVV-8 and MW-10. Low concentrations of MTBE were detected in the groundwater samples collected from
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