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Site History
<br /> . 14000 Highway 88, Lockeford CA
<br /> Time Oil Property No 04-049
<br /> each well was measured to evaluate elevation, flow direction, and gradient Groundwater with a
<br /> southeasterly flow at a rate of 0 14 ft/ft was encountered in the wells at depths of 73 27 feet to 84 96
<br /> feet below ground surface
<br /> Since the previous sampling event, groundwater elevation increased in each well by 0 15 feet to 0 78
<br /> feet, resulting in an overall increase of 0 78 feet across the site Groundwater flow direction remained
<br /> consistent with previously collected data, however, gradient increased significantly The variations in
<br /> groundwater elevation and gradient are most likely due to seasonal variation
<br /> Analyses identified 10,000 ppb gasoline, 600 ppb benzene, 2,900 ppb toluene, 440 ppb ethylbenzene,
<br /> and 1,900 ppb xylenes in the sample collected from MW-1 The sample collected from MW-2 contained
<br /> 340 ppb gasoline, 38 ppb benzene, 1 6 ppb toluene, 23 ppb ethylbenzene, and 39 ppb xylenes The
<br /> sample collected from MW-3 contained 2,400 ppb gasoline, 390 ppb benzene, 110 ppb toluene, 170 ppb
<br /> ethylbenzene, and 200 ppb xylenes, and the sample collected from MW-4 contained 170 ppb gasoline,
<br /> 10 ppb benzene, 3 6 ppb ethylbenzene, and 0 5 ppb xylenes
<br /> Between the Fourth Quarter 1995 and First Quarters of 1996, gasoline and BTEX concentrations
<br /> increased in MW-1, MW-2, and MW-3 and decreased in MW-4 The observed fluctuations in
<br /> hydrocarbon concentrations were likely a result of a general increase in the groundwater elevation,
<br /> however, not enough data had been collected to evaluate their significance
<br /> A copy of SECOR's "Quarterly Monitoring Report - March 1996" dated April 22, 1996 was forwarded to
<br /> the appropriate regulatory agencies on April 29, 1996
<br />• Second Quarter 1996 Groundwater Sampling Results- May 1996
<br /> On May 23, 1996, samples were collected from each of the groundwater monitoring wells (MW-1 through
<br /> MW-4) at the subject site Prior to purging, the depth to water in each well was measured to evaluate
<br /> elevation, flow direction, and gradient Groundwater with a southeasterly flow at a rate of 0 15 ft/ft was
<br /> encountered in the wells at depths of 72 50 feet to 86 40 feet below ground surface
<br /> Since the previous sampling event, groundwater elevation increased in each well by 0 46 feet to 0 77
<br /> feet, resulting in an overall increase of 0 57 feet across the site Groundwater flow direction and gradient
<br /> remained consistent with previously collected data The variations in groundwater elevation are most
<br /> likely due to seasonal variation
<br /> Analyses identified 9,320 ppb gasoline, 410 ppb benzene, 1,890 ppb toluene, 283 ppb ethylbenzene, and
<br /> 1,340 ppb xylenes in the sample collected from MW 1(located nearest to the existing pump islands)
<br /> The sample collected from MW-2, located to the east of the former tank bed (sidegradient) contained
<br /> 166 ppb gasoline, 11 ppb benzene, 6 8 ppb ethylbenzene, and 0 53 ppb xylenes The sample collected
<br /> from MW-3, located to the southeast of the former tank bed (downgradient), contained 795 ppb gasoline,
<br /> 137 ppb benzene, 11 5 ppb toluene, 19 3 ppb ethylbenzene, and 22 2 ppb xylenes, and the sample
<br /> collected from MW-4, located to the southwest of the former tank bed (sidegradient), contained 142 ppb
<br /> gasoline and 1 92 ppb benzene
<br /> Between the First and Second Quarters of 1996, gasoline and BTEX concentrations decreased slightly in
<br /> all of the wells The observed fluctuations in hydrocarbon concentrations may be a result of a general
<br /> increase in the groundwater elevation or a result of natural attenuation
<br /> A copy of SECOR's "Quarterly Monitoring Report, Apnl - June 1996" dated July 22, 1996 was forwarded
<br />. to the appropriate regulatory agencies on July 31, 1996
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