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Site History
<br /> • 14000 Highway 88 Lockeford,CA
<br /> Time Oil Property No 04-049
<br /> First Qorter 1996 Groundwater Sampling,Results-February 1996
<br /> On February 28, 1995, samples were collected from each of the groundwater monitoring wells (MW-1
<br /> through MWS) at the subject site by a representative of SECOR Prior to purging, the depth to water in each
<br /> well was measured to evaluate elevation, flow direction, and gradient Groundwater with a southeasterly flow
<br /> at a rate of 0 14 ft Ift was encountered in the wells at depths of 73 27 feet to 84 96 feet below ground
<br /> surface
<br /> Since the previous sampling event, groundwater elevation increased in each well by 0 15 feet to 0 78 feet,
<br /> resulting in an overall increase of 0 78 feet across the site Groundwater flow direction remained consistent
<br /> with previously collected data, however, gradient increased significantly The variations in groundwater
<br /> 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, and
<br /> 1,900 ppb xylenes in the sample collected from MW-1 The sample collected from MW-2 contained 340 ppb
<br /> gasoline, 38 ppb benzene, 16 ppb toluene, 23 ppb ethylbenzene, and 39 ppb xylenes The sample collected
<br /> from MW-3 contained 2,400 ppb gasoline, 390 ppb benzene, 110 ppb toluene, 170 ppb ethylbenzene, and
<br /> 200 ppb xylenes, and the sample collected from MW4 contained 170 ppb gasoline, 10 ppb benzene, 3 6
<br /> ppb ethylbenzene, and 0 5 ppb xylenes
<br /> Between the Fourth Quarter 1995 and First Quarters of 1996, gasoline and BTEX concentrations increased
<br /> in MW-1, MW-2, and MW-3 and decreased in MW-4 The observed fluctuations in hydrocarbon
<br /> concentrations were likely a result of a general increase in the groundwater elevation, however, not enough
<br /> 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 the
<br /> 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 /> MWS!) 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 66 40 feet below ground surface
<br /> Since the previous sampling event, groundwater elevation increased in each well by 0 46 feet to 0 77 feet,
<br /> 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 likely
<br /> 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) The
<br /> sample collected from MW-2, located to the east of the former tank bed (sidegradient) contained 166 ppb
<br /> gasoline, 11 ppb benzene, 6 8 ppb ethylbenzene, and 0 53 ppb xylenes The sample collected from MW-3,
<br /> located to the southeast of the former tank bed (downgradient), contained 795 ppb gasoline, 137 ppb
<br /> benzene, 11 5 ppb toluene, 19 3 ppb ethylbenzene, and 22 2 ppb xylenes, and the sample collected from
<br /> MW-4, located to the southwest of the former tank bed (sidegradient), contained 142 ppb gasoline and 1 92
<br /> ppb benzene
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