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Site History <br /> 14000 Highway 88, Lockeford CA <br /> Time Oil Property No 04-049 <br /> Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (18,500 <br /> ppb gasoline, 386 ppb benzene, 2,580 ppb toluene, 1,080 ppb ethylbenzene, 2,820 ppb xylenes), MW-2 <br /> (1,910 ppb gasoline, 31 8 ppb benzene, 12 8 ppb toluene, 2 0 ppb ethylbenzene, and 274 ppb xylenes), MW- <br /> 3 (838 ppb gasoline, 126 ppb benzene, 17 0 ppb toluene, 47 6 ppb ethylbenzene, and 77 8 ppb xylenes), <br /> MW-4 (901 ppb gasoline, 187 ppb benzene, 4 7 ppb toluene, 84 4 ppb ethylbenzene, 7 2 ppb xylenes), MW- <br /> 5 (5,600 ppb gasoline, 430 ppb benzene, 279 ppb toluene, 211 ppb ethylbenzene, and 1,130 ppb xyienes), <br /> and MW-6 (310 ppb gasoline, 24 6 ppb benzene, 1 9 ppb toluene, 7 6 ppb ethylbenzene, 55 5 ppb xylenes) <br /> Lower concentrations of hydrocarbons were found in the samples collected from MW-8 (1 8 ppb benzene) <br /> and MW-9 (76 5 ppb hydrocarbons and 2 8 ppb benzene) Hydrocarbons were not detected in the samples <br /> collected from MW-7 and MW-10 Low concentrations of MTBE were detected in the groundwater sample <br /> collected from MW-4 (41 2 ppb), however, it was not detected in any of the other samples <br /> The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW- <br /> 1) and sidegradrent of the former tank bed (MW-5) The groundwater plume does not appear to be migrating <br /> to any great extent When compared to the August 1998 sampling event, hydrocarbon concentrations <br /> increased somewhat in MW-2 and decreased slightly in MW-4, while they remained relatively unchanged in <br /> the remainder of the wells Changes in hydrocarbon concentrations are most likely a result of changes in <br /> groundwater elevation Additional monitoring data will be collected to further evaluate the extent of the <br /> dissolved hydrocarbon plume <br /> A copy of SECOR's "Quarterly Monitoring Report, October - December 1998" dated January 27, 1999, was <br /> forwarded to the appropriate regulatory agencies on February 1, 1999 <br /> First Quarter 1999 Groundwater Sampling Results—January 1999 <br /> On January 27, 1999, samples were collected from each of the groundwater monitoring wells (MW-1 through <br /> MW-10) at the subject site by a representative of SECOR Prior to purging, the depth to water in each well <br /> was measured to evaluate elevation, flow direction, and gradient Groundwater with a southerly flow <br /> direction and a gradient of 0 03 ft/ft was encountered in the wells at depths of 64 93 feet to 77 02 feet below <br /> ground surface Free product was not encountered in any of the wells <br /> Since the August 1998 sampling event, groundwater elevation increased in MW-5 by 0 38 feet, while it <br /> decreased in the remaining wells by 0 34 feet to 0 82 feet These changes resulted in an Overall average <br /> decrease In groundwater elevation of 0 47 feet across the site Changes in groundwater elevation are most <br /> likely a result of seasonal variation Groundwater gradient and flow direction remained consistent with <br /> previously collected data <br /> Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (G30 000 <br /> ppb gasoline, X334 ppb benzene, 2,670 ppb toluene, 1 170 ppb ethylbenzene, 3,570 ppb xylenes), MW-2 <br /> (1,670 ppb gasoline, 18 4 ppb benzene, 6 6 ppb toluene, 2 0 ppb ethylbenzene, and 107 ppb xylenes), MW-3 <br /> (309 ppb gasoline, 45 5 ppb benzene, 1 7 ppb toluene, 13 9 ppb ethylbenzene, and 18 4 ppb xylenes), MW-4 <br /> (660 ppb gasoline, 56 ppb benzene, 1 5 ppb toluene, 24 8 ppb ethylbenzene, 7 6 ppb xylenes), and MW-5 <br /> (2,060 ppb gasoline, 139 ppb benzene, 8 3 ppb toluene, 64 ppb ethylbenzene, and 445 ppb xylenes) Lower <br /> concentrations of hydrocarbons were found in the samples collected from MW-6 (68 ppb gasoline, 4 8 ppb <br /> benzene, 1 1 ppb ethylbenzene, and 7 2 ppb xylenes), MW-8 (1 0 ppb benzene) and MW-9 (173 ppb <br /> gasoline, 3 3 ppb benzene, and 0 6 ppb xylenes) Hydrocarbons were not detected In the samples collected <br /> from MW-7 and MW-10 Low concentrations of MTBE were detected in the groundwater samples collected <br /> from MW-2 (9 2 ppb) and MW-4 (9 9 ppb), however, it was not detected in any of the other samples <br /> 22 <br />