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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 (6,570 ppb
<br /> gasoline, 304 ppb benzene, 1,410 ppb toluene, 1,020 ppb ethylbenzene), MW-2 (875 ppb gasoline, 23 9 ppb
<br /> benzene, 38 3 ppb toluene, 5 3 ppb ethylbenzene, and 241 ppb xylenes), and MW-3 (935 ppb gasoline, 235
<br /> ppb benzene, 0 7 ppb toluene, 35 1 ppb ethylbenzene, and 24 5 ppb xylenes) Lower concentrations of
<br /> hydrocarbons were found in the samples collected from MW-4 (342 ppb gasoline, 44 3 ppb benzene, 8 6 ppb
<br /> ethylbenzene, and 1 8 ppb xylenes), MW-5 (102 ppb gasoline, 6 2 ppb benzene, 0 8 ppb ethylbenzene, and
<br /> 3 6 ppb xylenes), MW-6 (166 ppb gasoline, 18 8 ppb benzene, 2 0 ppb ethylbenzene, and 19 2 ppb xylenes),
<br /> MW-8 (1 2 ppb benzene and 0 5 ppb xylenes), and MW-9 (61 ppb gasoline and 1 6 ppb toluene)
<br /> Hydrocarbons were not detected in the samples collected from MW-7 or MW-10 Low concentrations of
<br /> MTBE were detected in the groundwater samples collected from MW-2 (5 4 ppb), MW-3 (9 3 ppb), MW-4
<br /> (12 6 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 MW-3) The groundwater plume does not appear to be migrating to any great extent When compared
<br /> to the October 1997 sampling event, groundwater concentrations decreased in MW-1, MW-3, MW-5, MW-6,
<br /> and MW-9, while they remained relatively unchanged in the remainder of the wells
<br /> A copy of SECOR's "Quarterly Monitoring Report, January - March 1998" dated April 15, 1998, was
<br /> forwarded to the appropriate regulatory agencies on May 4, 1998
<br /> Vapor Extraction Feasibility Testing- March 1998
<br /> On March 19 and 20, 1998, feasibility testing was conducted to evaluate the effectiveness of vapor extraction
<br /> In remediating hydrocarbon-impacted soils at the subject site Tests were conducted at eight separate wells
<br /> (W-1 through W-8) for a duration of 1 to 4 hours each using an internal combustion engine Due to low
<br /> oxygen in subsurface, the internal combustion engine was unable to produce a vacuum exceeding 4 inches
<br /> of water at any well, therefore, Induced vacuum could not be measured at any of the surrounding wells
<br /> Based on flow rates obtained during testing and their understanding of site conditions, SECOR estimates the
<br /> actual radius-of-influence at each well to be approximately 50 feet
<br /> A summary of pilot test data follows
<br /> Well No Screened Interval Max Applied Vacuum Resulting Air Flow TPH Concentration Initial Mass Removal Rate
<br /> W-1 10 -40 feet 2 in water 12 5 cfm 763 ppmv 3 8 lbs/day
<br /> W-2 5 -45 feet 2 in water 12 6 cfm 7 240 ppmv 6 5 Ibslday
<br /> W-3 5-40 feet 2 5 in water 19 9 cfm 179 000 ppmv 1 425 Ibslday
<br /> W-4 5-30 feet 3 5 in water 14 2 drn 3 130 ppmv 17 1 lbs/day
<br /> W-5 10-30 feet 3 in water 26 9 cfrn 221 ppmv 2 4 lbs/day
<br /> W-6 10-30 feet 3 in water 19 9 cfm 139 ppmv 1 1 lbs/day
<br /> W-7 25-56 feet 2 in water 19 6 cfrn 2 670 ppmv 20 9 lbs/day
<br /> W-8 25-56 feet 2 in water 20 7 cfm 23 000 ppmv 175 Ibslday
<br /> SECOR calculated the initial mass removal rates for each well using the average flow rate observed during
<br /> testing and the analytical results of vapor samples collected near the end of each test
<br /> Based on the results of the pilot test, it appears as though vapor extraction will be a feasible technology for
<br /> addressing hydrocarbon-impacted soils at the subject site The majority of impacted sods can most likely be
<br /> Influenced by vapor extraction from W-1 through W-8 with an assumed 50-foot radius of influence
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