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Site History
<br /> 14000 Highway 88 Lockeford CA
<br /> Time Oil Property No 04-049
<br /> ppb xylenes), MW-5 (157 ppb gasoline, 7 2 ppb benzene, and 2 2 ppb xylenes), MW-6 (88 ppb gasoline,
<br /> 12 6 ppb benzene, 2 8 ppb toluene, and 6 1 ppb xylenes), MW-8 (2 7 ppb benzene), and MW-9 (95 ppb
<br /> gasoline, 9 4 ppb benzene; 0 6 ppb toluene, 1 4 ppb ethylbenzene, and 4 2 ppb xylenes) Hydrocarbons
<br /> were not detected in the samples collected from MW-7 and MW-10 Per the County's request, samples
<br /> collected from MW-1 and MW-10 were analyzed for the presence of MTBE by EPA Method 8020 Analyses
<br /> identified 5 7 ppb MTBE in the groundwater sample collected from MW-1, however, MTBE was not detected
<br /> in the sample collected from MW-10
<br /> The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW-
<br /> 1 and MW-3) When compared to the February 1997 sampling event, groundwater concentrations increased
<br /> in MW-1, while decreases in hydrocarbon concentrations were observed in MW-4, MW-6, MW-7, MW-8,
<br /> MW-9, and MW-10 Hydrocarbon concentrations in MW-2, MW-3, and MW-5 remained relatively
<br /> unchanged
<br /> A copy of SECOR's"Quarterly Monitoring Report-April -June 1997" dated May 6, 1997, was forwarded to
<br /> the appropriate regulatory agencies on August 5, 1997
<br /> Third Quarter 1997 Groundwater Sam ling Results-July 1997
<br /> On July 14, 1997, 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 southwesterly flow and
<br /> . a gradient of 0 04 ft/ft was encountered in the wells at depths of 65 26 feet to 82 23 feet below ground
<br /> surface Free product was not encountered in any of the wells
<br /> Since the April 1997 sampling event, groundwater elevation increased in MW-1, MW-2, and MW-4 through
<br /> MW-10 by 0 51 feet to 1129 feet, and groundwater elevation remained unchanged in MW-3 These changes
<br /> resulted in an overall average increase in groundwater elevation of 2 04 feet across the site Changes in
<br /> groundwater elevation and are most likely a result of seasonal variation Groundwater flow direction and
<br /> gradient remained relatively unchanged from the previous quarter
<br /> Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (55,200
<br /> ppb gasoline, 1,470 ppb benzene, 11,300 ppb toluene, 1,800 ppb ethylbenzene, and 8,960 ppb xylenes),
<br /> MW-3 (2,970 ppb gasoline, 364 ppb benzene, 280 ppb toluene, 94 ppb ethylbenzene, and 329 ppb xylenes),
<br /> and MW-5 (5,580 ppb gasoline, 418 ppb benzene, 420 ppb toluene, 100 ppb ethylbenzene, and 898 ppb
<br /> xylenes) Lower concentrations of hydrocarbons were found in the samples collected from MW-2 (280 ppb
<br /> gasoline, 3 2 ppb benzene, 1 0 ppb toluene, 40 6 ppb ethylbenzene, and 280 ppb xylenes), MW-4 (197 ppb
<br /> gasoline, 5 9 ppb benzene, 10 ppb toluene, and 16 ppb xylenes), MW-6 (250 ppb gasoline, 35 6 ppb
<br /> benzene, 2 0 ppb toluene, 3 9 ppb ethylbenzene, and 31 ppb xylenes), MW-8 (69 ppb gasoline and 4 0 ppb
<br /> benzene), and MW-9 (141 ppb gasoline and 2 5 ppb benzene) Hydrocarbons were not detected in the
<br /> samples collected from MW-7 and MW-10 Per the County's request, samples collected from MW-1 and
<br /> MW-10 were analyzed for the presence of MTBE by EPA Method 8020 Neither sample contained
<br /> detectable concentrations of MTBE
<br /> The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW
<br /> 1 and MW-3) When compared to the April 1997 sampling event, groundwater concentrations increased in
<br /> MW-1, MW-2, MW-5, MW-6, and MW-8, while hydrocarbon concentrations in MW-3, MW-4, MW-7, MW-9,
<br /> and MW-10 remained relatively unchanged
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