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Site History
<br /> 14000 Highway 88 Lockeford CA
<br /> is Time Ori Property No 04-049
<br /> A copy of SECOR's "Vapor Extraction Feasibility Testing" report dated May 27, 1998, was forwarded to the
<br /> appropriate regulatory agencies on May 29, 1998
<br /> Second Quarter 1998 Groundwater Sampling Results-April 1998
<br /> On April 28, 1998, 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 Pnor to purging, the depth to water in each well
<br /> was measured to evaluate elevation, flow direction, and gradient Groundwater with a southwesterly flow
<br /> direction was encountered in the wells at depths of 66 50 feet to 81 31 feet below ground surface Free
<br /> product was not encountered in any of the wells
<br /> Since the January 1998 sampling event, groundwater elevation increased in each well by 0 65 feet to 147
<br /> feet, resulting in an overall increase in groundwater elevation of 1 07 feet across the site Groundwater flow
<br /> direction also changed from southeast to southwest Changes in groundwater depth and flow direction are
<br /> most likely a result of seasonal variation
<br /> Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (60,400
<br /> ppb gasoline, 2,200 ppb benzene, 12,500 ppb toluene, 2,200 ppb ethylbenzene, 10,300 ppb xylenes), MW-2
<br /> (2,370 ppb gasoline, 37 5 ppb benzene, 25 5 ppb toluene, and 578 ppb xylenes), MW-3 (3,110 ppb gasoline,
<br /> 411 ppb benzene, 99 8 ppb toluene, 103 ppb ethylbenzene, and 446 ppb xylenes), and MW-5 (4,460 ppb
<br /> gasoline, 388 ppb benzene, 494 ppb toluene, 92 8 ppb ethylbenzene, and 716 ppb xylenes) Lower
<br /> concentrations of hydrocarbons were found in the samples collected from MW-4 (340 ppb gasoline, 8 2 ppb
<br /> benzene, 1 7 ppb ethylbenzene, and 1 2 ppb xylenes) MW-6 (762 ppb gasoline, 79 8 ppb benzene, 7 0 ppb
<br /> toluene, 6 3 ppb ethylbenzene and 146 ppb xylenes), MW 8 (261 ppb gasoline, 2 7 ppb benzene, 0 6 ppb
<br /> ethylbenzene, and 1 4 ppb xylenes), MW-9 (137 ppb gasoline, 1 5 ppb benzene and 0 6 ppb xylenes), and
<br /> MW-10 (54 5 ppb gasoline) Hydrocarbons were not detected in the sample collected from MW-7 Low
<br /> concentrations of MTBE were detected in the groundwater samples collected from MW-4 (8 3 ppb) and MW-
<br /> 5 (12 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 The
<br /> groundwater plume does not appear to be migrating to any great extent When compared to the January
<br /> 1998 sampling event, groundwater concentrations increased in MW-1, MW-2, MW-3, MW-5 and MW-6, while
<br /> they remained relatively unchanged in the remainder of the wells
<br /> A copy of SECOR's "Quarterly Monitoring Report, April - June 1998" dated July 14, 1998, was forwarded to
<br /> the appropriate regulatory agencies on July 27, 1998
<br /> Corrective Action Plan -August 1998
<br /> At the request of the County, site assessment activities were implemented in July 1992 to evaluate the extent
<br /> of hydrocarbon impacts associated with former underground storage tanks at the above-referenced property
<br /> Site assessment activities included advancing 26 soil borings, installing 8 vapor extraction wells, installing 10
<br /> groundwater monitoring wells, performing vapor extraction pilot tests, and conducting quarterly groundwater
<br /> monitoring and sampling since First Quarter 1995
<br /> To date, it appears as though the extent of hydrocarbon impacts is fairly well defined Soil impacts appear to
<br /> remain limited to the immediate vicinity of the former tank system and pump islands Groundwater impacts
<br /> are somewhat more widespread, existing primarily in the vicinity of the pump islands and generally extending
<br /> to the property boundaries Continued groundwater monitoring efforts indicate that hydrocarbon
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