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PHONE 285 2400
<br /> CABLE ADDRESSTIM01_
<br /> SEATTLE T (FAX) 206-283-8036
<br /> TACOMA Ere " 1
<br /> PORTLAND I
<br /> STOCKTONM12TGRENO
<br /> RICHMONDTIME LOS ANGELES E ITs 2737 WEST COMMODORE WAY SEATTLE,WA 98199-1233
<br /> PRoauCT5 TQM P.O.BOX 24447 SEATTLE,WA 98124-0447
<br /> TIME TESTEa E
<br /> March 12, 1997
<br /> Mr. Harlan Knoll
<br /> San Joaquin County Public Health Services
<br /> Environmental Health Division
<br /> P.O. Box 2009
<br /> Stockton, California 95201
<br /> RE: Submittal of Fourth Quarter 1996 Groundwater Monitoring Report for
<br /> Jackpot Food Mart, 14000 E. Highway 88, Lockeford, California (Property No. 04-049)
<br /> Dear Mr. Knoll,
<br /> At the request of the San Joaquin County Public Health Services Environmental Health Division
<br /> (PHS/EHD), an additional environmental investigation was implemented at the subject site in December
<br /> 1994 to evaluate the extent of hydrocarbon-impacted soils and to determine whether or not groundwater
<br /> had been impacted. A total of four groundwater monitoring wells were installed during this investigation.
<br /> In July 1996, six additional groundwater monitoring wells were installed on and off of the subject site to
<br /> assist in defining the extent of groundwater impacts. Based on the results of the investigations, Time Oil
<br /> has implemented groundwater monitoring.
<br /> Please find enclosed Science & Engineering Analysis Corporation's (SECOR's) "Quarterly Monitoring
<br /> y. Report, October- December" dated February 28, 1997. This document presents analytical results and
<br /> field observations collected during Fourth Quarter 1996 groundwater sampling activities.
<br /> For your convenience a summary of previous site activities is attached.
<br /> Fourth Quarter 1996 Groundwater Sampling Results- December 1996
<br /> On December 19, 1996, samples were collected from each of the groundwater monitoring wells (MW-1
<br /> through MW-10) at the subject site by a representative of SECOR. Prior to purging, the depth to water in
<br /> each well was measured to evaluate elevation, flow direction, and gradient. As noted in the attached
<br /> report, groundwater with a southwesterly flow at a rate of 0.02 ft./ft. was encountered in the wells at
<br /> depths of 66.90 feet to 79.92 feet below ground surface. Free product was not encountered in any of the
<br /> wells. The locations of the wells are identified on Figure 2 of the attached report.
<br /> Since the Third Quarter 1996 sampling event, groundwater elevation decreased in MW-2, MW-4, MW-7
<br /> and MW-8 by 0.05 feet to 0.53 feet, and groundwater elevation increased in wells MW-1, MW-3, MW-5,
<br /> MW-6, MW-9, and MW-10 by 0.09 feet to 4.55 feet. These changes resulted in an overall average
<br /> increase in groundwater elevation of 0.63 feet across the site and are most likely a result of seasonal
<br /> variation. Groundwater flow direction and gradient remained relatively unchanged from the previous
<br /> quarter. Table 1 in the attached report summarizes all groundwater elevation data collected to date.
<br /> Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1
<br /> (21,000 ppb gasoline, 1,500 ppb benzene, 5,230 ppb toluene, 742 ppb ethylbenzene, and 3,590 ppb
<br /> xylenes), MW-3 (3,510 ppb gasoline, 522 ppb benzene, 184 ppb toluene, 191 ppb ethylbenzene, and 349
<br /> ppb xylenes), MW-6 (515 ppb gasoline, 45.5 ppb benzene, 45.2 ppb toluene, 7.5 ppb ethylbenzene, and
<br /> 124 ppb xylenes), and MW-9 (2,400 ppb gasoline, 140 ppb benzene, 90 ppb toluene, 88 ppb
<br /> �r ethylbenzene, and 173 ppb xylenes). Lower concentrations of hydrocarbons were found in the samples
<br /> collected from MW-2 (175 ppb gasoline, 3.7 ppb benzene, 1.2 ppb toluene, 1.6 ppb ethylbenzene, and
<br /> 8.3 ppb xylenes), MW-4 (284 ppb gasoline, 4.9 ppb benzene, 0.6 ppb toluene, and 0.7 ppb xylenes),
<br /> MW-5 (122 ppb gasoline, 9.6 ppb benzene, 0.9 ppb toluene, and 1.5 ppb xylenes), and MW-8 (102 ppb
<br /> gasoline and 10.1 ppb benzene). Hydrocarbons were not present at detectable concentrations in the
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