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WAsHiNGTON — T OREGON CALIFORNIA ! T (903) 2821 0035 bANOA I t2 2� Hf TIME O I L C O O 2737 WEST COMMODORE WAY SEAT fLE,WA 98199-1233 TIMEIMETESTED PRODUCTS T'u PO BOX 24447 SEATTLE,WA 98124-0447 / e April 30, 1999 Mr Harlin�Knoll San Joaquin County Public Health Services Environmental Health Division P O Box 2009 Stockton, California 95201 RE Submittal of First Quarter 1999 Groundwater Monitoring Report for Jackpot Food Mart, 14000 E Highway 88, Lockeford, California (Property No 04-049) Dear Mr Knoll, At the request of the San Joaquin County Public Health Services Environmental Health Division (PHSIEHD), an additional environmental investigation was implemented at the subject site in December 1994 to evaluate the extent of hydrocarbon-impacted sods and to determine whether or not groundwater had been impacted A total of four groundwater monitoring wells were installed during this investigation In July 1996, six additional groundwater monitoring wells were installed on and off of the subject site to assist in defining the extent of groundwater impacts Based on the results of the investigations, Time Oil has implemented groundwater monitoring Please find enclosed Science & Engineering Analysis Corporation's(SECOR's) "Quarterly Monitoring Report, January — March 1999' dated April 27, 1999 This document presents analytical results and field observations collected during First Quarter 1999 groundwater sampling activities For your convenience a summary of previous site activities is attached First Quarter 1999 Groundwater Sampling Results—January 1999 On January 27, 1999, samples were collected from each of the groundwater monitoring welis (MW-1 through MW-10) at the subject site by a representative of SECOR Prior to purging, the depth to water in each well was measured to evaluate elevation, flow direction, and gradient Asnoted in the attached report, groundwater with a southerly flow 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 ground surface Free product was not encountered in any of the wells The locations of the wells are identified on Figure 2 of the attached report Since the August 1996 sampling event, groundwater elevation increased in MW-5 by 0 38 feet, while it decreased in the remaining wells by 0 34 feet to 0 82 feet These changas resulted in an overall average decrease in groundwater elevation of 0 47 feet across the site Changes in groundwater elevation are most Itkely a result of seasonal variation Groundwater gradient and flow direction remained consistent with previously collected data Table 1 in the attached report summarizes ail groundwater elevation data collected to date Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (<30,000 ppb gasoline, <334 ppb benzene, 2,670 ppb toluene, 1,170 ppo ethylbenzene, 3,570 ppb xylenes) MW-2 (1,670 ppb gasoline 18 4 ppb benzene, 6 6 ppb toluene, 2 0 ppb ethylbenzene, and 107 ppb Xylenes) MW-3 (309 ppb gasoline 45 5 ppb benzene, 1 7 ppb toluene, 13 9 ppb ethylbenzene and 18 4 ppb xylenes), MW-4 (660 ppb gasoline, 56 ppb benzene, 1 5 ppb toluene, 24 8 ppb ethylbenzene, 7 6 ppb xylenes), and MW-5 ,2,060 ppb gasoline, 139 ppb benzene, 8 3 ppb toluene 64 ppb ethylbenzene, and 445 ppb xylenes) Lower