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SEATTLE TACOMA PORTLAND STOCKTONRENO RICHMOND TIME OIL co . 2737 WEST COMMODORE WAY SEA r T L E WA 98'99 1733 PRODUCTS P 0 BOX 24447 SEATTLE WA 98124 0447 �. TIr F TESTED August 2, 1999 Mr Harlin Knoll San Joaquin County Public Health Services Environmental Health Division P O Box 2009 Stockton, California 95201 RE Submittal of Second 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 (PHS/EHD), an additional environmental investigation was implemented at the subject site in December 1994 to evaluate the extent of hydrocarbon-impacted soils 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 implemented groundwater monitoring Please find enclosed Science & Engineering Analysis Corporation's (SECOR's) "Quarterly Monitoring Report, April - June 1999" dated July 28, 1999 This document presents analytical results and field observations collected during Second Quarter 1999 groundwater sampling activities For your convenience a summary of previous site activities is attached Second Quarter 1999 Groundwater Sampling Results—April 1999 On April 26, 1999, samples were collected from each of the groundwater monitoring wells (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 As noted 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 96 feet to 77 00 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 January 1999 sampling event, groundwater elevation increased in MW-3 by 0 02 feet and in MW-9 by 0 06 feet, while it decreased in the remaining wells by 0 01 feet to 1 00 feet These changes resulted in an overall average decrease in groundwater elevation of 0 23 feet across the site Changes in groundwater elevation are most likely a result of seasonal vanation Groundwater gradient and flow direction remained consistent with previously collected data Table 1 in the attached report summarizes all groundwater elevation data collected to date Analyses identified elevated concentrations of hydrocarbons in the samples collected from MW-1 (2,780 ppb gasoline, 97 ppb benzene, 96 ppb toluene, 216 ppb ethylbenzene, 163 ppb xylenes), MW-2 (515 ppb gasoline, 5 2 ppb benzene, 1 0 ppb toluene, 0 8 ppb ethylbenzene, and 43 8 ppb xylenes), MW-3 (306 ppb gasoline, 28 3 ppb benzene, 11 7 ppb toluene, 10 1 ppb ethylbenzene, and 26 5 ppb xylenes), MW-4 (1,810 ppb gasoline, 300 ppb benzene, 3 9 ppb toluene, 151 ppb ethylbenzene, and 7 1 ppb xylenes), and MW-5 (4,050 ppb gasoline, 395 ppb benzene, 22 ppb toluene, 177 ppb ethylbenzene, and 608 ppb xylenes) Lower