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CNIV o A S 5 0 C I A T E S 1 111 C current AST location contained elevated concentrations of total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), and methyl tertiary butyl ether (MTBE) The extent of impacted soil was defined and generally extended along the backside of the levee, west of the store The Ariel extent was approximately 200 feet in length and 65 feet in width and was limited to depths between 5 and 15 feet bgs Additionally, MTBE impacted soil extended eastward, between the store and office building The groundwater plume generally extended along the backside of the levee, west of the store, and was approximately 225 feet long and 70 feet wide Concentrations were highest in the boring adjacent to the former and current product lines The extent of TPHg in groundwater was not fully defined to the west and south but samples indicated that the borings in those directions were near the edge of the plume Additionally, TPHd and MTBE have migrated eastward GROUNDWATER MONITORING The second quarter groundwater monitoring and sampling of monitoring wells MWI through MW7 was conducted by ATC Associates Inc personnel on May 2, 2002 Water level measurements were collected from all morutonng wells prior to purging and sampling Well locations are shown on Figure 2 Subsequent to monitoring, each well was purged by extracting a minimum of three well casing volumes of groundwater While purging, groundwater parameters (temperature, conductivity, and pH) were monitored and allowed to stabilize before water samples were collected Samples were collected using dedicated, disposable bailers with bottom emptying devices to reduce volatilization All purged groundwater was contained in 55-gallon drums approved for hazardous liquid storage on-site pending appropriate disposal Groundwater well purge and sample logs are contained in Attachment 1 The groundwater samples collected from each well were placed on ice and transported under chain-of-custody documentation to Argon Laboratories (FLAP #2359) in Ceres, California The groundwater samples were analyzed for TPHd, TPHg, benzene, toluene, ethylbenzene, and xylenes (BTEX) and MTBE utilizing EPA methods 8015/8020 If MTBE was detected by EPA method 8020 then the sample was analyzed by EPA method 8260 to confirm the presence of MTBE RESULTS Water levels have decreased an average of 0 37 feet since the last monitoring event on January 14, 2002 (Table 1) A groundwater gradient map was created using the data collected on May 2, 2002 (Figure 2) Groundwater primarily flows east, away from the slough, with a gradient of approximately 0 07 feet/foot or 385 feet per mile TPHg and TPHd were not detected in any of the groundwater samples collected from wells MWI through MW7, although the detection limits for TPHg in the sample from wells MW5 and MW7 were elevated due to dilution factors BTEX were not detected in the groundwater samples collected from w lwordpro1625141quarilyl2gr-2002 doe 3