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� r T �AW W Working To Restore Nature wells at depths of approximately 30 feet below grade The purpose of these bonngs was to investigate and define the extent of hydrocarbon impaction in soil and groundwater. The bonng/well locations are plotted on Figure 2 Field activities performed at the site are summarized in separate Problem Assessment Reports submitted by RESNA on May 30, 1991 and May 20, 1992 QUARTERLY MONITORING AND SAMPLING Groundwater monitoring and sampling of site wells was conducted on February 2, 1994 by RESNA personnel Water level measurements were collected from each site monitoring well (Table 1) prior to purging and sampling Groundwater elevations across the site have risen an average of 1 4 feet since the last monitoring event in November 1993 The groundwater gradient was calculated using the February 2, 1994 groundwater elevation data and is illustrated on Figure 2 The figure depicts a variant gradient between 0 01 to 0 025 ft/ft, or 53 to 132 feet per mile in a southeasterly direction In accordance with San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) correspondence dated May 5, 1993, all monitoring wells were sampled this quarter Prior to groundwater sample collection, a minimum of 3 casing volumes of water was purged from each monitoring well All purged water was contained on-site in DOT approved 55-gallon drums pending analytical results Groundwater samples were collected from each well after stabilization of groundwater parameters (pH, electrical conductivity, temperature) Water samples were collected using dedicated disposable bailers Field purge logs are contained in Attachment 1 Groundwater samples were placed on ice and transported under chain-of-custody protocol to state-certified Sequoia Analytical in Redwood City, California All samples were analyzed for benzene, toluene, ethylbenzene, xylenes (BTEX) using EPA method 8020, and total petroleum hydrocarbons as gasoline (TPHg) using modified EPA method 8015 Dissolved petroleum hydrocarbons and BTEX constituents were not detected in monitoring wells MW1, MW4, MW5 and MW6 The sample collected from MW2 contained ethylbenzene, and TPHg at 6 2 and 120 parts per billion (ppb), respectively The sample collected from MW3 contained ethylbenzene and TPHg at 63 and 600 ppb, respectively The ethylbenzene levels in wells MW2 and MW3 were below the Primary Maximum Contaminant Level (MCL) for ethylbenzene established by the Department of Health Services Laboratory results are summarized in Table 2. Laboratory reports and chain-of-custody documentation are presented in Attachment 2 On March 10, 1994 approximately 1,100 gallons of stored monitoring well purge water was transported under non-hazardous manifest to Enviropur West (PRC) in Patterson, California for disposal 15000211QR-1994 FNL 2