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CvvATC A S S O C I A T E S I N C extraction/air sparge system at the site is not warranted However, Mr Knoll also indicated that either long term monitoring or another alternative would be required prior to the site being considered for closure The workplan for performing a groundwater extraction pump test at the site was submitted on March 1, 2001 This workplan was approved by Mr Knoll on March 9, 2001 SAMPLING ACTIVITIES On January 15, 2002, ATC Associates personnel collected groundwater samples from monitoring wells MW2, MW3, and MW4 The locations of the monitoring wells are shown on Figure 2 Pryor to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded A minimum of three well casing volumes was purged from each well prior to sampling The wells were allowed to recover and samples were collected from each well using disposable bailers A sample was also collected from the Thornton Municipal Supply Well The groundwater samples collected from each well were submitted to State-certified Argon Laboratories (ELAP Cert No 2359) for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg) utilizing EPA method 8015 modified, benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl tert butyl ether (MTBE) utilizing EPA method 8020 MTBE was detected in well MW4 so this sample was also analyzed for fuel oxygenates utilizing EPA method 8260 Groundwater monitoring well purge and sample logs are contained in Attachment 1 ANALYTICAL RESULTS Laboratory analyses results detected TPHg at monitoring well MW4 at a concentration of 5,600 pg/L At monitoring well MW4, benzene was detected at a concentration of 18 1tg/L, toluene was detected at a concentration of 15 µg/L, ethylbenzene was detected at a concentration of 71 pg/L, and xylenes were detected at a concentration of 180 µg/L MTBE was analyzed and initially detected by EPA method 8020 at a concentration of 110 gg/L at monitoring well MW4, but this was determined by the laboratory to be a false positive reading Analysis of the sample by EPA method 8260 determined MTBE was below the laboratory reporting limit of 2 0 µg/L Benzene, ethylbenzene, toluene, xylenes, MTBE, and TPHg were not detected above the laboratory reporting limit at monitoring wells MW2, MW3, and the Municipal Supply Well The California Primary Maximum Contaminant Level (MCL) for benzene of 1 gg/L was exceeded at monitoring well MW4 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 GROUNDWATER FLOW DIRECTION Water level measurements were collected from monitoring wells MW1, MW2, MW3, MW4, MW5, and MW6 on January 15, 2002 Depth to water measurements ranged from 9 78 feet to M 14 73 feet below top of casing representing an increase in the water table elevation of approximately 1 36 feet since September 2001 The water level elevations were used to develop w 1Wordpro1625821Quartiy\1QR-2002 doc 4