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r A 5 5 OCIATES INC On June 27, 1997 groundwater samples were collected from monitoring wells MW1, MW2, MW3, and MW5 Samples were collected after stabilization of pH, electrical conductivity (EC), and temperature All wells monitored were purged and sampled according to Smith Technology's Quality Assurance/Quality Control Plan on file with the PHS/EHD A minimum of four casing volumes of water were removed from each sampled well A dedicated disposable bailer was used to collect each water sample Purge water was contained in labeled DOT approved 55 gallon drums and stored on site pending laboratory analysis and proper disposal Field parameters and purged volumes are shown on well purge logs included in Attachment I LABORATORY ANALYSIS Groundwater samples collected from the monitoring wells and were placed on tee and transported under chain-of-custody protocol to State-certified GTEL Environmental Laboratories in Concord, California (DHS Certification No 2147) Monitoring well samples were analyzed for TPHg, BTEX, and methyl tertiary butyl ether (MTBE) by EPA methods 8015 modified and 8020, and for total petroleum hydrocarbons as diesel (TPHd) by EPA method 8015 Groundwater samples from wells MW1, MW2, and MW3 contained concentrations of benzene in . excess of the State of California Maximum Contaminant Level (MCL) of 1 part per billion (ppb) No other petroleum constituents were above MCLS MTBE was detected in the sample collected from well MW 1 at a concentration of 14 ppb, however this concentration is below the State Advisory Level (OEHHA) of 35 ppb 1 results for groundwater are summarized in Table 2 Laboratory data sheets and chain of custody documentation are included as Attachment II INTERIM REMEDIAL ACTION On June 27, 1997, subsequent to conducting quarterly monitoring activities, a Xitech Instruments, Inc , Hydro-Skimmer was installed in well MW2 This 2-inch passive recovery device includes a collection chamber with a 0 51 gallon capacity The site will be visited monthly for routine maintenance During maintenance visits, and in conjunction with quarterly monitoring events, the skimmer will be removed from the well and the collected free product will be stored on site in a 55-gallon drum 943341QUARTLYI2QR-1997 DOC 3