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d • Working To Restore Nature Groundwater elevation data suggests an irregular groundwater surface exists beneath the site The groundwater flow net beneath the site historically has vaned considerably. The irregularities in the measured depths-to-water may be due to the heterogeneous nature of the soils and/or the varying well depths. A groundwater gradient map for the September 21, 1994 monitoring event is presented on Plate 2. Groundwater samples were collected from wells MW2, MW5, and MW6, after purging at least three casing volumes of water or purging dry. No sample was collected from well MW 1 due to the presence of free product Monitoring wells were purged and sampled according to RESNA's Quahty Assurance/Quality Control Plan (on file with PHS/EHD). Well purge logs are included as Attachment 1 LABORATORY ANALYSIS Groundwater samples were transported under chain of custody protocol to Sequoia Analytical Laboratory in Redwood City, California (ELAP #1894) for analysis of benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA method 8020, total petroleum hydrocarbons as gasoline (TPHg) and as diesel (TPHd) utilizing EPA method 8015 modified; and halogenated volatile organics (HVOCs) utilizing EPA method 8010. Laboratory analyses of the sample collected from well MW2 detected the presence of a non- diesel mix in the TPHd range at 1,000 parts per billion (ppb) The sample from monitoring well MW-5 contained a detectable amount of benzene (2 5 ppb), TPHg (140 ppb); and a non- diesel mix of 130 ppb in the TPHd range. No petroleum hydrocarbon analytes were detected above method detection limits in the sample collected from monitoring well MW6 Analytical results of petroleum hydrocarbon constituents are summarized in Table 2 Laboratory data sheets and chain-of-custody documentation are included in Attachment 2 The sample collected from monitoring well MW2 detected only one HVOC constituent, chlorobenzene at 0 60 ppb Analyses of the sample collected from monitoring well MW5 detected several HVOCs including 1,3-Dichlorobenzene (1 3 ppb), 1,4-Dichlorobenzene (9 9 ppb), 1,2-Dichlorobenzene (18 ppb), 1,1-Dichloroethane (0.61 ppb), cis-1,2-Dichloroethene (2 3 ppb), trans-l,2-Dichloroethene (4.9 ppb), and trichloroethene (3 8 ppb). No HVOCs were detected in the sample collected from monitoring well MW6 Analytical results of HVOCs are summarized in Table 3 Laboratory data sheets and chain-of-custody documentation are presented in Attachment 2 • 15OO nQUARTL"QR-1994 @oc 2