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' 4 0 Third Quarter Groundwater Monitoring and Sampling 41 Monitoring The third quarter 1994 groundwater monitoring data were collected on ' August 29, 1994 Monitoring activities included measuring the groundwater elevation i in nine onsite monitoring wells shown on Figure 4-1 Groundwater measurements weie taken using an electronic oil/water interface probe. Free product was not detected in any of the onsite monitoring welis Depth to groundwater and well depth measurement~ were iecorded for each monitoring well and are listed in Table 1 ' Data collected were used to determine groundwater flow dtrection and gradient as shown on Figure 4-2 The general groundwater flow direction is to the southwest ' which is consistent with previous quarterly monitoring events However, during the third quarter 1994, a depression in the water table was measured in MW-8 resulting in a localized flow pattern towards MW-8 The cause of this localized depression is unknown Waste Science will continue to monitor the groundwater glow direction and gradient during subsequent quarterly monitoring events 4 2 Sampling Field grOUndwater monitoring data (conductivity, pli, tel-nperatUre, and tUrbldity) and groundwater elevation data were used to determine tilt Volume of purge water to he removed from each monitoring well prior to sampling Samples were collected after physical parameters stabilized and a minimum of three well volumes of water ' had been removed Purge water and other investigation-derived wastes (IDW) were placed in Department of Transportation (DOT) approved 17E/H drums IDW will be sampled and submitted to the District's laboratory for waste ' characterization as specified in the July 1993 AddittonalAsse%sment and Goluldwater Monitonng Work Plon (Work Plata) Upon receipt of the waste profile ' chaiacterization iesults, the IDW will be appropriately disposed Groundwater samples were coliected using Teflon bailers on August 29, 1994, ' from three of the nine monitoring wells (MW-1, MW-8 and MW-9) Additional groundwater analyses were performed during third quarter monitoring in preparation for the implementation of the proposed Remedial Action Plan One sample from each well was collected and submitted for analysis by United States Environmental Protection Agency (USEPA) Method 8020 for benzene, toluene, ethylbenzene, xylenes (BTEX), and Method 8015 Modified for TPH-g The groundwater sample 9488 r.iv Bay Municipal Ut,lit} Distrtct 40429600\3rdgtrpnv 3 slocklon S(.mc(. Center `ihnd Quarter 1994