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4.0 Third Quarter Groundwater Monitoring and Sampling <br /> ' 4.1 Monitoring <br /> The third quarter 1993 groundwater monitoring data were collected on <br /> September 16 and 17, 1993' Monitoring activities included measuring the <br /> ' groundwater elevation in nine onsite monitoring wells shown on Figure 4-1 <br /> Groundwater measurements were taken using an electronic oil/water interface probe <br /> ' Free product was not detected in any of the onsite monitoring wells Depth to <br /> groundwater and well depth measurements were recorded for each monitoring well <br /> and are listed in Table 1 Data collected were used to determine groundwater flow <br /> direction and gradient as shown on Figure 4-2 <br /> 4,2 Sampling <br /> Field groundwater monitoring data (conductivity, pH, and temperature) and <br /> ' groundwater elevation data were used to determine the volume of purge water to be <br /> removed from each monitoring well prior to sampling Samples were collected after <br /> physical parameters stabilized and a minimum of three well volumes of water had <br /> been removed Purge water and other investigation-derived wastes (IDW) were <br /> placed in Department of Transportation (DOT) approved 17E/H drums <br /> IDW will be sampled and submitted to the District laboratory for waste <br /> characterization as specified in the July 1993 Additional Assessment and Groundwater <br /> Monitoring Work Plan (Work Plan) Upon receipt of the waste profile <br /> characterization results, the IDW will be appropriately disposed <br /> Groundwater samples were collected using Teflon bailers on September 16 and <br /> 17, 1993, from seven of the nine monitoring wells (MW-1, MW-2, MW-3, MW-4, <br /> MW-6, MW-S, and MW-9) as specified in the September 1993 addendum to the <br /> Work Plan Groundwater samples were collected in three 40-milliliter (m]) volatile <br /> organic analyte (VOA) vials preserved with a hydrochloric acid solution and <br /> ' submitted for benzene, toluene, ethylbenzene, and xylenes (BTEX) and TPH-g <br /> analyses The groundwater sample from MW-9 was also collected in a 500-m1 plastic <br /> ' bottle preserved with nitric acid and submitted for total lead analysis All samples <br /> were submitted to the District laboratory along with the appropriate <br /> ' Chain-of-Custody forms <br /> ' 93R22 East Bay Municipal Utility District <br /> 40429500 a 3 Stockton Service Center-Third Quarter 1993 <br />