ARCHIVED REPORTS XR0000037 - Laserfiche WebLink

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2 0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS On December 19, 2003, to comply with quarterly groundwater monitoring requirements, Ramage Environmental monitored and sampled the three wells, for the fifth consecutive quarter 2.1 Groundwater Monitoring Depth-to-groundwater was measured using a water level indicator capable of measurements to ' within 0 01 foot The depth to the groundwater table, as measured in the three monitoring wells, ranged from 48 09 feet bgs in MW-2 to 48 53 feet bgs in MW-3 The corresponding groundwater surface elevations in the three wells ranged from a high of 27 00 feet below mean sea level (msl) at MW-2 to a low of 27 29 feet below msl at MW-3 The resulting groundwater surface appears as a regular plane dipping toward the north-northeast at a gradient of approximately 0 0015 foot/foot A groundwater surface contour map is included as Figure 3 The well construction details, wellhead elevations and groundwater monitoring data are summarized in Table 5 The sample information field sheets are included as Appendix A December 19 2003 the groundwater otentcometric surface rose an Between September 15, and g p average of 1 74 feet, the groundwater gradient decreased from 0 0020 to 0 0015 foot/foot, and the groundwater flow direction shifted approximately 40 degrees toward the north-northeast Over the past five quarters, the groundwater flow direction has been toward the north and northeast The historical groundwater flow directions are shown on Figure 2 22 Groundwater Sampling and Analysis Following groundwater level measurements, the wells were purged and sampled The wells were jpurged with a pump and dedicated disposable tubing until at least three well casing volumes had been removed and/or after groundwater temperature, pH and electrical conductivity values had stabilized Groundwater was sampled from the wells using disposable polyethylene bailers and laboratory-supplied containers Each sample container was transported in an iced cooler with chain-of-custody documentation to Excelchem Environmental Labs (Excelchem), a state of California certified hazardous waste testing laboratory (#2119) Excelchem analyzed each sample for TPH-as het fuel, TPH-as- gasoline and benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA Method 8020/8015M, and for methyl tertiary butyl ether (MTBE), di-isopropyl ether(DIPS), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether(TAME), and tertiary butanol (TBA) by EPA Method 8260B 6