ARCHIVED REPORTS_XR0006713 CASE 1

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2.0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS On August 27, 2004, to comply with quarterly groundwater monitoring requirements, Ramage Environmental monitored and sampled five of the six monitoring wells Monitoring well MW-2 was not sampled because the groundwater level was below the bottom of the well (i e , the well was dry) The on-site domestic water supply well was not sampled because it was taken out of service, when the site was converted to city water service 2.1 Groundwater Monitoring Depth-to-groundwater was measured in the five monitoring wells using a water level indicator capable of measurements to within 0 01 foot The depth to the groundwater table ranged from 24 35 feet bgs in MW-6 to 26 31 feet bgs in MW-4 The corresponding groundwater surface elevations ranged from a high of 12 54 feet above mean sea level (msl) at MW-1 to a low of 11 40 feet above msl at MW-5 The resulting groundwater surface appears as an irregular plane dipping to the north-northeast at a gradient of approximately 0 0084 foot/foot A groundwater surface contour map is included as Figure 5 The well construction details and groundwater monitoring data are summarized in Table 1 22 Groundwater Sampling and Analysis Following groundwater level measurements, the five wells were purged and sampled The monitoring wells were purged 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 monitoring wells using dedicated and disposable polyethylene bailers and laboratory-supplied containers All sample containers were transported in an iced cooler with chain-of-custody documentation to Excelchem Environmental Labs (Excelchem), a state of California certified hazardous waste testing laboratory (Certification#2119) Excelchem analyzed each of the groundwater samples for TPH-as-gasoline, benzene, toluene, ethylbenzene and xylenes (BTEX) by EPA Method 8020/8015M, and for MTBE, di-isopropyl ether (DIPE), ethyl tertiary butyl ether(ETBE), tertiary amyl methyl ether(TAME), tertiary butanol (TBA), and 1,2-dichloroethane (1,2-DCA) by EPA Method 8260B 7 •