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i i 2.0 GROUNDWATER MONITORING , SAMPLING AND ANALYSIS On December 11 , 2003, to comply with quarterly groundwater monitoring requirements , Ramage Environmental monitored and sampled the four existing groundwater monitoring wells. 2. 1 Groundwater Monitoring Depth-to-groundwater was monitored using a water level indicator capable of measurements to within 0 .01 foot. The static depth to the groundwater table, as measured in the four groundwater monitoring wells , ranged from 24. 83 feet bgs in MW-1 to 26 . 04 feet bgs in MW-3. The groundwater surface elevation in the four wells ranged from a high of 13 . 70 feet below mean sea level (msl) at MW- 1 to a low of 14.40 feet below msl at MW-4 . The resulting groundwater surface appears as an irregular plane dipping toward the east-southeast at a gradient of approximately 0. 0238 foot/foot. A groundwater surface contour map is included as Figure 4 , and the groundwater monitoring data are summarized in Table 3 . Between September 12 , and December 11 , 2003, the groundwater surface dropped an average of 0 . 38 feet, the groundwater gradient decreased slightly from 0 . 0263 to 0 . 0238 foot/foot, and the groundwater flow direction remained constant toward the east-southeast. The depth to groundwater beneath the site is at its lowest level , since the monitoring wells were installed in July 2002 . Otherwise , the groundwater surface characteristics are consistent with historical trends. 2.2 Groundwater Sampling and Analysis Following groundwater level measurements, the wells were purged and sampled . The 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 wells using disposable polyethylene bailers and laboratory-supplied containers. The sample information field sheets are included in Appendix A. 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 (Certification #2119) . Excelchem analyzed each of the samples for TPH-as- motor oil , TPH-as-diesel , TPH-as-kerosene, TPH-as-gasoline and BTEX by EPA Method 8020/8015M , and for MTBE, di-isopropyl ether (DIPE) , ethyl tertiary butyl ether (ETBE) , tertiary amyl methyl ether (TAME) , and tertiary butanol (TBA) by EPA Method 8260B . 7