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2. 3 Groundwater Monitoring <br /> During excavation and treatment, three on-site monitoring wells <br /> were destroyed (MW-1, MW-3 and MW-5) . On 3 September 1992 three new <br /> wells were drilled in the same locations. Two additional off-site <br /> monitoring wells were installed on 4 September 1992 . The wells were <br /> initially sampled on 11 September 1992 and results presented in the <br /> Monitoring Well installation and Sampling report dated 9 October <br /> 1992 . Nine monitoring wells were subsequently monitored in February <br /> 1993 , and groundwater elevation and contamination levels were <br /> reported in the First Quarter 2993 Groundwater Monitoring Report on <br /> 8 March 1993 . <br /> 3 . 0 PROCEDURES <br /> 3. 1 Measurement and Sampling <br /> On 20 May 1993 , a Solinist water level meter was used to measure <br /> the depth to water in each well. After measurements were made, a <br /> purge pump was used to surge and purge each well, and approximately <br /> 10 gallons of water were removed from all wells to stabilize <br /> temperature, pH and conductivity (Table 1) . The water was stored in <br /> 55-gallon drums on-site. <br /> Water samples were collected from each well using a new, clean, <br /> disposable plastic bailer. The samples were collected in 40 ml EPA j <br /> vials and transported in a chilled container to Alpha Analytical <br /> Laboratories in Ukiah. <br /> 3.2 Laboratory Analysis <br /> The samples were analyzed for total petroleum hydrocarbons (TPH as <br /> gasoline) and volatile aromatics (BTE&X) in accordance with EPA <br /> methods 8015/LUFT and 502 , respectively. The laboratory report and <br /> chain of custody are presented in Appendix A. <br /> 4 . 0 FINDINGS <br /> 4. 1 Groundwater Elevation and Gradient <br /> The relative elevation of the water table in each well was <br /> calculated by subtracting the water depth from the casing elevation <br /> (Table 2) . The data indicate that the water table has lowered an <br /> average of 2 . 3 feet. The level in on-site wells has dropped <br /> approximately 3 . 5 feet; to the north and east, the level has <br /> dropped less than 3 feet, and in MW-11, the level has actually <br /> risen 0. 45 feet. The reasons for these variations are uncertain. <br /> Groundwater continues to flow to the northeast, although at a <br /> somewhat steeper gradient than in February (Figure 3) . The gradient <br /> 2 <br />