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SECTIONFOUR 1 Constant Rate Pump Test URS retained a pump contractor to develop the wells and conduct a pump test. Sediment was first removed from the well sumps using a target bailer. A submersible electric pump was then installed and the wells were each pumped until the discharge water cleared and water quality parameters (i.e., pH, conductivity, and temperature) adequately stabilized. Groundwater samples were collected from the monitoring wells at the end of development. The submersible pump was then reinstalled in the extraction well, along with a pressure transducer, and the wells were allowed to set overnight prior to initiation of the pump test. The pump test was started at approximately 8:30 a.m. on October 21, 2000, and continued for 9 hours at a constant rate of approximately 6.9 gallons per minute (gpm). Water levels within the extraction well were recorded continuously using a pressure transducer and data logger. Water levels in the monitoring wells were measured manually using a sounding tape. A groundwater sample for lab chemical analyses was collected from the extraction well prior to termination of the test. Once the pump test was terminated, water levels in the three wells were monitored and recorded for approximately 1.5 hours while the aquifer recovered. Figure 3 is atime-drawdown plot of water levels in the extraction well. The delayed drawdown ' seen in the first 4 to 5 minutes can likely be explained as a casing storage effect. Drawdown generally stabilized at approximately 8 feet, then dropped more than 6 feet after appro~:imately 250 minutes of pumping. Drawdown stabilized again at around 13.5 feet bgs near the c;nd of the ' test. This suggests that the well has a specific capacity ranging from 0.5 to 0.9 gpm per foot of drawdown (gpm/ft). 1 1 1 Field personnel confirmed that the dischazge rate did not change, so the sudden increase in drawdown was likely not caused by a change in the pumping rate. This water level response probably indicates that a hydrologic boundary was encountered (e.g., edge of the alluvial channel) or that the portion of the aquifer yielding water to the well becomes less permeable as drawdown increases. Figures 4 and 5 are time-drawdown plots of water levels in the monitoring wells. Water level drawdown began at HMMW-02 (50 feet away) after about 7 minutes of pumping and n:ached a maximum of 0.16 feet after 9 hours. Similarly, the water level in HMMW-03 (100 feet away) began to draw down after about 10 minutes of pumping and reached a maximum of 0.15 feet after 9 hours. 4.1 DATA ANALYSIS Water level data collected during the pumping and recovery tests were analyzed to estivate alluvial aquifer parameters. Estimates of aquifer transmissivity ranged from approximately 3,000 to 50,000 gallons per day per foot (gpd/ft). Corresponding values of hydraulic conductivity ranged from approximately 15 to 238 feet per day (fUd). Specific yield was estimated from both time-drawdown and recovery data collected from the monitoring wells, and ranged from 0.01 to 0.05. The most representative values for aquifer transmissivity and hydraulic conductivity are believed to be from the extraction well recovery data (Figure 6). Analysis of these data suggests that the most representative values for transmissivity and hydraulic conductivity are 15,000 gptb'ft and 70 fdd, respectively. Our best estimate of specific yield is 0.03, which is an average of the values f~R09sRFlEf~EIRJ1AlEClSCIUSW_IIADERSOR_NILLFEIRSUB_OP6.O Ria DELWIEVISED TEb1 MEWRt DOgtMh 2tl PY ~ 1