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S E C 0 R . 7-Eleven Store#32262 Extended Groundwater Pumping Test and Oxygen Infection Feasibility Study November 15, 2005 Page 6 Constant-Discharge Pumping Test and Recovery The constant-discharge pumping test was performed at well EX-1 using 0 8 gpm as the initial pumping rate During the test, a maximum drawdown of 8 7 feet in extraction well EX-1 was observed After pumping from well EX-1 for approximately 4,800 minutes, the pump was shut down, and the groundwater recovery levels were monitored in wells EX-1, S-1, MW-5, and MW-4 Groundwater levels were recorded for approximately 1 hour There appeared to be no drawdown observed in wells S-1, MW-5, or MW-4 caused by the pumping of well EX-1 Drawdown and recovery water level data from well EX-1 compiled throughout aquifer testing was used to calculate hydraulic properties of the aquifer beneath the Site Data Analysis Drawdown data collected from extraction well EX-1 was analyzed using the Cooper-Jacobs (1946) method applied using the AQTESOLVTM software groundwater monitoring program (Attachment B) The recovery phase of the constant-discharge pumping test was not analyzed because of the rapid water-level recovery rate due to the inefficiency of the pumping well Groundwater level fluctuations (0 03 to 0 06 fee a occurre during the pumping test in monitoring wells S-1, MW-5, and MW-4 do not appear to be the result of pumping from well EX-1, but probably are the result of barometric effects, earth tides, or other temporal changes (Figures 3-5) Therefore, these data were not used for analysis The analyzed data were selected after borehole storage effects were considered negligible at approximately 100 minutes after pumping began (Hargis, 1979) Results of the analysis of drawdown data from well EX-1 indicated a transmissivity of 307 gallons per day per foot (Attachment B) The hydraulic conductivity was calculated by dividing the transmissivlty by the respective aquifer thickness of approximately 15 feet The calculated hydraulic conductivity was 19 feet per day (0 0067 centimeters per second) Generally, a very rapid water level recovery after cessation of pumping is an indication of a inefficient well (Todd,- 1980) Well EW-1 recovered to 100 percent of its initial drawdown in 42 minutes after being, pumped for more than 80 hours This rapid recovery indicates low well efficiency in well E -1 As a result of t IsoT w w I efficiency, no apparent drawdown was observed in the monitoring wells However, based on the calculated hydraulic properties of the water- bearing zone, the effective radius of well EW-1 (ie distance of observable drawdown) ,should have been approximately 180 feet if well EW-1 were efficient (Powers, 1992) ------------------ It should be noted that well EX-1 was constructed with a four-inch diameter PVC casing and a 0 010 inch circum slot screen in order to maximize well efficiency during groundwater extraction events Copies of the well completion logs for wells EX-1, S-1, MW-5 and MW-4 are included with the field notes in Attachment C Groundwater Sample Collection Grab groundwater samples were collected from well EX-1 before the pumping test on September 12, 2005 and after the test on September 16, 2005 from EX-1 and the holding tank containing the extracted groundwater The groundwater samples were submitted to 117-Elevenl7-11 Stores1322621Reports132262 Pump Test and 02 Feasibility 11-10-05 doc SECOR Intemationa!Incorporated