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Austin Road Landfill Appendix D Contaminant Plume Characterization Report Aquifer Test Methods Groundwater generated from the testing operations was conveyed by underground pipe to the onsite groundwater treatment facility. This permitted facility consists of an air stripper that treats extracted groundwater prior to its discharge into Little Johns Creek,adjacent to the site. Aquifer Test Results Aquifer pumping and recovery tests were performed December 4-191997,at the ARL site. The purpose of the aquifer test was to obtain information on the aquifer parameters that describe ground water flow in the alluvial aquifer in this region. The aquifer parameters of interest in this study are hydraulic conductivity(K),transmissivity(T)and storage coefficient(S). The K value can be used to calculate the flow velocity of ground water and of any dissolved phase constituents migrating in the ground water. The T and S values can be used to estimate long term aquifer yield, the size of cones of depression around pumping wells,and the size and shape of capture zones associated with pumping wells. This section discusses the methods and procedures used to evaluate the aquifer parameters.The _ procedures for analyzing the constant-rate pumping and recovery tests included downloading and conversion of the data from automated data loggers,correction of the data,selection and implementation of the appropriate aquifer analysis methods,and evaluation of the results. Data Handling and Processing Ten observation wells were monitored for changes in water levels associated with pumping of wells -1 and -2. Water levels were measured with downhole pressure transducer/data logger monitors(Trolls)throughout the recovery and pumping test phases,and were also measured manually during portions of the test. The Troll water level data were downloaded onto a laptop computer and evaluated every four to twelve hours to determine when each phase of the aquifer test could be terminated. The water level data files were processed by importing them into a spreadsheet software package (EXCEL)and combining the individual data files from a given data logger. Chronological gaps in the data files between the end of one test phase and the start of the next test phase at a given well were corrected by comparing times in the field log book with starting and ending times as indicated in the data files. In addition,the Troll data for new test phases had the initial water level set equal - to a drawdown of zero,so water level data in these situations was corrected by adding a constant value equal to the observed drawdown from the previous aquifer test phase. This step was undertaken to verify that the Trolls were recording data correctly at the start of each new test phase. All water level data were plotted and reviewed graphically for these and other data handling issues. The analytical methods used to evaluate the aquifer test data contain a variety of simplifying - assumptions which make the complex mathematics of the analytical methods solvable. Some of the assumptions include: • a constant aquifer saturated thickness, • an insignificant amount of water stored in the borehole of the pumping well. • a constant pumping rate at the pumping well, CDM Camp Dresser&McKee CS 0 D-5 W:IREPORTS4City of 10f Stockton 199 52 08550006