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Aquifer Testing Standard Operating Procedure SWE-FSOP-500,•Revision 0 Ahtna Southwest Environmental Operations 4.2 Slug Test Method A slug test is an aquifer test in which the water level in a well is changed by removing,adding,or displacing a known volume of water. The water level response is monitored in the slugged well. The water level response is generally proportional to aquifer transmissivity and hydraulic conductivity. A known volume of water can be removed relatively rapidly from the well with a submersible pump or bailer. Potable water can be added rapidly to a well by directly dumping from barrels or holding tanks. However, the most common method in environmental projects involves inserting and removing a solid slugging rod (or pig), which instantaneously displaces the water inside the well. Water levels may be measured with an electric tape during testing if the wells recharge slowly. However, pressure transducers(with associated data loggers) are more commonly used to measure water levels as they can record a large number of measurements on a more rapid basis. Many brands of transducer/data logger packages can pre-program the measurement rate, obtaining frequent measurements during the initial portions of the test and less frequent measurements near the end as the water level slowly stabilizes. The below procedures are used with a slugging rod and pressure transducer/data logger during slug testing.These procedures also cover slug insertion and slug withdrawal portions of slug testing. In certain instances,only the slug withdrawal test data are used for analysis. However, it is advisable to conduct the slug insertion test even if only using the withdrawal test data to evaluate aquifer parameters. The slug insertion test can provide information to make necessary adjustments to the withdrawal test in the field. The procedures described below are readily adaptable for the other slug testing methods. The project work plans will outline specific slug testing methods and procedures. • Any newly installed wells to be slug-tested must be developed before beginning slug testing activities. • Inspect the equipment to ensure that it is in good working order.Aquifer slug test equipment will vary widely depending on the formation, other site conditions,the diameter and depth of the wells, and the number of wells to be tested.The project work plans will outline the type of equipment to be used. • All measuring and testing equipment (M&TE) used for field activities will be calibrated by the equipment manufacturer or an approved calibration laboratory using standards that are traceable to the National Institute of Standards and Technology (NIST). Certificates of calibration for M&TE will be obtained from the M&TE supplier and kept in the project files. No M&TE will be utilized without verification of calibration certification. • Decontaminate all downhole equipment according to SWE-FSOP-801. Suppose the contaminant histories of the wells to be tested are known or anticipated. In that case,the slug tests should be performed, starting with the least contaminated well and ending with the most contaminated. It is recommended to replace the braided rope or line that has been submerged during slug testing of one well before moving on to another.These practices will reduce the potential for cross-contamination between wells. • Visually inspect and access the wellhead per SWE-FSOP-602. Page 9 of 17