Slug tests for determining hydraulic conductivity of natural geologic deposits

This paper reviews four methods for analyzing slug test data to determine hydraulic conductivity and examines the effects of slug size on slug test results. Data from more than 100 slug tests, including tests for low permeability (glacial tills and fractured rock) deposits, coarse-grained (sand) deposits, and simulated tests were analyzed. Analysis of the data showed that all four analytical methods can produce similar values of hydraulic conductivity for low permeability deposits. Values determined for coarser deposits were highly dependent on method; values commonly spanned up to two orders of magnitude. The method of Cooper et al. (1967) generally produced the highest values, followed by the methods of Bouwer and Rice (1976), Hvorslev (1951), and Nguyen and Pinder (1984). For sandy materials, tests were repeated on each well using several different slug sizes, ranging from 0.5 to 6 meters. Several of the glacial till materials were tested using two different slug sizes. Calculated hydraulic conductivity values were independent of these slug sizes.