Variations in hydraulic conductivity (K) between larger scale aquifer tests and smaller scale slug tests, and within individual aquifer tests, have been linked to method bias and aquifer heterogeneity. The impacts of varying slug sizes on K, which represents K dependence on a smaller scale, is not as well understood. To examine the relationship between K and slug size, a series of slug tests with a range of initial displacements were performed in three intermediate to high K, unconfined aquifers encompassing homogeneous, mildly heterogeneous, and moderate to highly heterogeneous conditions. Slug test estimated K values at Asylum Lake are compared to K values derived from a 28-hour aquifer pumping test to examine for method bias. A statistically significant increase in hydraulic conductivity with decreasing scale, or in this case slug size, was only found at the Grand Rapids site and is likely related to turbulent energy loss in the porous media surrounding the well screen for the largest slugs. Additionally, a series of multi-well pneumatic slug tests were performed at Asylum Lake in hopes of obtaining reliable storage parameters comparable to an aquifer pumping test and testing the effect of slug size on storage parameters. Results indicate that multi-well tests can produce reliable Ss estimates representative of the aquifer. Lastly, guidelines were developed for performing pneumatic slug testing in the field using a newly designed pneumatic slug unit.

The slug test can provide valuable information for hydrogeologic investigations ranging from assessments of sites of groundwater contamination to the monitoring of well deterioration through time. Inappropriate procedures in one or more phases of a test program, however, can introduce considerable error into the resulting parameter estimates. The Design, Performance, and Analysis of Slug Tests, Second Edition remedies that problem by explaining virtually all there is to know regarding the design, performance, and analysis of slug tests. The first edition has become the standard reference for all aspects of slug tests; this revised edition updates the earlier material and expands the topical coverage with new developments that have come to the fore in the intervening years between editions. Features: Describes and demonstrates the eight key steps for the performance and analysis of slug tests Presents new methods for the analysis of tests in unconfined aquifers and in highly permeable settings Expands topical coverage of LNAPL baildown tests and slug tests in small diameter wells Includes numerous flow charts that illustrate easy-to-use strategies for selection of analysis methods, and field examples demonstrate how each method should be used to get the most out of test data Offers straightforward practical guidelines that summarize the major points of each chapter Written for practicing groundwater consultants and engineers, The Design, Performance, and Analysis of Slug Tests, Second Edition will enable readers to get more reliable information from slug tests and increase the utility of this widely-used field method.

The slug test is currently the most common method for the in situ estimation of hydraulic conductivity at sites of suspected groundwater contamination. However, inappropriate procedures in one or more phases of a slug test can introduce considerable error into the resulting parameter estimates. This book remedies this problem by answering virtually every question regarding the design, performance, and analysis of slug tests. This is the first book to provide detailed information on the practical aspects of the methodology of slug tests. All major analysis methods are described in The Design, Performance, and Analysis of Slug Tests. Each analysis method is outlined in a step-by-step manner and illustrated with a field example. The major practical issues related to the field application of each technique are also discussed. This book will help the reader get more reliable parameter estimates from slug tests and increase the utility of slug test data.

Slug test methods are used to determine in situ aquifer hydraulic conductivity more quickly and economically than a pump test can. This study compares slug test methods for unconfined aquifers, looking at how to conduct a test using a physical slug, and at different analysis methods including Bouwer and Rice (1976), Kansas Geological Survey (KGS 1994), Hvorslev (1951) and Dagan (1978). Questions that motivated this study include: How well does the Bouwer and Rice method work? What is the most effective way to conduct a slug test? Does using a large physical slug relative to the well diameter and volume yield better results than a small slug? Do large initial water level displacements produce better results than small displacements? Ten wells were slug tested at two sites: a 2.00 m diameter culvert installed vertically in a 2.28 m deep hole and backfilled with uniform sand, and a natural unconfined aquifer. All wells were 0.050 m in diameter, and were tested using two sizes of slug rods, one that was half of the well diameter, and the other was three quarters of the well diameter. K values calculated from tests at both sites show that the Hvorslev values are 37 percent higher than the Bouwer and Rice results. Bouwer and Rice, Dagan and KGS K values are noticeably lower than Hvorslev Ks; the difference is statistically significant. Hydraulic conductivity values obtained from tests using a large slug rod are 1.5 times larger than Ks obtained using a smaller slug rod, regardless of analysis method chosen. The size of initial water level displacement was positively correlated with calculated K values for tests performed using the large slug but not for tests using the smaller slug. The question "Do large initial water level displacements produce better results than small displacements?" remains unresolved.

This research presents a hydraulic conductivity (K) analysis of unconfined aquifers using slug tests. Slug tests are used to determine in situ aquifer hydraulic conductivity more quickly and economically than by a pump test. This study examines how to best conduct a slug test using a physical slug. Different common slug test analysis methods are compared, including Bouwer and Rice (1976), Hvorslev (1951), Dagan (1978) and Kansas Geological Survey (KGS, 1994). Questions that motivated this study include: Which methods are better for performing and analyzing slug tests? Does the size of the physical slug affect the results? Do large initial water level displacements produce better results than smaller displacements? Slug tests were performed at two sites: 1- Asylum Lake in Kalamazoo, Michigan, in a well 0.33 ft in diameter and 97 ft deep. 2- Another unconfined aquifer in Portage, Michigan, in wells 0.167 ft in diameter and relatively shallow depth of 16 ft. Both sites were slug tested using two different sizes of physical slug rods. The smaller slug was 5 ft in length with 0.12 ft diameter. The larger slug was 6.91 ft long and 0.125 ft in diameter. The four-way analysis of variance (ANOVA) examination of 39 slug tests on wells in these two aquifers confirmed that log K depends highly significantly upon slug in/out, and as expected, the aquifer tested. What was not expected was the average log K for tests in 5-cm diameter wells using slug in was highly significantly larger than average log K for tests using slug out; these means also differed significantly by slug size. Importantly, mean log K’s produced by the Hvorslev (1951) method are highly significantly larger than mean log K’s produced by the other three methods above. The size of the initial water-level deflection, Yo, does not affect the results for log K. The use of a larger or smaller slug does not significantly affect the log K values. Finally, assuming that a large K value better represents the true value, closer to a pump test K value, Hvorslev (1951) gives the largest K values.

This edition serves as a resource for field practitioners in the planning, performance, and analysis of slug tests that will produce more reliable parameter estimates. It updates the previously presented material and expands the coverage into new areas. It includes a new set of practical guidelines for the design, performance, and analysis of slug tests; all new field examples; extensive coverage of slug tests in wells; considerations for barometric pressure changes; and discussions of new software for the processing and analysis of slug-test data.