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Title: Modeling cross-hole slug tests in an unconfined aquifer

Abstract

Cross-hole slug test date are analyzed with an extended version of a recently published unconfined aquifer model accounting for waterable effects using the linearized kinematic condition. The use of cross-hole slug test data to characterize aquifer heterogeneity and source/observation well oscillation parameters is evaluated. The data were collected in a series of multi-well and multi-level pneumatic slug tests conducted at a site in Widen, Switzerland. Furthermore, the tests involved source and observation well pairs separated by distances of up to 4 m, and instrumented with pressure transducers to monitor aquifer response in discrete intervals.

Authors:
 [1];  [2];  [3];  [4]
  1. California Polytechnic State Univ., San Luis Obispo, CA (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  3. AF-Consult Switzerland Ltd., Dattwil (Switzerland)
  4. ETH Zurich, Zurich (Switzerland)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1254150
Report Number(s):
SAND-2015-10322J
Journal ID: ISSN 0022-1694; 611808
Grant/Contract Number:
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Hydrology
Additional Journal Information:
Journal Volume: 540; Journal ID: ISSN 0022-1694
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; cross-hole slug tests; multi-level; unconfined aquifer; hydraulic conductivity; specific storage; specific yield

Citation Formats

Malama, Bwalya, Kuhlman, Kristopher L., Brauchler, Ralf, and Bayer, Peter. Modeling cross-hole slug tests in an unconfined aquifer. United States: N. p., 2016. Web. doi:10.1016/j.jhydrol.2016.06.060.
Malama, Bwalya, Kuhlman, Kristopher L., Brauchler, Ralf, & Bayer, Peter. Modeling cross-hole slug tests in an unconfined aquifer. United States. doi:10.1016/j.jhydrol.2016.06.060.
Malama, Bwalya, Kuhlman, Kristopher L., Brauchler, Ralf, and Bayer, Peter. 2016. "Modeling cross-hole slug tests in an unconfined aquifer". United States. doi:10.1016/j.jhydrol.2016.06.060. https://www.osti.gov/servlets/purl/1254150.
@article{osti_1254150,
title = {Modeling cross-hole slug tests in an unconfined aquifer},
author = {Malama, Bwalya and Kuhlman, Kristopher L. and Brauchler, Ralf and Bayer, Peter},
abstractNote = {Cross-hole slug test date are analyzed with an extended version of a recently published unconfined aquifer model accounting for waterable effects using the linearized kinematic condition. The use of cross-hole slug test data to characterize aquifer heterogeneity and source/observation well oscillation parameters is evaluated. The data were collected in a series of multi-well and multi-level pneumatic slug tests conducted at a site in Widen, Switzerland. Furthermore, the tests involved source and observation well pairs separated by distances of up to 4 m, and instrumented with pressure transducers to monitor aquifer response in discrete intervals.},
doi = {10.1016/j.jhydrol.2016.06.060},
journal = {Journal of Hydrology},
number = ,
volume = 540,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
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  • Double packer slug tests (DPST) characterize the vertical distribution off horizontal hydraulic conductivity (K{sub r}) in aquifers. In a DPST, pneumatic packers and a riser pipe are used to isolate a portion of the well screen, then the water level is changed, and the recovery response is recorded. The recovery response can be nonoscillatory or oscillatory depending on K{sub r} for the surrounding aquifer material and the water column length. K{sub r} is derived from analysis of the slug test response. DPST were performed at 156 elevations in seven fully and four partially penetrating wells at the Nebraska MSEA Site,more » near Shelton, Nebraska. The DPST apparatus includes three pipes of differing diameter. Springer and Gelhar`s (1991) method was modified to account for loss of momentum due to contractions and enlargements in the pipes. The resulting initial value problem for drawdown y(t), normalized by initial displacement is: y{double_prime} + F(y)y{prime} + H(y)y = {minus}G(y,y{prime})(y{prime}){sup 2} y(0) = {minus}1; y{prime}(0) = 0. The coefficients F, H, and G depend on well geometry and hydraulic conductivity. The equation was solved using 4th order Runge-Kutta method (Press et al. 1989). Algorithm for identification of K{sub r} was based on minimization of squared difference between observed and simulated well response in time. The method was applied to oscillatory and nonoscillatory responses. K{sub r} values are 28--192 m/day (K{sub r}/K{sub Z} = 1) and 36--250+ m/day (K{sub r}/K{sub Z} = 10). The K{sub r} profile obtained using the DPST results matches the profile obtained from grain size analysis. The mean well average K{sub r} for well in the pumping test area is 85 m/day (K{sub r}/K{sub S} = 1) and 125 m/day (K{sub r}/K{sub S} = 10).« less
  • Abstract not provided.
  • Aquifer test methods available for characterizing hazardous waste sites are sometimes restricted because of problems with disposal of contaminated ground water. Partly for this reason, slug tests have become a popular method for determining hydraulic properties at such sites. Slug interference responses within unconfined aquifers are characterized by an initial wave or hump, which is followed by a flat transitional plateau region and then by a declining, recessional limb segment. The shape and amplitude of the initial wave are primarily controlled by the elastic characteristics (i.e., S) and degree of anisotropy within the aquifer, while transmissivity is the principal parametermore » affecting the transmission (i.e., arrival time) of the slug interference response. Wellbore storage and delayed-yield effects tend to attenuate the test response. The transitional and late-time recessional segments are significantly influenced by the aquifer`s specific yield. In addition, test well/aquifer relationships, e.g., observation well distance, aquifer thickness, and well depth/aquifer penetration, also strongly affect slug interference characteristics. The sensitivity of the propagated response to test well/aquifer relationships indicates that slug interference tests can be designed to maximize the expected response for aquifer property characterization.« less
  • Slug interference testing may be particularly useful for characterizing hydraulic properties of aquifer sites where disposal of contaminated ground water makes pumping tests undesirable. The design, performance, and analysis of slug interference tests for two field test examples are presented. Results were compared with standard constant-rate pumping tests. The comparison indicates that slug interference tests provide estimates comparable to those obtained from short duration pumping tests for the determination of transmissivity, storativity, and vertical anisotropy. The close agreement in hydraulic property values obtained using the two test methods suggests that slug interference testing, under favorable test conditions (for example, observationmore » well distances {le}30 m), can provide representative aquifer characterization results. The quality and extent of test data obtained also indicate the potential use of slug interference testing for three-dimensional hydrologic characterization investigations, when conducted using multilevel monitoring facilities.« less