Georgia Water Science Center

USGS Open-File Report 2008-1349

Design and Operation of a Borehole Straddle Packer for Ground-Water Sampling and Hydraulic Testing of Discrete Intervals at U.S. Air Force Plant 6, Marietta, Georgia

This Web-only publication is available online in pdf format (3 MB): USGS OFR 2008-1349 (Opens the PDF file in a new window. )

Owen G. Holloway and Jonathan P. Waddell

U.S. Geological Survey Open-File Report 2008-1349, 24 pages (Published December 2008)

Prepared in cooperation with the U.S. Air Force, Aeronautical System Center

ABSTRACT

A borehole straddle packer was developed and tested by the U.S. Geological Survey to characterize the vertical distribution of contaminants, head, and hydraulic properties in open-borehole wells as part of an ongoing investigation of ground-water contamination at U.S. Air Force Plant 6 (AFP6) in Marietta, Georgia. To better understand contaminant fate and transport in a crystalline bedrock setting and to support remedial activities at AFP6, numerous wells have been constructed that include long open-hole intervals in the crystalline bedrock. These wells can include several discontinuities that produce water, which may contain contaminants. Because of the complexity of ground-water flow and contaminant movement in the crystalline bedrock, it is important to characterize the hydraulic and water-quality characteristics of discrete intervals in these wells. The straddle packer facilitates ground-water sampling and hydraulic testing of discrete intervals, and delivery of fluids including tracer suites and remedial agents into these discontinuities.

The straddle packer consists of two inflatable packers, a dual-pump system, a pressure-sensing system, and an aqueous injection system. Tests were conducted to assess the accuracy of the pressure-sensing systems, and water samples were collected for analysis of volatile organic compound (VOCs) concentrations. Pressure-transducer readings matched computed water-column height, with a coefficient of determination of greater than 0.99. The straddle packer incorporates both an air-driven piston pump and a variable-frequency, electronic, submersible pump. Only slight differences were observed between VOC concentrations in samples collected using the two different types of sampling pumps during two sampling events in July and August 2005. A test conducted to assess the effect of stagnation on VOC concentrations in water trapped in the system’s pump-tubing reel showed that concentrations were not affected. A comparison was conducted to assess differences between three water-sampling methods—collecting samples from the well by pumping a packer-isolated zone using a submersible pump, by using a grab sampler, and by using a passive diffusion sampler. Concentrations of tetrachloroethylene, trichloroethylene and 1,2-dichloropropane were greatest for samples collected using the submersible pump in the packed-isolated interval, suggesting that the straddle packer yielded the least dilute sample.


CONTENTS

Abstract

Introduction

Purpose and Scope

Description of Study Area

Method of Study

Straddle-Packer Design

Early Straddle Packers

Design of AFP6 Straddle-Packer Systems

Water-Quality Trailer

Tubing and Cable Reel Assembly and Trailer

Inflatable Packers

Dual-Pump System

Pressure-Sensing System

Aqueous Injection System

AFP6 Straddle-Packer Operation

Deployment of Straddle Packer

Isolation of Interval

Interval Purging and Ground-Water Sample Collection

Testing of Hydraulic Properties

Decontamination of Straddle Packer

Assessment of Straddle-Packer Performance

Pressure Sensing System

Dual-Pump System

Effect of Tubing Reel on Ground-Water Sample Collection

Sampling Method Comparison

Summary

Acknowledgments

Selected References

 


Suggested citation:
Holloway, O.G., and Waddell, J.P., 2008, Design and operation of a borehole straddle packer for ground-water sampling and hydraulic testing of discrete intervals at U.S. Air Force Plant 6, Marietta, Georgia: U.S. Geological Survey Open-File Report 2008–1349, 24 p., Web-only publication available at http://pubs.usgs.gov/of/2008/1349/

REPORT AVAILABILITY

This Web-only publication is available online in pdf format (3 MB): USGS OFR 2008-1349 (Opens the PDF file in a new window. )
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