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

Holloway, Owen G.; Waddell, Jonathan P.

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.

Genre:

USGS Numbered Series

ProdID:

97194

Citation Author:

Holloway, Owen G.; Waddell, Jonathan P.

Citation Contributing Office:

Georgia Water Science Center

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Citation Language:

ENGLISH

Citation Larger Work Title:

Citation LatN:

0335700

Citation LatS:

0335400

Citation LonE:

-0843000

Citation LonW:

-0843245

Citation Month:

Dec

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Citation Phsyical Description:

vi, 24 p.

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Citation Public Comments:

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

Citation Publisher:

U.S. Geological Survey

Citation Series:

Open-File Report

Citation Series Code:

OFR

Citation Series Number:

2008-1349

Citation Search Results Text:

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; 2008; OFR; 2008-1349; Holloway, Owen G.; Waddell, Jonathan P.