U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of
the Technical Meeting Charleston South Carolina March 8-12, 1999--Volume 3
of 3--Subsurface Contamination From Point Sources, Water-Resources
Investigations Report 99-4018C
Borehole Packers for In Situ Geophysical and Microbial
Investigations in Fractured Rock
By Allen M. Shapiro, John W. Lane, Jr., and Joseph R. Olimpio
Abstract
Bedrock boreholes act as unnatural, high-permeability pathways that
can disturb ambient hydraulic and geochemical conditions in the
bedrock. To avoid the disturbances caused by open boreholes, many
investigations require the use of packers to isolate discrete
intervals of bedrock boreholes; packers are either pneumatic or
mechanical devices that seal against the borehole wall and
hydraulically isolate a section of the borehole. Usually, packers
are constructed with a metal core pipe and metal pressure-tight
fittings; in some in situ investigations, however, a
metal-free environment is required. Pneumatic borehole packers
were designed and constructed using a polyvinly-chloride (PVC)
core pipe and teflon pressure-tight fittings. These PVC packers
were used to conduct borehole radar surveys during hydraulic and
tracer testing, as metal in the borehole attenuates the radar
signal. The PVC packers also were used to collect water samples
for analysis of dissolved hydrogen to characterize redox
conditions at a hydrocarbon-contaminated fractured rock site, as
metal-water interactions are known to produce dissolved hydrogen.
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