Abstracts

227 - Deep-Seated Aquiclude Groundwater Systems: Advances in
In Situ Hydraulic Testing
Richard L. Beauheim
Consulting Hydrogeologist, Grand Junction, Colorado, USA
Randall M. Roberts
HydroResolutions LLC, Parshall, North Dakota, USA
John D. Avis
Geofirma Engineering Ltd., Ottawa, Ontario, Canada
Mark Jensen
Nuclear Waste Management Organization, Toronto, Ontario, Canada
A key aspect of groundwater studies in deep-seated aquiclude systems relates to the estimation
of formation-scale physical hydrogeological properties. Within such extremely
low permeability (>10 -20 m 2 ), low storage (S s
≈10 -6 m -1 ), and typically saline groundwater
systems, this presents unique challenges. As part of site-characterization activities for a
proposed Deep Geologic Repository (DGR) for low- and intermediate-level radioactive
waste at the Bruce nuclear site, 90+ straddle-packer (30-m interval) tests were performed
in Silurian- and Ordovician-age shale and carbonate sediments intersected by 6,
150-mm-diameter vertical or dipping (60-65° from horizontal) boreholes separated by
approximately 1200 m. Estimates of in situ horizontal rock mass hydraulic conductivity
(K) within these Paleozoic-age sediments ranged between 2x10 -16 and 4x10 -8 m/s. The
tests were performed with a purpose-built straddle-packer assembly that included a surface-actuated
downhole valve and a fixed-volume downhole pulse generator. A typical test
sequence in the lower permeability sediments required a 3-day cycle involving multiple
pulses with real-time analysis to assess adequacy of data for detailed analysis. In addition
to hydraulic conductivity, estimates of static formation hydraulic heads were obtained that
indicated the presence of abnormal formation underpressure (≈250 m+) conditions within
the Ordovician sediments, since confirmed by Westbay multi-packer installations in the
boreholes. Estimates of K derived from the field tests of the low-permeability Cobourg
Formation compare favorably to estimates from laboratory tests on core samples (≈10 cm)
and to natural analogue formation-scale (≈100+ m) data. This presentation will describe
the borehole testing methodology and a comparison of test results to complementary measurements
in establishing a basis to assess aquiclude hydraulic properties.
170 - Pore Fluid Pressures in the Ordovician Sediments at
the Bruce site near Kincardine, Ontario: Potential Causes and
Analysis
Stefano D. Normani, Yong Yin & Jonathan F. Sykes
Department of Civil and Environmental Engineering – University of Waterloo, Waterloo,
Ontario, Canada
Site-specific analogues provide a unique means to assess groundwater system properties
and behaviour at time and space scales not otherwise achievable. Formation pressure head
measurements within low permeability Silurian to Cambrian age sediments on the east-
48 IAH-CNC 2015 WATERLOO CONFERENCE