Abstracts

using parallel computing techniques. In assessing this case, sensitivities are tested to the
geochemical reaction schemes appropriate to the site. The results of this work predict the
chemical environment at repository depth stabilises at around 20,000 AD and shows little
change beyond that. The salinity of the groundwater is governed by the low permeability
(ca. 10 -19 m 2 ) of the bedrock and rock matrix diffusion, resulting in relatively shallow and
slow circulation of groundwater. The chemical reactions influence concentrations of reactive
species, including pH and redox potential. In particular, the redox reactions thought
to be relevant for the Forsmark site maintain reducing conditions at depth favourable to
repository performance, even with infiltration at the ground surface of meteoric water with
relatively high redox potential.
Groundwater/Surface Water Interaction 2
Wednesday, October 28, 13:00 – 14:40
Chair: Steven Berg
Room: Strauss
135 - Pressure Pulses as an Indication of Recharge to a Buried
Esker-Aquifer Eastern Ontario
Jacques Sauriol
Stantec Consulting Ltd., Ottawa, Ontario, Canada
Recharge pressure pulses from significant rainfall events were correlated to near-synchronous
hydraulic head responses in both the overlying muds and the buried Vars-Winchester
esker aquifer in Eastern Ontario. These correlations were analyzed to gain a better understanding
of the recharge processes in this paired-system. Although causation was only
suggested, a correlation was nonetheless established between rainfall events and aquifer
head response suggesting that there is a hydraulic connection between the mud and the
esker units. Strong cross-correlations with short lag times were calculated (0.9 at lag times
of between 0 and 3 hours). Furthermore, response sequencing for the radar precipitation
events generated at the study site showed that the pressure pulses arrived in the overlying
muds slightly before the underlying buried esker, indicating a downward migration of the
pressure pulses. Mud layering deformation in seismic surveys had previously been observed
in the over-esker muds. These disturbed stratigraphic elements provide an avenue for migrating
water to transit through the muds. This paper hypothesizes that recharge pressure
pulses can rapidly reach the buried esker across the over-esker unit transiting through
preferential flow paths in deformed mud sediments. This revised model of understanding
challenges the natural safeguard allegations of marine muds and defies the widespread acceptance
of the mode of recharge of buried aquifer limited at esker outcrop. These findings
have implications for Source Water Protection Strategies.
IAH-CNC 2015 WATERLOO CONFERENCE
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