Abstracts

cross-sections to look for consistency with regional sequence stratigraphy and other bedrock
mapping studies. Continuous surfaces were then generated from the HGU picks and
used as the framework for the numerical model. This study provides an example of how
high resolution site scale characterization provides the data necessary to calibrate hydraulics
to geologic features resulting in a robust HGU framework and confidence in extending
that framework to the full flow system scale.
292 - Parameter Estimation in a Regional Groundwater Flow
Model to Represent Site-Specific High Resolution Head Profiles
Steven G. Shikaze, Beiyan Zhang & Daron G. Abbey
Matrix Solutions Inc., Breslau, Ontario, Canada
Jessi R. Meyer & Beth L. Parker
G360 Centre for Applied Groundwater Research, School of Engineering, University of
Guelph, , Ontario, Canada
In the 1950s and 60s, over 70,000 L of dense non-aqueous phase liquid (DNAPL) was
released into the subsurface at a site in Wisconsin. In the 1980s, contamination (chlorinated
solvents, BTEX, ketones) was discovered in the bedrock. Groundwater flow through
the source zone has resulted in a dissolved-phase plume that has migrated approximately
3 km downgradient. Remediation activities in the 1990s and 2000s included air sparging,
DNAPL pumping, and hydraulic barrier wells. Over the past 11 years, researchers from
the University of Guelph (UG) have been studying the site. This has included extensive
field operations to understand of the groundwater flow system at the site. UG has collected
high-resolution vertical hydraulic head data at various locations across the site, and this
information has been used to inform an evolving site conceptual model.
Groundwater modelling studies began in 2010 to aid in the understanding of the groundwater
flow regime. A regional scale, three-dimensional groundwater flow model was constructed
in FEFLOW. This model covers an area of approximately 300 km 2 and includes
nearby communities that rely on groundwater water. The model is refined in the area of
interest, which encompasses the plume area (approximately 16 km 2 ). Using the detailed
on-site data as well as the sparser off-site data, the FEFLOW model was constructed
from a site conceptual model that includes 21 model layers (6 overburden and 15 bedrock).
Initial estimates for the hydraulic properties of these layers were based on UG’s hydraulic
testing and detailed examination of borehole logs.
Parameter estimation (PEST) software (Doherty, 2010) has been used in conjunction with
the steady-state groundwater flow model in FEFLOW. PEST was used to adjust the
input parameters (i.e., hydraulic conductivity (K), anisotropy (K h
/K v
), recharge) to obtain a
good match with observed hydraulic heads. Emphasis has been placed on matching UG’s
high-resolution vertical head data on site. Preliminary results suggest that the initial estimates
for the range in K for most model layers need to be wider than the initial estimates.
By expanding the K range in PEST, a better match with the vertical head measurements
was attained. The results from this numerical analysis can be used to inform the site conceptual
model.
78 IAH-CNC 2015 WATERLOO CONFERENCE