HR: 0800h
AN: H51E-02    [Abstracts]
TI: A Comparison Between Solute Transport in a Discrete Fracture and in a Fracture Network Using a Novel Method for Tracer Detection
AU: Moore, B H
EM: brian@civil.queensu.ca
AF: Queen's University Civil Engineering Department, Ellis Hall, Queen's University, Kingston, ON K7L 3N6, Canada
AU: Novakowski, K S
EM: kent@civil.queensu.ca
AF: Queen's University Civil Engineering Department, Ellis Hall, Queen's University, Kingston, ON K7L 3N6, Canada
AU: * Schauerte, M
EM: morgan@civil.queensu.ca
AF: Queen's University Civil Engineering Department, Ellis Hall, Queen's University, Kingston, ON K7L 3N6, Canada
AB: Field scale characterization and modeling of transport in bedrock aquifers has become more widespread due to increasing occurrences of groundwater contamination in these settings. As a result of the difficulty in discrete sampling, the processes of large-scale transport in fractured rock aquifers are poorly understood. The objective of this study is to explore the transport of a tracer solute at large scale using in-situ technology which can identify breakthrough of tracer at discrete fracture locations within a borehole. The tracer experiment was conducted at a well characterized field site in Smithville, Ontario. The site is underlain by a flat-lying dolomite which is dominated by several large-scale bedding-plane fractures. A total of seven boreholes were used for this experiment, aligned closely to the direction of groundwater flow over a distance of approximately 200 m. For this experiment, water was injected to establish a flow field over the thickness of the upper aquifer (~10 m). The tracer was then introduced over a short period of time and the water injection was continued for an additional 69 hours. Lissamine FF, a conservative fluorescent dye, was used as a tracer. A submersible fluorometer was used to detect the tracer arrival in-situ and obtain vertical concentration profiles in each of the boreholes. Using the concentration profiles obtained with the fluorometer and based on previous hydraulic testing data, the dominate transport pathways were identified. A finite element model which solves for transport and flow in discrete fracture features (FRAC3DVS) was then used to simulate the tracer experiment and recreate the breakthrough curves measured in each borehole. The results of this modeling exercise were compared to those from a model study conducted on the results of a tracer experiment conducted previously in a single fracture at the same location. Assessment of the modeling studies at different scales provides insight into the difficulties of modeling transport at the network scale and into the importance of considering matrix interactions, and tortuous flow paths at either scale.
DE: 1832 Groundwater transport
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Joint Assembly