Cross-Hole Heat Tracer Tests to Assess Groundwater Flow in Fractured Rock: Successes and Lessons Learned
Tuesday, September 24, 2013: 3:25 p.m.
Peeter Pehme, Ph.D.
,
School of Engineering, G360, University of Guelph, Guelph, ON, Canada
Leanne Burns, M.Sc., P.Eng.
,
Golder Associates Ltd., Mississauga, ON
Beth L. Parker, Ph.D.
,
School of Engineering, G360, University of Guelph, Guelph, ON, Canada
John A. Cherry, Ph.D.
,
School of Engineering, University of Guelph, Guelph, ON, Canada
Characterization of groundwater flow through fractured rock is essential for assessing and predicting contaminant plume migration but is both difficult to perform and costly, while often yielding uncertain interpretations. Solute tracer tests are informative, but subject to regulatory approval. Furthermore, introduction and extraction of water as well as the use of conventional wells or boreholes with long open sections disturb the very environment being characterized. The combination of high sensitivity temperature techniques and removable borehole liners to eliminate cross-connection provide an improved means of using temperature as an innocuous tracer. Heat can be introduced under natural hydraulic gradients to assess ambient groundwater through fractured rock and provide a guide to a potentially complex flow/fracture pattern and the process can be easily repeated. This describes tests wherein heat is used as a tracer in fractured rock, the successes achieved, and lessons learned.
Three boreholes (each 150m deep, in a triangular pattern of ~10m sides, lined with FLUTeä sleeves) in Cambridge, Ontario, were used for the tests. The “natural” gradient in the area is controlled by several distant municipal pumping wells. The entire length of the upgradient borehole of the trio was heated for 5d in one test and 14d in a repeat experiment. Temperatures along the length of all three boreholes were measured regularly over the test periods.
In the first test an initial breakthrough arrived in one well after 49hrs of testing, resulting in a conservative estimate of groundwater velocity as 3.4m/d. The initial 0.050C¢ª response increased in magnitude and expanded to additional fractures/depths over the following 41hr, highlighting a complex distribution of numerous flow conduits. The repeat of the test did not provide as dramatic a result, presumably due to changes in the ambient groundwater flow direction; however, valuable insight was gained for planning additional cross-hole heat tracer tests.
Peeter Pehme, Ph.D., School of Engineering, G360, University of Guelph, Guelph, ON, Canada
Pete Pehme is the president of Waterloo Geophysics Inc. as well as a Research Associate In the G360 Group and an adjunct professor at the University of Guelph. He earned Ph.D. and M.Sc. degrees in Hydrogeology/Geophysics, from the University of Waterloo. His over 30 years of experience includes the application of a wide variety of surface and borehole geophysical techniques to hydrogeological and geotechnical investigations. Pehme provides support to the G360 research program at the University of Guelph, developing and combining innovative borehole geophysical technologies with hydrophysical techniques investigating flow through fractured rock.
Leanne Burns, M.Sc., P.Eng., Golder Associates Ltd., Mississauga, ON
Leanne Burns is a Professional Engineer and Project Manager in Golder’s GTA Operations – Mississauga office with over 10 years of experience focusing on site management through environmental site investigation and remediation, assessment of site management options, and site restoration through risk assessment. Burns has a bachelor’s degree in Civil Engineering and a master’s degree in Earth Sciences (Contaminant Hydrogeology) from the University of Waterloo. While at Waterloo, her field-based research focused on behavior and transport of dense non-aqueous phase liquids (DNAPLs) in fractured-rock environments within the Cambridge dolostone aquifer.
Beth L. Parker, Ph.D., School of Engineering, G360, University of Guelph, Guelph, ON, Canada
Beth Parker, Ph.D., University of Guelph Professor in the School of Engineering and Director of the G360 Centre for Applied Groundwater Research, has more than 30 years of experience investigating subsurface contamination at numerous sites around the world, using high resolution data sets for site conceptual model development and testing. Her current research activities emphasize developing improved field and laboratory methods for characterizations and monitoring of industrial contaminants in sedimentary rocks, clayey deposits, and sandy aquifers, and focus on the effects of diffusion in low permeability zones, plume attenuation, and hydrogeologic controls on remediation.
John A. Cherry, Ph.D., School of Engineering, University of Guelph, Guelph, ON, Canada
John Cherry holds geological engineering degrees from the University of Saskatchewan and the University of California Berkley, and earned a Ph.D. in hydrogeology from the University of Illinois. He joined the University of Waterloo in 1971, concentrating on field studies of the migration and fate of contaminants in groundwater, and continues research as a Distinguished Professor Emeritus. He has co-authored the textbook Groundwater and several chapters in the book on dense chlorinated solvents and other DNAPLs in groundwater. He is the Director of the University Consortium for Field-Focused Groundwater Contamination Research and is now based at the University of Guelph.
