Funding for this work was provided by an NSERC Industrial Research Chair (n. IRCPJ 363783) to Professor Beth Parker in partnership with the Boeing Company. Field work was supported by the site owner, their consultants (MWH Inc., now Stantec), and University of Guelph colleagues, especially Amanda Pierce from the G360 Institute for Groundwater Research. The authors also thank Dr. Nicholas M. Johnson from Stantec for helpful comments.
Eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern California, with thickness varying between 10 and 62 m, were analyzed for chloride (Cl) concentration to examine recharge mechanisms, estimate travel times in the vadose zone, assess spatial and temporal variability of recharge, and determine effects of land use changes on recharge. As a function of their location and the local terrain, the profiles were classified into four groups reflecting the range of site characteristics. Century- to millennium-average recharge varied from 4 to 23 mm y−1, corresponding to <1–5% of the average annual precipitation (451 mm over the 1878–2016 period). Based on the different average Cl concentrations in the vadose zone and in groundwater, the contribution of diffuse flow (estimated at 80%) and preferential flow (20%) to the total recharge was quantified. This model of dual porosity recharge was tested by simulating transient Cl transport along a physically based narrow column using a discrete fracture-matrix numerical model. Using a new approach based on partitioning both water and Cl between matrix and fracture flow, porewater was dated and vertical displacement rates estimated to range in the sandstone matrix from 3 to 19 cm y−1. Moreover, the temporal variability of recharge was estimated and, along each profile, past recharge rates calculated based on the sequence of Cl concentrations in the vadose zone. Recharge rates increased at specific times coincident with historical changes in land use. The consistency between the timing of land use modifications and changes in Cl concentration and the match between observed and simulated Cl concentration values in the vadose zone provide confidence in porewater age estimates, travel times, recharge estimates, and reconstruction of recharge histories. This study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location-specific recharge histories in fractured porous rock aquifers. The proposed approach can be applied worldwide at sites with similar climatic and geologic characteristics.
CaMI (Containment and Monitoring Institute), a business unit of CMC (Carbon Management Canada) established the Brooks field research station (FRS) to facilitate and accelerate research for geological containment and storage of CO2 as one of its many goals. Carbon capture and storage is a key component of Canada’s strategy for continued development of unconventional oil and gas deposits under growing global pressure to move toward a low carbon economy.
The G360 Institute for Groundwater Research, with Dr. Beth Parker as the Principal Investigator, have developed a growing collaboration with CaMI to lead the groundwater monitoring aspects of the study at the FRS. The primary focus of the G360 team, with Leon Halwa as Project Manager, will be to lead the groundwater characterization and monitoring of the shallow and intermediate zones before, during and after injection of the CO2, to better understand the mobility of stray gas.
On the 24th October 2017, CaMI had an official opening and celebration of the start of the injection program, after a decade of planning, collaborations and investments. The event was well attended with a turnout of over 70 people. The event is shown on the university of Calgary website at:
We are pleased to announce that three G360 team members were awarded the BP Safety Star in June of this year for their safe practices while performing field work at the Alice Street Site, a site that has been an active G360 research site as part of an NSERC CRD project under Dr. Beth Parker since 2014.
Here is an extract of the award nomination:
“During a Senior Management Observation, it was observed that the three University of Guelph students working on the project did an excellent job in identifying trip and slip hazards at the job site. A packer test was being performed on a well in order to measure vertical temperature changes in the well in order to evaluate groundwater flow in the bedrock. As part of the test, there were coils of wiring and tubing laying on the ground between the well and support trailer. The students placed caution tape around the area and placed several traffic cones on the edges. This was implemented on their own without any coaching or comments from AECOM supervisors. I personally thanked them and recognized them for doing a great job in identifying hazards and making the work area safe.”
Congratulations to Jonathan Munn, Carlos Maldaner, and Jeremy Fernandes.
We are pleased to announce the publication of a new open access journal article in the Journal of Contaminant Hydrology by G360 researchers in collaboration with researchers from the Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia.
Fugitive methane (CH4) leakage associated with conventional and unconventional petroleum development (e.g., shale gas) may pose significant risks to shallow groundwater. While the potential threat of stray (CH4) gas in aquifers has been acknowledged, few studies have examined the nature of its migration and fate in a shallow groundwater flow system. This study examines the geophysical responses observed from surface during a 72 day field-scale simulated CH4 leak in an unconfined sandy aquifer at Canadian Forces Base Borden, Canada, to better understand the transient behaviour of fugitive CH4 gas in the subsurface. Time-lapse ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) were used to monitor the distribution and migration of the gas-phase and assess any impacts to groundwater hydrochemistry. Geophysical measurements captured the transient formation of a CH4 gas plume emanating from the injector, which was accompanied by an increase in total dissolved gas pressure (PTDG). Subsequent reductions in PTDG were accompanied by reduced bulk resistivity around the injector along with an increase in the GPR reflectivity along horizontal bedding reflectors farther downgradient. Repeat temporal GPR reflection profiling identified three events with major peaks in reflectivity, interpreted to represent episodic lateral CH4 gas release events into the aquifer. Here, a gradual increase in PTDG near the injector caused a sudden lateral breakthrough of gas in the direction of groundwater flow, causing free-phase CH4 to migrate much farther than anticipated based on groundwater advection. CH4 accumulated along subtle permeability boundaries demarcated by grain-scale bedding within the aquifer characteristic of numerous Borden-aquifer multi-phase flow experiments. Diminishing reflectivity over a period of days to weeks suggests buoyancy-driven migration to the vadose zone and/or CH4 dissolution into groundwater. Lateral and vertical CH4 migration was primarily governed by subtle, yet measurable heterogeneity and anisotropy in the aquifer.
This research was made possible through an NSERC Strategic Partnerships Grant Project (SPG-P) awarded to Drs. John Cherry and Beth Parker (principal investigators), and collaborators Drs. Bernhard Mayer, Ulrich Mayer and Cathryn Ryan. Dr. Aaron Cahill provided a major role with proposal writing, experimental design and overall project management, both with field implementation and project reporting, and is now a research associate at the University of British Columbia Department of Earth, Oceanic and Atmospheric Sciences. An NSERC Banting Fellowship provided support to Dr. Colby Steelman.