November 29, 2021

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Frederic Cosme and Carol Cheyne to Present on Groundwater Remediation at the EcoForum 2021 Conference in Australia

Frederic Cosme, CPEng, Ir. (Victoria, Australia) and Carol Cheyne (Ontario, Canada) will present at the EcoForum 2021 Conference on Wednesday, December 1st, 2021.

Frederic's presentation is entitled "High Precision Downhole Fluorometer: A Cost-Effective Tool to Characterise and Support Remediation of Fractured Rock." Carol's Presentation is entitled "Evaluating an In Situ Groundwater Remediation Technology Using a Comprehensive CSIA Dataset." Frederic was also part of the organizing committee for the conference.

Frederic Cosme is a Principal Engineer based in Melbourne, Victoria, Australia with more than 20 years of experience focused on environmental consulting and hydrogeology. Frederic helps clients convert scientific outcomes of investigations into practical remedial engineering design considerations and tangible risk-based results.

Carol is an Environmental Scientist based in Guelph, Ontario, Canada with a focus on chemistry. Her work is focused on providing clients with solutions to their contaminated soil, sediment, and groundwater problems. She is experienced in conducting field and laboratory studies pertaining to the assessment and remediation of contaminated sites.

Australasian Land & Groundwater Association (ALGA) presents the EcoForum 2021 Conference held as a hybrid in-person and live-stream event at Sydney Olympic Park, Sydney, Australia on November 29 to December 3, 2021.

The EcoForum 2021 conference will explore the key challenges and solutions for the remediation industry. The event includes over 60 abstracts from some of the nation's leading companies, where experts in remediation and land management discuss case studies, lessons learned, and future solutions. Colleagues and industry professionals connect, share, grow and learn what changes and innovations will lay the foundations for a sustainable future for the land and groundwater industry.

Geosyntec Participation

Title: High Precision Downhole Fluorometer: A Cost-Effective Tool to Characterise and Support Remediation of Fractured Rock
Presenter: Frederic Cosme, CPEng, Ir. (Geosyntec)
Coauthors: Joe Duran, Christin Down (Golder Associates), Andrew Cooper, and Ben Schultz (Orica)
Time: Wed 1 Dec 11:20 a.m. Sydney AEDT
Abstract:
Background/Objectives. Characterising, and implementing remediation in fractured rock aquifers remain a significant undertaking that have a high propensity for uncertain outcomes. This is in part due to a lack of cost-effective tools that can (1) verify groundwater flow connections within the rock mass and (2) provide site-specific data to derive important properties such as effective porosity, dispersion or matrix diffusion.

Approach/Activities. Groundwater flow in fractured rock can be traced using small quantities of fluorescent dyes. Monitoring of the tracer concentration over time results in the generation of multiple breakthrough curves, which provide a unique insight in how zones within fractured rock aquifer behave and interconnect. Past attempts to undertake fluorescent dye tracer tests in fractured rock have proven sometimes logistically difficult, labour intensive and hence, costly. 

This has been addressed by the availability of a high precision downhole fluorometer, which has been tested at contaminated fractured rock sites. Although the fluorometer can be used to undertake field analysis aboveground, the device is designed to be placed inside groundwater wells and is equipped with data-logger and telemetry systems. It is also equipped with three different sensors, providing the possibility to test up to three different dyes at the same time and therefore, to conduct multiple tracer tests.

Tracer tests have been undertaken in basalt and granophyre and included push-pull tests and radially convergent tests. Quantities of tracer injected per test were small, ranging between 5 and 50 g. One of the tested sites involved high concentrations (up to 400 mg/L) of contaminants with fluorescing properties, providing an opportunity to assess interference between dye and contamination.

Results/Lessons Learned. The fluorometer was proven to be a cost-effective tool to undertake fluorescent dye tracer tests, achieving detection limit as low as 1 µg/L. Push-pull tests provided a rapid method to assess effective porosities while radially convergent tests also provided insight on the capture zone of extraction wells and the likely role played by preferential flowpaths.

Generating calibration standards using site-specific groundwater was an effective approach to address potential interferences between the tracer and fluorescing background contaminants. The results confirmed that the fractured rock systems investigated have effective porosities typically in the order of 1% or less which is significantly lower than is typically calculated using specific yield values estimated from hydraulic testing. The low effective porosities also indicate the potential for the remainder of the rock mass to act as a storage zone for contamination and for matrix diffusion to play an important role in long term remediation outcomes.

Evaluating An In Situ Groundwater Remediation Technology Using A Comprehensive CSIA Dataset
Presenter: Carol Cheyne (Geosyntec)
Coauthors: Julie Konzuk (Geosyntec), Camillo Coladonato (Dow Chemical), and Bryan Goodwin (Goodwin Consulting)
Time: Wed 1 Dec 2:05 p.m. Sydney AEDT time
Abstract:
Background/Objectives. Following a decade of Enhanced In Situ Bioremediation (EISB) in the source areas at an Australian site, a comprehensive groundwater monitoring dataset has been developed which includes an extensive delta carbon-13 (d13C) compound specific isotope analysis (CSIA) dataset for chlorinated volatile organic compounds (VOCs). To supplement previously reported analyses of microbial aspects and mass flux, further analysis of the CSIA dataset has been conducted to evaluate EISB remedy performance. The objective of this project was to evaluate the extent of degradation, potential degradation mechanisms, degradation rates, and temporal and spatial changes in degradation activity for chlorinated VOCs in the source areas and downgradient plumes.

Approach/Activities. d13C CSIA data for groundwater and dense non-aqueous phase liquid (DNAPL) samples collected from over 50 monitoring wells were used to estimate best-fit site-specific isotopic enrichment factors for five chlorinated VOCs (1,1,2,2-tetrachloroethane [1,1,2,2-TeCA], 1,1,2-trichloroethane [1,1,2-TCA], 1,2-dichloroethane [1,2-DCA], tetrachloroethene [PCE], and trichloroethene [TCE]). Enrichment factors were derived using Modified Kuder plots and compared to literature-derived enrichment factors to identify dominant degradation mechanisms in the active remedy area and in the downgradient natural attenuation area. Further, the site-specific enrichment factors were used to estimate first-order degradation rates across the site, and associated half-lives for the chlorinated VOCs.

Results/Lessons Learned. Site-specific enrichment factors supported dominance of anaerobic biodegradation pathways for all five VOCs in the areas where electron donor persists. Outside of the bioactive zone, there is some evidence for abiotic degradation of 1,1,2-TCA in the downgradient natural attenuation area. Calculated half-lives were typically shorter in the bioactive zone and longer in the downgradient area, consistent with enhancement of bioactivity in the EISB area and natural attenuation downgradient. Several calculated half-lives were less than one year, most often for locations downgradient of the source areas where concentrations are typically lower. This observation suggests that bioactivity is pronounced downgradient of the source areas where electron donor persists, and that attenuation may be somewhat masked in the source areas due to dissolution of DNAPL. The results of this evaluation confirm that the EISB program has had a beneficial influence on mass destruction, and that natural attenuation is ongoing at slower rates in the downgradient area outside the bioactive zone. The results of the isotopic assessment are being used to streamline future sampling events, targeting key locations to monitor EISB performance and changes in offsite degradation activity, coupled with microbial analysis at select locations to gain further insight into dominant degradation mechanisms.

More Information

About the event: ALGA EcoForum 2021
About ALGA: Australasian Land and Groundwater Association
For consultation regarding groundwater remediation, contact Frederic Cosme at This email address is being protected from spambots. You need JavaScript enabled to view it..
Learn more about Frederic: https://www.geosyntec.com/people/frederic-cosme
Learn more about Carol: https://www.linkedin.com/in/carol-cheyne-5688a270/