Chlorinated Ethene Remediation in Northern Quebec

Using Direct Push Technology to remediate impacts near an active railway.

Background

Along an active railway in a remote region of Northern Quebec, an historic spill was discovered during environmental investigations. The groundwater impacts required remediation to mitigate potential negative impacts on local receptors. The location, on an active railway line, required careful planning and execution to ensure employee safety without disrupting rail schedules ad to ensure safe conditions for staff.

Location: Northern Quebec, Canada

Client: Environmental Consultant

Duration: 1 week

Geology: Sand

Permeable Reactive Zone Size: Approx. 100 m long

Approach

An environmental consultant hired by the railway characterized the site and determined that the groundwater was impacted with chlorinated ethenes. The consultant sub-contracted IRSL based on their expertise, health & safety training, and experience in remote regions.

In-Situ Adsorption with Abiotic and Biotic Dechlorination using PlumeStop, Plume Fe and Hydrogen Release Compound (HRC)

To treat the chlorinated ethenes with minimal disruption to the surrounding area, IRSL implemented a Direct Push injection program that used PlumeStop® Liquid Activated Carbon™ along with PlumeStop Fe™ and Hydrogen Release Compound (HRC®) to stimulate adsorption and break down the contaminants through abiotic and biotic dechlorination.

Analysis

To develop an optimal injection design, IRSL used their proprietary analytical and numerical models, which incorporated contaminant concentrations, groundwater flow rates, reaction rates, temperature and inorganic parameters, within the subsurface. Through this process, they discovered the required mass and injection pattern that led to the successful remediation of the remaining impacts.

Construction

Based on their analysis, IRSL created and implemented a design that created a permeable reactive zone that intercepted the groundwater plume.

Direct Push Technology: To ensure vertical and lateral coverage of the plume, IRSL used Direct Push Technology that extended down to a depth of 16 m, with spacing to provide a continuous barrier, to create a permeable reactive zone that effectively intercepted the groundwater.

Treatment

The Direct Push Injection program consisted of one injection of a combination of PlumeStop, PlumeStop Fe and Hydrogen Release Compound (HRC) to stimulate adsorption and abiotic and biotic dechlorination. This combination effectively reduced the contaminants within the groundwater to below the regulatory limits. It also created a geochemical environment that enhanced biological degradation reactions that resulted in the re-generation of the activated carbon itself.

  • Adsorption with PlumeStop Liquid Activated Carbon: Once in the subsurface, PlumeStop acted as a colloidal biomatrix, binding to the aquifer matrix and rapidly sorbing contaminants out of the dissolved-phase. Once contaminants were concentrated within the PlumeStop biomatrix, they were completely biodegraded in place through the following processes.
  • Abiotic Dechlorination with PlumeStop Fe: Through the process of chemical reduction, the Iron in the PlumeStop FE donated electrons to the chlorinated ethenes, transforming them into harmless compounds.
  • Biotic Dechlorination with Hydrogen Release Compound: HRC enhanced naturally occurring anaerobic biodegradation by adding hydrogen (an electron donor) to the groundwater, thereby increasing the number and vitality of the native anaerobic bacteria and enhancing reductive dechlorination within the biomatrix.

Chlorinated Ethenes

Chlorinated Ethenes include tetrachloroethene (PCE) and trichloroethene (TCE). Since the 1930s, these solvents have been used in dry cleaning operations and degreasing applications due to their non-flammable and chemically stable nature. Unsafe disposal practices have led to widespread environmental contamination.
 
Remediating Chlorinated Ethenes requires converting them into benign ethene and chloride.

 

Activated Carbon

Activated Carbon can be applied as a powder or a liquid, depending on the unique needs of the remedial situation. Most forms of activated carbon are injected with a supplemental material to aid in the degradation of the compounds of concern through abiotic (e.g. beta elimination) or biotic reactions (anaerobic or aerobic).

 

PlumeStop

PlumeStop® liquid activated carbon™ is a relatively new, dispersible substrate, capable of rapidly capturing and dropping a range of contaminant concentrations in days to weeks, while effectively biodegrading them over time. Developed by REGENESIS, USA, PlumeStop allows remediation practitioners to achieve fast treatment of groundwater with a high degree of certainty that the contaminants are biologically degraded.

PlumeStop FE combines liquid activated carbon with iron.

 

Hydrogen Release Compound (HRC®)

Also by REGENESIS, USA, HRC® is an engineered, hydrogen release compound designed specifically for enhanced, in-situ anaerobic bioremediation of chlorinated compounds in groundwater or highly saturated soils.

 

Rebound

Perhaps the biggest challenge associated with oxidants in general, is the plateauing or “rebound” of contaminant levels above the remedial objective for the site. Often referred to as rebound, it usually results from diffusion of the contaminants from finer-grained layers and lenses, or the rock matrix, back into zones of higher hydraulic conductivity.

 

Monitoring

Throughout the project, an independent consultant monitored the process and conducted a rigorous Quality Assurance-Quality Control program.

Challenges

  • Working on an active railway line required careful attention to health & safety practices to ensure employee safety.
  • The application of PlumeStop FE, a brand-new product that had never been used in Canada, required significant improvisation.
  • At over 50 feet deep, the injection depth created significant additional challenges.

Results

  • The remedial program was executed in one week with one injection and no environmental footprint.

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