An introduction to the Interstate Technology and Regulatory Council (ITRC) Optimizing Injection Strategies and In Situ Remediation Performance technical regulatory guidance document will be presented. The comprehensive web-based interactive regulatory guidance document and companion web-based training were developed to guide remediation practitioners through the design and implementation of successful in situ remedies.

In-situ remediation technologies have advanced to mainstream acceptance and can offer performance, cost, and schedule advantages over many ex-situ soil and groundwater treatment approaches. Developing a detailed, site-specific strategy is critical to the success of such in-situ remedies. Central to this strategy is the collection of site characterization information sufficient to develop a conceptual site model (CSM) that is detailed enough to guide in-situ design – amendment selection, delivery approach and performance monitoring program. In the interest of developing expedited solutions, many in-situ remediation projects have been executed based on an incomplete understanding of site geology, hydrogeology, geochemistry, microbiology, and contaminant nature and extent. Some sites have undergone multiple rounds of in-situ injections but have not progressed toward closure. Better strategies and minimum design standards are required to decrease uncertainty and improve remedy effectiveness.

The remedial design process is commonly represented and approached as a linear sequence of steps that begin with the conceptual site model. In practice, a properly executed in-situ remedial design process is iterative and cyclical with feedback loops at each step connecting to earlier and/or later steps. This iterative process needs to be taken into account in the federal contaminated sites process. The remedial design process involves combining an understanding of site characteristics (including contaminant properties and distribution), the physical properties of amendments, amendment delivery method and dose.

The Optimizing Injection Strategies and In Situ Remediation Performance guidance identifies challenges that may impede or limit remedy effectiveness and describes strategies for developing specific actions that can be applied to optimize the design and performance of in situ remediation projects. The guidance document and presentation will include case studies and a review of commonly encountered field and design issues and resolutions.

Suzanne O’Hara, Senior Hydrogeologist, Geosyntec Consultants, Inc.
Suzanne O’Hara is a contaminant hydrogeologist with over 20 years of experience focusing on investigation and remediation of groundwater and soil using innovative and more conventional technologies. She has directed, managed, or provided technical support for multiple projects ranging from overall strategy development, site investigation, remedial design, costing, implementation, and conceptual site model development. Her technical expertise involves contaminant fate and transport in fractured porous media and use of innovative in-situ remediation technologies for complex sites, including use of three-dimensional data visualization tools for mapping contaminants in the subsurface.

There is growing interest in the use of colloidal reagents to expedite groundwater clean-up though combinations of sorption, biological degradation and chemical reduction. This presentation examines the use of a colloidal suspensions of activated carbon and zero valent iron (ZVI) for in-situ remediation. Colloidal suspensions of activated carbon and ZVI allow for low-pressure injection and uniform distribution of solid-state reagents. ZVI has long been used as a solid-state reagent for reactive barriers in the treatment of chlorinated solvents. The development of colloidal activated carbon has demonstrated its ability to act as a passive barrier while treating chlorinated solvents. With the introduction of colloidal ZVI, these two reagents may be co-applied. This innovative combined remedy allows for a duel approach and the rapid removal of contaminants, providing long term in-situ treatment with a single application of the amendments.

One of the advantages of this treatment approach utilizing colloidal activated carbon is the ability to sorb and treat a wide range of contaminants including chlorinated solvents, petroleum hydrocarbons and PFAS compounds. The treatment of petroleum contamination using injectable activated carbon amendments is also increasing in popularity, in part due to the rate with which drops in contaminant concentrations are usually seen after application. Rapid removal of contamination from groundwater by adsorption is attractive, yet in-situ biodegradation is often also needed to properly manage higher contamination levels frequently seen in petroleum sites. Here we present a new activated carbon-based amendment that combines micron-sized activated carbon with nitrate (NO3-) and sulfate (SO42-) salts serving as electron acceptors. Results from field testing indicate that the conditions in the treatment area appear to be favorable for long-term biodegradation of hydrocarbons as indicated by increasing methane concentrations and increases in the populations of BTEX (benzene, toluene, ethylbenzene and xylene) degrading bacteria while also decreasing contaminants concentrations.

Alana Miller, Northeast District Manager, REGENESIS
Alana Miller has four years of experience in the environmental industry and holds a Bachelor of Science in Civil and Environmental Engineering from Princeton University. Her experience includes field and laboratory research with the Princeton Environmental Institute where she studied methane emissions from abandoned oil and gas wells. Alana also worked as an environmental consultant for LANGAN on brownfield projects across New York City. In her current position as Northeast District Manager for REGENESIS, Alana works with environmental consulting and engineering firms to develop remedial approaches by offering design, application, and performance review services for in-situ groundwater and soil remediation.

SNC-Lavalin Inc. designed and oversaw the completion of one of the largest full scale in-situ hydrogen peroxide injection programs ever completed in Canada at the Muncho Lake Maintenance Camp along the Alaska Highway.

Soils at the active Maintenance Camp (highway maintenance yard) had been impacted with F2 hydrocarbons from operation and maintenance activities stretching all the way back to the construction of the Alaska Highway. Peroxide injection was identified as the most effective approach for remediating petroleum hydrocarbon (PHC) impacts in soils at a depth that precluded remediation through excavation. PHC impacts identified for remediation with hydrogen peroxide were extensive and generally observed in the smear zone at a depth of 7.5 meters (m) to 11 m below ground surface (bgs) covering an estimated 5,000 m2 of the site. PHC F2 fraction impacts were targeted for remediation as this was the parameter that primarily exceeded criteria. To evaluate the degree to which hydrogen peroxide could affect remediation, the approach was first pilot tested. Pilot testing was followed by a first stage injection program to achieve the following three objectives:

• Complete the injection of hydrogen peroxide in a representative target area to achieve a measurable reduction in F2 concentrations;
• Collect data and develop methods that can be used for the optimal hydrogen peroxide application at the maintenance camp during a later stage full scale application; and,
• Confirm remediation performance and associated costs to inform decision-making with respect to a larger scale hydrogen peroxide remediation program at the site.

Following completion of the first stage injection program and identification that up to a 70% reduction in F2 concentrations was achievable, a full-scale injection program was designed to target elevated F2 concentrations associated with the smear zone. The full-scale program involved the injection of over 4.7 million liters of hydrogen peroxide at 568 injection locations at a concentration of 17.5%.

The program development process will be presented from pilot testing to full scale hydrogen peroxide injection. Results, conclusions and lessons learned for the completion of the hydrogen peroxide injection programs will also be presented.

Francis Galbraith, SNC Lavalin Inc.
Francis Galbraith, P.Eng., is a mechanical engineer and environmental scientist with over 18 years of environmental consulting experience. Francis has extensive experience with mitigating impacts and treating contaminants having designed, installed, and applied a wide variety of remediation approaches across Canada’s north and west. He has evaluated treatment and remediation options for a host of sites and is very knowledgeable in the considerations and limitations of applying associated technologies. Experience in pilot testing remediation and treatment options has provided him with insight into site conditions and equipment requirements for making a full-scale application successful, or for identifying issues that preclude effective remediation. Finally, his experience in the ongoing operation and maintenance of in-situ remediation and water treatment systems along with the completion of chemical injection programs has provided him with an opportunity to identify means for optimizing remediation, ensuring equipment or programs operate efficiently and remediation objectives are achieved while minimizing the input of resources.

Self-sustaining treatment for active remediation (STAR) is an innovative remediation technology based on smouldering combustion where the contaminants are the fuel. Like all in-situ techniques, STAR faces many challenges for successful implementation. This presentation highlights the interplay between key controlling variables and design to achieve optimal application of STAR in complex, real-world environments.

Field applications of STAR (full-scale and pilot) will be presented, highlighting the challenges associated with implementing the technology in complex environments, as well as the techniques and strategies developed to mitigate these challenges. Additional data collected from rigorous laboratory studies elucidating key features of smouldering combustion critical to the successful implementation of STAR in the field will also be presented. Challenges such as “clean” gaps and interbedded clay layers, and mitigation strategies such as “seek and destroy” and surrogate fuels will be discussed.

STAR is best suited to the treatment of low volatility compounds (e.g., coal tar, creosote, heavy hydrocarbons) in silts or coarser materials. STAR is rapid, scalable, sustainable and safe, and can be implemented surgically to focus remediation efforts to specific target treatment zones.

However, as the contaminant is the fuel source for remediation, STAR requires a minimum total petroleum hydrocarbon (TPH) concentration (typically on the order of 3,000-5,000 mg/kg TPH) to remain self-sustaining (i.e., for the reaction to propagate without energy input following ignition).

Concentrations below this level will be combusted and the process can tolerate “gaps” in contaminant distribution on the order of feet, as a rigorous combustion study will illustrate.

High volatility compounds can be challenging for STAR, as these compounds (e.g., gasoline) are typically volatilized faster than they can be combusted during the ignition process. However, a surrogate fuel such as vegetable oil can be added to the target treatment zone to act as the primary fuel for combustion, which in turn volatilizes the contaminants for subsequent capture and treatment at ground surface. The effectiveness of this method will be illustrated by comparing “standard” STAR versus “vegetable oil-enhanced” STAR in a pilot test at a former refinery site.

Soil type is also an important consideration for STAR. STAR cannot be applied in clay units; however, STAR is tolerant of clay layers and lenses within a generally coarser target treatment zone. Two case studies will illustrate how the smouldering process is able to overcome the presence of soil heterogeneity.

The advantages and limitations (including their mitigation strategies) of STAR will then be summarized through the presentation of a full-scale application of STAR at a former industrial facility. Operations involving ~2,000 ignition points, as well as remedy verification activities, were successfully completed in September 2019, demonstrating how STAR can meet remedial goals in complex environments.

Gavin Grant, Senior Principal and Operations Manager, Savron
Gavin Grant, Ph.D., P.Eng., is a Senior Principal and Operations Manager of Savron, a division of Geosyntec Consultants International, Inc., based in the firm’s Toronto, Ontario office. Gavin has more than 15 years of experience in the field of environmental remediation and the development and implementation of the self-sustaining treatment for active remediation (STAR) technology.

Gavin completed his Ph.D. studies at the University of Edinburgh, Scotland, under the direction of Dr. Jason Gerhard – co-inventor of the STAR technology. Gavin is the Operations lead for Savron and has been the primary project manager, director, or technical lead on all STAR-related projects to date. He has completed dozens of STAR projects for top-tier clients in the chemical manufacturing, oil and gas, and utility industries.

Gavin is an Adjunct Professor at Western University, supervising numerous graduate students studying smoldering combustion for remediation. He continues to advance the state of the practice as a frequent presenter at events and lectures focused on soil contamination and organic waste disposal.

The management of sites impacted by light non‑aqueous phase liquid (LNAPL) has historically focused on the quick implementation of aggressive techniques to mitigate perceived risks. While this course of action might be relevant for new releases, it will often be relatively ineffective at sites where LNAPL has been in the ground for more than a few years. Years of academic study and empirical field observation have revealed that:

• Engineered solutions may not result in a tangible beneficial change in conditions at LNAPL sites;
• The risks associated with LNAPL sites are often lower than historically assumed; and,
• Natural LNAPL biodegradation processes (referred to as natural source zone depletion or NSZD) can account for much higher LNAPL mass loss/degradation rates than previously thought.

Recent years have brought a new understanding of the potential magnitude and importance of NSZD in the remediation and management of petroleum-contaminated sites. It is now understood that most of the petroleum degradation happening at LNAPL sites will be manifested through observable changes in LNAPL composition over time, soil gas content, and/or vadose zone temperature profiles. These changes will represent the majority of the petroleum degradation at LNAPL sites, with rates that can be orders of magnitude higher than the biodegradation represented by changes in dissolved concentrations and groundwater geochemical parameters. It is also now understood that NSZD can occur at rates that rival or exceed what can be achieved via conventional LNAPL remedial techniques, without the associated environmental footprint or remedial risk. Accordingly, the assessment of NSZD is becoming a more standard consideration in LNAPL conceptual site model development and site management decision-making as evidenced by recent publications from the American Petroleum Institute (U.S.), the Interstate Technology and Regulatory Council (U.S.), CL:AIRE (UK) and Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE) (Australia). Assessing NSZD can serve a number of purposes including:

• Providing a rapid, non-invasive method for delineating LNAPL (at some sites);
• Quantifying NSZD as the baseline remedy consideration;
• Scrutinizing the costs and benefits of engineered remedies over NSZD; and,
• Supporting line of evidence of the appropriateness of risk-based LNAPL management strategies.

This presentation will discuss NSZD processes and the most commonly used techniques for estimating NSZD rates. In addition, a case study will be presented illustrating how NSZD fit into the overall site management strategy, including detail on the implementation and results of the NSZD monitoring itself, at multiple sites at 5 Wing Goose Bay.

Matthew Rousseau, Associate Engineer and LNAPL Subject Matter Expert, GHD
Matthew Rousseau is an Associate Engineer and LNAPL Subject Matter Expert with GHD based in Windsor, Ontario, Canada. His work focuses on the preparation of LNAPL conceptual site models (LCSMs), the design of LNAPL site investigation programs, the evaluation of LNAPL mobility/recoverability/stability and natural source zone depletion, as well as the development of LNAPL remediation and management strategies with a focus on sustainable risk-based solutions. He co-founded GHD’s North American LNAPL technical group and advises on LNAPL projects globally. Matt regularly provides training related to LNAPL behaviour, site characterization and remediation and has been involved in the development of several LNAPL technical guidance documents in the U.S., Canada, and Australia.

Matt has both B.A.Sc. (1997) and M.A.Sc. (2000) degrees in Environmental Engineering from the University of Windsor in Windsor, Ontario, Canada.

Benzene, toluene, ethylbenzene and xylene (BTEX) are widespread groundwater pollutants. Groundwater contamination with benzene is of particular concern due to its persistence in anoxic environments and confirmed carcinogenicity. Intrinsic anaerobic processes impact the fate of BTEX, as well as other hydrocarbons, at petroleum contaminated sites. Recent research has shown that anaerobic bioremediation processes represent viable options for plume control and site clean-up for BTEX.

Benzene, the most toxic of these compounds, is also the most challenging for bioremediation, because the requisite microorganisms are relatively difficult and slow growing and reaction mechanisms are not well understood. Thanks to molecular genomics, the microorganisms responsible for benzene transformation have been identified and bioaugmentation cultures are now being grown in volumes sufficient for field application.

This presentation highlights significant milestones in characterizing anaerobic benzene biodegradation and their applications to developing better groundwater bioremediation solutions. It has recently been documented that anaerobic benzene biodegradation is catalyzed by a very narrow subset of microorganisms. Two such microbes reside in a methanogenic consortium (DGG-B; harbors Deltaproteobacteria ORM2) and a nitrate-reducing consortium (NRBC; harbors Peptococcaceae sp. Pepto-Ben). ORM2 and Pepto-Ben-like microbes have been detected in almost every established benzene-degrading enrichment culture worldwide and are frequently present in benzene-contaminated groundwater. In nature, however, their concentrations are often several orders of magnitude too low to contribute to active benzene biodegradation. Indeed, this emphasizes that effective anaerobic benzene bioremediation technologies should aim to enrich or augment ORM2 and Pepto-Ben-like microbes in-situ.

Results from laboratory treatability studies demonstrated enhanced benzene biodegradation rates with DGG-B bioaugmentation and provided information to aid in field pilot-test design. One field pilot-test performed in November 2019 at a site in Saskatchewan included three injection points, two of which received up to 10 liters of the DGG-B culture. A third injection point received killed culture, which will serve as a control to rule out if dead cells, or media components, can promote benzene degradation. It is anticipated that benzene degradation rates will be accelerated in-situ through bioaugmentation as observed in corresponding treatability studies. This first-to-field project will establish clear guidelines and approaches for using these novel bioaugmentation cultures, including a better understanding of dosing requirements, timeframes for obtaining results and ranges of conditions over which the cultures are effective. As with chlorinated solvents, bioaugmentation for BTEX compounds has the potential to decrease remediation time frames and increase the range of sites to which bioremediation is applicable providing a much-needed, cost-effective alternative for BTEX remediation in groundwater.

Sandra Dworatzek, Principal Scientist, SiREM
Sandra Dworatzek is a Principal Scientist at SiREM and has been with the company for over seventeen years. Sandra is an environmental microbiologist with advanced technical experience in bioaugmentation cultures and laboratory treatability studies. SiREM maintains state-of-the-art treatability, molecular testing and microbial culture production facilities in Guelph, Ontario. She currently oversees maintenance and culturing of microbial cultures that have been widely used to improve the rate and extent of bioremediation of chlorinated solvents in groundwater. As well as promoting the development of new bioaugmentation cultures for a wide range of environmental contaminants, including 1,4-dioxane, 1,2,3-trichloropropane, benzene, toluene and xylene. She provides technical oversight for laboratory treatability studies for a wide range of environmental contaminants, including halogenated organics (e.g., solvents, pesticides, etc.) and inorganics, both alone and in complex mixtures.