Remediation Myth Debunker Edition – Part 1
It’s Myth Debunking time!
VEI Contracting reaches out to the environmental community via these newsletters, conference presentations, webinars, lunch and learn, SMART Remediation, etc. to disseminate information regarding recent advancements and capabilities in the remediation world.
In speaking with consultants, owners, lenders and other stakeholders we routinely hear statements that are based on outdated information, their own or others’ previous bad experiences, and misconceptions that we address by providing reality checks and case study examples. Since this happens quite frequently, we thought it might be time for a remediation Myth Debunker edition newsletter.
Below we touch on a few of the more common remediation myths and explain the reality. We hope you find this interesting and informative – enjoy!
Also, keep an eye out for Remediation Myth Debunker Edition – Part 2 coming out in November, which will include even more myths as well as the biggest myth of all…!
MYTH #1: YOU CAN “RISK AWAY” ANYTHING AND EVERYTHING
Risk assessments (RAs) are commonplace in assessing risks to human health and the environment at impacted sites and for identifying remediation needs. Most jurisdictions used risk assessment methodologies to develop their “generic” regulatory standards. But by using actual site-specific conditions and constraints, instead of conservative assumptions, property-specific remedial standards are often less stringent than generic standards and can eliminate the need for remediation.
A complicating condition at sites undergoing RAs is the presence of light, non-aqueous phase liquid (LNAPL) in the subsurface; but there are ways to manage this.
Most jurisdictions in Canada that allow RAs on petroleum hydrocarbon (PHC)-impacted sites require that mobile LNAPL be removed “to the extent practicable”. To a regulator, cost doesn’t factor into practicability. Most risk assessors will tell you that trying to get an RA approved by a regulator for an LNAPL site is exponentially more difficult, time consuming and costly than a regular RA.
Assuming that LNAPL removal via extraction methods have been exhausted, these LNAPL destruction and immobilization technologies can help:
- Engineered remedial amendments, like Trap & Treat® BOS 200+®, have been specifically designed to adsorb and degrade LNAPL over time. This technology overcomes the limitations of activated carbon (AC) adsorption capacities by coupling multiple, synergistic biodegradation pathways.
- Small amounts of LNAPL (like PHC sheens) may be immobilized using AC alone. If more than a sheen or thin film is present, a more powerful immobilization technology can be used like Block & Adsorb©, which combines AC for adsorption and Portland Cement to reduce hydraulic conductivity to more effectively immobilize LNAPL than either amendment can alone.
Even when an RA gets “passed” or is accepted, it doesn’t necessarily mean that all is smooth sailing. This is where Risk Management Measures (RMMs) come into play.
The presence of volatile organic compound (VOC) contamination at a site, particularly chlorinated solvents like trichloroethylene (TCE) and vinyl chloride (VC), often pose unacceptable human health risks if there is an inhalation exposure pathway. Soil vapour intrusion mitigation measures (SVIMMs), which can take the form of physical barriers and/or sub-slab depressurization systems to prevent the vapours from entering occupied building spaces, are then required. There are many forms of SVIMMs, and solutions are customized to the site, whether they be new-build or existing building retrofit scenarios.
Human health and environmental risks are not the only risks associated with contaminated sites; off-site migration needs to be addressed too!
Ask an environmental lawyer and they will tell you that even if an impacted site is acceptable for its intended use under an RA scenario, off-site migration of contaminated groundwater onto neighbouring properties can represent a third-party liability risk – especially when the neighbouring properties include more sensitive receptors like residential properties or surface water bodies. This is where permeable reactive barriers (PRBs) are an essential tool!
PRBs are sustainable remediation approaches that allow groundwater to pass through while removing or transforming the contaminants via chemical, biological, physical, or adsorptive processes. PRB technology has improved to the point where they are now able to provide long-term, passive treatment of most environmental contaminants including PHCs, chlorinated solvents, heavy metals, per- and polyfluoroalkyl substances (PFAS), etc.
Implementation of these RMMs can vastly simplify the review and approval process for RAs as well as mitigate risks from a variety of sources.
MYTH #2: IN-SITU REMEDIATION IS A LONG-TERM, SLOW PROCESS THAT REQUIRES MULTIPLE APPLICATIONS AND CARRIES HIGH UNCERTAINTY
When in-situ remediation was in its infancy, like when VEI was founded as Vertex Environmental in 2003, the primary technology used was in-situ chemical oxidation (ISCO). It is now a well-known fact that the subsurface (soil particles and minerals, organic matter, etc.) reacts with oxidants and can consume much of their treatment capacity. This is known as soil or natural oxidant demand (SOD or NOD).
Oxidation reaction chemistry is better understood today, making ISCO remediation programs much more certain.
As a direct result, multiple oxidant injection events are required to overcome NOD before contaminants can be fully treated. This is well-understood today, as is reaction chemistry in general, so ISCO programs are better designed to account for this fact. Persistence of some oxidants in the subsurface can still be an issue, however, there are slow-release oxidant solutions, as well as other forms of long-lasting, solid particulate remedial amendments that may be better suited than oxidants to overcome back diffusion concerns in fine-grained soils and bedrock settings.
Bioremediation has also been around for a long time. Biological systems are sensitive to variables such as temperature, pH, dissolved oxygen, the presence and types of nutrients and electron donors/acceptors, toxicity effects, etc. As a result, biodegradation is typically a slower approach to site remediation than more aggressive, and typically more expensive, approaches. This may still be the preferred option.
Biodegradation approaches are a great, inexpensive, passive solution to site remediation when the site owner has limited budget and/or lots of time on their side!
The science of in-situ remediation continues to advance at a tremendous rate! There are ever more effective ways to speed up remediation and minimize uncertainties in outcomes including:
- High-Resolution Site Characterization (HRSC) testing to gain a much more detailed understanding of the physical, chemical and hydrological conditions of the subsurface.
- Remedial Design Characterization (RDC) involves high density soil and groundwater sampling at sites for pro bono analytical laboratory analysis if Trap & Treat® technologies are being considered.
- Bench-scale treatability testing to provide site-specific proof-of-concept and/or design optimization for remedial approaches.
- Pilot-scale testing to confirm essential implementation details, such as drilling methods/rates, injection flow rates/pressures, radius of influence, etc., that allow a comprehensive remedial design and cost to be finalized.
- Solid particulate amendments, like Trap & Treat® or Fluoro-Sorb Adsorbent® products or even ZVI, combine effective treatment with long-term persistence in treating contamination and are excellent choices that speed up treatment, overcome back diffusion issues and improve remedial outcomes.
Implementing any or all of these will make the ultimate remedial design for a site more efficient, cost effective and certain, and they usually pay for themselves in terms of overall cost savings and increased certainty.
MYTH #3: COMPETITIVE, LOW-BID CONTRACTS ARE THE BEST APPROACH TO TENDER REMEDIATION PROJECTS
Some remediation projects are offered as open tenders where the scope of work, or objectives, are specified and whoever submits the lowest cost wins the contract. While on the surface this might make sense from a budgetary perspective, that is not necessarily guaranteed and there can be other drawbacks to this approach.
There is a significant risk that the low bid process can drive some bidders to cut corners or look for loopholes (which can lead to cost overruns) and even for unqualified contractors to bid on the work, jeopardizing project success.
Specialized remediation contractors are up to date on the latest advances in remedial amendments, application technologies and other details of the art/science/engineering blend that is in-situ remediation. A better approach is to have an invited group of pre-qualified bidders participate in the tendering process or to employ a “two-envelope” process where there is a mandatory minimum qualification stage before financial bids are considered in the second stage.
This allows for innovative solutions and cost savings measures to be incorporated into the design and increases the probability of remedial success.
We can hear the push-back now: “If we do that, we’ll get 20 different designs and costs from 20 different bidders. How can we possibly evaluate those when it’s not apples to apples?” The answer to that question is simple and, in our opinion, the best option: create a working partnership between the owner, consultant, remediation contractor (like VEI!) and other stakeholders to collaboratively design, cost and implement a remediation program that is best suited to the site conditions and designed to meet project objectives, including budget and schedule.
QUICKY MYTHS
Sadly, there are an abundance of remediation myths that we encounter and try to debunk as they arise. We hope that this newsletter has gone a long way towards that goal! But, to close out. we thought we’d highlight a few “quicky” myths that also need debunking.
QM#1: YOU CAN’T INJECT A PRB
We do this almost every day. In fact, VEI has successfully injected over 20 functioing PRBs in the past 2 years alone! Whether it be in soil or bedrock, it all comes down to a proper design, using particulate remedial amendments and advanced delivery techniques. VEI is by far the leader in injected PRBs across Canada!
QM#2: YOU CAN’T REMEDIATE BEDROCK OR TIGHT/DENSE SOILS
Again, we do this almost every day! There can be complications when dealing with fracture flow regimes and pilot-scale testing is essential, but we have been actively remediating bedrock sites for many years using techniques like pressure packers and using pre-drilled direct push injection points (GeoTAP®) for sites with tight/dense soils and transition zones.
QM#3: THE SAME IN-SITU REMEDIATION TECHNIQUE CAN BE APPLIED TO ANY CONTAMINATED SITE
Every site is different and there is no “one size fits all” solution. Feel free to reach out and talk to us about your site and we can design a remediation program custom-tailored to your objectives, budget and schedule.
We’re also happy to answer any questions you may have about in-situ environmental remediation – myth or otherwise!
Contact us at (519) 653-8444 or info@vei.ca