We are pleased to have with us Matt Burns. Matt Burns is an engineer with a chemistry and microbiology background. He is a senior vice president and technical fellow within the WSP Earth and Environment Practice and currently the national director and global practice area network leader for emerging contaminants.

He brings more than 30 years of practical experience in chemical and microbial process to assist local teams with challenging investigation and remediation projects in the U.S. and across the globe. He is a frequent author and lecturer on innovative investigation and remediation techniques to address metals, petroleum hydrocarbons, chlorinated VOCs, and emerging contaminants such as PFAS.

We’re also pleased to have with us today Maureen Dooley, Vice President, Industrial Sector at Regenesis. Maureen Dooley has over 25 years of experience in many aspects of the remediation industry, including project management, research and development, senior technical oversight, remedial design, and laboratory management. In her current role at Regenesis, she provides technical leadership for complex soil and groundwater remediation projects, including PFAS groundwater contamination treatment throughout North America, as well as remediation design strategy and business development.

All right, that concludes our introduction, so now I will hand things over to Maureen Dooley to get us started. Well, thank you, Dane. And as always, I appreciate the opportunity to co-present with Matt Burns today. And as Dane mentioned, the title of our talk today is proven strategies for saving money using in-situ colloidal remediation technologies.

So a little backstory on this topic and how we came about to having this as our topic today. So Matt and I were, you know, have presented before, and we were thinking, you know, what might be a topic, you know, for this particular presentation. And one of the first things we thought it was, okay, let’s not talk about PFAS.

But then we got thinking, we had made a presentation around 2020, and what we were talking about were a couple of projects. They were at industrial sites, and they’re chlorinated solvents.

And this was one where in situ was chosen over a traditional groundwater extraction sort of technology. And we evaluated what site conditions were, results at that time. And we thought it would be really a nice idea to go back and look at that project and see where they are today.

Were we able to meet those site objectives and were we able to realize some of the cost savings?

So that’s really what we’re gonna talk about today are a couple of projects that we were involved with that go back to 2017.

An ebook was prepared by Regenesis that details a lot of the information. So we may refer back to that over the course of the presentation. So to get started, of course, I’m with Regenesis for those that don’t know, we are a company that provides turnkey remediation focusing on in-situ remediation of a wide range of contaminants and we do provide services and technologies for you know a range of in-situ remediation approaches.

So I think it’s you know important to reflect a little bit just generally on the evolution of groundwater remediation and in doing so you know thinking back and going back to the 80s which sadly I can have direct experience with.

Many of the approaches were physical removal. And so a lot of that really had to do, we were stealing a lot of oil patch technologies and starting to apply that to environmental contaminants.

So that’s excavation, groundwater extraction. But what happened is we started moving into the 90s. Some of these technologies were not necessarily getting the results we needed in a timely fashion. And so a lot of research started in the 90s and a lot of focus on bioremediation.

Maybe they were combinations of physical methods like a biosparge, air sparge to get bio plus physical removal. And then you also had this transition into a lot of biology chemistries that were focused on complete in-situ application like bioremediation or in-situ chemical oxidation or reduction. And I think by the time we got into the 2000s, many of these in situ approaches had been proven, used almost as best practices in many cases for many contaminant groups.

But you also had the onset of using risk-based closure as opposed to always just having a fixed target, combining technologies and then also using, monitored natural attenuation is perhaps part of the remedy.

And so as we get into today, we have quite a few technologies and approaches available to us as remediation practitioners. We don’t always have to get to 100% removal, and really what’s important is understanding what your conceptual site model is, what are your site-specific remedial objectives, and really designing an effective remedial approach that is able to hit that and also do that in a cost-effective manner.

So in getting traditional groundwater extraction methodology versus in situ, why are you looking at in situ?

And I think really one of the biggest concerns or issues associated with a groundwater extraction system is that you’re trying to overcome this persistent back diffusion.

What do I mean by that? So we’re talking about chlorinated solvents today. You may have some source material, NAPL that has worked its way into some, maybe the finer grains material.

And so you’re always having to wait for this contamination to diffuse out of this finer grain material, you know, maybe into a more permeable zone. And this takes a great deal of time. And so if you’re relying on a groundwater extraction system to flush all of this contamination out, it can take decades in many cases to be able to achieve some of the targets.

So some of the in situ methods, which can be, chemical oxidation, sorption, bioremediation, these can be tailored to focusing into the zones that really need to be addressed. So you can really look at the site specific conditions and optimize your results.

And then the onset of the colloidal technologies, that gives even better distribution, better targeting, and you can get a more rapid reduction in your contaminant concentrations. And I think one of the other big pieces is in what’s going to be shown in the case studies following that Matt’s going to present is some of the dramatic cost savings and the rapid degradation that’s indicated when compared to general pump and treat systems.

So Matt, Matt, if you want to go over what you’re going to be covering today in our agenda.

Thanks, Maureen. I know we wanted to point out to everyone and where they can get ahold of the e-book that we’re gonna be discussing today. So you can download the e-book from the Regenesis website. You’ll find e-books under the resource tab. You’ll have to scroll down quite a bit to get to the business case e-book.

I mean, I think it’s in chronological order and this one was published in 2019, 2020 timeframe. So it’s a little bit of a scroll. But from the title of the e-book and the images you can see here, you get the feel for what’s in this e-book. you know, there’s a few case studies. All of them are very complex sites where hydraulic containment would often be considered the presumptive remedy.

But, you know, hydraulic containment can be very effective, but it can also be very costly. So the e-book presents an economic and technical rationale for selecting an situ barrier technology over that presumptive pump and treat remedy.

You know, when drafting the e-book, you know, the technical efficacy was developed nearly contemporaneously with the economic analysis.

So maybe there was a couple years of data available to demonstrate back in 2019 when we were writing this ebook. But you know, Mario and I thought, hey, this is a great opportunity to give an update. It’s like, how did reality really track with the efficacy assumptions and cost projections?

Yeah, that would make a great presentation. So you’ll see from our agenda, It’s very simple, we’ve already covered the introduction, the e-book started with a couple pages on new technologies, so I think we should do the same here, Maureen, before we move on to the case studies.

So here’s the second page of that e-book, so Maureen, what notable developments have you seen have gained traction since the timeframe when we published this e-book? Yeah, I think that’s interesting, Matt, because when we were talking about this, what did we have available then and what is different now?

And it’s something that we can address even later on. Is there anything we might’ve done different? And what I want to show is since we’re focused on chlorinated solvents, what are the reagents that we were considering for this particular barrier?

So in this case, we’re looking at the colloidal group and that’s, you know, PlumeStop, our sulfidated ZVI. Now we have something newer now in AquiFix, but at the time we used HRC as the, you know, our original HRC as our electron donor for this particular project.

But, you know, for Regenesis, we’re always trying to continue to evolve and have new products. So we’ll talk about some of the new things that have come about since 2020. But just as a review for the colloidal technologies for people that may not be familiar.

So what is a colloid? So that’s a homogeneous and stable mixture of a micron sized particle that’s dispersed in liquid.

And this is an example of the colloidal activated carbon, which is used for sorption. And in many ways, this colloidal activated carbon is a game changer because it’s something that, this is a material that can be injected under low pressure. You can get really widespread distribution and it’s going to capture your contaminant.

Now it says biodegrades on this particular slide, it helps facilitate the biodegradation. Biodegradation will be happening naturally with the bacteria that are there and maybe any other co-reagents that we may apply. But really the big takeaway for using a colloidal activated carbon is you’re going to get a very rapid reduction in the concentration of the contaminant in groundwater.

But when dealing with chlorinated solvents, there’s really a wide range of technologies that can be used. You know, sorption, in-situ chemical reduction, or enhanced reductive to chlorination, all can be used individually, but there’s a lot of synergy when you combine these technologies.

So for instance, with sorption, that’s going to the contaminant flow through the matrix. So you’re gonna have a little more retention time if you’ve created a barrier. In situ chemical reduction, I mean, that’s really fantastic at targeting your parent compounds, PCE, TCE, things like that.

And you’re going to minimize the production of DCE or vinyl chloride. And then your reductive dechlorination, your bioremediation component, that’s going to be very effective at degrading all the daughter products and making sure you’re getting to ethene.

And also by using the ISKR and the ERD, you’re reducing the sorbed mass that’s on the carbon. So it’s regenerating it. So you can have more contaminant sorb onto the activated carbon.

So that allows us to work in a wide range of sites, concentration, size, different hydrogeological conditions, where ultimately we’re looking to get these low targets, rapid results and cost-effective because we’re going to have, you know, looking back and comparing groundwater extraction, you know, we’re not going to have any O &M, you know, we don’t have disruption at the site, and we are also able to really focus in on applying materials where it needs to be applied.

And ultimately, this is the sort of results that, you know, you want to see, you want to see when sorption is included, you want to see this very rapid reduction in the contaminant levels, but also make sure that they’re maintained.

So very specifically since 2020, what are some of the technologies that we have available now? I’d say number one is better delineation. This is using Flux Tracer, which is our passive flux meters. And so they’re used to measure contaminant mass flux and delineate the vertical concentration and also the vertical flux.

We also have an improved ERD product with AquiFix, which is a colloidal electron donor that can be used with the plume stop. And we also have something called IBIS, which is an improved delivery system.

But focusing for a minute on the passive flux meters or flux tracer. When you’re looking to design a permeable reactive barrier, a permeable retention barrier, anything like that, it is critical to understand what groundwater flow is and what the flux of contamination is coming in to your barrier.

So, your standard methodology of pump tests or slug tests, they’re really looking at what an average is across a particular zone. By using a passive flux meter, you’re able to delineate this vertical zone.

And you can see that there can be a lot of variation in either groundwater velocity or contaminant concentration. So, you know, what that translates to is you’re able to have better resolution in where your treatment zone is by identifying these flux zones.

And so this way you know where to put the product. So if this is where the flux is or this is where your concentration is, perhaps this is where you should focus where your reagents are. At the end of the day, you’re going to get better results and a more cost effective solution.

And just to highlight this, this is an example of a project where we had an original seepage velocity estimated at 1200 feet per year, which is pretty robust. And after running the flux tracers, we were able to collect data that showed it was closer to 300 feet per year.

It reduced the barrier length by 44% and it ended up saving close to $380 ,000. So, the Regenesis process has changed since 2020, where if we have any kind of barrier, we strongly recommend, you know, including Flux Tracer as part of the learning and understanding your conceptual site model, and we’ll use that information to revise the design.

The other technology I want to highlight is our AquiFix. So this is a long-term solid colloidal organic suspension. And so this is used for enhanced bioremediation.

You can inject this under low pressure and you can have longevity of up to 10 years. And this is something that can be combined directly with the Plum Stop or the colloidal activated carbon. It is not going to interfere with sorption at all and you still are going to get the enhanced degradation.

And then the other new technology we have is our inline blending injection system. And why this is important is, you know, we don’t have to have the mixing tank. We can just plug right into the IBIS system, you know, dial in what reagent blend we need for a particular zone.

And so that again gives us, you know, more accurate dosing and more rapid application. So these new technologies, in situ technologies when comparing it to groundwater extraction or pump and treat, you know, what we’ve seen is you can have substantial cost savings, you know, it can be up to a third.

But at this point, I want to turn it over to Matt and he’s going to get into the details of some of the case studies that were highlighted in the e-book that we referenced.

Thanks, Maureen. I have a few technologies that I think are notable to this audience. They’re not new, like meaning that they were around before 2019, but they were underutilized then and I think they’re still underutilized.

So the first is the microbial insights in situ microcosm. These are low-cost experiments that are set up within impacted monitoring wells. They allow for testing of remedial amendments to prove efficacy of stimulating targeted degradation pathways.

They’re low-cost and invaluable, especially when you’re trying to demonstrate degradation along novel pathways. I use them frequently. You can find additional information on in situ microcosms at the microbial insights website microbe.com.

Stable isotope probing, the next one over there on the right, is a subset of in situ microcosm testing possibilities that can definitively demonstrate degradation of contaminants used as electron donors.

With this technology, a stable isotope labeled contaminant is baited within the loaded ISM, so the loaded with degradation stimulants. So, if the contaminant is degraded, the label is traced into the microbes as they reproduce and incorporate the carbon from the contaminant, or into carbon dioxide, the product, the microbe respiring the contaminant.

The third 14C assays developed by David Friedman at Clemson, 14C assays are performed in the lab where labeled contaminants are traced to degradation products. They also provide definitive proof and even rates of degradation if it’s occurring across.

They are ideal for demonstrating activity along the novel pathways like reduction caused by native ferrous irons or co-metabolic oxidation of chlorinated. Yeah, I’ve found these MNA degradation pathways to be active in oxic conditions and I was to demonstrate that the degradation pathways were active by using the C14 assays.

So the Microbial Insights has some information on their website about this, including a webinar by Dr. Friedman. So I encourage everyone to check that webinar out. The document to the right is probably the most underutilized guidance in the industry.

It provides a framework for selection of mediation approaches including MNA along those C14 assay proving pathways. So on to the case studies now that we’ve gotten the updates done.

So case study one, this case study is a PlumeStopand S-MicroZVI application and the site is located in northern Quebec.

The site is a real yard that historically used chlorinated solvents. Operations led to the release of petroleum and chlorinated solvents.

I’m going to be focusing on groundwater where the chlorinated ethenes and ethanes and their reductive data products are the primary concern. It’s the primary concern because the presence of downgradient residential potable wells. MNA is occurring at the site.

We have lots of good data that shows that, including isotopic data that demonstrate DCE fractionation without accumulation of vinyl chloride. So sequential reduction isn’t responsible for that vinyl chloride going away or being skipped or the DCE being destroyed.

So it’s definitely not a hydrogenolysis pathway just taking it to complete degradation. So the remediation concept at this site was to limit mass flux of the chlorinated solvents that needed to be managed by this MNA that was ongoing, either by installing a hydraulic containment pump and treat system or by installing a passive treatment barrier like bio and abiotic pathways that Maureen was talking about.

So a cost comparison was performed to figure out which is going to be the best alternative. And it, you know, zoom in here a little bit, pump and treat and capital costs were estimated to be about a half a million dollars. And the in situ barrier capital costs were estimated to be about $165 ,000. So that’s a $355 ,000 in potential cost savings.

So the potential O &M cost savings were even bigger. Cost of annual sampling plus maintenance injections versus the cost of annual sampling plus the costly pump and treat O &M. So in total, the potential savings offered by the in situ approach were about a million dollars.

So we decided to recommend to our client a large pilot test and they commissioned it. So let’s talk about this pilot test. The site had been investigated for years and there’s nowhere near enough time to go through the level of information that we have.

But one of the key pieces of information was something that Maureen mentioned earlier, the MIP investigation to precisely identify the conductive flow zones and where the mass was located.

Specific findings of that survey included that the bulk of the VOC mass was limited to these really narrow intubated transmissive zones in the heterogeneous silt that was present. So there was a little bit of a sandy zone and a silty aquifer.

And the plume was relatively narrow as you can see in the image in the log book. Anyhow, this is where we decided to perform the big pilot test is this area right over here in red.

Here I zoomed in on the pilot area to show the injection of monitoring well layout. You can see the red mip points and the green direct push pilot injection points and the four monitoring wells installed to assess performance of the pilot. You know, two points in the treatment zone and one point up gradient and one point down gradient.

Here’s a photo of the injection point layout. And one thing I really want to note here is something I do a lot of times with my PlumeStop-applied sites. As before the injections, we deployed native aquifer material in situ microcosms into each of the monitoring wells, two within the barrier and one up gradient and one down gradient.

Here are some of the photos of the ISM, as you can see in this image. We took aquifer material that had been dried out and placed it into one inch screened casing. And then we deployed that native aquifer material that had been dried out into each well so they could be collected discreetly.

Again, these native aquifer material ISMs were deployed a few days before the amendment injections were made. The goal of the ISM samples was to quantify the degradation on the PlumeStop particle because sorption will limit our ability to assess degradation from the aqueous phase samples alone.

So we’re gonna put this native aquifer material back into the aquifer, allow it to be exposed to the plume stop, collect the ISMs and run soil analysis on the ISMs. So moving into the implementation, here are the amendment application statistics.

We applied PlumeStop, what is now called S-MicroZVI, I think, HRC primer, HRC, and a bio-augment.

Overall, the application went well, considering it was a wintery time in early November up in northern Quebec. Minimal applied pressure was needed, although we did see some back pressure following the injection, so we were slow removing the rods, but normal stuff.

We also saw immediate indications of the distribution of the amendments and geochemical shifts observed in the two monitoring wells located within the barrier.

Footprint of the amendment distribution and expected geochemical changes in response to the amendment are shown here. The heat map columns show rounds of observations, one during injections, which includes visual and field parameter observations, and one 10 months after the application with a more comprehensive analytical list.

The green shows changes consistent with delivery, like the water turned black, the same color as bloom stop. Yellow indicates moderate changes, and red really no changes at all. For example, the top row is visual observation of the amendment.

It’s green within the application area and yellow to red indicating little to no presence in the up-gradient and down-gradient wells. You can see within the barrier there’s strong evidence of delivery with ORP, DOC, BOD, iron and sulfide data, all showing strong indications of delivery as compared to the up-gradient and down-gradient locations.

This slide shows SORB VOC data and mole fraction information collected from the ISMs. The x-axis of each plot shows the dates of the baseline and performance monitoring sampling. The y-axis is the total VOC concentrations in milligrams per kilogram. The mole fraction is shown here in the pie chart that plots the total VOC concentrations.

So red in that pie chart is TCE and TCA, yellow is DCE and DCA, and green, vinyl chloride. So we mathematically subtracted the VOCs in the soil moisture by using the percent moisture and the groundwater analytical data. So this is as a dry weight with the VOCs attributable to the groundwater subtracted out. So, the plots of PO2 and PO3 data, they show no or next to no sorb VOC mass after the treatment. So, no VOCs in the groundwater and no VOCs sorb to the plume stop.

This means the mass balance demonstrates contaminant destruction, not just partitioning, right? So, we’re able to demonstrate that any degradation that we see in the aqueous phase, which we’ll see that data in a minute, is not related to just partitioning of the TCE onto the plume It means there’s none on the plume stop.

So we’re able to prove that, hey, it’s not going there. It must be being destroyed. So we- I’m gonna chime in on this because this data is really unique. This isn’t the type of data that’s typically collected.

But I think it’s really important because you’re able to demonstrate that the contaminant isn’t just sorbed stain in that form that you’re actually have, it’s what’s sorbed to the PlumeStop is actually undergone degradation and you’re seeing this whole ratio change of what’s there and even, you know, to get to a non-detect. So I think that methodology that you use is really interesting and really informative.

And it’s really easy to do, Maureen. So we also backed this information up with all sorts of advanced diagnostics like isotopic data and all that that I won’t be presenting today, But I thought I’d present this in situ microcosm approach because it’s really, really easy.

Just take some of the native aquifer material, pack it into a small screen, put it down the hole, do your injections, and then your injections will coat the ISMs. And then you can look at specifically at what the impacts of the PlumeStop were.

Like is the PlumeStop responsible for the mass reductions that you see or is it not?

So in this case, we’re able to demonstrate that, hey, no, there’s no sorbed VOCs on the PlumeStop that we just applied there.

The PlumeStop is doing a great job at slowing things down, but it is not sucking up the mass and falsely contributing to almost a false positive of degradation.

So I guess at this point, we established that we delivered the amendment successfully. Those heat maps were great. The geochemical parameters look like everything was distributed as intended within PO3 and PO2.

And at least initially, we showed that the VOCs were not simply partitioning into the sorb phase. So let’s take a look back at those heat maps, updated with the more recent groundwater data.

This actually looks pretty good. So look at the data from PO3 and PO2. There’s still a lot of green and some yellow in those plots. So looking pretty good and not so good in PO1 and PO4, the upgrading and downgrading at wells.

They look pretty consistent, not much stimulation going on. But you can’t see some problems developing. Right, so it looks like there could be some more donor.

If you take a look at where it says e-donor on the row, that’s the bottom parameter in that favorable conditions, they’re starting to get a little yellow and red. So there can be some more donor added. And the pH, the pH went outside of the optimal range for the helicoides in PO2.

So spotting some issues. For now, what really matters though is the treatment efficiency within the barrier, right? So this is the real data. The plots have the same setup as we presented for the soil, but the ethane and ethane info has been added and is plotted in blue.

So overall, the barrier has been working well. More recently, the impact of pH and PO2 data is apparent. You can see a bit of an uptick there in the VOC concentrations and even the changing ratio of daughter products.

So rather than have all those ethanes in there, we’re seeing some, it looks like a little bit of DCE stall, which is kind of expected after eight years following application of all those amendments. PO3 looks great. There might be a slight uptick in total VOC concentrations, but that’s expected.

The microbes are a little bit hungry, but the concentrations are very, very low within the barrier, which is our objective. So through year eight, I think it’s safe to say that the cost savings have been realized overall that we predicted back in 2019.

I won’t include any additional savings due to kind of skipping the plan 2021 maintenance injections that are shown on the table here. Those injections probably should have been made.

Overall, we demonstrated the concept that our in situ treatment would be both effective and cost efficient.

And early on, our client was very happy about this.

And I know we’re running out of time, so I’ll just quickly go through very quick synopsis of the second case study, the economic analysis. This site was a full-scale application to treat a very large plume in fractured bedrock. And we treated it in several different transects, the barriers that we installed. Again, this was a very similar mixture, a cocktail that we used that involved PlumeStop and stimulation of biodegradation.

And we also did some in situ formation of biogeochemical formation of ferrous iron in here. This would be a topic all on its own. But this past summer, in this case, we actually performed our first maintenance injections as we started to see the performance flag a little bit.

So since those injections, the maintenance injections to add more donor, and we actually added some more pH buffer in here as well. The performance or the efficacy has picked right back up and we’re seeing great treatment within each of those transects.

So I guess the one thing that I say we were off a little bit with respect to the cost estimate is that we had put in a couple hundred thousand dollars for every other year for maintenance injections here. And that was due primarily to site conditions.

The groundwater was flowing pretty fast through those fractures and we weren’t sure we were gonna be able to hold up the electron donor within there very well. But the performance monitoring data which we consistently collected at this site didn’t show problems until 2024.

So that’s why we did 2025 applications. So I think it turns out that we do not need injections as frequently as initially planned. So the estimated net savings of about $1.4 million is probably a little bit underestimated as compared to what reality is going to bring.

And with that, I want to ask Maureen, just for a little bit of input, and I think this is ideal situation where the new electron donor might even provide even a further extended longevity.

Yeah, I mean, that’s exactly, you know, because this new donor can be used with the plume stop, because the PlumeStop and the earth-activated carbon, that still is maintained, and so we could very easily apply that, and that’s going to have a lot more longevity.

It can be looking at eight to 10 years. So we used a shorter acting electron donor initially. So this could certainly expand it beyond what you observed from after your initial injections using the AquiFix.

Yeah, I’m excited to use it, unfortunately. So this was probably designed in 2003 and got the approval and it was a little late to use the new donor, but I’m looking forward to using it.

I haven’t used it yet, but I’m very intrigued And I think from these past two case studies, you can see the benefits of not having to go out and do those maintenance injections as frequently. So yeah, I’m looking forward to using it.

Well, Matt, I want to thank you for sharing this new information and giving us an update on these two case studies. I found it really interesting and informative.

And I was happy to see that, generally things have been maintained and have met the objectives. And I think with some of the new tools that we have now, we can, you know, keep these going in an even more cost-effective way in the future.

Yeah, thanks, Maureen. I appreciate the opportunity to present these case studies. And obviously, it’s tough to fit everything into an hour. So please reach out to me or Maureen if you have any additional questions.