Today’s webinar will focus on PFAS monitored retention and PFAS enhanced retention.

With that, I’d like to introduce our presenters for today. We are pleased to have with us Dr. Charles Newell. Dr. Newell is a Vice President at GSI Environmental. He has co-authored more than 30 technical publications on PFAS fate, transport, and remediation, and has led multiple PFAS research projects funded by the U.S. Department of War. His honors include the 2014 CERDIP Project of the Year, the 2016 ITRC Environmental Excellence Award, and the 2024 Gordon Maskew Fair Award from the American Academy of Environmental Engineers and Sciences.

We’re also pleased to have with us today Dr. David Adamson. Dr. Adamson is a Vice President and Principal Engineer with GSI Environmental and has more than 26 years of environmental project experience in environmental consulting and academic research. He is a licensed professional engineer in Texas. Since joining GSI in 2004, Dr. Adamson has served as a principal investigator or co-principal investigator on over 25 DoD-sponsored research projects, including those focused on 1 ,4-dioxane, PFAS, innovative long-term monitoring strategies, enhanced amendment delivery systems, and improved characterization and treatment methods for contaminants in low permeability matrices.

We’re also pleased to have with us today Dr. Paul Erickson, Vice President of Research and Development at REGENESIS. Dr. Erickson oversees the commercialization of new environmental solutions to address complex remediation challenges. During his time with REGENESIS, Dr. Erickson has led the development of a number of remediation products and technologies, including PetroFix, AquiFix, SourceStop and FluxTracer. He is an author on over 20 peer-reviewed scientific publications, mainly in the area of environmental chemistry.

All right, that concludes our introduction. So now I will hand things over to Dr. David Adamson to get us started.

Yeah, thanks. This is Dave Adamson, once again from GSI Environmental in Houston, Texas.

Happy to share a summary of a project that we recently completed for ESTCP on an important topic of how we handle some of these challenging PFAS problems that we have at groundwater sites and in particular developing this framework which we’re going to talk about today that sort of translates some of the information that we learned about how you’d use natural attenuation for lots of other contaminants and translating that to PFAS.

So happy to be joined by my colleague here, Chuck Newell, let him introduce himself and tell you a little bit more about what we what we’d be talking about today. Yeah, Dave, thanks.

And again, Chuck Newell, GSI Environmental, and to help tell this story, we’ve got a lot of different elements here, but some of the stuff you’ll see today are a cube-shaped planet.

We’ll talk about the revenge of the geologists and really talk about how this PMR and PER are a new incarnation of monitored natural attenuation and sort of explain how all that works. But first, let’s go down our roadmap.

I’m going to start with number two, and the stark information or situation we find ourselves in as groundwater PFAS remediation people, maybe we only have two choices right now on how to manage some of these plumes.

Then I’m gonna dive into the meat of our talk and talk about this PMR PFAS monitor retention, and then talk about how mass discharge, travel time to the nearest receptor in a tiered line of evidence really is the heart of this framework to understand, can I use PMR at my site?

Then we’re gonna talk about some enhancements, wait, there’s more, how can you improve this retention with this concept called PFAS enhanced retention and then go into field results and take home messages.

But really gonna start with number one, PFAS bizarro world for groundwater remediation.

Dave, why do we talk about bizarro world and what is bizarro world?

Well, we probably have to provide some context to start with but consider PFAS sort of this bizarro world And I’m a little bit of comic book nerd, I will admit that.

And so this was something that Chuck, early on, was talking about, finding these parallels.

So the Bizarro world, it’s this cube-shaped planet that Chuck alluded to earlier, also called Htrae, Earth spelled backwards. That’s this fictional planet that appears in DC comic books. And it’s this home to Bizarro and all his companions.

So you’ve got the Bizarro version of Superman, Lois Lane, and everybody else. And so we’ve now used this term in popular culture to sort of describe situations where everything is weirdly inverted or opposite to its expectations.

So this sort of fits in with PFAS, right Chuck? For us and these groundwater people doing this remediation business, it is bizarre world and we got these bullets and why it’s so strange and unusual to us, and I’ll do the first one. You do the second one. But first, there’s no evidence of any institute natural degradation of these key PFAAs, these key regulated PFAS like PFOS and PFOA.

Yeah. And then biodegradation, in this case, doesn’t really help us.

You’ve got these precursors out there, transform those, it might actually be a less preferred outcome.

And then one of our frontline technologies is groundwater pump and treat.

What is this? Back in the 1980s, you know, is that Duran Duran I hear on the radio going on there?

And then we’ve got concentrations, a single digit nanogram per liter, concentrations so low, it’s really hard to imagine.

Thousands of individual PFAS, there’s the smorgasbord, the things out there, these precursors can transform, the PFAS can’t.

And then this inventory of tens of thousands of PFAS sites.

So some something’s going to have to be done on a scale that’s sort of unimaginable thus far.

And then one last thing that’s slowly coming to focus, I think there may be more expanding plumes than we’re used to compared to chlorinated solvents sites or hydrocarbon sites.

And all this means this is a big problem on the right-hand panel is this is from the excellent Environmental Business Journal Grant Farrar’s publication.

Where they have since 2019 have come up with the estimates, how much might it cost to handle this?

And for the remediation world, the current estimate from 2025, maybe $88 billion.

So we’re talking about some big hunk of change. But the key point is this business as usual won’t work for PFAS ground or cleanup. But we’ve got actually some hints of this.

We’re seeing some of the data, Dave, that you might talk about in terms of plume lengths.

Yeah. So this is from a study that we worked on a year ago and published, Poonam Kulkarni at GSI is a lead author on this.

And this is just trying to say, okay, take all these sites out there, including PFAS sites.

What is the plume length? And you’ve got this graph there on the right where the median plume length of multiple sites for each of these compound classes is plotted out there.

And you sort of see a comparison between some of these things sort of at the bottom like MTBE, BTEX, 1 ,4-dioxane, going all the way up to PFOA on the top.

And so PFOA in this case, this was 37 sites, right, Chuck, that we compiled data on. Turns out that the median characterized distance to date was about 380 meters.

So somewhere the order of what we were seeing for these sort of non-degradable chloride type plumes. There was this exercise of going out and figuring out, you know, that’s the characterized distance.

What was maybe the inferred plume length if you went all the way out to sort of a four nanogram per liter? Maybe that’s more in the 800 meter range, but you can sort of see in terms of like what these plumes potentially look like.

They’re sort of on the order of maybe twice as big as some of the plumes that we’ve been dealing with previously. So no problem.

Let’s just go out and We’re going to make it roll out some of our existing groundwater treatment processes.

So let’s just go down there and certainly let’s see what works for PFAS and what doesn’t. So in-situ bioremediation, what are the prospects for this working on PFOS or PFOA, Dave?

Not too good. We don’t have a lot of mechanisms or at least to date that have been shown to degrade it.

So a vapor extraction, can’t we just blow this stuff out of the ground?

Uh, no, not really. A lot of these things being very volatile where that would be very effective.

Okay. How about ISCO? Can we just use to put the Draino in there and just destroy the stuff?

Uh, some evidence that it could work, but probably not at a field scale. It’s very practical.

Okay. Institute chemical reduction.

Same thing. Not, not really viable.

Just think a trend here. How about thermal remediation?

Not necessarily in soils, but I’m talking about thermal remediation in groundwater.

Yeah. You can run into this problem of what are you going to transform them to?

You can’t necessarily volatilize them the way you would with most thermal technologies.

Okay.

How about primal reactive barriers and reactive, we’ve defining this as something that can destroy your…

Yeah, and that’s the key word in there, the reactive part.

PFAS is not necessarily going to be something you can transform easily.

Okay. And what’s the story about air sparging?

I think we’ll talk about that a little bit later as we move into here, but a little bit promising in there in terms of sort of moving those things around, maybe concentrating them.

So then we have monitored natural attenuation, which is really the focus of this talk, right?

And then finally, we’re left with these passive sorbent barriers, something we’re putting in this PFAS enhanced retention category.

And then there’s this pump and treat scenario.

So putting all this stuff together, we come up with this groundwater mediation calculus, right, Dave?

And so how does this high level math work?

This is sort of the math of sort of saying these combinations of things.

If you got non-degrading plumes, plus this lack of in-situ technologies, the equation says you’re probably gonna have more expanding plumes than we’re used to, and that’s sort of borne out in those plume data that we looked at earlier.

So that leads us to then, well, if you’ve got more expanding plumes than we’re used to, and the action levels are low, nanogram per liter, we may find ourselves in a situation where if those are the only options that we have available to us, those two at the bottom that Chuck mentioned before, then you’re doing lots and lots of those at a scale sort of hard to believe, right?

And that goes into this next slide where we’re talking about potential futures for PFAS management.

I think this is from this paper that we wrote in 2022. We talked about three scenarios for PFAS management. So the stuff you saw on the last slide, all those red things, that was really 2026.

But there’s one scenario over the next 10, 20 years. We just put in a lot of pump and treat systems and, you know, and then some injected sorbets in here, but pump and treat, can we put this at 60,000 pump and treat sites?

You know, probably not, right?

And scenario two is researchers and maybe somebody listening to this webinars out there, they’re going to provide this silver bullet of something that destroys this PFAS Institute and it’s rapidly adopted.

Dave, what’s the prospect on that?

There’s been a lot of work put into this, a lot of research funding, a lot of, you know, attempts at commercialization. So far, we’re still waiting for things.

You know, progress is probably a little slow in this and not something that’s necessarily going to be available, you know, tomorrow to apply at your site. So we have this idea that you’re going to, maybe people are going to start looking at these sites and do this risk or this triage strategy, think about various approaches.

And one of them, in terms of these limited things that you can do these sites may be this retention-based M &A. So we’re going to talk about that.

And that’s this most likely outcome in the near future. So not all sites can be this retention-based. There’s going to be a lot of these sorbent barriers used. They’re going to be pump and treat. But we’re going to talk about this retention-based idea here.

And to start out, maybe in the spirit of Julie Andrews, Dave, maybe you’re going to start at the very beginning regarding monitored natural attenuation and give us some context, you know, fundamental.

What is what’s M &A all about?

Yeah, I think context is important here in sort of building the case for how we apply these sorts of things to PFAS. And it is this idea of like, you know, it is expensive to go in there and apply these sorts of in-situ technologies.

So if there’s cases where we can take advantage of what natural processes can do in terms of managing these chemicals, let’s take advantage of that. And that’s the whole sort of basis for M &A, natural attenuation as a technology, but there’s these sort of three fundamental things you have to understand and do in order to make that successful. And first is protect.

We need to make sure there’s no risk to any potential receptors. Secondly, we have to understand. We have to really understand the science behind why an attenuation or retention or anything like that is happening.

And then watch. We’ve got that sort of watchful waiting.

That guy, I guess he’s waiting for a train, right, Chuck?

But in our sense in the groundwater world, it’s collecting the data you need to do in order to make sure that that remedy or approach or anything is actually doing what you said it was going to do.

Then from a sororical perspective you can sort of look at these different arrows in here and they sort of pop up over time that that x-axis goes from the 1990s to 2020s and certainly my career early in 1990s I was very involved in the hydrocarbon and the chlorinated solvent M &A so I remember some of the stuff and in some ways how controversial it in the beginning. Oh, we’re doing nothing. How do we deal with this?

But this hydrocarbon seminate was the first, shortly followed by the chlorinated solvents seminate. Then MTBE, an oxygenate, which at one time we thought wasn’t going to degrade.

Then very interesting to us in this PFAA world, this PFAS world, since these PFAs don’t degrade, there’s actually US EPA guidance, some magnificent, you know, three tiered volumes about metals and radionuclides MNA, so related to mobilization.

And finally, we’re saying, hey, it’s time for PFAS, monitored retention, or PMR.

So on the right are some of our papers, writing COVID, we were writing this stuff in 2020, monitored natural change from PFAS, but the story’s changed.

We’ve added some enhanced retention, but we’re going to go through one key word there, immobilized, and there’s definitions are important here, Dave.

Let’s go through the definitions. I think it is important to understand the difference between immobilization or retention. And as Chuck mentioned before, for metals, radionuclides, this immobilization concept becomes pretty important.

And when we say that, we’re referring to sort of this permanent trapping or isolation of the chemical in the environment. So some sort of precipitation or something that you’re not expecting to be reversible. Tension’s a little bit different.

We’re talking about, you know, the storage of a chemical in the environment.

So, it’s isolated from potential receptors for a certain time, or you’ve slowed it down in some way that it wouldn’t necessarily happen as fast as it would if that retention process wasn’t active. This becomes an important thing because it is an idea that we need to incorporate into how we describe the processes that we’re going to talk about today.

This PFAS-monitored retention relies on the second part, not anything that’s necessarily permanent immobilization, but describing these processes like air-water partitioning, sore disruption, matrix diffusion processes that lead themselves to acting on PFAS in the environment.

So we’ve got a little graphic there, this M &A crossed out and then to a PMR and I think Chuck is going to talk about that, what we mean by that.

Yes. So this is our transition is early on we developed this conceptual and technical basis, some of the papers on that previous slide.

Then we had an ESTCP project that Dave led to develop this framework and we’re going to talk about what came out of that project.

We have decided that PFAS is retained in the subsurface, but it doesn’t destroy.

But then we had this idea, the original vision was PFAS monitored attenuation and enhanced attenuation, but then talking to several regulators, we sort of reimagined it to make it more specific so people don’t get the idea we’re talking about PFOS or PFOA or any of those PFAs being destroyed, but we’re retaining it.

And that’s why in this reimagination, this approach or this rebranding, we’re calling it PMR, you know, and PER in here. So with this, as we now maybe put our nerds hatch in, go a little more detail about the different processes.

Yeah, the basis for retention of PFAS in the subsurface looks a little bit like this. And obviously, it’s this sort of simplified graphic, but you sort of think about the vadose zone, the transmission zone, and low K zones as different compartments.

So you’ve got PFAS as a source moving sort of driven by infiltration through that vadose zone But you’ve got processes like geochemical retention.

So that’s interaction with the with the geologic formation So things like air water sorption a hydrophobic sorption take place within that zone well as chemical retention and we we sort of coined that term to refer to the fact that PFAS in its precursor form tends to be chemically a lot more a or less mobile than it would be if it was transformed into a PFAA.

Within the transmissive zone, some of that mass might make its way down there. You’ve got plume migration being reduced, again, by some of those same geochemical retention.

In this case, though, you’re sort of lost out on air-water sorption, as well as chemical retention, such that the PFAS moving should move slower than what groundwater itself would move.

And then finally, you’ve got this locative zone.

So that could be like a clay or silt rich underlying that your aquifer where it’s not necessarily as transmissive. Those soils can actually have diffusion of PFAS mass into them, which can lead to sort of shortening of the plume.

And we’ll show that over a few slides.

So this is about matrix diffusion. And to me, this is another great example of Bizarro world because middle part of my career, I spent all this time originally thinking that all you have to do is I’m a chemical engineer, that’s my background, just mix these chemicals on the subsurface and you don’t really have to worry about the geology too much.

But it turned out we do these amendments, you destroy mass, but you can never get down to these cleanup levels.

And all of a sudden, the devil in the detail is that, I call it the revenge of the geologists, is these chemicals would get into these clays and then they would slowly leak out.

You couldn’t get to that source mass. And so it’s a bad thing, this matrix diffusion of the chlorinated solvent world. But in Bizarro world part, it really might help because it slows down the migration of an expanding plume.

So here’s some modeling paper by our colleague Shala Farhat. We’re using a model that accounted for this different revenge of the geologist, this matrix diffusion.

And if you’re in a sandbox, that plume after a hundred years, PFOS, 1300 meters, you put aquatars on the top and the bottom, and some of that PFAS, PFOS mass got into these, these clays or at the top of the bottom. And then if you really, you know, load this thing up with layers and lenses, so it’s got a lot of this low K or this low premium material, that thing’s only 250 meters.

So if you’re at a site with a lot of heterogeneity, maybe that’s a good thing because it will slow down that expansion of that one. We have it a field example too, right?

Yeah, so a second example with some field data is shown here. And so this is a situation where we had PFOS coming from a source, moving down gradient. And so this graph is showing x-axis being distance from that source and PFOS concentration on the y-axis there.

And so field data at this site is those blue dots. And we’re trying to match this with the model that Chuck had described in the previous slide. And it turns out when you have matrix diffusion on in that model, you can sort of see that you’ve got a pretty good match.

That purple flash line fits our field data real well and shows that the ultimate plume length, in this case, we were delineating back to the old 70 nanogram per liter, it was just under 400 meters.

We did the same modeling simulation, turned matrix diffusion off as an active process. In that case, the plume was out over 800, almost 900 meters long.

Just sort of showing a very good example of the amount of shortening of that plume that occurred just from this matrix diffusion process that Chuck had mentioned before, that mass moving into the clays as opposed to moving out into the plume.

And this is all summarized in a paper that our colleague Pullam Korkarni published in 2022. And some of the other implications here are these things that Dave talked about the plume shortening if you have all the heterogeneity, but there’s also this idea of peak dampening.

What sort of goes to this idea about how flood control reservoirs, if there is a place to store that water, and if you have a very high flood wave going to this flood control reservoir, then there’s less flow that comes out because you’re storing some of that high level flow in there.

So you convert that red line, which in a flood control aquifer might be a hydrograph, to the green line. But the same thing happens if you have a storage place in the subsurface for the mass. And on that top panel A, you can see this red is something that’s uncontrolled, just moving through a sand.

But if you have a lot of places to put this stuff in the matrix diffusion, you get this green line in there. So you can have these concentrations over time and see this peak dampening, you know, that occurs there.

Okay. So this does bring us finally to the PMR framework.

So this is PFAS monitor retention.

What we wanted to do here was try to build a lines of evidence type approach for how would evaluate a site or many sites and determine what type of remedy might be appropriate for that particular site.

And what we chose as our primary lines of evidence are listed here and also then plotted in this sort of representation, cartoon representation on the left.

And so these two lines of evidence are plume mass discharge, we’ve got that plotted there on the x-axis, as well as long travel times in the nearest receptor, and those are what are So, we sort of imagine this, you’ve got it turned almost like a baseball field, right, Chuck.

And if you’ve got more retention moving down and to the left of this graph, so those are situations where you’ve got sites where there’s probably relatively limited risk, long travel time of the receptor, very low plume mass discharge.

Those are the sites that are probably most amenable to using a managed approach, this monitored retention approach where those natural processes are working to minimize the amount of risk to a receptor.

As you move farther away from that sort of home plate area maybe out into the infield, you see this blue area where we’ve got PFAS enhanced retention, PER.

So that’s this area where maybe one of those criteria, one of those lines of evidence maybe doesn’t quite fit with the site specific parameters that you might set up.

You might have to do a little bit more.

And so we’ll talk about different PER approaches as we move through the rest of this talk.

And then finally, if you move out far, maybe that’s the outfield where you’re sort of in the red, you’ve got maybe a short travel time, the receptor are pretty high mass discharge.

Those are the sites where you probably have to do something right away because those criteria, and that might be a pump and treat system or point of use system where you really gotta mitigate that risk right away.

So we set up this framework, sort of think about where conceptually sites might fit.

Let’s do the x-axis and then the y-axis. So on that x-axis is mass discharge.

We have a lot of tools for this.

A lot of times you use this transect method where you have these wells that are perpendicular to groundwater flow, this vertical curtain in the subsurface, and then you’re just, what is that groundwater Darcy velocity going through there?

What is the area of that subsurface curtain in the saturated zone? What’s hydraulic conductivity?

What’s the you want to get this grams per year.

And with that, you can put that on the x-axis.

Then you’re talking about travel time, right?

And how does that work?

Yeah, so when we’re talking about travel time, we’re thinking about the edge of the plume to whatever receptor that you’ve identified down gradient.

It’s not necessarily a complicated equation.

It could be done with modeling, but it could also be done with sort of back-of-the-envelope type of calculations that we’re showing here.

In this case, you’re just trying to determine what is the distance to that receptor, and then dividing that by some estimate of the plume expansion rate.

That plume expansion rate is probably gonna be a function of how long PFAS has actually been released at that particular site, and then a measure of where it is right now, and you can get sort of a feet per year or a meter per year in terms of your rough expansion rate, and then determine what that means in terms of how long it would take the current PFAS plume to reach that particular receptor.

So we’re calling those the primary line of evidence, and that’s this line of evidence 1A, line of evidence 1B.

We have some secondary line of evidence as well, but then we put it into this tiered process where tier one, sort of the simplest approach, maybe smaller sites are the focus of this, and you just might estimate that mass discharge with a few data points.

You just do this, extrapolate out that length that occurred when you measure the plume into the future to see how far it might take to get to the receptor.

And then looking at some screening tool to determine how much matrix diffusion may be in there tier two We turn up the music more samples.

Maybe we’re doing some simple fate and transport models Collecting paired soil and groundwater samples in tier three are the projects that certainly we like to do.

It’s got everything You know, you’re you got a lot of really detailed data high resolution Maybe you’re using some of these complex 3d models like Modflow USGT BFAS a REMFluor MD, and with this you can get to figure out, is PMR gonna work at my site?

Where are you on this baseball field?

Let’s just give an example of a research site, mass discharge and mass balance at that site.

Yeah, and this serves as sort of a way to do some secondary lines of evidence that you understand that retention is active at your site.

And so as Chuck mentioned before, this is a mass balance, AFFF release site, a paper we published a couple of years ago, where we’re basically saying, and where is that PFAS mass at this site?

And so moving from sort of left to right on these boxes there showing the source zone immediately there to downgradient to the far downgradient plume.

And we’ve got these different colors and shading that shows what type of class of compounds that mass represented.

And so if you just sort of look at the source there, you see that a lot of that mass is there.

Those boxes are sized by the amount of mass.

And most of that mass is in these sort of blue hatched it’s actually these precursor compounds, these cationic and zwitterionic compounds that tend to be pretty strongly retained because of the chemical properties of them and interacting with the surrounding soil matrix.

So that was pretty good evidence.

And then as you move downgradient, you sort of see a shift in the amount or the type of compounds.

So less mass and it becomes more of these PFAAs and then even moving farther downgradient to see more of that sort of shift Along with the decrease in the mass discharge that’s shown it’s decreasing from three point six kilograms per year to one To much less than one as you move far down gradients So again, these are these are supporting data that are collected at a site to sort of show Support for these retention based processes It’s a little bit about how you can might apply this framework Here’s our baseball field again plume mass discharge in the x-axis plume travel time to receptor notice.

That’s a flipped Axis on the y-axis zeros on the top and 15 years is on the bottom But you could we populated this with some hypothetical sites and if you’re down there You know in a low area where the green are that PMR works and if you’re way out in the outfield Oh, you’re gonna have to do something else and maybe that’s gonna be pump and treat putting filters on drinking water wells and in the middle is this PFAS enhanced retention We envision if you have this portfolio of sites you could map them on here you get some idea What how this stuff what we do at each one of these sites?

So the key word here applying this at an individual site is to try to decide what those values that are on those X and Y Axis might be and that might differ depending on What your receptors at that site are or or so forth?

And so this is an example that goes through sort of how we determine what those values are So, for example, the mass discharge in this particular case, we’re sort of thinking about high, low, high, medium, or low, anything that’s in the low would just, sorry, that reflects of how strongly does it support the use of PMR. So, high in this case is low mass discharge.

Because the receptor in this case was a river which provided quite a bit of dilution for the groundwater, those values ended up being relatively high, you know, mass discharge numbers.

If you look at the second row on there, the travel time to the nearest receptor, those could be somewhat arbitrary depending on what you’ve agreed to with a regulator, for example.

But thinking about anything that’s 10 years or longer being something that would be more supportive of PMR, while those in between 5 to 10 years or 5 years or less might mean you need to do something else.

Okay.

Let’s now focus.

So we talked a lot about PMR.

Let’s talk about PER, P-FAST Enhanced Retention.

That’s this blue bar in the middle and where it goes so there’s a panel a some of these are you know Have the right under the right conditions might have be this monitored retention sites But if you need some more more protection, then you’re gonna do something with under this PER category And then you know with this this goal of PRs to increase the ultimate Viability of PMR sometime down the road maybe with some of this peak shaving We’re talking about some of these examples of PER on this next chart, which makes me think of a college-level biology textbook with, you know, there’s the endoplasmic reticulum and all that stuff.

But that’s not what we’re talking about here, right?

No, it is.

It’s got a lot of great stuff on this, and we’ll talk in a little bit more detail about some of these.

But again, this is a paper that we wrote back in 2022.

it went through eight different PER approaches, anything from ejection of particulate sorbents, capping, gas sparging, PFAS salting out, placement of particulate sorbents, veg oil emplacements in different ways, as well as sparging and veg oil combined.

So sort of some of these move from maybe more established, maybe into more sort of speculative type of approaches.

I’d call the ones maybe on the far right bat **** crazy, maybe. Okay, keep going.

Yeah So, uh, so let’s talk about a couple of these in detail Okay, so we’re gonna first just go number two and some of this is capping and soil stabilization We think this is certainly going to be a big market I’ve had anecdotal reports in australia that they’re using a lot of this a lot of their a triple f sites But in some sort of cap or adding a stabilizer in there, you know to absorb this stuff and we’ll give you a couple examples in here. Both methods are being done now.

They reduce this mass discharge by increasing this retention.

For example, if you stop this recharge from going down into the Vado Zone as you’re looking at those two panels in there, then this air water partitioning will hold that stuff in place and that retention that won’t be washed away during these rainstorms.

So that’s a key key piece. So let’s do an example here. I think this is a paper from Craig Devine, is that right?

Yeah, so Craig and his colleagues did this demonstration, field demonstration, essentially where they were, and the graphic is showing it right here, taking a site where normally you’d see sort of infiltration driving that PFAS mass in the shallow soils down into the groundwater.

So that’s something you want to try to prevent in this case.

They’re going about it fairly simply, but just adding an amendment directly into those shallow soils.

So in this case, a Rembind 100X, adding it at about a 3% weight per weight to 3 feet and in a 100 by 100 foot test plot and Binding that stuff up finding that material up and trying to prevent then on the far right The amount of mass of the PFAS mass that would be leaching into groundwater So they had a 19 month demonstration period turned out at the end of that They had reduced the PFAS mass discharge by about 95% Without impacting the amount of rainfall that was making its way ultimately into that aquifer So they did all this without really needing a cap, which requires long-term maintenance or any cement or anything like that.

So the goals of this project worked out pretty well for reducing that PFAS mass discharge to groundwater.

So here’s another example of paper by Ask-A-Land 2025.

This is at an Australian airport, 8,000 tons of the stockpiled A-triple impacted soil.

They started adding this RIMBIND one to 2% weight by weight.

And one of the key things here is they said, if you’re using these smaller volumes, You know, this batch mixing with an excavator, you know, works well.

Portable trommel is something in the mid-range, and these really big jobs, you’d use this pug mill in here.

So they’re talking about potentially, and this last one, for example, you can do thousands of tons of blending per day, put that stuff in there.

And again, this would prevent a large fraction of that PFAS mass from going down into the subsurface.

So those are sort of VADO sown applications.

The next one we’re looking at here is more going into groundwater, and so this is the idea of injecting permeable, creating permeable sorption barriers through the injection of material.

And so colloidal activated carbon, one of the important amendments used here.

And so the graphic is sort of showing what you’re trying to do here.

You’ve got a rig out there pushing this material into the subsurface, into a PFAS affected groundwater, and then basically creating this sort of barrier at which you’re not going have nearly as much PFAS mass discharge moving outside or downgradient of that particular zone because the material that you’ve injected has caused PFAS to partition into it and keep it from moving downgradient. So a lot of this is being done right now.

There are different technologies in here, but certainly the predominant one is this plume stop, a REGENESIS type of coiled activated carbon.

I imagine a lot of the people listening this, know this story, but just going clockwise around from the top left.

Here’s the material they inject. It’s in this polymer, this dispersant. You inject this in the ground.

You’re trying to turn that brown soil to this black soil. And then the PFAS would go there and be absorbed.

And you can see the pictures that you see down in there. So you just got a couple of data.

We did collaborate with Genesis as part of a SIRTA project to try to understand and model how long these last? And so the next slide goes through some of the data.

A lot of these from different, you know, pilot tests and early or even first attempts at this. But, Dave, what’s going on here?

So this is about 17 different installations.

So each of the each of those are represented by a blue dot right on this particular graph where we’re plotting the fraction of CAC that was added, colloidal activated carbon per mass of soil. So that’s that x-axis.

And then the mass flux of that site is plotted on the y-axis.

And so you imagine you’re putting this stuff in, the idea here is that you’re maintaining a barrier or installing enough material to prevent further mass discharge moving beyond that barrier.

And then that has implications for how long it will take stuff to eventually break through.

And so this plot lays it out pretty nicely.

Let’s maybe look at a couple of sites.

So you’re sort of looking at this site number two.

The gold found after that is the actual estimated longevity in years.

So this is a modeled value, right, a predicted value.

But for that particular site, you know, not a lot of mass flux actually has a longevity predicted of about 1 ,100 years, so pretty good.

Not all sites necessarily fell exactly like that.

We’ve got this other site, much higher mass flux, added a little bit more carbon on a Longevity was about seven years.

So pretty big range in here in terms of those longevity’s the median Across all of these 17 sites about a hundred and fifty years, right?

Very dependent on that y-axis right that mass flux where you’re looking at What is that five orders of magnitude in terms of that?

So certain sites are gonna last longer certain sites, you know may not be appropriate, you know because of the mass flux is so high Just an emerging method is gas sparging.

We’ve got this approach where you just do a typical air sparging down in there and you have these channels that go up. It’s not bubbles, it’s channels.

And then our idea is to concentrate the PFAS near the surface.

And there are three variants if looking where that concentrated PFAS is.

Number one is you can just do a small skimming pump and treat system to remove the really concentrated material while most of your saturated zone is clean.

Then variant two is you could excavate this stuff out or just leave it in place under PMR And then number three you could add sorbents in here as well to then permanently tie all that stuff up So with this we’ve got some key tools you want to talk about Yeah, and I think this is important because that a lot of these sites, you know, we’re trying to evaluate them We don’t necessarily have a lot of long-term monitoring data to evaluate So we need to figure out ways in order to get data that would support site decision-making PMR, PER types approaches.

And we’ve got three of those laid out right here.

The first one is this model, the REMFluor MD model.

This is being developed of it’s an adaptation of existing REMFluor model to the REMFluor version through an ESTCP project.

This is sort of an Excel-based sort of interface on here.

But it’s a mid-complexity model.

It helps you answer some pretty key questions, like how far a plume might extend, how long you might take to get to particular concentrations.

So these are valuable for different PMR lines of evidence, and it can also simulate performance and longevity of these permeable sorption barriers that we’ve talked about.

Secondly, mass flux and mass discharge tools.

This is a combination of just thinking about high resolution methods.

There’s a lot of different ways to go about getting these data across these transects, and these are important.

Passive flux meters can also help out in that.

And then we’ve got software, things like the Mass Flux Toolkit, free software can help you with these sorts of calculations.

Then finally, one that was just released is this PFAS Arc Clearinghouse. This was developed during the ESTCP project.

It’s essentially taking a lot of performance data that’s out there, putting it in an interface that’s easy to sort of visualize what the concentration before and after the application of these different treatment technology have done.

So this is sort of a new thing that’s out there that can provide some for understanding or setting expectations for what happens after you apply these technologies.

Okay, last slide. This PMR framework, the document’s available to support this.

It’s not quite up on the ESTC web page yet, but you can email us if it’s not there.

It should be up there anytime now. These concepts appear to be slowly gaining ground. It’s in the ITRC tech reg.

There’s some certain sweet spots, say, for PMR, and we’ve got these four listed down in there in terms of interim rods, a polishing step, near-term containment, a resource allocation tool for the site characterization.

But that sort of sums up, I think, our presentation.

And now I think we’re going to hand it over to Dr. Paul Erickson of REGENESIS to sort of work out the questions, and let’s take it to the next step.

Okay, hey, thanks, Dave and Chuck, that was a great presentation.

What I’ll do now is just run through some of the experience that REGENESIS has over the past years in implementing some of the PER techniques that Dave and Chuck talked about.

When sites in your portfolio, perhaps you get to the realization that you do need to do some form of remediation.

And we’ve been doing this now at REGENESIS for the better part of 10 years in various forms. And so we like to break down these three different zones that Dave and Chuck talked about in various forms, places that you can implement PER.

And that’s the source zones, both in the VEDA zone and the saturated zone when you’ve got high concentrations, and then the plumes that these PFAS-impacted sites can form.

And we’ve got both different amendments and techniques that we use to get these amendments in the ground that I’ll just touch on.

And that’s, you see here, SourceStop for Veto-Sown Soils and PlumeStop that we’ve used now for quite some time. And so, you know, our experience, as I mentioned, has been now over 10 years, and we’ve got now 90 different projects, both in North America, Europe mainly, and a few other countries is that we’ve put these materials in the ground and started to collect quite a bit of performance data, some of which the basics of it, Chuck and Dave talked about in a recent study that they did looking at the longevity of these sites.

And so, you know, what the amendments are, I’ll touch on first plume stop.

This is, it’s a form of liquid activated carbon.

They, Dave and Chuck set it up nicely. The idea is that we can build these permeable and retention barriers using this flowable activated carbon, small particle-sized activated carbon that is suspended in a polymer, and that allows us to get this distribution, get this soil coating that then allows us to make these permeable barriers.

My colleague Jeremy Bernstingl recently put out a publication in Groundwater Monitoring and remediation, looking at the past 10 years of work that we’ve done with PlumSOP primarily, the principles, the performance expectations, what have been the lessons learned and there’s been many over the decade that we’ve been implementing these projects.

And what I’ll do is just touch on the highlight reel, I’d say from this publication, and give you an idea of where we’ve used this approach and what the, you know, what the range of its abilities have been.

And so, you know, you can see here the range of compounds that you can treat PFAS, you know, this refers to the PFAs, you know, C4 to C10 are, you can get retention on these, quite a lot, quite a big range of concentrations that we’ve done, applications to treat, and over quite a large variety of groundwater velocities, as you can see, and those two things combined, the groundwater concentrations and velocity, those give you the mass flux that was mentioned earlier that is really what you’re treating when we use these permeable absorptive barriers with plume stop.

And there’s those five orders of magnitude that was mentioned earlier. So that really determines, that mass flux determines the longevity and really the treatment expectations that you get out of these. But this just gives you a good window of what we’ve gotten into.

And the scale of these projects has steadily grown.

You know, as the concept has been demonstrated and studied at both the CERTUP ESTCP and other research levels and put into practice, you know, the scale of these projects has grown and the depth you can see, you know, we’ve got a lot of flexibility in the ways that we apply these amendments and how we get them where we want them to be.

And so there’s still a lot of room for us to learn in terms of where we can implement PER using both PlumeStop and SourceStop, which I’ll talk about.

But the creativity of how we implement these projects and really the asks that we get have only grown over the years. So I say here we’ve got a large and expanding possibility of treatment objectives and application modes.

So, you know, PER will look a variety of different ways depending on what sort of release you’re dealing with, what sort of PFAS-impacted places you’ve got. AFFF releases, you know, chrome plating facilities is another one.

And they all sort of have these unique challenges that with amendments and situ treatment, you’ve got a lot of flexibility in how you deploy your retention-based strategies.

And so, you know, a variety of pictures here to demonstrate that from the classic in situ injection using direct push. We can use injection wells as well.

We’ve done trenching projects with our amendments, colloidal carbon forms, ex situ mixing, and the one that’s on the far right is an interesting one.

We’ve started to do some surface applications where you’ve got these large diffuse areas where you had drift even around fire training areas, where you maybe just have soil impacts in the top, six inches to one foot, and using a colloidal activated carbon like PlumeStop or something like this, you can spray and successfully get retention of the low level impacts that are present in these soils and help push to PER this idea that we’re overall trying to lower or minimize the discharge from our vadose on soils to groundwater.

So if you’ve got ideas, bring them to us, we’d be happy to work through projects with you. So one of the, the amendment that is a bit newer to the market, you know, Chuck and Dave talked about some of the in situ soil mixing that’s been done on Vado sown soils.

You know, REGENESIS, we developed a product called SourceStop and that’s what this is intended use is. So it’s, it’s a soil additive for immobilization. And, you know, we started early on in the development using other amendments and sort of realized just how messy things like powdered activated carbon can be.

And so that was one of the driving things in developing this amendment was, how can we develop something that is gonna perform obviously what we’re looking for and that’s retaining our contaminants, retaining our PFAS and these soils that we’re treating, but make it user friendly.

So superior distribution and mixing, dust is a big issue with a lot of amendments. So this one’s formulated to be low dust. And, you know, again, the key is that we’re trying to get adsorption.

And so, you know, that’s what this amendment is intended for. And really the objective, and I’ll show you with a quick mention on how we’ve used this and studied the applicability of it, is the goal is reducing leaching to groundwater when these areas will retreat them.

And so the idea is that you can soil mix this amendment and easy to handle. Like I mentioned, the dust free part is worth highlighting and I’ll show you here just to give you a sense of how dusty pack can be.

And really on a site, on a works project, that can make a big difference in how not only the project goes, but how it’s perceived to be going when you’ve got a big dust cloud surrounding area.

So again, these are just practical things that we put into consideration when developing SourceStop as a product.

So, initial testing, as I mentioned, you know, these amendments that win soil mix, the objective is reducing leachability when we’re going to leave these soils in place, reducing that discharge from these soils in the vadose zone down to groundwater.

And so, I’ll walk you through to end here a quick case study on how this looked on one of our early pilot tests. And so, former fire training area that had quite a lot of PFAS in the fill soils, which is really what this was.

PFAS dominated, quite a high amendment loading in this case, but you can see here a fairly limited scale treatment area that we were testing. Here’s some photos to give you an idea of what the mixing looked like in this case.

And to demonstrate this ability to control leachability from these soils after treatment, we took some soil isometers and place them in a control area next to the place that we worked, and then also right within the zone that we did the soil mixing with SourceStop.

And this is going to give us a way to go back and do repeated sampling on the pore water, which is really, that’s our conduit from our rainfall that hits the surface of it, comes down through these soils on its way to the groundwater.

Is that pore water cleaning up? Are we cutting off the leachability in these soils is what we’re going to be able to look out with these lysimeters.

So this is a picture of what these devices look like. There’s a little ceramic cone on the end that you can draw on your soil moisture and use that as your analytical sample to measure how the leachability is looking.

Here’s a picture of them going down the end of the ground.

And the results here, so you can see that when we compare our untreated area, which you can see is starting out with a total PFAS in the pore water of over 4 ,000 nanograms, four to 10 ,000 nanograms per liter depending on when we did the sampling, you get these reductions that we’re looking for.

So after adding source up into these soils, we’re able to reduce the leachability in that pore water, which again is the compound to the groundwater, and we’re stabilizing. This is PER in practice and using SourceStop in this case to achieve that.