Hello and welcome everyone. My name is Dane Menke. I am the digital marketing manager here at Regenesis and LandScience. Before we get started, I have just a few administrative items to cover. Since we’re trying to keep this under an hour, today’s presentation will be conducted with the audience audio settings on mute. This will minimize unwanted background noise from the large number of participants joining us today.

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We are recording this webinar and a link to the recording will be emailed to you once it is available. In order to continue to sponsor events that are of value and worthy of your time, we will be sending out a brief survey following the webinar to get your feedback. Today’s webinar will discuss PFAS source differentiation at airports.

With that, I’d like to introduce our presenters for today. We are pleased to have with us Dan Schneider, Senior Principal and National Director for Site Investigation and Remediation at Terracom. Dan Schneider has over three decades in environmental and geotechnical engineering and remedial construction management and leads TerraCon’s nationwide PFAS professionals’ network, which consists of over 100 environmental professionals currently involved in PFAS projects across TerraCon’s national footprint. He is a subject matter expert on PFAS projects across the country, including commercial and Department of Defense airports, as well as facilities related to fire training, power generation, and other industries evaluating PFAS risk. For the ACRP research project, he was the team lead as well as a contributing author for Technical Report 255.

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 contamination treatment for PFAS, chlorinated solvents, and petroleum hydrocarbons, as well as remediation design, strategy, and business development throughout North America.

All right, that concludes our introduction, so now I will hand things over to Dan Schneider to get us started. Thanks, everyone. We appreciate the opportunity to be here today to talk to you about PFAS source differentiation at airports. I wanted to give a quick shout-out to my co-authors on this report, Dr. Janet Anderson with GSI Environmental, Matt Knudsen with TerraCon, as well as Zachary Puchatz with Mead & Hunt.

Our goal for the research was to provide a document that any airport manager across the could use in a simplistic form. We didn’t want another technical paper. We actually wanted something that would be used consistently and developed it accordingly. Today’s presentation comes down to three different areas that I’m going to talk about: where Airport PFAS landscape currently is, developing a lines of evidence approach to support the differentiation, and finally, a desktop review progress tracker, which we developed as part of the project.

So what’s inside the guidebook? There’s a couple of boxes underneath the document. If you could only read part of the document, those key details and technical overview really help us with coming up with talking points within each chapter. So again, there’s a QR code there for you to scan. This is a free download. If you want a printed version, it’s $79.

So we’re going to talk a little bit about airport issues. And again, the guidebook is for a wide-ranging audience, so we included basic PFAS 101 information. We also included frequently asked and answered questions about PFAS at airports, as well as AFFF. And we’re going to talk a little bit more about regulatory review, especially in light of EPA’s recent actions.

And then we’ll talk about potentially triggering events that may drive differentiation. And so just as a PFAS 101 quick hitter, we’re going to be talking about the non-polymer PFAS. We call these PFAS of relevance. We’re not taking on the entire group. And if you think about the PFAS of relevance, it’s really the basic 1633 compounds that are analyzed. Again, continuing on, there’s really three different sources.

Potentially, you have the primary manufacturers, you have secondary manufacturers that use PFAS in their products. And then you actually have the product users. All of these have the potential to get to landfills that get into releases into the environment through spills, runoffs. So you can imagine that this is a very complicated conceptual site model that you start to develop as well as associated potential liabilities.

So I was talking earlier about EPA’s recent actions. I like to call them the trifecta PFAS-related actions. The interim guidance on the PFAS destruction and disposal document outlines three acceptable practices for managing PFAS-impacted materials: deep well injection, thermal destruction, as well as landfilling. The interesting thing about the landfilling option is that there’s no difference or no preference by EPA as to whether materials go to a subtitle C hazardous waste facility or that they go to a subtitle D municipal solid waste facility.

The second of the trifecta is the final national primary drinking water regulation that went into effect April 26th, 2024. So this was the first MCL that covers the six PFAS compounds. And again, this is EPA’s making good on their action to come up with a national drinking water standard across the country.

The final rule, and probably the most important one, in my opinion, is the designation of PFOA and PFOS as hazardous substances under CERCLA. What that basically means is that now, during real estate transactions, PFOA and PFOS will have to be considered to complete the all-appropriate inquiry and bona fide purchaser protections under CERCLA. And so now, when phase 1s are done on properties, any potential PFAS impacts will have to be looked at as a recognized environmental condition.

What’s interesting is that when along with that designation was the discretionary enforcement and settlement policy that EPA published at the same time, what that document basically says is that along with EPA’s the polluter pays principle, they’re designating certain industries that will not be enforced upon unless they have significantly contributed to PFAS impacts. It’s kind of interesting because what they’re basically saying is we’re good with going after the polluters that we think are really responsible for this. We understand there’s passive receivers that have kind of gotten whipped by the tail on this whole thing, so we’re going to put those kind at the bottom of the list, but again, this policy is really not enshrined in the regulation. It’s actually something that can be changed, it can be discarded, it can be modified.

So very interesting perspective from the EPA. So I’m going to talk just a little bit about the landscape at airports. On the screen you can see there’s a list of potential PFAS release areas. We’ve looked at several airports, and actually the list that was put together for the ACRP document was pretty comprehensive. There may be some others, though, that are out there. Along with that, it’s not just AFFF. Most of the folks on the phone will note that there are many, many different compounds that have PFAS as part of their process that can potentially contribute to PFAS impacts at an airport.

So, one of the things that we were charged with in our research was, number one, how do we come up with an approach to differentiating PFAS at airports, where you might have several different of those sources that we talked about on the screen earlier. So our approach was, we analyzed over 800,000 PFAS data across the country to develop PFAS source patterns. And so one of the things that we came up with is a lines of evidence approach was really the best way that we saw to approach this problem.

And so when you think about it, there’s really three different categories that we think support differentiation. That’s desktop review, conventional sampling, and advanced forensics. Under desktop review, we’re looking at on and off airport sources of PFAS. We’re also looking at the actual site characteristics, and we’ll get into these a little bit more in the next slides. Then you go to conventional sampling. It’s kind of interesting because a lot of times we’ve seen airports rush to sample, and so we wanted to provide a sampling rationale of how to maybe look at this first bit desktop review to see where and what media is appropriate to sample prior to going out there. Also, with conventional sampling, we can do some preliminary source screening. Then the final one is the advanced forensics, and that’s the stated science.

What we wanted to do is provide a when to consider and what to expect if you’re looking at advanced forensics.

We live in a data-rich environment today. You’re able to access tremendous amounts of information from your phone. This list that’s on here is just a partial list of what we provided in table 3.5 in the research report. But there’s a tremendous amount of information that’s out there, more being developed every day. I think the last count was the number of PFAS databases had quadrupled in the last four years to the point that almost every state has their own PFAS database. So again, tremendous amount of information that’s available at the tip of your fingers.

We did talk about conventional sampling And we wanted to also emphasize the importance of not focusing just on the risk-thriving PFAS. What that means is looking beyond PFOA and PFOS. We also wanted to talk about how important it is to understand the geology, the hydrogeology, all the things that go along with developing a robust conceptual site model. And also take into account things like stormwater infrastructure, extremely important for transport of PFAS at airports. A lot of the time-drilled responses were done in areas that when the response was completed, this area was basically washed down, and then you had transport into stormwater infrastructure potentially.

So again, for completeness, we also wanted to talk about precursor transformation and transport specific to PFAS.

What we came up with is, if you look at the bottom of the screen, you’ll see the data visualization categories. So from that 800,000 data points, we were able to come up with what we call PFAS signatures for these six different categories of sites. Airports, chrome platers, industrial, cleanup sites, wastewater treatment plants, and landfills. Now, it’s important to understand that the data that we evaluated, there was no geospatial information available. So we don’t have any idea if that sample that we took into our database for analysis is at the toe of the plume, if it’s at mid plume, or if it’s cross gradient. So again, there is some room there for interpretation. We’re assuming that they’re close to where the source actually is the strongest.

So this slide shows some of the visualizations that we put together. You can see, familiar to most people, box and whisper plots, we put together these as different ways of demonstrating what quote unquote the fingerprints. And then one of the upper right hand corner is the one that most people kind of lean to because it shows up very easily. And again, dating myself, I like the pie charts because to me they’re pretty simple to look at.

Now, one thing is, we’re also thinking about how does the airport person that’s responsible for PFAS assessment at the airport, how do they convey this information, both upward and downward, and possibly to stakeholder groups. So again, while some of these visualizations You know, we’re pretty familiar, think about it in terms of if you were explaining this to a care report executive, you know, would you want to use a ratios plot or would it be better to use a simplistic pie chart?

So one of the things that we were able to determine is that looking at the detection and frequency PFAS sources by category, we were able to come up with some interesting things. This is probably pretty common knowledge to most folks. But you can look at this in two ways. One, it looks very, very distinct. Certain compounds are showing up in certain categories. However, if you only looked for PFX HA, you would see that it’s common to all of them. So that’s where that lines of evidence approach is really important to differentiate potential sources.

So let’s talk a little bit about advanced forensics. So the box at the right, really the limitations I are important to understand. It’s extremely challenging area right now of PFAS assessment to look at forensics from a quantitative standpoint. Most of the work that’s being done is at a qualitative standpoint. It’s mostly unvalidated and it’s also extremely difficult to communicate. You know it’s one of those things that you know amongst PhDs it’s probably one thing that if talking to a stakeholder group that’s trying to understand why you don’t think that it’s your PFAS in their drinking water, it’s probably going to be extremely challenging. It’s also done in a very high level, at a very high cost. And so again, I want to present kind of the approach that there certainly is a place for the advanced forensics. It’s probably not on every project, but it may be important in certain circumstances. So again, some really good work being done out there by folks like Patel and others.

So lastly, I want to finish up with a tool that we developed to help the airport manager understand where they’re at on the PFAS journey. This is a very simple Excel-based application. It’s available on the ACRP report download page. And it really focuses on those two columns, the desktop review and the conventional sampling. And what’s really cool about it is, as I say, it’s pretty simple. We came up with 82 questions. We wrote a real simple algorithm to weight them differently, and we came up with a speedometer to visualize kind of where you’re at in the beginning, increasing, good, or excellent as far as the progress in that one area. And so you can see some of the questions are up on the screen, you know, does the hangar fire suppression system, is it charged with AFFF, you know, pretty basic questions that you can probably answer, and then you can see the drop-down, and it shows whether we haven’t thought about it, yeah, we’re sort of thinking about it. We’ve spent a lot of time and really reviewed this extensively, or maybe it’s not applicable.

And so when you look at those three different areas, the on-airport, off-airport, and site characteristics, and these 82 questions, you can basically then roll this up into one large site-wide progress for your PFAS assessment. And again, this was never intended to be able to compare between airports. So, you know, are airports doing better or worse than airport B? It was more to help understand and help communicate to the folks that are needing this information in a very simplistic form. And so what that rollup looks like is this, you have the three miniature speedometers, and then it rolls up to the overall progress. So as you input the responses to these questions, the speedometer will continue to move to the right and show your progress.

So again, if you’re still trying to understand more, say, outside characteristics, and you’re just in the beginning, that would be the opportunity to be able to say, you know, we’ve got a pretty good handle on what our sources were on-site. We think we have a good handle on what’s going on off-site. But you know, we just need more boring information. And so that could be an area that you could look for increased funding, say, from the airport.

So the last part of it is really this comparative analysis tool. And remember, we talked about those pie charts that were basically tied back to the industries. So now with this tool, you actually can put in your site data, and it will visualize that data from a composition standpoint. And you can actually then take a look at it, comparing it to the fingerprinted segments that we’d already developed.

So, in conclusion, again, I think it’s pretty obvious, but to state it anyway, there really is no silver bullet when it comes to source differentiation. We’re still learning. We’re still trying different things. I think we’re getting better, but a lines of evidence approach is really the best approach because it allows you to look at lots of different things from different perspectives and see if you can come up with a conclusion based on all of these things. And again, the last part is really the visualizations are only part of the evidence. They should be used with the other lines to build that approach and consideration. You don’t just wanna plug in your lab data and it spits out, gosh, it looks like wastewater treatment plant, great, that’s it. It’s more like, okay, so what other evidence do we have that it could be that? And when you start looking at these, They actually are a lot closer together than they would first appear.

So with that, I’d like to turn it over to Maureen Dooley with Regenesis.

Well thank you, Dan. That was a really interesting presentation and you can see the work and effort that was put into developing this tool and will be really valuable for those that are investigating these complex PFAS sources. So, staying on the topic of airports, you know, what I want to discuss today are some of the issues the airports or maybe, you know, these municipal fire training areas, you know, might be confronted with, and then share some of the experiences we’ve had working on some of these different sites.

So jumping into the conceptual site model, looking at the PFAS contamination, quite typically we might have a point source where there was fire training activities and in those locations you’re going to have elevated concentrations of the PFAS in the soil and then through leaching and rainwater eventually these PFAS contamination is going to move its way and make its way into the groundwater. Something that you typically see is that the PFAS is going to get hung up in that fringes and right in that zone.

But important points are the PFAS are resistant to any kind of degradation, biological, chemical, and these remediation programs and trying to figure out what to do can be really quite challenging. So what are the options and what are some of the issues that the airports are really looking to try to deal with?

I have this full spectrum remediation I’m showing which is the A, B, and C is related to some of source material and then we have at the property boundaries quite typically you know this is where groundwater is often addressed so starting with groundwater and I mean the real issue is keeping PFAS from moving off site and so you’re looking at some sort of mitigation effort because what are the drivers you have the potential for having private wells impacted and I think even importantly is this a contributing source to impacting municipal water supplies?

And also you can have sensitive eco receptors. And so it’s really critical to be able to stop the migration of the PFAS going off the property. And then there’s other activities that may be focused on the source. And that’s really at your point source where you might have had historical fire training activities, but also, you know, during construction, you may have waste that’s generated that had been impacted by the PFAS. And so I’m going to touch on all of that, but really to get started, remediation itself, what are we talking about here?

Well, remediation is some sort of process that we’re going to use to reduce exposure to a harmful chemical, some sort of process. And by reducing this exposure, we’re then going to eliminate the risk that’s associated with these hazardous compounds. So you have your PFAS hazard, and you have this potential exposure pathway to groundwater or contact with soil. And if you’re able to eliminate that, then we eliminate the risk. So because we don’t have the ability to use degradation sort of mechanisms, then we’re looking at other sort of processes.

Insorption is one that certainly can be used to mitigate the exposure pathways for PFAS. So what are some of the challenges that we see at the airports? Well, number one, you’ve got a lot of sensitive infrastructure. You’ve got issues with just having access to contamination. You know, the airport operations, there’s a lot going on. You have a lot of construction activities. So being able to manage contaminated soil and water, just generally, and you have other contaminants that may be present, say for instance, petroleum hydrocarbons. And now you have this emphasis on the emerging contaminants because all of these airports had fire training. So there’s, you know, a high likelihood that PFAS contamination is present at these sites. And you have these obviously very low regulatory standards.

So starting with groundwater, we really only have two options. One is groundwater extraction or an in situ remediation. So starting with the groundwater extraction, the remediation is removing the groundwater from the ground. People sometimes talk about destruction, but that’s related to managing the waste that you’ve just removed from the ground. So you pump the contaminated water out and you have to go through some sort of activity of either ion exchange, carbon, SAF units, and you’re either going to ship it off to a landfill or perhaps some other destructive technology. But it’s really, really important to note that this is an engineered control. So, you’re not cleaning up the aquifer.

And, you know, to get into a little more detail on that, let’s think back to the 80s when Superfund sites were first getting started and the remedy that was typically employed was a groundwater extraction or pump and treat system. Well, many of these systems have been operating for decades and and they have not been able to achieve the targets. And, you know, so the question is, well, why would this be any more effective for PFAS compounds? Well, PFAS, they soar more tightly or more strongly to the aquifer material. So they’re going to be harder to flush out and you have cleanup standards that are significantly lower. So parts per trillion versus parts per billion. And so it’s even more difficult to try to achieve these targets. So it’s important to consider this when you’re thinking about the remedy for a site like an airport that’s going to have a lot of activity.

And the other thing is you’re going to have to manage the waste that’s generated as part of the groundwater extraction or pump and treat system. And this is something that you’ll be having to do for 10, 20, 30, 40, 50 years. So, Scott Wilson did a webinar focusing a lot on the groundwater extraction pump and treat system. And so I would suggest listen to that webinar and there’s some really good references that are also associated with these slides. So feel free to look at that and get more information on some of the challenges associated with the groundwater extraction. So what I’m going to talk about is in situ remediation using colloidal activated carbon. So in this process, we’re going to inject colloidal activated carbon into the subsurface. It’s going to coat the soil and as groundwater flows through this colloidal activated carbon barrier that’s been established, the PFAS is removed from groundwater and then sorbed onto the colloidal activated carbon.

So what’s a colloidal activated carbon? So we take activated carbon, we mill it down to like one to two microns, and then it’s expended in a polymer.
And that allows us to apply the material under low pressure and get widespread distribution and coverage. And so we have a number of different formulations of this. We now have a liquid and a solid formulation and I’ll get into more detail on that a little bit later.

So as I mentioned, so how does this work? So the colloidal activated carbons, they permanently coat the aquifer matrix and then the PFAS is immediately removed from groundwater. And in this way, you’re removing that exposure pathway to the receptors and you’re reducing the risk associated with the PFAS that’s in groundwater.

So, I mean, the big question, I mean, does it work and for how long? I mean, that’s the question that we get all the time. So we had a paper that was published by Dr. Grant Carey and he and the authors were looking at 17 different airports. And here’s some of the takeaways from this. Number one, the typical PFAS compounds that are present in AFFF and at airports are dominated by PFOS and PFHXS, and they are preferentially sorbed to the activated carbon, meaning carbon is just a really good solution for the predominant AFFF PFAS compounds. You often may have some co-contaminants are there. The activated carbon is also very effective with other hydrocarbons or chlorinated solvents that may be present. And some of the really important takeaway is the modeling that was conducted shows that you can have decades of treatment with a single injection. And just to get into a little bit more detail on that, so we talk about longevity.

Well, what does this mean? They say decades. Well, what we do is we at what the flux of PFAS is that’s coming into a barrier. And there’s a fixed amount of carbon that’s applied, but we’re able to model or determine the amount that’s required to deal with the amount of PFAS that’s going to come into the system or come into the barrier. So we’re able to estimate how much is required and then model how long it’s going to be there. And so we can look at something being in the longevity of something like decades.

Well, if there’s some concern that you might get some breakthrough coming through, you can always apply additional material and extend it. Well, I think what’s really critical is, if you are able to address the source, quite often a single injection can be all that’s needed or all that’s required to address the PFAS that’s at a specific site. And again, getting into a little more detail on this.

So once you treat a source, maybe it’s bound up so it’s not leaching into groundwater or perhaps you even have some sort of cap or an asphalt cap so you don’t have any leaching, you’re going to minimize PFAS discharge into groundwater. So you’re going to limit the amount of flux that’s going to be coming into the barrier.

So if you look at this figure here, you see the red representing the PFAS. And so if you have a barrier down gradient of that, what happens is groundwater flows through, you’ve changed the equilibrium. So now that you have the carbon there, the PFAS very rapidly sorbs onto this carbon. And so it’s removed from the groundwater. But the desorption or the equilibrium has been shifted so much that you really don’t see any of the PFAS showing up in the groundwater. And if it actually does at some point in that so-called breakthrough, it’s going to be below the regulatory standards.

Now, it was really interesting. I was at this PFAS forum in Florida, and somebody used the term monitored natural retention. And I just thought that was just a great term because that’s exactly what’s happening here. You’re creating this retention, this change in equilibrium, and this can be maintained for decades and decades and decades. And if you are able to address that source and in combination with that barrier down gradient, you can have a complete solution with a single application.

So as I mentioned about designing the treatment, so what is the information that we need? What is the information we’re using? Number one, we’ve got models and we can take into account isotherms and this dynamic sorption. And some of this information that’s really important to us is the flux that’s coming in, what kind of contaminants, what are the PFAS levels? And is there any other combined treatment that’s taking place at the site?

So we take all of this information And then using this model, the dark area represents the barrier and the lines are the different concentrations of the contaminants coming into it. And we can look at this over time and get an idea at 10, 20, 50 years, what the concentrations may or may not be on the other side of the barrier. And so using that, we’re able to one figure out how much carbon or colloidal activated carbon is required for a particular treatment. And then secondly, what sort of longevity we can get at a particular site. So the installation itself can be quite simple. You can use direct push and apply that. We also can look at other things like trenches, but direct push is really most typical for any of these groundwater barriers.

So this is a snapshot of some of the results that we’ve had at other airport sites. And you can see, you know, in this table that we’re able to meet objectives in a very short period of time, and you can get some of the concentration range that we’ve had of the PFOA and PFOS at some of these sites. But what I want to do is just, you know, jump in to a couple case studies and just share some more specific data, you know, again, staying with the groundwater.

The first site I just wanted to mention is the Martha’s Vineyard Airport. So, as you may know, this is an island off the state of Massachusetts. And so there were fire training activities that had taken place at this site. And one of the real concerns was the potential for some of the private water wells to be impacted by any PFAS that may be migrating off site. So they’ve undertook an investigation, they had identified where a fire training location was and had looked at some of the groundwater concentrations. And so a design was prepared to have a barrier in place down gradient from the fire training area. And our goal was to reduce the concentration of primarily six PFAS compounds.

This is the Massachusetts 6. So you can see these listed here. And so we’re looking at the sum trying to achieve 20 nanograms per liter or less. A really important factor in deciding to use the colloidal activated carbon barrier was they did not want to have to deal with any hazardous waste disposal there on an island and the idea of managing that was just not something that they were interested in pursuing.

So this is a figure just showing where the barrier is up in the red here and this is where the former fire training area was. So We had a barrier roughly 60 feet in length, covering a 10 foot section. We had approximately 10 ,000 gallons injected. So this was a coarse sand with silts and where normally you think this is pretty homogeneous, we did have some variation in some of the groundwater flow at depth within the subsurface. And so we really focused on the flow zone that was most conductive so we could deal with most of the PFAS was running in that zone the highest flow.

So the results, just showing where the wells are. So we have the barrier, we have an up gradient well, we had a well-placed very close proximity to the barrier, and we find that that’s really critical. So we understand what’s happening in the barrier itself or right down gradient from the barrier. And then we had another well that was 25 feet down gradient.

So the results that we had showed that the well that was immediately next to the barrier within in three months was 99.9% reduction. And they had maintained over that whole year long period that the test was conducted under. And then looking at data from 25 feet down gradient. So this is the up gradient well. And in blue, you see the reduction in concentrations of the Massachusetts six over the year. And so by day 343, we were at five nanograms per liter for the combined six compounds. So we’re able to see and show that we were able to achieve these targets. And it was nice to see how quickly that the groundwater responded even down gradient. And so I think that was a really an ideal location and ideal site for this type of application.

So a second site, got a very similar scenario. This is an airport site that was in Michigan. This is another situation. So this is where we’re at the property boundary, groundwater is moving to the south and you see we have contamination particularly in this well and you can see some of the zones where most of the PFAS is and so there was concern about PFAS contaminated water migrating off-site because there were private wells and there wasn’t any municipal water available. So the idea of putting people on a poet system indefinitely you know is ideal.

So the program that this airport utilized was some funding that was available in the state of Michigan as part of the investigation. They incorporated this pilot test to get information to help them as they want to move forward for full-scale remediation. And so this is the area where the barrier was applied. And just showing some of the results here. So there is PFAS contamination at depth. And the barrier was focused just on these two segments, this section here. So you can see the results that you had significant reductions immediately in the two zones where the groundwater was flowing through the colloidal activated carbon barrier. And then in the deeper where they didn’t have any exposure to the colloidal activated carbon barrier, you obviously didn’t see any change.

So again, it’s showing a very rapid reduction and your ability to achieve and maintain the low targets. So kind of getting back, we’re talking about groundwater and then the idea of source remediation. How does that fit in? As we mentioned before, if you’re able to address the source, that’s also going to significantly increase the lifespan of the barrier you’re using to mitigate groundwater contamination.

So, what I want to talk about is source treatment. So focusing on source treatment, what our objective here is to stabilize the PFAS contamination the source and what that means is we’re going to reduce leaching. So we’re going to apply a colloidal activated carbon or source stop formulation, mix that in directly or inject that in target areas, and that’s going to be protective of groundwater meaning it’s going to keep the PFAS in place so it’s not going to leach into the groundwater and then halt the migration of the PFAS. So we have two formulations that we’ve developed. One is a liquid formulation that we’re able to inject. And I’m really excited about the second formulation, the solid, which is a combination of colloidal activated carbon and granular activated carbon. And it has a lot of really interesting features.

So, looking at the conceptual design or conceptual site model for some of the source you know how might we apply these materials. Well, say for instance there’s been construction activities and you’ve got stockpiled soil, or you have a point source and you’ve got some vadose contamination, you can take something like the solid material and just mix this directly in with the soil. and that’s going to again stabilize the PFAS contamination. Another option is you may just need to have some containment at this capillary fringe at that VADO saturated subsurface line, that capillary fringe. And so you can have a direct application or injection using the liquid material or you may use some combination thereof or sometimes people may use something like an approach at the capillary fringe and then perhaps the asphalt cap.

So there are a number of different ways that you can use these materials is part of either beneficial reuse or other just source mitigation activities and we’re happy to work with you and sort of brainstorm what makes the most sense for your particular site. But I just wanted to show some additional information on the solid source stop.

So what’s really interesting about this is the combination of the colloidal activated carbon plus granular activated carbon. But when you see when this is placed into some water, that the colloidal activated carbon releases. So just the moisture in the soil is going to release this. And why is that important? Because that’s going to move and penetrate and get into some of the finer grain materials and just give you much better coverage. So at the end of the day, you may end up needing less material because this is a more efficient application of a sorbing reagent. And so it can actually be quite cost effective in methodology for stabilizing the PFAS contamination.

So there’s a number of different field applications that we’ve used to apply the material. So anyway you can just see some of the direct mixing with excavators. We’ve also used trenching but you also look at the difference in the color and you can see the distribution of the source stop material in the soil once it’s been mixed in.

And so just finally just showing one last case study. This was used at a site in Grayling, Michigan and this was application of source stop with the objective to reduce PFAS leachability. So in this case we had a direct mixing equipment and you can see how black this is so it’s another advantage to the source stop as you can see where the mixings take place and what soils have been applied so you can ensure you’re getting really good distribution of the material and this is what looks like after the fact and so the results.

The testing that was conducted for this was a leaching test SPLP so at baseline you see the level of PFAS and the SPLP leachate. The first test that post-treatment that sample was taken immediately after the source stop was applied and then you see it six months and 12 months that you have this continued stabilization you aren’t seeing any PFAS showing up in the leachate.

All right, so finally, people always want to know about costs, so what are the costs of these applications? Jumping back to some groundwater treatments, one small application of the plume stop was used at a particular site, and we see that the cost was only $73 ,000 versus a groundwater extraction, which would total about 1.3 million. But one of the larger projects that was completed recently was we had a large scale plume stop barrier and so that application was at 3.5 million and the estimated cost of using a pump and treat sheet pile system would have been over 20 million. So in addition to being able to very quickly get results and maintain these results, it’s also extremely cost effective.

So with that I just want to wrap up and also just mention we have all kinds of ongoing research efforts taking place and we’re happy to discuss those or any other sites that you may have, but we’ve been really happy with the results that we’ve had at some of our airport sites and with that happy to answer any questions.