Hello and welcome, everyone. My name is Dane Menke. I am the digital marketing manager here at Regenesis and LandScience.

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Today’s presentation will discuss PFAS lessons learned from treating a large-scale AFFF site using in-situ colloidal activated carbon.

With that, I’d like to introduce our presenters for today. We’re pleased to have with us Rebecca Mora, Associate Vice President and Senior Technical Leader at AECOM. Rebecca Mora has over 25 years of environmental investigation and remediation experience. She specializes in the design and implementation of innovative technologies, particularly for groundwater sites contaminated with current or former emerging contaminants, such as PFAS, 1,4-dioxane, perchlorate, and hexavalent chromium. Most of her career has focused on in-situ remediation, with an emphasis on developing cost-effective solutions for industrial and federal clients’ environmental challenges.

We’re also pleased to have with us today Ryan Moore, PFAS remediation program director at Regenesis. Ryan Moore has over 20 years of experience as an environmental project manager and laboratory account executive relating to multimedia contamination sites throughout the U.S. His experience has focused on in-situ groundwater and soil treatment, site investigations, corrective action evaluations, operation and maintenance of remediation systems, large soil removal remedial projects, vapor intrusion assessments, and environmental laboratory operations such as QA, QC evaluations, data interpretations, and business development.

All right, that concludes our introduction. So now I will hand things over to Rebecca Mora to get us started.

All right, thank you, Dane. Thanks for that introduction. And thank you all for joining today. I’m looking forward to sharing the results and lessons learned from an interesting site we’ve been working on for more than two years now, where we’re treating PFAS and groundwater at a former fire training area. And based on recent discussions with Regenesis, I believe this project is still the largest full scale PFAS treatment with colloidal activated carbon to date in the world. So that may provide some perspective as we go through the presentation. So this is a brief overview of what I’ll talk about today. I’ll just have one slide on what is plume stop just in case there’s anyone out there that isn’t familiar with it. I’ll go over some site background that’s relevant to the rest of the slides. I’ll go over a pilot study very briefly that supported our injection design. Then I’ll spend most of the time on the full scale.

We’ll talk about the installation of the barrier, we’ll talk about results of two years of monitoring, and then I’ll summarize all of the lessons we learned during this project to share with all of you. So what is Plum Stop. Well, it’s colloidal activated carbon, so very small particle sizes about one to two microns. And it’s suspended as a colloid in polymer solution. So that helps it be distributed in the subsurface. And essentially, Plum Stop coats the subsurface soils and turns them into a purifying filter. The carbon in the subsurface absorbs contaminants. And you can inject this product perpendicular to groundwater flow as a treatment barrier, which is what we used at this site.

So, here is an aerial view of the site. It is a former fire training area. Over on the left-hand side, you see those green rectangles. Those are the former source areas. The black dashed line around the property is the property boundary. And then you can see just outside of that property boundary are a couple of ditches. This solid blue line is a ditch that always has water in it. and that is because there is groundwater venting to that ditch. Over on the left-hand side is another ditch that is dashed that only seasonally has water in it. So we have about constant groundwater flow over on this part of the site that is towards the ditch. Over in this area we have variable groundwater flow depending on the season. And when we first arrived on this site there were only about five wells here and so we chose the highest concentration well to perform our pilot study at. And that is over here, just down gradient of one of the source areas.

So this is the approach we used for the pilot study. We had five injection points represented as those red dots. We had six temporary piezometers that are the blue triangles. And those were used to evaluate plume stop distribution during injections, both down gradient and cross gradient. We also had two performance monitoring wells located seven and nine feet down gradient of the injection points. And after injection, we collected seven post injection soil cores to confirm distribution. So that gray shading around the wells and cores and piezometers, that represents the extent of plume stop distribution. And below is a photo of an example confirmation core which shows plume stop distribution within the more permeable soils here in this black area and as well as down here.

So what did we see in the pilot study? Well, we saw very rapid decreases in concentration. We had more than 99% reduction of PFAS, PFOA, and PFHxS. There was significant reduction in concentrations in both wells by the first monitoring event, which was about one month after injections. We had a little more gradual reduction of PFOS in well PZ1, and that’s because it was further downgradient. If you look at the total PFAS in MW11, you do see that there’s a little bit of increase after injection, and that was due to some rebound of short-chain PFAS compounds. So after the first sampling event, which was performed in the end of March, we received the data probably about the end of April. And as soon as the client saw that, they said, we’re sold. We want you to move forward with full scale. And we want it installed in June of 2021, which was two months away.

So let’s talk about that for a second. Because normally, when I work on remediation sites, I like to have a fully developed conceptual site model, understand a site better. And that just wasn’t going to happen at this site. The client was interested in moving rapidly to full scale. There was perceived regulatory as well as public pressure. They wanted to show action that they were being proactive. And so what we agreed on as an objective is to reduce PFAS concentrations in groundwater migrating towards the nearby offsite ditches. So we did not have numerical criteria for this installation.

Okay, so let’s talk about the site characterization we were able to do. So actually, while we continued monitoring the pilot test, we went out and installed a bunch more wells around the boundary of the site. So we installed about 14 new wells and we collected samples and analyzed them for PFAS compounds, as well as potential co-contaminants that could also be competing for plume stop absorption sites. So what we found was only one significant co-contaminant, which was DRO or diesel range organics. And this map shows kind of the range of concentrations that we detected.

So we’ll start with PFAS first. Those are the red, orange, and green colors. You can see that red is the highest concentrations. This well over here on the left-hand side was the highest concentration at the site. Total PFAS of about 550 ,000 parts per trillion. The orange wells, which are primarily over here on the left-hand side, near the former source areas, those range from 20 ,000 to 100 ,000 parts per trillion total PFAS. And then when you get further away from the source areas, you get down into the green color, which is about 1 ,000 to 20 ,000 parts per trillion total PFAS. The DRO concentrations are represented by single yellow circles or double. The single circles indicate DRO concentrations between 1 ,000 and 5 ,000 parts per billion. then the double circles here represent 5,000 to 10,000 parts per billion. So DRO was primarily detected over in this portion of the site as well as this high concentration PFAS well over here.

And one thing that’s really important and interesting I think is this well with the highest DRO concentrations had the lowest total PFAS concentrations. You know a good order of magnitude lower than its neighboring wells. So that’ll come back up when we look at the results. This is a cross section of the site and there’s so much I could talk about on this slide but in the interest of time I’m going to limit it to what’s important to share with you all for context when we discuss the injection activities and results.

So the first thing that’s important to point out is that it’s a perched water table at this site. So depth to water is generally about two to four feet below ground surface but deeper as you get towards the right hand side of the section because of that hill. The top few feet is reworked urban fill with high permeability. Below that we’ve got sand and sand-silk mixtures and then followed by a thick continuous clay layer that starts at about six to eight feet below ground surface. So these are really favorable site conditions for plume stop. You know you’ve got permeable sediments for good distribution of boom stop, it’s not deep, and so you save on drilling costs, and then you have that nice confining layer with the clay to tie your barrier into.

On the northern end of the site, which is the right-hand side of the figure, you can see depth to water gets deeper, and also depth to clay gets deeper. So we’re dealing with a thicker saturated zone over there. Also note the six-foot-thick gravel deposit over on the side of the cross-section. that will come into discussion later when we’re looking at results. Also, something important to look at is over here, there is a highly transmissive shallow zone in the vadose zone in this area that extends from this MW08 over to about MW11. So that’s down to about over here, this part of the barrier. This is a very highly transmissive zone and we’ll talk more about that when we get to the injection activities. So we perform slug tests in each of these new wells to provide estimates of hydraulic conductivity. And then with that information, as well as the lithology and the concentrations, we put together the full-scale design.

Okay, so this slide kind of shows the design of the barrier and I’ll walk you through it because there’s a lot to talk about here. First thing we’ll look at is the barrier geometry. So, you may notice that the barrier is a decent distance away from the site boundary. And that’s because we don’t know how exactly how long this barrier is going to last and how long it will be needed. So, we wanted to leave room for a future second barrier should it be needed in the future. You can see how it’s nice and straight along the left-hand side of the figure. And then you turn the corner and it’s definitely not straight. We had a lot of subsurface obstructions that we ran into. We did actually perform geophysics along this whole area before injection, but ground penetrating radar does have some limitations. So we still had several unexpected subsurface obstructions that we were able to work around because we were using an injectable technology.

So moving on to the color coding. Over here in the legend, you can see what the colors represent. So you’ve got green is 100% plume stop concentration, yellow is 150, and red is 200. So the 100% is essentially the calculated plume stop demand. And then the yellow and red represent safety factors that were applied to that calculated plume stop demand. And that was either due to the presence of DRO at that location or really high PFAS concentrations. These safety factors were also applied because we were trying to manage the risk of having a less detailed conceptual site model. The different dashes along the barrier represent deep injections. So sections E, F, and G are where we had the deep injections. And then over in section A, we actually performed intentional mounding over there. And that’s because in section A, the water table can be very shallow, six inches to near surface sometimes of the year, but we can’t directly inject that shallow. So what we did is created some mounding during injection, which resulted in some distribution above the injection interval. So in the middle there, we’ve got kind of what I call our injection statistics.

It took us about three months to install this barrier. It’s about 1 ,635 feet long, required 660 injection points. We injected primarily from three to seven feet below ground surface, except for the deep injections, which were 6.5 to 14.5 feet below ground surface. And then all in all, we injected about 295 ,000 pounds of Plum Stop. Okay, this slide talks about the injection approach as well as it has some photos from the injection. You can see over on the left-hand side there, we had injection points every five feet, and they were in two staggered rows. We did have two injection rigs out there, each of them injecting into multiple injection points at once, trying to be as efficient as possible with the timing. We had piezometers and confirmation cores every 50 feet to evaluate distribution. That’s called design verification.

We installed the piezometers ahead of injection and then we also used that lithology data to update the injection design as necessary because if you recall you know we had just 14 monitoring wells around the perimeter and they were a hundred to two hundred feet apart so it was really helpful to collect some additional information in between those monitoring wells while we were out there. And because we were gathering this additional lithology data and also encountering subsurface obstructions while they were injecting, we used Microsoft Teams chat where we had the field crew from AECOM and Regenesis and then the office staff from AECOM and Regenesis all on the same chat and the field folks were able to tell us what they were seeing. We were able to have input, make decisions real time and keep things moving. So it really ended up being kind of a best practice.

We did experience some surfacing during the injections especially in the shallow water table areas. But we essentially contained those and let the plume stop infiltrate back into the ground over time. So at this site, that wasn’t a particularly big deal. We also had one instance of plume stop daylighting in the ditch. And this was due to that shallow, highly transmissive zone I pointed out previously on the cross-section that’s right below ground surface. And what happened was is when we injected, And there was some mounding, and it raised the water table to intersect that highly transmissive vadose zone, and Plum Stop traveled along that transmissive zone to the ditch.

So for the rest of the injections along that highly transmissive zone area, we used what is referred to as a parking agent. So the parking agent was either liquid calcium chloride, or in some cases we used gypsum as a solid, which is calcium sulfate, and the calcium component destabilizes the colloids in plume stop and flocculates the carbon so that it is no longer mobile. So while we were still injecting in that, you know, troublesome area, we used the parking agent, injected it down gradient or emplaced it down gradient of where we were injecting, and that limited the migration of plume stop beyond that point. So this approach resulted in no more daylighting during the rest of the effort.

Okay, I wanted to, before we get into results, I wanted to talk about our monitoring approach. So we designed this monitoring program to have two types of wells, in-barrier wells, which are shown in blue, and downgradient wells that are shown in purple. So the in-barrier wells, we used those to evaluate the health of the barrier itself, and then the downgradient wells, we wanted to be able evaluate improvement of downgradient water quality over time. So the way it worked is if Plum Stop was detected in an existing well during injection, or even slightly after injection, it became an in-barrier well. And then we installed a downgradient well outside of the Plum Stop distribution in that area. If Plum Stop was not detected in an existing well after injection, that became the downgradient well, and then we installed another well up-gradient of that well within the barrier.

So you’ll notice over on the left-hand side of the figure that some of the down-gradient wells are further away from the barrier. So over on this side, the purple wells are pretty far away from the barrier compared to some of these over here. And that’s because we have a above-ground utility over here that we can only get so close to. And so this comes into play when we look at results and where we might expect downgradient effects already or not.

All right, now we’ll transition to results. And I’m gonna show results from five locations around the barrier that I think are interesting or might illustrate a point. So each slide will have graphs of the in-barrier well and then a corresponding downgradient well for that location. So this well pair is located very close to the source area. You can see in the top right here, I’ve circled where it’s located. So if you look at the in barrier well, there is a 99% reduction in PFAS and PFOA concentration, but not until after May, 2022. And this is after we replaced this monitoring well.

So why did we do this? Well, as I mentioned, there were some historic wells on site when we first took on this project and MW05 was one of them. So when we saw that the results were not what we were expecting in the in-barrier well, because we did see plume stop distributed to this well, not as much as we saw distributed to other wells, but it did arrive. So we made it an in-barrier well. We didn’t see the performance that we were expecting. So we looked back at the borehole log for this well, as well as we looked into many other things too. And we noted that this well was not screened across the primary transmissive zone. So we replaced this well with PZA1, which is located just a few feet away, and we collected a core ahead of time to ensure that we were intersecting the main transmissive zone and that there was also evidence of plume stop in that area. And then we installed the well, started monitoring it, and you could see that we had much better results, more representative of an in barrier well had about 99% reduction and holding pretty steady.

If you look at the downgradient well, it’s located quite a distance away, about 53 feet downgradient from the barrier. And the groundwater velocity at this site is only about 10 feet per year. So we weren’t really expecting to see much impact in this well from treatment yet, but we’re certainly continuing to monitor it. And one thing we did notice that I’m sure jumping out at all of you is we had a very significant spike in concentration followed by you know going back down and the reason for this is because this well is close to the source area and there is likely source material present down gradient of the barrier and these temporary spikes can happen during wet periods as this area is prone to flooding. So we’ll talk more about infiltration in the next few slides. OK, moving around the barrier, now we’re up here. And this, as you may recall, is the highest PFAS concentrations at the site. And I’m just personally really impressed with the graph on the left. I mean, that is almost 100% reduction in concentrations and holding steady for at least two years so far. So very pleased with those results.

Again, the downgradient well to the right is located 54 feet down gradient. So again, we’re not expecting to see much effective treatment at this point, but certainly we see some interesting behavior in that well. And these spikes in concentration are likely due to infiltration and leaching of PFAS mass from the Betosone. And we’ll show you some other lines of evidence for that theory in a minute. But the concentrations do decline after each peak, suggesting that the base flow is really at that lower concentrations. And it’s going to take some time to see downgrading and effects of treatment at this location. But the barrier itself is really holding strong and mitigating further migration of very high concentration groundwater towards the ditch.

So we took a look at these PFAS concentration fluctuations and graphed them against temperature to see if there was correlation. And as you can see, there’s a very strong correlation with temperature. You know, we have a 34-degree swing in temperature where the increases correspond to increases in PFAS concentration. So what that indicates is that warmer water during the wet summer months is infiltrating from ponded areas at the surface through the veto zone down to groundwater. And so this becomes an additional line of evidence supporting that what we’re seeing with these swings is leaching of PFAS mass to groundwater due to infiltration. Similarly, we look to see if there was a correlation with conductivity. And as you can see, there was also a good correlation. So the high conductivity corresponds with the high PFAS concentrations and the values we’re seeing for conductivity indicate an anthropogenic source. So that makes sense that it was in the fire training area. So if these PFAS spikes were due to just regular groundwater advection, we would not see these kinds of swings in geochemistry. So these graphs show how you can look at other water quality parameters to help you make sense of the concentration variability in your results.

Okay, moving along to this part of the barrier here. And again, this is where we had the high DRO concentrations and the low PFAS concentrations. I just want to point out over on the y-axis here, and we look at these numbers, they’re just so much lower than what we’re seeing in the other wells. So what we saw here was a very slow decline in PFAS concentrations, about 34% over two years in the in-barrier well, and this is likely due to competitive sorption from DRO. And that’s supported by the fact that DRO has been reduced about 97% at this location. So we have limited reduction in PFAS in that in-barrier well, but also concentrations are very low, so it’s not a lot of risk to our receptor. If you look at the downgradient well, it looks like there’s a lot of fluctuation there, but really, if you look at it closely, the PFAS concentrations are fluctuating between 150 and 450 parts per trillion. So not really that significant and we’re not expecting to see you know real impacts down gradient until we see more treatment in the in barrier well at this location. So this area highlights the potential impact of co-contaminants on plume stop applications and fortunately for us the PFAS concentrations at this area were three orders of magnitude lower than other parts of the barrier. So it’s not a real concern for us.

OK, we’re going to wrap up with two more areas of the barrier that actually are showing improvement already in downgradient water quality. And this is because of two reasons. First, these wells are away from the source area. And two, the downgradient wells are closer to the barrier. So if you look at the in-barrier well here, we show about 99% reduction. We do see a recent uptick at the two-year mark, so we’ll continue monitoring to see if that’s just transient or if the trend continues. But it’s important to note that all of the PFAS compounds showed the same concurrent slight uptick, which means that it’s likely not breakthrough. If it were breakthrough, we would see short-chain PFAS breakthrough first. In the downgradient well, we see about 80% reduction to date and holding steady there. This indicates that the barrier is effectively reducing groundwater concentrations downgradient migrating towards the ditch.

Okay, now we’re going to talk about our last well pair, which is up here in the top right corner at the end of the barrier. And this area of the barrier is also showing improved downgradient water quality, but after some optimization efforts. As you can see, there was a quick rebound after the initial injection for the in-barrier well, and no real significant decreases in the downgradient well for about the first year. So if you recall, this was the area with the longer, deeper injection interval and also that six-foot-thick gravel deposit. So that’s important to consider because the initial injections were what’s called bottom up, which means you push the direct push rod to depth and then you expose the injection screen and then inject the plume stop as you pull up the rod. And based on what we were seeing, we thought maybe the plume stop may have followed a down and out preferential pathway near the bottom of that target interval where that gravel deposit was.

So what we did is we performed some supplemental injections in this same area, but we used a top-down approach to ensure that the distribution into the shallower portion of the injection interval. So cores were collected to confirm distribution in the shallower interval, and then after the injections, we had 99% reduction observed in both the in-barrier well and about 96% reduction in the downgradient well. So we’ll wrap up the results with a summary. So based on two years of monitoring data, the barrier appealers to be holding with no evidence of breakthrough, even in those really high PFAS concentration areas. The in-barrier wells respond more immediately, and the down-gradient wells’ response depends on distance from the barrier and also whether there’s residual PFAS mass already down-gradient of the barrier. Down-gradient wells located in areas away from the historical source area are performing best. DRO can compete with PFAS for sorption to plume stop. And then finally, we’re going to continue monitoring to further evaluate longevity of the barrier, improvement in downgradient water quality, and the need for any further injections.

So this is my my last and favorite slide, frankly, that summarizes the lessons we learned during this project. And again, when you install a barrier this large and it takes three months to inject it, you learn a lot of lessons. So, what we learned is daylighting of plume stop can be effectively managed using calcium-based parking agents. We learned that co-contaminants compete with PFAS for sorption sites, particularly if those co-contaminant concentrations are high. So, if you have a site with high co-contaminant demand and it’s affecting your ability to meet your treatment objective, you may need to have supplemental injections. If early results are not as expected, we recommend revisiting lithology and also your plume stop distribution. This might involve collection of additional cores in the areas where you’re not seeing good results, and it might show that you may need supplemental injections if you have gaps in your distribution or installation of new monitoring wells if they’re not screened appropriately.

We learned that you can look at geochemical data to help understand trends in PFAS monitoring data. The plume stop barrier is performing best away from the source areas, which is really a more typical location for plume stop to be applied. It’s kind of at the toe of a plume. However, we did see that increased concentrations of plume stop have been effective at addressing really high PFAS concentrations for at least two years. So something that we learned is that this could be applicable to source area control objectives. And then finally, the biggest thing we learned is that while it was challenging, we were able to design and implement a rapid full-scale plume stop barrier installation that was successful at significantly reducing PFAS migration towards a receptor.

All right, thank you everybody for your time and Ryan, we’ll pass it over to you.

All right, well, thank you, Rebecca. That was a great presentation. As Dane introduced me earlier, my name is Ryan Moore. I’m the Program Director for PFAS Remediation here at Regenesis. It’s a newer role for me. I previously have been in the last 11 years with Regenesis as the Great Lakes District Manager. And now I’m taking over this exciting role as the Director of PFAS Remediation. Real quickly on the presentation this afternoon, just gonna get into kind of a typical PFAS site conceptual model that we review when these projects come in.

A little bit about plume stop and source stop. So I’m gonna talk a little bit about some common treatment approaches and then a couple of project examples in addition to what Rebecca presented earlier. So full spectrum treatment for PFAS. What does that mean? When we get project data packets, oftentimes we’re trying to look at the PFAS contamination in multiple areas within a project site. On this graphic here, we have this labeled as A through D. A being that VADO’s unsaturated soil, typically the source mass that needs to be addressed if you’re wanting to look at a long-term remediation effort for P-VASP. B is that capillary and fringe area. This is really important because oftentimes many of these PFAS compounds want to hang out at that air-water interface.

So if you’ve got a treatment approach that you can attack that, you can significantly reduce mass discharge into the groundwater. Obviously, when looking at source groundwater concentrations, having that tool to be able to address that is beneficial. And then most often when we’re utilizing just Plum Stop or just a groundwater treatment approach, we’re looking more of that distal end of the plume for lower concentrations. So just kind of think about these different areas as we walk through this. I’m not gonna get into very much about what Plum Stop is. Rebecca did a great job in explaining the technology. I do just want to mention that, you know, we have SOARSTOP as well, which is another formulation of our colloidal activated carbon. As the name suggests, it is formulated for those source area projects. For the soil treatment, what are we typically trying to do and how are you utilizing the colloidal activated carbon?

In this case, we’re going to use SourceSTOP. Again, if you’re looking at the unsaturated soils, oftentimes, we will implore a stabilization or mechanical mixing of the soils with the Source stop. This has a couple of benefits, you know, the main one is we’re trying to reduce that leachability of PFAS from the soil to the groundwater, right? We’re trying to be protective of the groundwater or prevent additional mass discharging to that groundwater. The same thing is with this kind of excavation application or horizontal barrier. Again, we want to kind of coat the bottom of the excavation, allow that sore stop to kind of permeate in that capillary fringe to attack zones that we know they’ll be high mass residing.

An example of what we’re doing from the source treatment in 2022, we did a pilot test or a proof of concept test at the Grayling Army Airfield where we had one building where they to park fire trucks outside of it, and the fire trucks leaked with the foam, and so instead of fixing them, they would just continue to add foam to it, and it created these kind of like mini-source areas. We just wanted, again, to do a demonstration of the effectiveness of the source treatment, and so we picked a small area around this building where we knew we had high impact, and did a stabilization treatment effort. So what did that look like?

Again, this is kind of a combination of the horizontal barrier and the stabilization. We just picked a small area, kind of a test cell that we used where you could see the source top going in. It’s a black coloration liquid. We apply it in the bottom excavation, kind of spread it around. And then we would backfill and mix the overburdened soils with the source top as well. Again, the goal is to reduce the leachability of the PFAS from those soils. Looking at what the summary of the scope, this is really small. Again, 225 square feet, zero to ten feet. You know, groundwater is typically around 14 to 15 feet in this area, I believe. We’re really just looking at preventing leachability of the soil. When you’re completed, this is ideally what it’s going to look like. You spread everything back out, get it compacted in, and then restore the site surface. So when you’re done, it would just be clean grass here.

So what does data look like now? Well, we collected the baseline sample. These are soil samples that were ran through the SPLP leach analysis. And you can see from right after we completed the mix, we collected that sample, we sent it to the lab, we had a 99.4% total PFAS reduction of the leachate. We then went back out to the project site about six months later and collected some additional soil cores and wanted to see how is it holding up. And as you can at six months, all the results were not detected in that leachate. So it demonstrates the power of coming in and treating site soil. So now no longer have that PFAS leaching into the groundwater.

What are our groundwater approaches? Again, going back to the full spectrum graphic that I showed a minute ago, we’re looking at both the source and plume areas. he source, we can inject the source stock right below where you may do soil treatment or soil removal or soil stabilization, whatever it may be, come in and do the injection. Again, we’re trying to attack the areas with high PFAS levels, and we’re trying to help with any type of treatment downgrading it or to help attenuate that PFAS plume with other efforts downgrading. On the more traditional groundwater plume treatment, oftentimes this is a PRB, or criminal reactive barrier. These PRBs can be installed through traditional direct push injection just like the site Rebecca was showing you and that’s how that project was completed. But you can also come in and if it makes sense and do more of a soil trench application.

We’re doing a project right now actually as we speak where they’re going in and doing a 600 foot long plus trench along a construction area where we’re blending in the stop into an aggregate so that as site groundwater migrates through from the construction site it’s being treated through that source stop trench. You can do the same thing with a traditional plume if it’s shallow enough where it makes sense but oftentimes it’s more of the direct push in traditional injection scenarios. The example project I want to show is this is a New York ground field site where the client came to us a few years ago. The project itself was a former bulk storage refinery area. So very similar setups where Rebecca was just talking about. In our case, however, where we were treating, there were no co-contaminants. The site was only concerned with PFAS and PFOA.

The objectives of the site was to do some source stabilization that the client did on their own and then utilize the plume stop as a PRB. This soil stabilization area is highlighted here in this kind of red oval. And this was directly upgrading where we did the plume stock barrier along the property boundary here on the bottom right. The geology of the project site was mostly silks and clays, but they did have some high permeable sandy zones where that groundwater and that PFAS migrated through. So what did it look like in reality? So we go out, this MW-12 was the original monitoring well that was kind of used as our baseline for our design criteria. And then MW16 was the monitoring well that was installed later as the downgrading monitoring point of how well is this working.

Before we actually did the application in MW12, we did deploy our flux tracer mapping tool. Our flux tracers are units, I know we’ve had previous webinars on these, but if you haven’t seen these, they’re really cool. But in essence, they’re units that go down into the monitoring well and help us really identify flux zones within that monitoring well screen. and so that’s what we did here. We wanted to really confirm the groundwater velocity and make sure that we didn’t underestimate the speed of groundwater or underestimate the contaminant mass flux. If you did, you may have to do some modifications in design. The application here was a permeable zone between 13 and 17 feet, and in this case, we actually applied about 12 ,000 gallons of bloom stop in a three-row configuration. So we wanted good overlap and kind of a nice thick treatment zone perpendicular to groundwater flow. You can see too that the concentrations were not nearly as high as they were at Rebecca site, but about 2000 part per trillion total PFAS. Again, PFAS and PFOA are the primary constituents of concern.

So what did the data look like after the application? Here’s the baseline. This is the downgrading monitoring well. Let’s see where the application occurred. They did some sampling about 10 months and 17 months post-application. We’ve maintained a greater than 96% reduction in that monitoring well about 15 feet downgradient. Unfortunately there’s no in barrier monitoring wells to kind of show like what the barrier itself is doing but this was great news and kind of a great data set that we expected and then it’s been maintaining over time. So I think when they get more data in we’ll be able to update these graphs accordingly. More importantly, at this project site, again, being part of the New York Brownfields program, they had to get this remediation completed as part of the development so they can be issued their certificate of completion through the New York Brownfields program.

This is a really important step for developers in New York, where oftentimes it’s kind of a betterment approach. They need to go out and do the best that they can or the most good when they’re going out for the development to achieve ultimate risk reduction of these contaminants, which is what happened here. So as I close, I just want to kind of talk about some common scenarios. We’ve kind of went over a couple of project sites that we’re seeing treatment from both the source and groundwater. We’re doing a lot of projects right now that are kind of formed around construction activities. Oftentimes these are airports, right? Where airport, it may be building new hangars or you’re going to be doing runway reconfigurations. At that time, you know, it’s great to get the treatment of those site soils done then, right?

What’s the benefit? Well, one, what they’ve done in the past when they had these PFAS-impacted soils is they’re just stockpiling it. They’re building kind of a temporary holding cell, they’ll stockpile it, they’ll cover it with plastic, and it just sits there, and they don’t really know what to do with it. So if you could do the treatment during the activities, then you can get to more of a reuse scenario very quickly versus stockpile and holding onto that. The other alternative to what they’re often doing as well they may just try to go for disposal. They’re going to send this, you know, they’re going to excavate the soils. They’re going to take it to a landfill. And really they’re just transferring their risk or their liability from onsite to offsite, you know. And then they have risks along the way of that transport. So a better way to do it would to just go ahead and treat while you’re there.

We do this a couple of ways. I just talked about the excavation application. You could do blending the site soils and reuse onsite or different areas are spreading out anything you can do to not take the soil off site. At the end of the day, ultimately, again, why are you doing it? We want to be more protective of the groundwater in these areas. Real estate transactions. My second example was the New York Brownfields program, right, you know, redevelopment. A lot of times, a lot of these sites we’re looking at is, hey, I’ve got this Brownfield project. I would really like to, you know, do something for PFAS. Maybe the regulations really aren’t there for them in that area, but they want to do good at the project site. So they see it as an opportunity to do treatment because of the transaction or because of the development.

The other ones we’re seeing a lot of is where, you know, a company is selling an existing facility and they know they got PFAS impacts. And so it speeds up the need for remediation prior to that transaction closing. Again, what are they doing? Both the source treatment of soils and then groundwater treatment. And then finally, the most common scenario I think we get or existing properties, very similar to what Rebecca presented on you. You’ve got a project that may have a contributing source to a larger plume. They’ve got to be protective from receptors because they have regulatory agencies asking questions or requiring them to investigate. And they’re looking at ways to be proactive and try to do treatment now, while they have a little more control of the process. Additionally, one thing I really haven’t talked about, we’re not going to get in too much, is that in all these cases, We do have a 10-year warranty through our plume shield program to offer warranties for long-term groundwater treatment at project sites.

My final slide here and then we’ll open it up for questions. I just wanted to kind of highlight again the diversity of the types of projects that we’re working on. Yes, airports are a big component, you see that in the left, but this is just an example set of our sites. This is by far not the full list. We’ve got over 50 projects worldwide now, so you can’t get them all on this slide, which is good. We’re doing a lot of good there. But again, airports are a big component. Department of Defense facilities, you know, the Graylink facility is one. We’ve done several different confidential Air Force and Navy facilities. We’re doing research through different DOD programs as well. So we’re constantly learning and doing more with DOD.

Commercial manufacturing is another big component the project sites we’re looking at. And this could be anything from former paper mills to chrome facilities, any manufacturing facility that probably either utilize PFAS in their processes or utilize raw materials that had PFAS on it that maybe they didn’t know or did know that it was there, but they’ve had a release in some place. And then finally, you know, landfills and bulk fuel storage and refineries. Again, this is the exact same example of what Rebecca had. We’re seeing a lot of those, and why are we seeing this? Because all these facilities had firefighting booms there because it’s the best approach when putting out fires of those nature. So, most often, if you start looking for PFAS, they’re gonna be there, and you’ll need to address them at some point.

With that, I appreciate your guys’ time. Thank you again, Rebecca, for such a great presentation, and we’ll open it up for questions.

All right, thank you very much, Ryan.