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. If the webinar or audio quality degrades, please try refreshing your browser. If that does not fix the issue, please disconnect and repeat the original login steps to rejoin the webcast.

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With that, I’d like to introduce our presenters for today. We’re pleased to have with us, Rick McGregor, president of in situ remediation services limited. Rick McGregor has over 30 years experience in groundwater and soil assessment and remediation, has worked in over 30 countries, and has authored numerous papers on groundwater assessment and remediation. He holds a Master of Science degree from the University of Waterloo in hydrogeology and geochemistry and is a certified groundwater professional in Canada and the United States. We’re also pleased to have with us today Gareth Leonard, Managing Director of Regenesis Europe. Gareth Leonard manages a dedicated team of in situ remediation specialists to provide the design and implementation of remedial solutions for environmental consultants, remediation contractors and end users. He’s worked in the remediation industry for over 25 years, having provided successful remediation designs and implementation for over a thousand projects across Europe, the Middle East and Africa.

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

Thank you, Dane. I’m Rick McGregor and I’ll be talking to you today about a study we did a couple years ago focusing on the Vado zone or the air-water interface in a source zone that had PFAS at a fire training area. So well we’ll start with a really brief introduction. I don’t I think most people here will understand PFAS and know the issues with it so we won’t spend much time at all on that. And then we’ll move on to basically an update of where this kind of all at least for us, from the in situ point of view, just give you a brief update of a study that’s been ongoing for seven years now, where we treat a PFAS in a groundwater situation, and then we’ll review the study itself, and then we’ll give you a brief update on some other studies that have been going on for a few years now, and keep it pretty limited, but we’ll give you the update.

So some of the challenges of PFAS remediation is, most of you probably already know, are there is really very limited options for both above ground and in situ for the treatment of PFAS itself. And there’s a variety of reasons for that. One being it is very resistant to degradation by chemical oxidation or biodegradation. It’s really those have been tested a fair bit and while those things are still emerging, it is very limited what we can do with the traditional remedial efforts. The other challenges is we have to treat down at very, very low concentrations in the nanograms per litre, which makes processes like back diffusion, matrix diffusion very, very difficult to overcome over the long term. The other thing is we’re dealing with very large diffuse plumes, which can stretch for kilometers or miles long and be very widespread. Those are just some of the challenges we face when we’re dealing with remuneration of PFAS.

Right now, the current approaches to treating PFAS Above ground is basically pump and treat using adsorptive based materials like granular activated carbon or ion exchange resin. Those are the two probably the dominant treatment approaches for PFAS. Foam fractionation is emerged and it looks very promising and is starting to be used more and more. However, the problem with any of the pump and treat bringing the things above ground is you are generating a concentrated waste that has to be disposed of eventually or treated somehow. And then you’re running a pump a tree system, which we all know can be very expensive and they tend to Go on for decades and decades and I don’t want to say never-ending But they go on for a long time and can cost a lot of money to operate For in situ we’re almost even more limited of what has been demonstrated There are lots of technologies out there being tested right now and being researched But right now we’re basically for demonstrated technologies. We’re limited to absorb the face technologies including colloidal activated carbon and sold under brand name PlumeStop by Regenesis, which we’ll talk about today.

There has been some work using powdered activated carbon, but studies have shown that distribution and the injection of the powdered activated carbon could be very challenging to do just because of the grain size. So you get fairly uneven distribution. And then ion exchange resin has been tested in lab in some small scale field studies, but once again, distribution and injection challenges for the coarser grain ion exchange, as well as ion exchange resin itself is very expensive. So we’ll start here with a brief review of where this all started. So I was working on a site in 2016 where the petroleum hydrocarbons were spilled and we’re remediating the petroleum hydrocarbons in the groundwater and soil. These just give you some of the concentrations. It was a moderate plume, but prior to us doing our injections, which we had designed using plume stop as well as oxygen-reducing compound produced by Regenesis, we were told by the consultant that the area had been used as a fire training site.

So, prior to us injecting, we ran around and grabbed some samples for PFOA and PFOAs back then. Those were really the only two PFAS that could be commonly analyzed. And then we did our injection of the plume stop as well as the ORC. Sure enough, two weeks later, we got back our water results and we had both PFOAs and PFOA concentrations in the low nanograms per litre, but still significant. That site was a glacial fluvial deposit here in central Canada, near Ottawa, Ontario. It was a silty sand and with a sand lens. Anybody who’s done in situ remediation knows that things heterogeneity, which always occurs, but heterogeneity with things like sand lenses can cause a very challenging environment for injection. So that was a worrisome thing.

The groundwater here occurred about one meter below ground, which is very shallow So anybody who’s been in situ knows that day lighting is always an issue It was an unconfined act for with a groundwater velocity about less than a meter per day So fairly high velocity at this site The plume stop in ORC was injected using direct push technology on a fairly dense grid about a 7 to 8 foot grid with 20 locations is a fairly limited area we had to do and this just gives you some of the parameters that were detected. So it wasn’t a big injection with about 600 pounds of plume stop being injected, but we did instrument this site and monitor the site extremely detailed because we’re very interested in the distribution of the plume stop as well as the treatment. So we took a lot of cores for both looking at the distribution of the plume stop, as well as the radius of influence and a lot of geochemistry. And this just gives you a summary of what some of the stuff that was time.

The key to any in situ program is distribution of your reagent. And there’s two factors there. One is you want it to be homogeneously as best as possible to be injected over the area of impacts. And you wanna minimize the injection of the reagent in areas that you don’t need treatment. That’s just basically a waste of reagent. So in this case, we did a lot of detailed sampling of the cores post injection to look where we’ve seen the plume stop versus where we didn’t want the plume stop. And you can see here with these graphs, these four cores that we took at distances from two to 15 feet from the injection point, you can see the plume stop itself as measured by organic carbon was well distributed in the zone that we wanted, which was about three to 5.8 feet below ground. And then once you got outside of our target injection zone, we didn’t see hardly any plume stop, which was good all around. So we were pretty pleased with the distribution and the injection technique.

At the end of the day, we’ve seen 96% of the plume stop was based on mass balance injected into the target injection zone. And we’ve seen a fairly uniform distribution with a radius of influence up to five meters. So we are very pleased with that. From a chemistry point of view, both the PFOS and PFOA have been non-detect for seven years and we’re still counting. We just got back to the latest results two weeks ago. So the plume stops performed extremely well and kept the PFAS below target concentrations. About two years in, we were able to increase the number of PFAS compounds analyzed to about 23, and all those compounds have been non-detect as well. From a regulatory point of view, the BTECs and the gas and diesel range parameters have stayed under regulatory limits for four years, and they’re deemed no longer necessary to be monitored by the regulator.

Dr. Grant Carey has published, did some numerical modeling on the performance of the plume stop and predicting some of the lifespan of it, and that’s been published in the paper. The other thing we noticed, and this was done seven years ago, is the biogeochemistry of the plume varied extremely differently with the presence of PFOS versus the PHC plume itself. And we did a lot of DNA analysis on that, but we won’t get into that. So, to sum it up, the field study as well as the numerical modeling has been published and summarized in these two papers. If everybody wants a paper, I do believe we genesis can supply them or we can ourselves. So that said, we’ll get into the actual focus of today’s study, which is the treatment of an alcohol and air water source zone at a site. So most of these source zones, even though it’s being very limited for PFAS, are dealt with here by treating the plume itself, which can be, as we discussed earlier, very expensive because the plumes become very diffuse and very low concentration as you get away from the source. Or they’re excavated and contained somehow, or there are a couple of products out there that actually aim to stabilize the PFAS within the soil itself.

Those are the main approaches right now, with plume treatment being the number one, excavation probably being number two, and the stabilization number three. They all involve mechanical mixing, large footprints, a lot of infrastructure and very expensive. But what has been determined by a couple a lot of authors and Hunter Anderson and Brousseau have been part of the two leaders in this group is that the air-water interface underneath these source zones tend to focus the amount of PFAS within that zone itself and that’s due to a variety of factors mostly from physical chemical related to the PFAS itself but as well as the aquifer and ionic strength, presence of L- NAPL, or I guess even case of D-napple, being in these source zones in this air-water interface. And what happens is the PFAS is preferentially, I don’t want to say contained, but in those areas, and it can be orders of magnitude above what we see in the plume below.

So why is that important? Well, that will act as a long-term source. Even though there are mechanisms trying to find the PFAS in that area, it will be slowly released with time. So you’ll have a long-term source and we’re talking years to decades. So if we can limit the mass flux out of that zone, then obviously that’s gonna have a beneficial impact on down gradient of the source zone itself. So that’s kind of what spurred our interest in trying this out at a site. So the state itself is a former fire training area with a silty sand geology. I won’t say it’s uniform, but you can see on the right here, we took about 30 samples of the aquifer above and below the water table. And we looked at doing flexible wall permeameter test arm to look at what kind of range and hydraulic conductivity we had. And you can see here, we had a range of about one, just over one order of magnitude.

So this aquifer, at least in the shallow part in the Vedosome was fairly uniform. I hate using that word, but in this case, it was fairly uniform. so we didn’t seem to have much preferential pathways or much variation in geology itself, so that was good. Our water table is about 18 feet below ground surface or about 5.3 meters. It varied about over the course of the 18th month study. The water table varied about 25 centimeters, so we did have some fluctuation there. We had a fairly moderate groundwater velocity about 50 feet per year. And as you expect, in a source zone, we had an iron sulfate reducing environment. So we instrumented sitin, and I’ll get into that a little bit later, but just to give you a little background. So the shallow groundwater, so immediately below the water table in the source zone itself, had both petroleum hydrocarbon and volatile organic compounds present within the groundwater. Most of the VOCs were TCE, CIS, and vinyl chloride, whereupon the petroleum hydrocarbons were mostly gasoline with some diesel range organics in it. And these are the concentrations.

So nothing overwhelming or scary here. No evidence of NAPL. We analyzed for 23 PFOS within the groundwater and detected six. They were carbon five to carbon nine chains in these other concentrations. Nothing too high, but not low either compared to standards or our targets. So in this case, we had a fairly high numbers and groundwater immediately below the source zone. Above the water table and immediately at the water table, we instrument the site with lysometers to try to get some of the pore water samples. And in this case, we were only able to get enough pore water to do PFAS analysis. And once again, similar to with the shallow groundwater, which was underlying this, we detected six PFAS, the same PFAS compounds as we detected in the groundwater range from C5 to C9 carbon chains. And once again, you’ll notice here that our concentrations within the pore water that we were able to extract were orders of magnitude greater than what we observed in the groundwater itself.

So once again, the earlier work done by numerous researchers showed here at this site that our PFAS were accumulating preferentially within the air-water interface. So we took a 100 square meter area and we injected into the air-water interface, which we interpreted be about a one meter thick area. We injected plume stop itself, 800 kilograms at a 10% solution, so fairly high concentration, generally higher than we typically inject at, but we knew we had high concentrations of the PFAS. We did a six-foot grid, which is a fairly dense grid, so we had 23 injection points. We used a geoprobe to inject it, and we did it over two intervals, so about 18 and 20 feet intervals over the whole area. And then the instrumentation, if we go back to this side, you’ll see here the black dots here, the injection points, the Li or the L are the lysometers, and the lysometers were stacked as multi-levels.

So one really shallow at the water table, above the water table, one just above the water table, one slightly below the water table, so that we could get some depth integrated data. The MW are traditional two-inch monitoring wells, and then the cores are the stars there, and we took eight cores. you’ll see three are distributed within the area and then two, five, six, seven, and eight were to look at distribution of the reagent with distance from the injection point. So this kind of just summarized. We installed two two-inch wells, nine nizometers in groups of three, and then we analyzed, in the groundwater we analyzed PLCs and gasoline, diesel range, inorganics, general chemistry and PFAS. In the xometers, we just were able to analyze for PFOS. We did five sampling events for the groundwater and seven events for the pore water using the xometers. So we had two pre-injection events to get some sort of background ideas and then we did five post-injection for the pore water.

We took cores of the aquifer to look at pre and post-injection total organic carbon content, which would give us an idea of the distribution of the plume stop, as well as the radius the detection of the plume stop. And then we did some expert testing looking at the moisture content, as well as collect cores for the flexible wall fruit meander test. So this just gives you the moisture content of the four cores we collected. As you can see here, you’ll see the water table, the maximum and the minimum water table that we observed during the thing. So we’ve seen about a 20 to 25 centimeter range over our test period. And you can see, due to the relatively coarse nature of the Vado zone here, we don’t see much of a saturated zone above the water table itself we see maybe a 20 to 30 centimeter area and then once we hit the water table obviously the aquifer becomes saturated so we see it a very consistent profile over the four cores we collected at this site.

Pre-injection total organic carbon so get idea basically the FOC of the aquifer itself due to the properties of activated carbon we have to use a modified method we can’t use a true total organic carbon analytical method we have to use it basically a combustion method then we have to correct that for inorganic carbon i.e. something like carbonate or something we have to correct for that so I won’t go into that one of the papers describes that method but at the end of the day our detection number is 0.005 grams per kilogram and you can see here our aquifer is basically at detection limit so we did not have much natural FOC within the zone that we’re looking at you can here between five and six meters below ground that was our targeted area that we wanted to inject in. So after the injection we went back and collected four more cores and those graphs here are on your right and you can see where we tried to inject in and once again you can see from all four cores we got pretty good distribution of the plume stop within their targeted injection zone.

We did see some what I call rising of the reagent so we did see some detection of plume stop above our targeted injection zone, and that’s just because it’s fairly common when you inject things, they’ll rise due to the pressures within the aquifer, but it was fairly minimal and we didn’t see that. So from a statistics point of view, we collected 88 samples after injection, and basically 100% of the samples within the target injection zone showed elevated concentrations of total organic carbon. And that was on the order of two to three, mainly two is greater than the background concentration. So we definitely seen a vast enrichment of the organic content of the target injection zone, which is great. That’s what we wanted. Outside of the target injection zone, just less than 10% of the samples did have elevated concentrations of TLC, which means we’re basically injecting, we’re wasting about 10% of our reagent outside of the injection zone, which is still excellent from our history, from our experience.

So, the other thing we want to study here was, did we meet our design objectives was about five to six feet radius of influence, and we wanted to see that. Unfortunately, sorry, I’m Canadian, so I’m switching back and forth between metric and imperial, but these are obviously metric. So we wanted to see if, did we meet our design radius. In this case, so five to six feet is about two meters away. So as you can see from the graphs here, we’re seeing very good distribution out to about two and a half meters, which is about eight feet and they need about 10 feet. We’re still seeing some enrichment within target injection zone. So we’re seeing very good distribution and we’re seeing very good vertical and lateral distribution of the swim stop. So from a design and implementation point of view, everything seems to go according to plan. So we’ll get to the results. So we’re going to start with the lysaminer. So basically at the air-water interface. So these graphs, there’s three graphs. The top one is the most shallow loss emitter, so well above the water table. The second one, one L is just above the water table and one D is just below the water table. So these are spread out over about a one meter vertical interval.

So the graphs are with time, concentration with time and all the PPOS detected originally are plotted on each graph. You’ll see the concentration and this is a log scale for you for the concentrations. So you’ll see at the start, the two first sample events before zero, and then immediately after injection at three months was the first sampling event of the lysimeters, we seen that concentrations for all six PFAS went down to non-detect, so which was about 10 nanograms per litre, and that was held for over a year in all of the summers, except then at about a year and a half sampling event, we did see a bit of breakthrough for the PFPEA, which is basically a five-chain carbon, so a short-chain carbon PFOS. We’ve seen it was detected after about a year and a half, but still at fairly low concentrations. I think it was about 50 nanograms per litre. So above our, it’s usually not regulated, but we did see some breakthrough at a year and a half.

In the Lasomner II, similar vertical setup, we did see breakthrough of the PFPEA and all three the sonometers after a year and a half. But prior to that, all six PFAS were a non-detect, and five of those stayed at non-detect at a year and a half. Almost exact same similar results at the summer three where we’re seeing exactly same observations with the PFPEA breaking through at a year and a half, but the remainder stayed at non-detect. We also looked at the groundwater immediately below the source zone, and then I just highlighted them here on the map here at MW1, MW2. And what we’ve seen at both wells where similar type results, where these once again are product logged, is for the first nine months to a year, we didn’t see much change in the groundwater concentrations for the PFAS itself. At approximately nine months, we started to see decreases and those decreases continued at the year and a half symbol. So that kind of gives us an idea is yes, we are actually reducing the mass flux of PFAS into the shallow groundwater. So that was very encouraging and showed that what we’re doing in the air-water interface was actually having an effect on the plume.

So summary of what we’ve seen there was, is from the distribution point of view, which is the key to the whole success or failure of any injection program, is we had excellent distribution of plume stop within the target injection zone with the concentrations going up by almost three hours of magnitude on average. And 97% of those samples have an elevated concentrate. We’ve seen very little waste of the plume stop outside of the zone we’re trying to inject. So that was, that’s good from a, we know that we can get it where we want it. And as well as our design radius was met with no problems. The PFAS within the pore water, so the beta at the air water interfaces, they were all decreased to non-detect within three months of injection and then remain there for the year and a half of the study, with the exception of PFPEA, which popped up to a maximum of 55 milligrams per litre. In the groundwater, immediately below the shell, immediately below the lysimeters, we’ve seen a mass flux of about 81% for PFPEA, ranging up to 97% for PFOA over the 18-month period. Most of that decrease happened between nine months and 18 months.

So once again, we’re seeing a very good reduction of mass flux into this shallow groundwater. So that study for anybody that is currently in peer review right now, and hopefully it’ll be published shortly. From that though, and if anybody would like a copy, let me know and we can get that to you. This is gonna be a quick overview of some of the studies that are going on right now. We have four or five going on right now. We have a fractured bedrock site in Canada that we’re monitoring that’s had excellent results. It’s been published and that was treated with plume stop. A unique part of that was is the plume stop was since we’re in fractured rock, we had to what we call park the plume stop so that we did not have it migrate too far from the injection points within the fractures themselves. And that seems to have worked extremely well. And I’m sure the people at Regenesis can give you some tips on how to best park plume stop in these highly fractured environments.

We have a couple of sites going on in the Middle East where we have saline aquifers. So PFAS as well as activated carbon self can be affected by the ionic strength of the groundwater. These aquifers range from slightly saline to very highly saline. So try that in both cases. They’re both studies around 36 months and still being non-detect for PFAS. So things seem to be working there. And then the site I talked about at the start, in central Ontario here has been going on for seven years and we’re still at non-detect. So everything looks great till date and a lot of numerical modeling is starting to go on to look at that sort of stuff. So this is from the Procter Proc site. VAMBI wants is this has been published so I can provide that to you. As I was saying, a lot of we’re involved in a couple research programs here that we’re looking at laboratory as well as numerical, as well as field applications, the ones that are in CERC, which is kind of a Canadian government research funding organization, as well as a CERDEP study.

So there’s a lot of contest analytical issues being coal competition studies, which is a big topic right now in the PFAS absorption onto media such as carbon and ion exchange, looking at isotherms and that and then not a numerical modeling being done by Grant Carey at Poor Water Solutions, as well as the graduate students at University of Toronto and Carleton University up here in Canada. And there is a schedule of field studies, supposed to be maybe happening at CFB Boarding, anybody who knows hydrogeology probably knows all about boarding. So anyway, hopefully that will happen in the near future. These are some of the papers that have been published by myself or co-authors over the last two or three years on a lot of these sites if anybody wants them. There is a very excellent two papers put out by a peer review group for the remediation journal. The last one was just issued last year by a lead offer with Stu Adams, Abraham, sorry. And I would highly, it gives you a nice overview of what’s really currently available for in situ remediation, as well as what’s coming down the line.

That’s a very good paper to read and gives you a good update of what’s going on in the industry. Finally, I’d just like to thank our academic partners, the University of Toronto, Carleton University and University of Waterloo, as well as the two industrial partners, Grant Carey at Port Water Solutions and my team at In-Situ Remuneration. And with that, I will pass it off to Gareth. Thanks, Rick. That was really great. And I’m looking forward to seeing that paper coming out very soon. Hi, everyone. My name is Gareth Leonard. I’m the Managing Director of Regenesis in Europe. So I just wanted to take about 15 minutes to build a bit on what Rick was saying there in terms of treatment of the air-water interface in the capillary fringe and really look at the PFAS source plume system as a whole and where we can do in situ treatment.

So here’s your typical airport site, you’ve got a spill at the fire training ground, it’s moving down into the groundwater and discharging into that groundwater creating a long-term plume which is then going offsite, and what you’re having is the several areas where you’re having contamination hanging up and creating a large reservoir of PFAS, which can then generate problems for a long, long time. So the first place is when you have the spill, the AFFF will soar to the soils in the shallow part of the Vado zone. This creates a large mass that will start to then move vertically through the Vado zone. It’ll move because of further applications of AFFF, if it’s a training ground, or simply because of infiltration of rainwater. And it’s going to firstly, soar to the soils, soar to the carbon within the soil, soar to the air water interface of the moisture in the Vado Zone. But then it will leach off into this infiltrating groundwater and move down through the Vado Zone. It will then reach the capillary fringe. And as Rick explained, within the capillary fringe, is going to hang up there. Because of the surfactant properties of PFAS, it likes to essentially stick at the air-water interface. One part of the molecule sticks in one side, and the other side sticks in the air or the water.

So you end up with this second reservoir of a much higher concentration than in the groundwater, weeping into the groundwater and creating these large plumes. So we need to look at the system as a whole and how we’re going to treat it. So here you can see we’ve gone in and we’ve done treatment in the source area and we’ve done treatment in the plume downgrading, we’ve created a barrier there. So I’ll go into what we do here. So in this source area, we’re looking at treating the vedosum soils, we’re looking at treating the capillary fringe source, and also underneath that you can treat the plume head or the core, so the really high concentrations of PFAS in the groundwater. I say really high, obviously, compared to other contaminants. The groundwater contamination concentrations are quite low, but for PFAS, this is where you find the highest concentrations. And then downgradient in the body of the plume or at the distal end of the plume, you might want to then do treatment there as well.

So there’s four areas and options for remediation. You’ll do different things and you’re trying to achieve different things. So Rick mentioned the colloidal activated carbon. We’ve got source stop and plume stop, two different varieties of colloidal activated carbon. What we’ve done is we’ve milled activated carbon down to one to two micron. So it’s the size of a red blood cell, each particle the size of a microbe. And basically we suspend these in water with dispersion agents so that we create a colloidal liquid. So like water, like milk, like blood, something that will flow through the formation. The particles don’t block the pore throats, so you’re able to inject at a very low pressure, unlike trying to inject powdered activated carbon or get anything else in, you’re not fracking it into the formation. So it flows through the flux zones through which the contamination moves. It coats the aquifer in a thin layer of activated carbon, converting the aquifer into a subsurface filter that takes that contamination out of the groundwater. The other great thing about using the small particle size is the sorption sites within the particles are much closer to the surface, so they all get used more rapidly. So you get much more rapid sorption of the contamination, you get much more efficient and effective treatment of the contamination.

So firstly, we’ll look at treating the contamination that gets into the vedosone, so it’s hanging up. Normally in the higher part of the vedosone, but this is dependent really on the amount of carbon in the subsurface, so a clean sand, your contamination is going to make it down through the vedosone more readily. Because you’re dealing with a very high mass, it’s worth mixing in powdered activated carbon at this point. What you’re looking at doing here is treating the sorbed contamination. So it’s already sorbed, it’s on the soil itself, but what it’s doing is it’s leaching off and it’s moving down and discharging into the groundwater. What you wanna do is stop that process. So you’re putting in a lot of carbon at this point, you’re sorbing the PFAS and you’re preventing it from moving any further. So you’re immobilizing the mass at this point.

The other thing you might wanna do, and this is optional, is put something in that prevents further infiltration of the rainwater and so that you don’t have this water coming through so you can’t have any further leaching, but that is optional. A lot of the work is done by the activated carbon. SourceStop is then used. It’s mixed into the mix if it’s a clay material so it can penetrate the soil that’s being mixed, but it’s also applied at the base of the treatment so that it penetrates the vertical pathways through which the contaminated water is infiltrating. It coats those pathways to absorb that contamination and take out any residual leachate coming from above as well as infiltrating rainwater comes down. So it’s like a horizontal barrier to prevent discharge to the groundwater. And that can be mixed in or it can be sprayed in an excavation depending on what you’re doing on the site.

So here’s an example from the U.S. It’s a military base. It’s a very clean sand here. So actually what you’ve got is the highest level of contamination further down into the Vedos zone towards your capillary fringe. And we’re looking at leachate analysis here. So SPLP analysis of the leachability of the contamination in the soil. So we’re trying to reduce that leachability. So the first thing we do is we dig out the contaminated soil that we want to treat. We then spraying the source stop into the base of the excavation to penetrate those vertical pathways, create this horizontal barrier, we then mix in the contaminated soil with the powdered activated carbon, and we’re using a hydraulic mixing bucket just in situ at this point, and then these are the results. We took several samples at several depths and what we got is non-detect in every sample for every compound in all tests except one where we got a small ding of PFOS of 25.5 nanograms per litre. So overall, we reduced the leachability of this contamination by 99.4%.

So essentially, this contamination now is not moving down through the vedosone and it won’t be discharging into the groundwater or it’s discharging into the groundwater. So slowly, it’s not going to drive a risk and the plume will attenuate. As Rick talked about, you can then treat the capillary fringe. So, you would use source stop injection using direct push technology and you just inject across the capillary fringes, Rick talked about. You can continue that injection downwards or you can start further down and come back up in order to absorb the contamination that has already got into the groundwater and help cut the head off the plume there and then that allows the downgradient plume to attenuate. So, these three treatments that I just talked about, you’ve got the vedosone treatment, including the SourceStop, the capillary fringe treatment, and then the injection in the groundwater. What that does then is it stops the discharge of contamination into the groundwater, and it allows the plume to then attenuate below action level.

So, essentially, you then don’t need to do any further work. It’s not driving a risk at that level. That’s the intention there. However, if the plume is higher than acceptable levels of contamination, or perhaps at the edge of the site there, you’ve got a surface water or a receptor that is particularly sensitive, then you can inject colloidal activated carbon in the form of plume stop at the edge of the site. And that is a permeable reactive barrier. And the idea is then that you’re shutting the gate. So that residual plume will then be absorbed into the plume stop barrier and it will stop any further egress of contamination off the site. So this is what plume stop looks like. It’s a liquid activated carbon. It comes as a concentrate. We mix it with water on the site and then it’s injected into the subsurface under low pressure. So here you can just see it on the left flowing through a column basically under gravity with water behind it powdered activated carbon there, would need to be fractured in. It would need to be forced in to get it to move through the formation. So plumestop nicely coats the subsurface through those flux zones.

Looking at your site, you’ve got the airport where you’ve got the AFFF’s been used. It’s got into the groundwater. It’s now moving beyond the site boundary. So you might have an offsite liability. It’s getting under properties. So there’s a human health risk. The aquifer itself may be considered a receptor by the regulator. There might be potable drinking water wells, or there might be surface water that is becoming impacted. So you simply inject the product through direct push technology just along the edge of the site, and that cuts off any further egress of the contamination from the site. So we design using the flux of the contamination. So what contaminants have we got? What’s the concentration? What’s the groundwater flow? So what’s the movement rate of that contamination? And it’s based on sorptions because there is no biological degradation going on.

So we consider the type of contaminants. We consider competitive sorption from natural organics that are in the subsurface. As Rick showed, you often get other contaminants in there, particularly fire training grounds, they’re burning things. So they tend to be using petroleum hydrocarbons as well, which are gonna take up sorption sites too. So all of this becomes part of the design. So we can then work out what dose to put in and what the configuration of the barrier is, how big, how wide the barrier essentially needs to be. And we can work out how long that barrier will last for. And it tends to be an extremely long-term solution with decades and decades of treatment. As Rick said, he’s got a long running project, but also he’s been involved in studies to emulate these sites. And this is a really nice paper that he put together with Dr. Carey, where they emulated a barrier. And for P4, they were looking at a lifespan of anywhere between 66 and 265 years from a single application.

Now, if you then needed for the barrier to last longer than that, what you’d do is you’d go back and you’d reapply. But in all that time, you’ve never had to pump anything. you’ve never had to use any electricity, you’ve not disturbed the site, etc. There’s no waste coming to the surface. That, of course, assumes a constant challenge concentration. If you combine it with source treatment, then actually the challenge concentration, the contaminant flux entering the barrier is reducing over time or is reducing very rapidly. So then the barrier will last even longer and so we warranty the treatments as well. So this is an example site from the UK. I’m just going to jump forward two slides because it actually shows you the better there. So this is an airport international airport on the left nice flat ground and then on the right you see all those trees that’s actually a slope dropping away in the woods. What we’ve got is we’ve got PFAS coming off this fire training ground.

I’ve blanked out because fire training people can recognize each other’s sites. So this contamination is coming off the site, it’s moving through alluvium and river terrace gravels above London clays and then it’s coming out and you see a spring at the bottom there, it’s coming out into what we call the SSSI, so a protected area beyond. Now there’s no targets to be met at the moment but what we needed to do is it was a voluntary system that the airport wanted to reduce as much as possible the contamination coming off their site. So we were aiming for something like a 90% reduction. So if I just go back to the start here, this is us zooming into the pilot study. So if you look at the cutout on the left, the groundwater is moving from left to right. We inject in an arc because the groundwater itself is we’re not entirely sure that it’s perpendicular flow there. So we’re just giving ourselves a chance with an arc there in case it moves over time.

We use direct push rigs to also sample in between the points during injection to ensure that we’re getting good overlapping radius of influence so that we’ve got a solid barrier. And then we’re using a parking agent as well to ensure that we get the right configuration of the barrier. Basically that breaks the dispersion agents, drops the product out and we can design the barrier nicely using that parking agent. So these are the results. So basically you are looking at the in barrier wells here. We’ve got a downgrading well, nine foot downgrading, and we’ve got two downgrading wells, shallow and deep, about 15 foot downgrading. And you can see that we get a rapid reduction after the treatment. We’re really looking at PFAS and P4, but PFHXA and 6-2-F2S were the main constituents on the site, and you can see we get a big reduction there. So we were looking to really look at a greater than 90% reduction in PFAS and P4. We actually got to non-detect for both of those compounds and maintained that, and we got a 96 to 99% reduction in the total PFAS on the site.

So, the full-scale barrier then, you can see the orange is the pilot study area. We then extended this to a full-scale treatment. We just did that towards the end of last year. We finished about a month ago just doing the injections there. So, 228-foot extension of the barrier, done some upgrading wells. There’s in-barrier wells, and those are mainly for us so that we can check that the barrier working as we go along and it helps us make an accurate application as we go along. But then there’s six downgrading monitoring points that are used by the regulator and they’re going to monitor every six months for two years and then continue just monitoring yearly. And that’s all you need to do. That’s all you need to do. There’s no pumps, there’s no pipes, there’s no contamination coming to the surface. It’s an entirely passive solution to prevent egress from the site. Thank you very much.

All right. Thank you very much, Gareth. That concludes the formal section of our presentation.