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Does PlumeStop retard PFBA, PFBS, PFPEA, PFP…sorry, I’m getting here, PFHXA commonly found in AFFPFAS signatures. Do these PFAS compounds require additional management compared to the longer-chain PFAS compounds?

Well, I can’t answer all those compounds. I showed a slide near the start some of the isotherms that REGENESIS have been working on, that showed some of those shorter-chain PFAS compounds which show that they are absorbed. They obviously do breakthrough faster than the longer-chains but they are absorbed, and I think some of the shorter-chain ones, I think they’re absorbed at 98% at very high concentration. So, yes. You would expect them to be absorbed. It’s just a question of how long they will be absorbed for? So they will have breakthrough sooner than some of the longer-chains, but you would expect them to be absorbed. So I can’t go through every compound but some of the people at REGENESIS might have done some more experiments with some of those specific compounds that be able to or there might be some papers out there. But one of the challenges here and sort of your question outlines it quite clearly, is there’s a lot of compounds out there and every site has its specific ones that we’re of concern. So, unfortunately, we cannot analyze for everything right now. I know there are some analytical methods out there. One is called a top method which tries to get a grasp about how many overall view of the compounds available. But, hopefully, that kind of answers your question, but I know I can’t answer it totally directly within this hour.

Hey, this is Maureen. I’ll just add a little on that. You know, with the isotherms, we do have some software internally that we can have a multi-component. We can we can look at, you know, many different components and different isotherms to try to get an idea of how much sorption capacity we would have so we can try at least model, you know, a particular site to be able to achieve and then adjust the application rates as needed to try to meet the objectives of the specific site.

How was the reagent injected specifically, pump and pressure flow rates in each case?

So, in that case, is we try to keep it from an experimental point of view. We try to keep everything uniform i.e. the pump pressures, the pump flow rates, and the method of injection were all kept…so they’re all injected by direct push using a low pressure about 25 psi with a flow rate of less than 20 liters per minute. That is just to try to keep everything the same. I do know that for a powdered activated carbon, some of the manufacturers out there recommend it injected at higher pressures and at higher flow rates to keep it suspended. But in this case, in order to look at, keep the parameters similar, that’s the way it was applied in this case. So, yes. Personally, I would think if you gonna higher pressure, higher flow rates, the heterogeneity may, may or may not be overcome, and I mean, that’s gonna be a very specific question. But in this case, at this site, we kept all the parameters the same as best as we could.

How do you explain the 40 parts per trillion PFOS concentration after 18 months?

That’s a tricky question. You know, we’re dealing with such low concentrations here, parts per trillion, that is it a laboratory artifact, or is it a sampling artifact, or is it real?

And it was just in one well of all the well samples. So, you know, we’re treating it as a real number. So it might just be, you know, if you wanna think positively, it just might be a one-off and hopefully next sampling event it disappears, or it maybe it could be the start of a trend. Right now with one data point, it’s kind of hard to guess. You know, the laboratory numbers look fine so I don’t think it’s a laboratory error. It may be a sampling byproduct but, you know, once again, we were very careful how we’re sampling. So, I think right now, we’re treating it as a real number but for one data point, we’ll see what the next data point comes in. If it goes up, then we may have a trend, if it goes down, then that might just be an artifact type thing. Unfortunately, I don’t wanna go too far out online right now based on one data point at one well of on the site for five sampling events. But sorry, I can’t really answer your question, that would be a crystal ball raising on that one.

What is the estimated plume size limitations on controlling the injection to get effective treatment in a fine to coarse sand aquifer?

I’m not quite sure I understand the question, but if you, you know, heterogeneity, this is in general. This just isn’t what PlumeStop or any…this isn’t what reagent. It’s heterogeneity always controls the success usually of an injection. And there are some things we can do to overcome heterogeneity but in a lot of cases, heterogeneity is something we have to deal with. And that comes down to pressures, flow rates, number of injection points as well as…by that I mean vertically and laterally. A lot of times, vertical injection points are overlooked. We see a lot of times where people are trying to inject over 10 feet and use one injection point to cover a 10-foot vertical.

In our opinion, we like to break that down. The most we like to inject over vertically is two to three feet and use multiple points vertically. Once again, you can get in discussions both top-down versus bottoms-up versus different types of tools. It gets quite complex. At the end of the day, your applicator should be able to help you, advise you on which best way of doing that. And of course, that comes down to detailed site assessment is a lot of times this one to two-inch sand seems coarser and they may be just one or two orders made to a higher hydraulic connectivity. They will control where things go in the sub-sources. So those are the things that really we find when we have better characterization of sites by the consultants, we get better treatment. It really comes down to that.

When you collect groundwater samples from monitoring wells in the midst of the PlumeStop injection area, what do you see in the water? Do you see any of the black PlumeStop carbon suspended in the water?

Definitely after the short-term, if we try to sample two or three weeks after, we’ll definitely see. We did try to sample I think about three weeks after we did the injection. And we just had PlumeStop was definitely suspended in some of the wells. Discussing with the lab, that was gonna be a major issue. So, we decided not to submit those samples and we waited till three months, and by then, all the PlumeStop had basically been removed from the groundwater and that groundwater was basically back to its natural turbidity, for lack of a better word. So, in this case, we’ve never tried to analyze any of the samples immediately after or shortly after the PlumeStop is because the water itself can sometimes be quite gray or in some cases black. In which case, that causes some issues with the laboratory.

What other types of sites has PlumeStop been used on? Have they all been PFAS-contaminated?

Just speaking for us up here in Canada for InSitu, this is the first site that we know of that’s being had PFAS. So that’s the only one up there…I think we’ve did about 23 sites now. The other sites have been a mixture of chlorinated solvents and petroleum hydrocarbons. I would say maybe 60% petroleum hydrocarbons, 40% chlorinated solvents. The geologies we’ve injected PlumeStop in is anything from a glacial till to glacial fluvial deposits and that sort of thing and even fractured limestone and metamorphic rocks. So, we’ve got quite a bit experience and it’s worked quite well in quite a wide variety of geology. So, you know, the nice thing and I don’t like to keep going back to it, but what I call the injectability of this product is it’s a very easy product to inject. So, I mean, from that point of view, I don’t mean to make it sound simple, but that is one of our biggest challenges injecting products is how well does it go into the ground? And then once it goes in the ground, how well does it distribute? And in this case, I hope we find this product actually distributes very well in the ground and injects very well easily into a variety of geologies.

Just one comment I wanna add and it’s a question that came up and it was when you’re talking about the PlumeStop getting into the wells. It is a common practice say after the application to flush the wells and to remove some of the carbon in the wells. I don’t know if you wanna comment on that, Rick, but I know that’s a common practice that we utilize.

At this site, we did do a small flush afterwards, and that’s one reason why we left it for three months. The flush we find also for the ORC because it also can…I don’t wanna say clog up the wells but it can clog up the wells if it gets in the well. So we try to flush it right afterwards but we’re not talking, in this case, we usually talk maybe two to three gallons at most, and we put a tracer. Before anybody asks, we put a tracer into our water that we flush out the well so that when we sample, we analyze for that tracer to make sure we’re just not sampling water that we injected to flush out the well. So we know the water we sample is aquifer formation water. So, to answer that question before it gets asked.

Video Transcription

Dane: Hello, and welcome everyone. My name is Dane Menke, I am the Digital Marketing Manager here at REGENESIS and Land Science. 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 disconnect and repeat the original login steps to rejoin the webcast. If you have a question, we encourage you to ask it using the question feature located on the webinar panel. We’ll collect your questions and do our best to answer them at the end of the presentation. If we don’t address your question within the time permitting, we’ll make an effort to follow up with you after the webinar.

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 presentation, we’ll focus on a case study on the successful In-Situ remediation of PFOA and PFOS using PlumeStop Liquid Activated Carbon. With that, I’d like to introduce our presenters for today. We are pleased to have with us Rick McGregor, president of InSitu Remediation Services Limited. Rick has over 26 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 Maureen Dooley. Director of strategic projects at REGENESIS. Maureen has more than 25 years of experience in the remediation industry. In her current role at REGENESIS, she provides technical leadership for complex soil and groundwater remediation projects throughout North America as well as remediation design, strategy, and business development in the Northeastern United States and Eastern Canada. All right. That concludes our introduction. So, now, I’ll hand things over to Maureen to get us started.