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With that, it is my pleasure to officially welcome you to today's Cleanup Information Network or CLUIN webinar.

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My name is Jean Ballant. I'll be serving as the technical moderator in the background coming to you from EPA's Technology Innovation and Field Services Division.

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I want to wish you all a happy new year. And I'm really happy to be here starting 2025 with our very first webinar where our topic today is going to be thermal remediation of napples.

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Our session today has been sponsored by EPA's Office of Research and Development.

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We are joined yet once again by Dr. Ava Davis from EPA ORD.

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She's going to carry on with a multi-part webinar series that she started in December. She completed two talks and she's here to deliver a third session related to napples. We have a fourth session scheduled with her tomorrow. And I'll tell you a little bit more about that one at the end of today's broadcast.

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But for today's session, before we officially begin with our technical content, I'd like to walk through just a few gentle housekeeping items to make sure that everyone understands how to participate.

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As I am going through these instructions, I'll kindly ask those of you who have participated in our webinars, if you could open up the Q&A, let me know, are you completely comfortable with Zoom and you do not need instructions on how to use it? Because I will skip over some things.

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I recognize some parties may be brand new to the world of Zoom, so I want to be sure everyone knows how to participate.

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But I can streamline our instructions today based on some real-time feedback. So as I'm going over some basic ground rules.

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Please, by all means, send in a quick message in the Q&A and just let me know if you'd like to skip the Zoom instructions.

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So while I continue to call and collect those responses. I'll just remind everyone that there is a unique seminar homepage that's been set up for today's session.

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That URL is shown in red on the top of this slide. It's the same website you were directed to when registering. It's the same one I sent you in reminder and confirmation emails. It's the same website that I'll point you to right now if you're looking for copies of the presentation materials or want to follow up and access resources after our live broadcast, that website will remain active from today forward.

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I also have a QR code that you'll see on some of these slides at the start at the end of our session as well that will point you to that seminar homepage.

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We have already posted a PDF copy of the presentation materials on that seminar homepage. If you scroll down.

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Head over to the webinar slide section. You can download it from there. Simply click on that or use the plus icon to expand the section and access those links.

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We'll be hosting our broadcast today through Zoom, so you can participate in that free Zoom application or browser.

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And as noted, when you check in, you can simply download the slides on Kluwen and then follow along by phone if you have issues with Zoom. But I'm here to help troubleshoot. So let me know if you're having any technical difficulties and I'll be happy to work with you to get you on board for that fully interactive delivery.

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Audio is available online through Zoom or through your device's speakers, headsets. You can also choose to call in. Regardless of how you're listening, though, all participants are muted, so you don't need to worry about finding your mic or muting yourself. I've taken care of that for you.

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Same thing applies to your camera. If you need help with the online audio, check your local volume settings or try disconnecting from a VPN. If that doesn't fix the issue, let me know using the Q&A and I'll work with you to troubleshoot and get that issue resolved.

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As I hinted at earlier, there are some buttons at the bottom of your screen. As I'm scrolling through the results, the bulk of you would like to skip the Zoom instructions, but I do have two newbies who are asking for a quick tutorial. So I'm going to cover two important things on the screen here and then we'll move on. So thanks for that feedback, everyone.

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Just noting at the buttons at the bottom of your screen, the meeting chat is disabled for you as attendees, but I may send links to you in the chat. Instead, if you have questions, need to report a technical issue.

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Or would like to share thoughts with our speaker, you're going to use another button called the Q&A. If you click that Q&A, you can use that window to privately submit comments, questions, or report technical issues at any time.

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There is also a raise hand feature, but we're going to hold off on using that unless we have time later on during our Q&A break.

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So if you have a question or need assistance, I encourage you to submit it in writing using the Q&A, or you can send me a direct email at ballant.gene at epa.gov And I'll work with you to troubleshoot any issues you might be having.

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Her session is being recorded today. We do have live closed captioning available. Use the CC or closed caption button at the bottom of your screen. You can adjust the size and controls.

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Other controls for captions in Zoom locally. And then I'll ask that you stick with me until the very end because I'm going to walk through some very important reminders on how you can access materials, share feedback, and get a certificate. That is the number one question I get from people.

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Because they don't know how to get a certificate. And I promise you, I will tell you at the very end. So please stick with me until the end of our broadcast today.

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All right. So I know most of you already know how these controls work, but for the two individuals who have requested for a quick overview.

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This is visually what you should be seeing on your screen.

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Audio controls will be available to you here in the lower left. The most important buttons are in the bottom middle of your screen.

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So if you have a question or need to report a technical issue, you're going to click the Q&A button at the bottom.

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And then, of course, if you would like to turn on transcript or CC options, you'll use that CC icon at the bottom of your screen.

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If you need any further assistance with Zoom, please click the Q&A button and send me a message. I will reply to you directly and help explain how some of the additional controls are working in Zoom.

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All right, I think we've gone through enough of a tutorial today.

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And at this time, it is my pleasure to get ready to introduce our speaker, the fabulous Dr. Ava Davis.

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From EPA's Office of Research and Development. So Dr. Davis, you are welcome to unmute as well as start to share your screen. And as you get your screen set up for us.

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I'm going to provide a brief introduction to you for our audience.

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So Dr. Davis has started her time here at EPA in 1990 after completing a degree in agricultural engineering.

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Where she specialized in groundwater contamination at Colorado State University. She's a hydrologist in the Office of Research and Development, where her research has included the effects of temperature on physical properties of organic contaminants.

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Thermal degradation of contaminants, and steam injection into fractured rock. Dr. Davis has provided technical support for numerous Superfund sites and other contaminated sites for thermal remediation, including site characterization.

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Evaluation of remedial technologies, setting remedial goals, and then monitoring the implementation of these technologies.

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She's also the author of a groundwater issue paper on thermal remediation, and I'll be sharing a link to that paper later on today.

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So Dr. Davis, I'm going to go ahead and turn off the screen share. If you'd like to say hello to confirm, I think you're unmuted.

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Hello. Thank you, Jean.

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Thank you. So go ahead and share your screen. I'll confirm that the slides are up and then I'll turn the floor over to you.

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I'm sharing now. Do you not see them?

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No, I'm going to ask you to try one more time. You might want to click that green share button and then I'll confirm when it is up.

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Okay?

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And now I close out my slides.

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Can you see them now?

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I can not see them, so… I can do one of two things. Dr. Davis, at the bottom of your screen, do you see the bright green share button?

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Yes, share screen. Yes. Oh, oh. I forgot a step.

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Okay. Yep. Yep, you got to pick that one window. There we go. Beautiful. Now the screen share is starting. We'll minimize this window and call up those slides.

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All right, beautiful. Let's go into from beginning in your presentation mode.

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And then that little button at the bottom, hide it, your slides look great. I'll turn the floor to you, Dr. Davis.

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Okay. Thank you, Jean. I should know this as my third presentation in a couple of weeks. As Jean mentioned, this is the third in the series I've done on NAPPLS. The first one was meant to introduce people to what people

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Types of napples there are out there. Very large number of them. And I know I didn't cover all of those that are out there, but I tried to cover most of them that I have encountered and talk about how they migrate in the subsurface. Because once you have some understanding of the properties of the different napples, whether it's elm apples, those are lighter than water or dean apples, those that are

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More dense than water. Once you understand how they flow through the subsurface, then that can help you with planning for how to characterize It's an apple site in order to determine where those napples are And also to find out

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To determine the geologic and hydrogeologic properties of the subsurface in which they reside.

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And then the next logical step from there is, okay, now what do we do about it? How do we remediate?

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The Napples. One of the questions I had after the last presentation was about the fact that NAPLs can show up where you least expect them over time as they continue to migrate and i that does bring up the point that, yes, indeed, Napples, even when they've been in the ground for a long time, they can continue to migrate

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Different forces can create that gradient that then creates migration of the Napples. And they can show up in places where you really don't want them.

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And my response and the question was. Would you recommend characterizing again for the Napples like every decade. So you always know where they are. And my response to that would be.

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Why would you want to leave them in the ground? There are ways to remediate them.

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And thermal remediation technologies have been proven to be very effective for their removal.

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And I hope that with today's presentation that will be obvious.

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So with that. I'd like to point out, too, something that we found I was made aware of recently is the 2023 Superfund report that's put out by EPA.

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Shows that thermal treatment is now the most common source remedy for sore zones.

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That's based on rods that were signed between fiscal year 2018 and 2020.

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So that's, I think, is great that more of these technologies are being used on source zones, but I think we've got a ways to go and we still got bioremediation and chemical treatment on as many as there are.

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So just a quick present. Presentation outline for today. I'm going to talk about the important mechanisms. What happens to these organic contaminants when you start heating the subsurface?

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And I'm going to describe the commonly used thermal technologies. And as I described, the technologies, we'll do some very brief case studies for each of these technologies and At the end, there'll be a Q&A.

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My next presentation in this series of four, the fourth presentation will be on challenges met with thermal remediation.

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And the reason why I want to do that is that I get a lot of questions. I have gotten a lot of questions over the years about you know what you're the technologies might have been great on somebody else's site but

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It won't work on my site because of this or because of that.

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Learned how to overcome a lot of the challenges that can rear their ugly heads on Superfund sites or other contaminated sites.

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And I've always been impressed with the thermal vendors and their willingness to address those challenges head on and find a way to overcome them to to be able to perform the remediations where they are needed.

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So just in general, in situ thermal remediation These are very aggressive technologies. Generally, they're applied to source zones to recover an apple.

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Although. In more recent days, I am seeing more cases of sites where Maybe there's not a lot of napple, but there's high concentrations that are really causing a high groundwater dissolve phase plume.

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Maybe not an apple, but it's in the low permeability soils and they're looking to apply thermal In another case, they had injected hundreds of thousands of pounds of chemical accidents or substrates for substrates for in situ bio and still there was enough of the breakdown products, CIS12 DCE and vinyl chloride left that it threatened down gradient

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Water supply wells and we were looking at thermal for that side as well so the As these technologies are expanding further, we're addressing more different types of sites with them.

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And of the other sites, of the other technologies out there.

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Such as ISCO or Institute bio you know those actually do work in the dissolve phase. And so the thermal technologies are really some of the only ones that directly address NAPL, whether it's DNAP, Or Elnapple. So these technologies are applicable to

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Both VOCs and SVOCs, the volatile organic contaminants and semi-volatile organics They've been applied in a wide variety of hydrogeologic settings.

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And simple and highly heterogeneous lithologies. And we'll talk about how those are addressed that can be applied both above and below the water table They've been applied at sites where there's surface structures and even in fractured bedrock.

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When you apply these technologies and apply them aggressively, you can expect a large percentage of the mass is going to be recovered.

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Which leads to orders of magnitude reductions in the soil and groundwater concentrations.

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And this comes about in a relatively short time. Most of the technology applications on smaller sites are going to be completed in less than a year.

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And you're going to see orders of magnitude reductions in the mass flux to the down gradient plume.

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And then once the NAPL mass is recovered. Generally.

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Something like pump and treat or monitor natural attenuation may be very effective for the remaining dissolved phase and down gradient plume.

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We have seen the plumes then disappear after an aggressive application of these technologies.

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So what are the mechanisms that come into play here and are important for these technologies?

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Going back to my PCAM training, when you increase the temperature of these organic liquids.

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The one thing that happens is the exponential increase in vapor pressure and that's perhaps the most important mechanism for recovering, especially the volatile organic compounds When you increase their the temperature up to 100 centigrade you're going to increase their vapor pressure by more than an order of magnitude.

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And for the semi-volatile compounds, it doesn't increase that dramatically going up to 100 centigrade. Temperatures have to be taken higher in order to recover some of the semi volatiles. We'll talk about that a little bit more. With that temperature increase, there's also an exponential decrease in the viscosity of water and NAPL.

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And this then becomes very important for the higher boiling compounds, creosote, coal tar, some of the crude oils.

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It would also apply. If there's PCB.

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Liquids in the subsurface. And being able to decrease their viscosity then allows them to flow more freely to wells and for them to be pumped more freely from the subsurface.

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The increase in temperature can also increase the solubility of these organic contaminants.

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To a certain degree. That's not as it's not all that great of an effect. However, there does seem to really be an increased rate of solubilization as the temperature is increased so that we normally see much higher groundwater concentrations as a

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Ground is heated. The increase in temperature for a lot of these types of compounds is also going to decrease their adsorption and their absorption into naturally occurring organic matter and it may increase their desorption rate. So some of the tailing you might see with a pump and treat system

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Then this helps to overcome. I want to talk co-boiling that occurs when you have both a VOC NAPL.

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Present with groundwater. And this process does require the presence of two liquid phases, the groundwater and the nappal.

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And both of these liquids then contribute to the vapor pressure.

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And the boiling is going to occur when the combined vapor pressure from the two two liquids equals the local ambient pressure.

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Yeah. And thus a volatile organic Napple is going to boil at temperatures that are less than the boiling point of water. Because like I said.

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Two liquids are both providing vapors. And so for PCE, which has a normal boiling point of 121 centigrade.

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When it's present as an apple with groundwater, it boils at a temperature of 88 centigrade, as you can see here.

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2ce, which has a lower boiling point, it will boil earlier, other compounds like chlorobenzene, a common contaminant that will also then boil away at temperatures less than 100 centigrade.

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So when you start heating the subsurface, you get up to that co-boiling temperature.

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Then the NAPLA is going to vaporize. It's not stable in the presence of groundwater at those temperatures is going to volatilize.

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And be recovered. However, you're still going to have dissolved and absorbed phases that will remain and the As I said, heating the heating the soil can increase solubilization.

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Of the compounds. And so you're going to generally have pretty high concentrations in groundwater, even at the time that the napple is gone.

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And that there's likely going to that those groundwater concentrations are well above the MCLs. And so to continue heating until you get to the boiling point of water that continues to drive off those that are in the dissolve phase.

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And they absorb contaminants so that lower concentrations can be reached.

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There are… three main thermal technologies that are used today. I'm going to talk about each of these steam enhanced extraction, electrical resistance heating, and thermal conductive heating.

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They differ really just by the means in which the energy is added to the subsurface.

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But there is another what I would call innovative or emerging thermal technology that goes by the acronym of self-sustaining Treatment for Active Remediation, or STAR. It's actually an in situ combustion process. I'm also going to talk about that briefly and

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With all of these technologies, you're going to have thermocouples in the subsurface to monitor temperature to make sure that you're heating your entire treatment zone. You're going to have the extraction of vapors and steam using vacuum extraction. With some of these two you're going to have

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Groundwater extraction and then the treatment of the vapors and the steam after it's been condensed to water above ground.

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Those are common components of all of these technologies. So let's talk about steam injection first. This technology has an additional recovery mechanism in addition to those I mentioned a couple of slides previously.

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In that is displacement. As you inject steam into the subsurface.

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It's going to displace the groundwater and any napple in front of it.

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Oh. Let's try that again. Okay.

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Um and So that then.

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With multi-phase extraction well as you extract both all the groundwater and apple and as well as vapors of steam and the contaminants.

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The steam is going to flow in the more permeable strata when you've got a heterogeneous subsurface. But those less permeable zones that don't as readily take steam will be heated by conduction.

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In general, the minimum hydraulic conductivity for steam injection would be about 10 to the negative five centimeter per second, which is roughly equal to like a silty sand type stratigraphy.

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Pressure cycling is used with steam injections so that as they reduce the steam being injected while continuing aggressive extraction, which helps to recover the contaminants also from those low permeability zones.

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Because, as you know, if you heard my previous presentations. Napples as well as dissolve phase will migrate into the lower permeability zones. And it's important that those are addressed.

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The steam ejection technology is most appropriate for large deep sites.

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Because just for one thing that allows significantly greater well spacings than what you can have with the other technologies we'll be talking about.

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And that's this is the C technology is one that is most applicable in highly permeable sands and gravels that have high groundwater flow rates.

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That injection of that steam helps to keep groundwater from flowing into your treatment area.

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And so… taking the heat away with it.

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And steam injection is the best way to get the large amount of energy into the subsurface for the remedial purposes.

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So let's look at a little cartoon here that shows what happens when you inject steam.

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What we like to do is to have steam injection wells that encircle the NAPL contaminated area.

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And then apple contaminated area here is kind of shown by the the dotted line.

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And the… steam injected then goes in radially. Different wells are going to accept a little bit different amount of steam most likely But as that steam zone grows, then it pushes groundwater in Napal to the extraction well that's at the center.

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And as I said, an MPE well then, a multi-phase extraction well will extract groundwater and Apple, and vapors.

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If the contaminated area is large enough that you can't completely surround it with just Six Wells is shown here, then a seven spot pattern is shown on the right can be used this is a Like the technology itself, it's adapted from the oil industry.

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To talk about a couple of places where steam injection for remediation has been used. The very first, I believe this was the first Superfund site where any thermal technology was used. This is Southern California Edison's Visalia polyard where uh

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Power poles were treated with creosote. They had… instituted pump and treat back in 90s but then from May of 1997 to June of 2000, over 660 million pounds of steam were injected into about a two acre area from which about 1.3 million pounds of wood preserving chemicals were recovered.

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There was also some breakdown of these PAHs and creosote at the higher temperatures and some enhanced biological degradation perhaps with the injection of air.

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And after the after they stop recovering creosote with the steam injection, then the pump and treat did continue. So to give you some statistics on this. Like I say.

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The first application of thermal technologies at a Superfund site but they I had been running this pump and treat system well from 1975 And they were spending more than a million dollars a year on that system. And they really wanted to get out of the pump and treat business. That was their motivation.

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For wanting to try the steam injection, even though it was unproven for this type of contaminated in this type of a setting.

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So after the they spend a total of 21.5 million on the steam injection if they had if they had had known upfront everything we knew by the end of the project, the actual cost would have been less than what they were.

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But it's interesting then to compare the costs of of the recovery of the creosote. With the pump and treat system they were it was costing them about $26,000 per gallon of creosote that they recovered. The steam injection was 130.

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Dollars per gallon of creosote recovered. And if you look at the time required, okay, they injected the steam for three years But to recover that same amount of mass with a pump and treat system would have taken in excess of 3,000 years and as

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Pump and treat systems get less effective as you recover some of the mass that time probably would have been even longer.

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So they have chewed. Their objectives, they were able to close down the pup and treat in 2004.

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By 2009, they met all of the groundwater cleanup criteria and they were delisted from the national priorities list in 2010.

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Another site, this was a site waste oil site, the BD site.

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We did a steam injection to recover the waste oils there that were an elm apple.

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Mostly floating on the water table with some smearing below it.

00:25:14.000 --> 00:25:35.000
The waste oils contain chlorinated volatile organics, TCE, PCE, that have been used as degreasers. Two different areas we delineated there where there was an apple that was addressed by two phases of steam injection.

00:25:35.000 --> 00:25:52.000
For the first area, about 95 million pounds of steam injected to recover 54,000 gallons of napple and in the cleanup criteria were met there as well.

00:25:52.000 --> 00:25:58.000
The former Williams Air Force Base site just outside of Phoenix, Arizona.

00:25:58.000 --> 00:26:11.000
They had a very large jet fuel spill. The amount that was spilled Estimates for that ranged from about a million gallons up to 11 million gallons.

00:26:11.000 --> 00:26:22.000
And the soil stratigraphy there is very heterogeneous. Which didn't stop the downward migration of the jet fuel.

00:26:22.000 --> 00:26:39.000
But once that water table started to rise again. Then the jet fuel was trapped below some of these less permeable zones so that we ended up with jet fuels.

00:26:39.000 --> 00:26:53.000
Trapped below the water table. From about 240 feet below ground up to about 160 feet below ground at the time that the sea was performed there.

00:26:53.000 --> 00:27:12.000
The Vedo zone is being treated with SVE still. Some of the early attempts at remediating this jet fuel was to try to use horizontal wells to recover the LNAPLE, and that was not successful.

00:27:12.000 --> 00:27:34.000
But esteemed pilot scale demonstrated that steam injection could be effective and that was what was used And this was a very large site. As I already said, it extended to 240 feet below ground surface. There was a total of

00:27:34.000 --> 00:27:51.000
Over 400,000 cubic yards that were treated with more than 300 million pounds of steam and more than two 0.5 million pounds of petroleum hydrocarbons were recovered. Half of it came out as an apple.

00:27:51.000 --> 00:27:58.000
Which was of a quality that could be burned on site or sold or recycler.

00:27:58.000 --> 00:28:04.000
But most rest of it came as vapors because this is a volatile.

00:28:04.000 --> 00:28:26.000
Compound, volatile petroleum hydrocarbons. The problem… And this is why, too, I emphasized characterization for uh napples. You can see The light blue area is where we see was applied.

00:28:26.000 --> 00:28:32.000
But the NAPPL had extended. Further than that.

00:28:32.000 --> 00:28:45.000
That… And when the whole apple and the whole apple affected areas not treated.

00:28:45.000 --> 00:29:05.000
There is less less benefit to the overall benefit to the overall remediation as high groundwater concentrations remain in some places. We are still looking at methods to address the remaining elm apple.

00:29:05.000 --> 00:29:17.000
To finish this remediation. Moving on to electroresistance heating for remediation.

00:29:17.000 --> 00:29:33.000
With this technology, electrodes are installed in the subsurface. An alternating occurrence is applied to the electrodes and the current is actually carried between the electrodes by the water that is in the pore spaces.

00:29:33.000 --> 00:29:42.000
And that the soils are pretty resistant to current flow. And it's that resistance then that produces the heat.

00:29:42.000 --> 00:29:53.000
And the full scale application of this technology now generally uses three phases of current coming off of the power.

00:29:53.000 --> 00:30:20.000
Line power. But for those who have uh heard some of the or seen some of the older literature you might have heard this technology called six-phase soil heating or jewel heating. Originally, six phases were used Now, currently the They generally use three phases of current for the technology.

00:30:20.000 --> 00:30:38.000
So you start by constructing the electrodes either vertically or angled electrodes angled when you have to have to under a building or around some other kind of subsurface structure.

00:30:38.000 --> 00:30:45.000
They're installed in a triangular or hexagonal array as shown here.

00:30:45.000 --> 00:30:55.000
With a typical diameter. Of the array of about the array of 40 feet, that's about 20 feet between the electrodes.

00:30:55.000 --> 00:31:03.000
Typically, 100 to 600 volts are applied per electrode. That's going to depend upon the resistivity of the soils.

00:31:03.000 --> 00:31:25.000
You can reach steam temperatures in about three to six months. Generally the time for one of these remediations is less than a year. Vapors can be extracted at the electrodes or at MPE wells that are between the electrodes.

00:31:25.000 --> 00:31:35.000
With this technology, the heating is dependent on being able to conduct the current between the electrodes.

00:31:35.000 --> 00:31:40.000
That does require water to be in the pore spaces to carry that current.

00:31:40.000 --> 00:31:50.000
Which means that maximum temperature achievable with this technology is going to be the boiling point of water.

00:31:50.000 --> 00:32:02.000
Generally, the lower permeability zones are going to heat first because they can have a higher cation content in the groundwater And because there's less groundwater flow through those areas.

00:32:02.000 --> 00:32:21.000
It does work both above and below the water table. If you're working above the water table and there's not enough water to maintain the current flow, water can be added at the electrodes to overcome that.

00:32:21.000 --> 00:32:32.000
Contaminants are generally collected as vapors, although there are some applications of this technology will also include extracting of groundwater.

00:32:32.000 --> 00:32:49.000
Particularly in cases where the groundwater flow rate is higher. But generally, the these this technology is limited to situations where the groundwater flow rate is less than about a foot per day.

00:32:49.000 --> 00:33:05.000
But it does work very well in low permeability soils and being able to heat them to the boiling point of water And the vapors that are generated do a good job then of increasing the permeability enough that they can be

00:33:05.000 --> 00:33:15.000
Recovered at extraction wells. Erh has been used under buildings, as I've mentioned.

00:33:15.000 --> 00:33:40.000
Picture on the left is an old one where the system was installed within a warehouse. In this case if you've got a the enough clearance so that you can get a rig into the building and install the electrodes vertically. That works very well. In other cases, the picture on the left

00:33:40.000 --> 00:33:47.000
Is where they're installing angled electrodes underneath the active manufacturing facility.

00:33:47.000 --> 00:34:07.000
And that manufacturing facility was manufacturing facility very sensitive production going on there. So they had to ensure that there was no vibrations in the building, but they were able to maintain production during the time of installation of the system and its operation.

00:34:07.000 --> 00:34:28.000
Going back again to one of the earliest applications of thermal technologies at Superfund site. This is the Fort Lewis Army logistics center east gate disposal Yard. Again, it's a waste oils and chlorinated solvent sites from this first from this first

00:34:28.000 --> 00:34:45.000
Treatment area that's shown in red there in the figure we recovered over six 6,600 pounds of chlorinated compounds and it's really the chlorinated compounds that were targeted with this technology.

00:34:45.000 --> 00:34:55.000
But the petroleum hydrocarbons or the TPH that was co-located was also recovered.

00:34:55.000 --> 00:35:04.000
And there was over 8,800 pounds of TPH. These were highly permeable soils with high groundwater flow rate.

00:35:04.000 --> 00:35:09.000
So in order to be able to reach the target temperature.

00:35:09.000 --> 00:35:38.000
Groundwater was extracted up gradient and then re-injected down gradient to sort of neutralize the neutralize the gradient across the treatment area so that we're able to to reach the target temperature. Remediation was continued until diminishing returns. This was… a mass removal exercise.

00:35:38.000 --> 00:35:46.000
And… As I said early on in the talking about the mechanisms with these technologies.

00:35:46.000 --> 00:35:56.000
It usually… When you start heating the ground, it will increase the solubilization rate of VOCs.

00:35:56.000 --> 00:36:08.000
If we compare the area within the treatment zone the concentrations we were seeing before treatment, they're all pretty low.

00:36:08.000 --> 00:36:16.000
But then once we start heating. The concentration at one of the wells in particular went out very substantially.

00:36:16.000 --> 00:36:32.000
And this is something that's expected during heating. It's a good way to monitor the progress of the remediation is to see these concentrations increase and then decrease as that mass is recovered.

00:36:32.000 --> 00:36:49.000
Just to show you how things can What normally happens after a remediation is complete a year and a half or so after the completion of remediation in the first area.

00:36:49.000 --> 00:37:07.000
That you see there on the right hand side most of the most groundwater samples from that area. We're now meeting MCLs. The second area that we treated on the left, the red outlined area.

00:37:07.000 --> 00:37:20.000
Their concentrations are significantly reduced. And if you look about a year later, you see that those concentrations are continuing to go down.

00:37:20.000 --> 00:37:29.000
In this case, it was pretty quick because of the high groundwater flow rates through these areas.

00:37:29.000 --> 00:37:36.000
Now, looking at the other end of the spectrum, at Camelot Cleaners in Fargo, North Dakota.

00:37:36.000 --> 00:37:43.000
The top layer of soils was a tight fat clay that contained little groundwater.

00:37:43.000 --> 00:37:51.000
But this tight fat clay overlaid an aquifer that provides Fargo's water supply.

00:37:51.000 --> 00:38:05.000
And initial concentrations of PCE, the dry cleaning liquid at this site were as high as 2200 milligrams per kilogram.

00:38:05.000 --> 00:38:12.000
This site was treated using electroresistance heating as a EPA.

00:38:12.000 --> 00:38:26.000
Recovery operation and over 5,000 pounds of PCE were recovered. Of the 80 groundwater conformation samples that were obtained, most of them were non-detect.

00:38:26.000 --> 00:38:33.000
Only two of them exceeded the cleanup goal of three ppm. After this removal action.

00:38:33.000 --> 00:38:39.000
No further action was needed then to protect Fargo's water supply.

00:38:39.000 --> 00:38:45.000
Dr. Davis, I just wanted to give you a quick time check. It's approximately 1.45 p.m. Eastern.

00:38:45.000 --> 00:38:54.000
Okay, I'm trying to make up a little time here. Erh site, Cleburne Street in Region 7.

00:38:54.000 --> 00:39:13.000
Chlorinated solvents were recovered here and in this case they found that they could not heat the bottom of the heat bottom of the low permeability soils because of the rapid groundwater flow in the aquifer underneath.

00:39:13.000 --> 00:39:22.000
And so the ERH technology was supplemented with steam injection in the underlying aquifer.

00:39:22.000 --> 00:39:35.000
And they did then achieve 99% reduction in the contaminants and both and reduce the concentrations in the down gradient plume.

00:39:35.000 --> 00:39:51.000
South Municipal Well, another site where we used ERH. And recovered pce over 4,500 pounds were recovered.

00:39:51.000 --> 00:39:57.000
And this, which included angled electrodes underneath the building. And as you can see here.

00:39:57.000 --> 00:40:16.000
The parking lot was where most of the treatment occurred, but they maintained an area for driving through by burying the system within this area.

00:40:16.000 --> 00:40:26.000
Just to give you a little bit of a feel for what can happen at these types of super fun sites that can confound us terribly.

00:40:26.000 --> 00:40:38.000
We were supposed to have a PRB treating the dissolve phase at the TIA waiver boundary but the PRB was not working.

00:40:38.000 --> 00:40:47.000
And then we found even after a high resolution characterization of the To determine the source zone.

00:40:47.000 --> 00:40:51.000
There was still source that was missed outside of that zone.

00:40:51.000 --> 00:41:00.000
So the ERH was very successful in the area that we treated, we got to temperatures.

00:41:00.000 --> 00:41:11.000
We used… sheet pile electrodes at this site and it worked very well But there is still dissolve phase.

00:41:11.000 --> 00:41:19.000
To be reconciled. Recontaminating the area from other sources.

00:41:19.000 --> 00:41:30.000
On the site. Concentrations here fluctuate widely. The remediation was done between 2016 and 2017.

00:41:30.000 --> 00:41:47.000
And as they said, there was a recontamination from an up gradient source is heartbreaking to me to see that occur after the because of other source areas that were missed.

00:41:47.000 --> 00:42:02.000
And that's why I emphasize characterization. Okay, the third of the technologies, thermal conductive heating When the heat is carried from the heater well.

00:42:02.000 --> 00:42:06.000
By the thermal conductivity of the soil.

00:42:06.000 --> 00:42:12.000
Heater wells are generally in the range of about 700 to 900.

00:42:12.000 --> 00:42:31.000
Centigrade and they're installed in a triangular pattern, much as the electrodes are for ERH with a Spacing being in the same range. Vapor extraction wells can be co-located with the heater wells or they can be centrally located between heater wells.

00:42:31.000 --> 00:42:39.000
The energy for this system can be either electrical or a gas combustion fuel.

00:42:39.000 --> 00:42:56.000
And when you're working above the water table, you can reach temperatures that are higher than the boiling point of water for treating VOC temperatures as high as 300 centigrade have been used.

00:42:56.000 --> 00:43:08.000
So thermal conductive heating then relies on the thermal conductivity of the soil to heat the ground. And the thermal conductivity of various soils and rocks is fairly uniform.

00:43:08.000 --> 00:43:17.000
Thus, you get a pretty uniform heating of the subsurface But that thermal conductivity is pretty low.

00:43:17.000 --> 00:43:24.000
And that's why you have to have that high driving force of having a very high temperature at the heater wells.

00:43:24.000 --> 00:43:33.000
As well as having a relatively close spacing of the heater wells.

00:43:33.000 --> 00:43:54.000
And I think covered the rest of that. The higher temperatures than the higher than come into play when you're looking to remediate semi-volatile compounds, which includes PCBs, PAHs, creosote and coal tar and dioxins.

00:43:54.000 --> 00:44:24.000
This picture just shows a system where the system where gas powered conductive heater wells are being installed This is Diaz Superfund site, unusual SVOCs at this site and that we were able to recover with recover with conductive heating.

00:44:24.000 --> 00:44:47.000
Soft and Recovery Services of New England was about 1.7 acres were 700 heater wells were installed to recover more than 430,000 pounds of petroleum hydrocarbons and the and chlorinated solvents. This again was a waste oil site.

00:44:47.000 --> 00:44:55.000
And this site, because of the lower permeability, instead of using steam injection, conductive heating was used very effectively.

00:44:55.000 --> 00:45:03.000
This was one of the earlier rods that was signed for the use of thermal technologies.

00:45:03.000 --> 00:45:16.000
And so The objective was that the objective was you know pretty lenient, allowing just for to eliminate the napple.

00:45:16.000 --> 00:45:33.000
That cleanup criteria was exceeded by several orders of magnitude. And then once that NAPA was recovered, you can see here from this graph, they had been operating the pup and treat system for quite a few years and recovering a

00:45:33.000 --> 00:45:42.000
About 150 kilograms of VOCs per year. And after the thermal remediation was complete.

00:45:42.000 --> 00:45:50.000
The amount of mass that they were covering was pretty steadily dropping off. And a couple of years later.

00:45:50.000 --> 00:46:06.000
It had decreased to about seven kilograms of VOCs per year, meaning they no longer then had to use it advanced oxidation system to treat those organics that they were recovering.

00:46:06.000 --> 00:46:17.000
So they were quite happy with the reduction in costs that came then to reduction in the cost of the pump and treat system after the thermal remediation.

00:46:17.000 --> 00:46:28.000
Southern California Edison had not just the vicellular polyard, but also a site in Lambra, California that was contaminated with wood preserving sites.

00:46:28.000 --> 00:46:48.000
And in this case, the creosote was in low permeability soils. They went to a depth of 100 feet, but that was all above the water table. And so conductive heating was used here as well. This was the elective electoral conductive heating site where they were able to meet

00:46:48.000 --> 00:47:05.000
The goals for recovery of benzoipyrine and dioxins, meeting those goals with temperatures greater than 300 centigrade.

00:47:05.000 --> 00:47:17.000
Coal tar has also been remediated using conductive heating. This site used a site used a very unique approach.

00:47:17.000 --> 00:47:23.000
For treating the coal tar that was contained within a holder at the site.

00:47:23.000 --> 00:47:32.000
The temperature has ramped up in three phases. At 80 centigrade, they were able to remove most of the water.

00:47:32.000 --> 00:48:00.000
As STEAM. Then they took the temperature up to about 100 centigrade to lower the viscosity of the coal tar further to aid in its migration to wells and then in being able to pump it out to recover it. And once they recovered what NAPL they could, then they took the temperature up to 325 centigrade to recover the higher

00:48:00.000 --> 00:48:27.000
Boiling point PAHs that remained in the system. That kind of approach overall is going to reduce the energy consumption needed to remove these types of contaminants whenever you can remove these higher boilers at temperatures less than you know that 325 centigrade that's used for the last of it.

00:48:27.000 --> 00:48:35.000
Thermal conductive heating can also be used to. In this case.

00:48:35.000 --> 00:48:40.000
Defoliants that have been used in Vietnam during the Vietnam War.

00:48:40.000 --> 00:48:53.000
They contaminated the shallow soils, but their adsorption, strong adsorption under the soils meant that they did not penetrate deep into this soil strata.

00:48:53.000 --> 00:49:04.000
So the topsoils were excavated. And stockpiled until they came up with a way of treating them. Conductive heating was tested and found to be effective.

00:49:04.000 --> 00:49:10.000
You can see the structure that was built in order to contain the soils that had already been excavated.

00:49:10.000 --> 00:49:19.000
And build the conductive heating system within it. And they were treated at 300 50 centigrade.

00:49:19.000 --> 00:49:31.000
Again, a successful remediation meeting their remedial goals. The in situ combustion, a star self-sustaining treatment for active remediation.

00:49:31.000 --> 00:49:48.000
In situ smoldering combustion. I would call this an emerging technology but i I think it definitely has some applications at a number of these creosote coal tar sites where there's heavy hydrocarbons.

00:49:48.000 --> 00:50:01.000
That are not especially volatile. But have a high BTU content and are present at concentrations of greater than 300 milligrams per kilogram.

00:50:01.000 --> 00:50:10.000
Ignition point is used to start the in situ combustion. Air is injected with it.

00:50:10.000 --> 00:50:17.000
To continue the… for that combustion to be self-sustaining.

00:50:17.000 --> 00:50:24.000
It is a rather limited radius of influence of around 10 feet.

00:50:24.000 --> 00:50:36.000
Normally, that that is… contained by how much air can be injected, being able to get air in there to sustain the combustion.

00:50:36.000 --> 00:50:49.000
And it works both above and below the water table. Below the water table, the vapors that are generated will displace the groundwater sufficiently to allow the combustion to occur.

00:50:49.000 --> 00:50:55.000
So I look to see that technology being used more in the future.

00:50:55.000 --> 00:51:11.000
We've already mentioned combining technologies at the Cleburne site and this combining technologies has been done at any number of different sites where you've got both high and low permeability that need to be addressed.

00:51:11.000 --> 00:51:35.000
The picture in the picture shown here ERH was technology that was being used, but it was found that it was difficult to heat the soils right underneath the cap here close to the ground surface and so steam spears were installed shallow there in the area that they needed to heat and

00:51:35.000 --> 00:51:44.000
They were then able to heat the entire area so that you don't have condensation occurring in the colder soils.

00:51:44.000 --> 00:51:55.000
When I review. Designs for thermal remediation systems, what I always look for is a monitoring.

00:51:55.000 --> 00:52:18.000
That's included because that's important, I think, from the viewpoint of the site owner So the first thing that's always monitored is the subsurface temperature distribution. And as I mentioned earlier on there are Thermocouples that are placed throughout the treatment area in order to be able to monitor the

00:52:18.000 --> 00:52:26.000
The subsurface temperatures. You want to always maintain hydraulic control when you're working below the water table.

00:52:26.000 --> 00:52:44.000
And the best way I think, to monitor that is with thermocouples that are placed outside of the thermal treatment area. Pneumatic control, you also always want to maintain. And so we normally put vacuum measurement points co-located with those exterior

00:52:44.000 --> 00:53:07.000
Thermocouples so we can make sure that There is not a pressure buildup outside of the treatment area. You're always monitor the extraction rate of the contaminants, both all NAPA phase, vapor phase, and the aqueous phases that helps you know

00:53:07.000 --> 00:53:27.000
The progress of the remediation. You expect to see the extraction rate increase as you're heating up And then decrease once the NAPPL is gone and and become low rates when there's just an aqueous you know dissolve phase remaining.

00:53:27.000 --> 00:53:35.000
And so then groundwater concentrations are always helpful in monitoring that progress.

00:53:35.000 --> 00:53:46.000
And in a lot of cases, too, soil concentrations, in-room soil samples, as well as spinal soil samples are used.

00:53:46.000 --> 00:53:56.000
So temperature monitoring outside of the treatment area. Think is very useful for demonstrating hydraulic control.

00:53:56.000 --> 00:54:07.000
The black line in this graph shows what you would, the temperature that you would expect outside of that treatment area just based on conductive heat.

00:54:07.000 --> 00:54:18.000
Outside of the zone. And as you can see the these exterior temperature monitoring points, initially all of them were lower than that.

00:54:18.000 --> 00:54:36.000
Expected temperature which is because you're pulling groundwater towards, you're pulling cold groundwater from outside of your treatment zone towards your treatment area, helping to to keep the temperatures lower there.

00:54:36.000 --> 00:54:52.000
But then when there is a loss of hydraulic control, it does become real obvious that the hot water is leaving the treatment area In this case, and in fact, in both of the cases where I've seen this happen.

00:54:52.000 --> 00:55:16.000
This didn't happen until this didn't happen until far enough along in the remediation that contamination was not lost with this hot groundwater. This is groundwater from the more permeable strata that had already been effectively treated before it left the

00:55:16.000 --> 00:55:30.000
The treatment area and these exterior areas we did take a look at after the thermal remediation and found that no contaminants then remained out there.

00:55:30.000 --> 00:55:41.000
Pneumatic control, we had pressure monitoring points along the property boundary to make sure that we vapors were not leaving.

00:55:41.000 --> 00:55:49.000
The treatment area and going on to private property adjacent to us. In this case, there's quite a bit of variability.

00:55:49.000 --> 00:55:55.000
In the vacuums that we were measuring along that site boundary.

00:55:55.000 --> 00:56:07.000
But the big thing we want to see is that they're not going positive and that that variation is actually pretty common.

00:56:07.000 --> 00:56:27.000
How many monitoring points are needed? Well, that There's not one size that fits for all for all areas that are treated. You should consider the size of the treatment area and the heterogeneity of the soils. Is it going to be hard to

00:56:27.000 --> 00:56:45.000
Possibility to treat some of these areas. Consider the cost of installing the monitoring point and that can be Especially important when you've got a really deep site where that installation can be quite costly.

00:56:45.000 --> 00:57:03.000
But you should also consider the consequences of not knowing if an area is protected, especially if it's a sensitive area close by the thermal treatment area that you want to make sure is not impacted by the remediation.

00:57:03.000 --> 00:57:09.000
So all those should be taken into consideration when determining how many points to include.

00:57:09.000 --> 00:57:14.000
And the big question I get a lot is how do you know when you're done?

00:57:14.000 --> 00:57:22.000
First criteria is Have you met the temperature goals throughout your treatment area?

00:57:22.000 --> 00:57:29.000
And once you have met those temperature goals, then you start looking for diminishing returns.

00:57:29.000 --> 00:57:35.000
As I said, you should be monitoring the mass recovery rates throughout the remediation.

00:57:35.000 --> 00:57:47.000
And you want to see those recovery rates reduced to a small uh amount. Groundwater concentrations should have peaked and then decreased significantly.

00:57:47.000 --> 00:57:56.000
And groundwater concentrations can vary quite significantly throughout the process.

00:57:56.000 --> 00:58:02.000
I like to see more than just one round of groundwater samples that are showing the concentrations remaining low.

00:58:02.000 --> 00:58:19.000
Soil concentrations, interim soil samples can also help with uh determining just when you're meeting your cleanup criteria.

00:58:19.000 --> 00:58:35.000
Just to say diminishing returns here. Now, if you look at the temperature graph here. It looks like they turned off the heat at this at about 12.

00:58:35.000 --> 00:58:39.000
And you can see that the recovery rate's up into that time.

00:58:39.000 --> 00:58:48.000
We're quite low. There's some variation in it. But quite low, well below what the peak recovery rates had been.

00:58:48.000 --> 00:58:56.000
And that's what we'd like to see with diminishing returns. The recovery rate becomes low because at this point an apple's gone.

00:58:56.000 --> 00:59:08.000
But you're still recovering contaminants out of the groundwater. Remember, as I said the Groundwater concentration is likely going to increase as you start heating.

00:59:08.000 --> 00:59:20.000
But it's still going to be orders of magnitude above the MCLs. And so while we don't normally continue heating until we reach MCLs.

00:59:20.000 --> 00:59:29.000
It is very helpful to go ahead and reduce those concentrations by feet.

00:59:29.000 --> 00:59:37.000
Some amount. Before turning off your extraction system.

00:59:37.000 --> 00:59:51.000
So a successful thermal remediation requires that the site be adequately characterized So that your treatment area contain essentially all of the significant napple.

00:59:51.000 --> 01:00:01.000
If you leave Napa. Adjacent to your treatment area, but just outside of it, it can be pulled into the treatment area by the extraction system.

01:00:01.000 --> 01:00:19.000
And then the influence and groundwater concentrations will remain high for an extended period of time As you're looking for that diminishing returns as to when to turn the system off. It's more effective to go ahead and include that NAPA area within your treatment area

01:00:19.000 --> 01:00:24.000
Get it up to temperature and recover that napple more quickly.

01:00:24.000 --> 01:00:43.000
Than to have to extend your treatment time. And then, of course, too, as I discussed on a couple of the sites, contamination remaining up gradient can recontaminate an area that has been successfully treated.

01:00:43.000 --> 01:01:02.000
You need to… implement the appropriate technology for the for the site geology and hydrology Several of the case studies that I briefly presented on in this presentation were for waste oil sites.

01:01:02.000 --> 01:01:11.000
But different technologies were used at them because of the differences in the site geology and hydrogeology.

01:01:11.000 --> 01:01:27.000
At the site that had the permeable soils. We used steam injection At the sites with tighter soils, either electroresistance heating or conductive heating are generally used.

01:01:27.000 --> 01:01:32.000
And where you have really heterogeneous hydrology within your treatment area.

01:01:32.000 --> 01:01:40.000
Combining the thermal technologies it may indeed be the best route to go.

01:01:40.000 --> 01:01:56.000
The design of the heating extraction systems is crucial because you want to be able to heat all of the treatment area to the target temperature And you want to be able to extract all of the contaminants that are mobilized.

01:01:56.000 --> 01:02:05.000
For VOCs, the VOCs. Target temperature that I always recommend is the boiling point of water.

01:02:05.000 --> 01:02:25.000
And for SBOCs, the target temperature then is going to depend upon just what it takes for that contaminant, creosote, coal tar type contaminants may indeed be 300 centigrade dioxins may take even higher temperatures.

01:02:25.000 --> 01:02:36.000
Lessons learned. When it comes to defining the treatment area, remember that NAPL can continue to migrate.

01:02:36.000 --> 01:02:49.000
Recent data is always best for designing a system. The characterization methods must be appropriate for the site that you're characterizing.

01:02:49.000 --> 01:03:13.000
Estimating mass in the ground is an art that I have quite often is quite often not real accurate, but some kind of estimation of the mass that's in the ground is needed in order to size the extraction system and the above ground treatment systems.

01:03:13.000 --> 01:03:33.000
And then there are uh various methods of various methods destroying what is recovered either on site or shipping it off site. And that all needs to be considered in designing the system. And with that, I'm afraid I'll probably go on over my hour.

01:03:33.000 --> 01:03:35.000
But I will look up for questions.

01:03:35.000 --> 01:03:53.000
All right. Thank you so very much, Dr. Davis. We're going to transition over to our Q&A segment and all throughout your presentation, we've received a number of questions that were submitted in the Q&A. I'm going to start reading through the ones that we've already received. However, I encourage participants, if you have not yet submitted a question.

01:03:53.000 --> 01:03:58.000
Please look for that Q&A button at the bottom of your screen. You are welcome to continue submitting them.

01:03:58.000 --> 01:04:03.000
And we'll try to get through as many as we can in the time that we have allotted here today.

01:04:03.000 --> 01:04:31.000
So Dr. Davis, one of the earlier questions that were coming in while you were presenting is that while you were sharing situations or subsurface conditions when thermal might be a good candidate. A couple of people have asked, are there conditions when thermal just won't work? If I have this at my site, I should immediately put thermal off to the side.

01:04:31.000 --> 01:04:52.000
Oh, that's a good question. I don't know that… Well, early on, I thought that early on fractured bedrock would be a no-go area, but I have certainly been uh proven wrong on that because although I didn't present any here, I have other

01:04:52.000 --> 01:04:58.000
Canned presentations on thermal treatment in fractured rock.

01:04:58.000 --> 01:05:09.000
You know these technologies have been used in very permeable soils and in very impermeable soils.

01:05:09.000 --> 01:05:15.000
There was a case where there was a case where

01:05:15.000 --> 01:05:25.000
The… differences in resistivity made An ERH site.

01:05:25.000 --> 01:05:39.000
Ineffective, but now you could use conductive heating likely at that A couple of things I think that we have seen that have made

01:05:39.000 --> 01:05:48.000
Super challenging to the point that the attempts at remediation were unsuccessful.

01:05:48.000 --> 01:05:58.000
Was trying to deal with a contaminant that broke down at the temperatures they were using and created acid.

01:05:58.000 --> 01:06:09.000
That then ate through the steel of the heater wells and of the extraction system.

01:06:09.000 --> 01:06:28.000
Today, maybe, you know, if an attempt were to be made to treat that kind of a site And that maybe they would know in advance to use in advance to materials that would not be affected in the same way.

01:06:28.000 --> 01:06:34.000
But that is something that you need to know up front and it's probably going to increase the costs.

01:06:34.000 --> 01:07:04.000
If you've got something that is very sensitive to would be very sensitive to subsidence like peat soils underlying railroad tracks that might be a situation you would want to avoid because peat soils will can compress and can compress cause subsidence when they're heated and railroad tracks would be very

01:07:05.000 --> 01:07:17.000
Sensitive to those kinds of changes in the elevation of the tracks.

01:07:17.000 --> 01:07:18.000
Okay.

01:07:18.000 --> 01:07:24.000
But there's not there's Those are a couple of things that I can think of. There may be others you'd have to throw at me. The actual conditions you're talking about.

01:07:24.000 --> 01:07:33.000
But I've tried to present enough different sites to show you some of the variability.

01:07:33.000 --> 01:07:42.000
In the sites that have been addressed. And I'll try to cover that more too with the next presentation then uh of the Okay.

01:07:42.000 --> 01:07:57.000
Okay. Okay. You actually have hit on several subsequent questions that were coming in, many people asking if this would work in fractured bedrock sites. And clearly you have examples where it has been applied.

01:07:57.000 --> 01:08:08.000
And someone else asked, is soil subsidence a potential issue of heating and then drying out soil near infrastructure? So it sounds like that is something to be concerned in those peat soils.

01:08:08.000 --> 01:08:23.000
In peat soils and in the very tight soils, if I can find it right quick.

01:08:23.000 --> 01:08:43.000
At this site where they described it as a tight fat clay there was some subsidence that occurred at this site. A couple of the electrodes ended up about two feet or a foot or two out of the ground before

01:08:43.000 --> 01:08:49.000
This remediation was complete. However, with most soils.

01:08:49.000 --> 01:09:06.000
It is not a problem. This was a unique case. Case, as I've mentioned, is peat soils which can be broken down by the heating process and cause subsidence.

01:09:06.000 --> 01:09:21.000
But at a variety of sites they have look for any kind of changes in the elevation, you know, when there's a sensitive building above the site.

01:09:21.000 --> 01:09:24.000
Generally subsidence has not been a problem.

01:09:24.000 --> 01:09:29.000
Okay. And real quickly, while you have the Camelot cleaner slide up.

01:09:29.000 --> 01:09:37.000
The 5,000 pounds of PCE that were recovered, was that PCE napple or was it dissolved?

01:09:37.000 --> 01:09:47.000
At a PCE concentration in the soil of 2,200 milligrams per kilogram, that is going to indicate that it was an apple.

01:09:47.000 --> 01:09:51.000
Okay. Okay. All right, thank you.

01:09:51.000 --> 01:10:09.000
I see a few other themes in common questions from the participants and one of the common themes that some of them are asking about are those sensitivity areas that you wouldn't want to be affected by thermal remediation.

01:10:09.000 --> 01:10:14.000
So I see a few individuals asking if you could give them some examples of these sensitive areas.

01:10:14.000 --> 01:10:28.000
That you would need to be bearing in mind, for example, a consideration of thermal treatment zone and your proximity to sensitive receptors. What are some examples of those receptors?

01:10:28.000 --> 01:10:54.000
And one of the sites I'll talk about tomorrow that was not far from what they called a brook, New England site. So a surface water that we were trying to protect. Luckily, it had already been impacted by the contaminant, so it wasn't like it was a pristine

01:10:54.000 --> 01:11:04.000
Creek going through there. But, you know, there was some We made some attempts to try to keep the heat away from there.

01:11:04.000 --> 01:11:25.000
As you might expect. I mean, it was not a a big enough creek to contain fish, but still we've tried to protect the surface water That is one of the main things. Now, if you Well, at another site too there was another

01:11:25.000 --> 01:11:30.000
Wetlands close by. We tried to stop short of the wetlands.

01:11:30.000 --> 01:11:42.000
Those are the biggest types of areas that I can think of. There may be others Something else.

01:11:42.000 --> 01:11:53.000
Those are the biggest ones that I've had experience with. The thermal vendors may indeed have other have additional examples.

01:11:53.000 --> 01:11:59.000
Of sensitive areas that you would want to try to not take the temperature up too high.

01:11:59.000 --> 01:12:07.000
Okay. When we're looking at the vapors that get created when using thermal.

01:12:07.000 --> 01:12:13.000
Some people are asking about safety considerations when you have high pressure and steam.

01:12:13.000 --> 01:12:32.000
And then there's concern about these vapors and if they can be 100% captured or are there now new concerns about air pollution or vapor intrusion Once you implement thermal remediation. Is this going to further enhance contaminant migration? Are you suddenly mobilizing your contaminants to start moving in new ways?

01:12:32.000 --> 01:12:41.000
We always… design them with very aggressive vapor extraction systems.

01:12:41.000 --> 01:12:42.000
Okay.

01:12:42.000 --> 01:12:58.000
Which is not to say that in an early steam injection, there was indeed a problem with some of the steam making it to the surface We have learned what it takes to ensure that that type of thing doesn't happen.

01:12:58.000 --> 01:13:05.000
And in limiting the injection pressure of the steam

01:13:05.000 --> 01:13:31.000
And so we're so Particularly if it's within a populated area within a community as any number of these have been, we always monitor the ambient air the continuous monitoring is done as well as intermittent monitoring with PIDs and sewer canister samples.

01:13:31.000 --> 01:13:47.000
So that we can ensure that If there is some problem that is causing emission of the vapors it can be addressed quickly, efficiently.

01:13:47.000 --> 01:13:53.000
And we have always been able to overcome those problems once we know that there is a problem.

01:13:53.000 --> 01:14:04.000
Okay. All right. I'm just mindful of the time. We've got about five more minutes where I'll take questions with Dr. Davis. And there are plenty more in the queue. So let me just jump into this very next one.

01:14:04.000 --> 01:14:11.000
What would you recommend in areas with permafrost?

01:14:11.000 --> 01:14:25.000
Well, I believe that that both electroresistance heating and conductive heating have been used in Alaska in permafrost areas.

01:14:25.000 --> 01:14:47.000
Many years ago, made a trip up to Alaska, where ERH was used at a site more recently, something I had should have mentioned is that situ treatment of using conductive heating is now being applied with PFAS.

01:14:47.000 --> 01:15:06.000
There's not an apple new use for the thermal technologies and that uh treatment was done is being done up in Alaska, a couple of pilots have already been done And that were successful.

01:15:06.000 --> 01:15:13.000
Either of those technologies have been found to be effective in areas with permafrost.

01:15:13.000 --> 01:15:14.000
Okay. Just circling back earlier to the question that you just had answered before this one.

01:15:14.000 --> 01:15:20.000
Just circling back. Okay.

01:15:20.000 --> 01:15:28.000
I see a related question that would you say you always recommend groundwater extraction to run simultaneously? And there's quotes around that.

01:15:28.000 --> 01:15:41.000
With thermal treatment. They're wondering if you have had success with a phased approach. Tch with vapor extraction only, and then that's followed by groundwater extraction and treatment of the dissolved plume.

01:15:41.000 --> 01:15:54.000
With steam injection, you're always going to extract groundwater. Because you have to, in order to maintain hydraulic control, you've got to extract more groundwater than what you inject.

01:15:54.000 --> 01:16:06.000
And with the ERH or conductive heating if you're NAPL is only in the Vedo Sound.

01:16:06.000 --> 01:16:13.000
And is only dissolved phase in the groundwater. Then.

01:16:13.000 --> 01:16:26.000
They can be treated separately. But generally, these napples have a way of making it not only to the groundwater table, but below the groundwater table.

01:16:26.000 --> 01:16:37.000
And so then the most efficient way of doing it is to treat both the beta zone and the groundwater, below the groundwater table at the same time.

01:16:37.000 --> 01:16:55.000
This doesn't say you necessarily have to necessarily But it can often you install the system just once and you know to the depth that's needed without having to go back and install deeper later.

01:16:55.000 --> 01:16:56.000
Okay. A number of individuals are asking

01:16:56.000 --> 01:17:05.000
Okay. A number of individuals are asking about depth limitations. So this question is coming in the form of how deep can it go?

01:17:05.000 --> 01:17:17.000
Other people are asking, how deep would you go? How far should you go beneath an apple plume if you're using it in steam enhanced extraction.

01:17:17.000 --> 01:17:27.000
And then I've got other attendees who are just curious if I have a 10 acre site and I'm trying to clean up in the depth range of 20 to 25 feet, would this work for me?

01:17:27.000 --> 01:17:34.000
So can you talk a bit about depth constraints or recommended target depths?

01:17:34.000 --> 01:17:35.000
Okay.

01:17:35.000 --> 01:17:50.000
Well, there's not really depth constraints on these technologies. All three of these technologies. I think even the in situ combustion were really developed by the oil industry for an enhanced oil recovery. And so they're often going far deeper than what

01:17:50.000 --> 01:17:57.000
We do here. The deepest that we've gone from remediation, I believe, is at 240.

01:17:57.000 --> 01:18:06.000
Three feet at Williams Air Force Base with steam injection

01:18:06.000 --> 01:18:17.000
We've also treated with steam injection very shallow sites. The BD site was quite shallow, about 20 feet was where steam was injected.

01:18:17.000 --> 01:18:47.000
And that was over a fairly large areas. So it takes matching the technology to the geology and then and to the Even with conductive heating or ERH, they've been treated as adapts, I believe, at 150 feet. And that's not a limitation. That's just what we've done so far.

01:18:47.000 --> 01:18:48.000
Okay. Okay.

01:18:48.000 --> 01:18:52.000
But… I'm not aware of limitations on depth.

01:18:52.000 --> 01:19:05.000
Okay. All right, Dr. Davis, it is 2.25. I'm going to ask one last question and I'm hoping we can sneak in a quick response to because this has been brought up by a few other participants. And then we'll close out the Q&A period and I'll wrap things up for today.

01:19:05.000 --> 01:19:14.000
Several people have commented and asked about environmental or ecological impacts of the temperatures that you wind up creating in the surface.

01:19:14.000 --> 01:19:26.000
They've expressed concern if the naturally occurring bacteria survive. They've asked if the soil is essentially devoid of microbial life and then therefore need to be reseeded.

01:19:26.000 --> 01:19:35.000
That would then help future remediation at the site. So what happens in the subsurface from an ecological perspective when you use this technology?

01:19:35.000 --> 01:19:53.000
Well, these temperatures, particularly if you're going after semi-volatiles and go to temperatures above the boiling point of water, yeah, that's fairly well going to sterilize the the soil however it does not really alter, you know, once the site cools

01:19:53.000 --> 01:20:10.000
We have found that they can repopulate. Some of the petroleum hydrocarbon degrading bugs seem to be able to survive and thrive at the higher temperatures.

01:20:10.000 --> 01:20:28.000
What they found for those that that treat the chlorinated solvents they're not active for the most part above about 25 to 35 centigrade.

01:20:28.000 --> 01:20:39.000
There has not… really been a limitation of them coming back.

01:20:39.000 --> 01:21:04.000
Oh, at the… Southwell site in particular, there was there hadn't been a whole lot of dechlorination going on beforehand, but in some areas afterwards there was, which may have a lot more to do with just a lot more iron from the electrodes that's still in the ground that is uh

01:21:04.000 --> 01:21:13.000
Promoting an abiotic degradation of the remaining contaminants.

01:21:13.000 --> 01:21:37.000
But I haven't yet heard someone really complain about And in fact, normally, as in you let the hot groundwater migrate down gradient uh It generally has the effect of enhancing biodegradation you know down gradient by that increase in temperature.

01:21:37.000 --> 01:21:38.000
But it is 227.

01:21:38.000 --> 01:21:48.000
All right. Well, it is 2.27 p.m. Eastern by my clock. So I'm going to close out our Q&A period. I want to thank you so much, Dr. Davis, for sharing your time and expertise.

01:21:48.000 --> 01:21:54.000
I know there are a number of additional questions in the queue, which we just simply didn't have time to get to.

01:21:54.000 --> 01:21:58.000
This is not the last time that Dr. Davis is going to be with us.

01:21:58.000 --> 01:22:07.000
So I want to remind everyone that she's going to join us tomorrow for our fourth seminar in this series where our topic will be challenges met.

01:22:07.000 --> 01:22:16.000
Case studies of thermal remediation. So for those of you that were asking questions about scenarios or sites or could you use it in this type of a condition or could you use it at this type of a site.

01:22:16.000 --> 01:22:25.000
I encourage you to sign up and join us for tomorrow's session because some of those case studies might be exactly the answers you were looking to get for.

01:22:25.000 --> 01:22:38.000
So I also want to walk through just a few more final reminders before I close out today's broadcast. So I want to thank the over 270 individuals who joined us for today's live broadcast from all over the world. I know we had a number of international attendees on the line.

01:22:38.000 --> 01:22:50.000
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01:22:50.000 --> 01:23:03.000
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01:23:03.000 --> 01:23:10.000
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01:23:10.000 --> 01:23:26.000
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01:23:26.000 --> 01:23:32.000
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01:23:32.000 --> 01:23:49.000
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01:23:49.000 --> 01:24:00.000
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01:24:34.000 --> 01:24:49.000
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01:24:49.000 --> 01:24:57.000
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01:25:03.000 --> 01:25:13.000
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01:25:13.000 --> 01:25:22.000
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01:25:22.000 --> 01:25:31.000
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