Cost-Effective Remediation through Enhanced Characterization

Dane: Hello and welcome everyone. My name is Dane Menke. I’m the digital marketing manager here at Regenesis 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.

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In today’s presentation will focus on Defining Cleanup Success For Groundwater Remediation. With that, I’d like to introduce our presenters for today. We are pleased to have with us Dr. John Wilson, principal scientist at Scissortail Environmental Solutions. Prior to working with Scissortail. Dr. Wilson served at the U.S. Environmental Protection Agency from 1979 to 2014 as a technical expert in bio-transformation processes of organic compounds in groundwater and the subsurface environment.

He’s the author of 61 journal articles and 14 books or book chapters on the topic of environmental science and groundwater remediation, as well as numerous government reports and conference proceedings. He owns a patent for biodegradation of halogenated alipathic hydrocarbons, and is the recipient of numerous honors and awards for his contributions to the field of environmental remediation.

We’re also pleased to have with us today Todd Herrington, Global PetroFix product manager for Regenesis. Mr. Herrington collaborates with sales, operations, and R&D departments at Regenesis in order to provide environmental practitioners with a complete solution to quickly and effectively reduce petroleum hydrocarbon contaminants using PetroFix remediation fluid. Mr. Herrington has over 20 years in environmental remediation experience and has been with Regenesis since 2004. All right, that concludes our introduction, so now I will hand things over to Dr. Wilson to get us started.

Dr. Wilson: Today, I wanna talk with you about the issue of how to tell when we’re done with a cleanup. U.S EPA risk management paradigm addresses this question from the point of view of hazard and exposure. The states that implements UST programs put most of their attention on cleanups to destroy the hazard. There hasn’t been as much emphasis on evaluating the exposure. Result of that is we as a research community and a cleanup community are managing the contaminants instead of managing the aquifer as water supply.

That puts us in a little bit of a conundrum. We have one class of aquifers where groundwater moves readily through sands and gravel. Once a spill occurs, there’s a lot of contamination, it can move quickly to the water supply well, the risk is high. That’s the bad news. The good news is our technologies for cleaning these sites up actually are effective. We can deal with this kind of spill. We have a large number of spills into clays and silts, the good news is these plumes don’t move very far, they rarely impact a monitoring well. But the bad news is they’re very difficult to clean up to the drinking water standard.

And these clay overburden sites are very common, and so there’s a good number of UST spills that fit this category. Many of our major cities are built on the floodplains of major rivers. So what I’m going to talk with you about today is approaches to characterize this particular category of sight to see when we’ve done enough clean up to justify calling it a success. A lot of my ideas are borrowed from work that’s published by Murray Einarson and Doug Mackay. And I direct your attention to this paper. This is definitely worth your time to dig down the library and spend a few hours with.

So let’s understand first how contamination behaves in these two layered systems. Where the NAPL is confined to silt or clay, it’s actually lying above the transmissive material that comprises the effective portion of the water supply aquifer. Let’s spend a little time with this. The well on the left is a well that’s screened exclusively in the silt and clay overburden across the NAPL. Groundwater produced from the well on the left is highly contaminated. The well in the middle is one that’s sort of a representative well it’s very common at our UST sites is screened across the NAPL and collects water from both the silt and clay and the aquifer underneath. It’s not nearly as contaminated but the contamination is high.

And then the well to the right is one that’s far down-gradient. And you can say that even though the wells that are screened across the NAPL show screening in high concentrations, of contaminants concerned, these wells often show marginal contamination fairly close to the drinking water standard. And the point I’m trying to make with my cartoon is that the highly contaminated water that’s produced by wells that are screened across the light on aqueous phase liquids are not representative of the concentrations that are actually moving away from the source toward a potential water supply well and the aquifer per se.

I’d like to walk you through to case studies that illustrate that particular perspective. In the case studies, we measured the vertical distribution of total petroleum hydrocarbon using core samples. We also measured the vertical distribution of contaminants to the groundwater with conventional push tools. And then we did something that unfortunately is not very common in the underground storage tank market, and we measured the vertical distribution of hydraulic conductivity actually using the same push tools.

Some years ago, John Cho and I published a paper on a little technique that I had developed that allows you to use a Geoprobe tool to estimate the hydraulic conductivity of the material around the screen. It turns out that the rate of production of water into the well is proportional to the hydraulic conductivity. And so all we do is we would set a tube at a certain distance below the water table and we pump it until we had both air and bubbles. And the rate of production of water at that distance is directly proportional to the hydraulic conductivity.

So we use that tool and that approach to evaluate two spills. This is probably the most famous MTBE spill in California, maybe the most famous one in the world. This is the one in Port Hueneme. The red dot is a sampling point that is about one year’s worth of groundwater flow travel time from the leading edge of the NAPL toward the most contaminated location at the site. So what is plotted here is the vertical extent of total petroleum hydrocarbon as determined in analysis of the core sample.

And then the vertical extent of hydraulic conductivity determined with that technique that I mentioned using the Geoprobe push tools. So, each of those little vertical reach is the vertical screen interval and the tool. We measure, okay, and we push it down that length again, measured again push it down that length again. We see that sort of stair step figure that represents hydraulic connectivity in this particular sampling location. We use the push tools also to produce water for measuring BTEX compounds and then also the electron acceptors that control the behavior and distribution of the BTEX compounds in the aquifer.

So you can see that in the first sample of the aquifer between 10 and 12 feet, there’s no sulfate in the water, we have the very highest concentrations of benzene. We go down another 18 inches, we’re starting to see some sulfate and there’s much less benzene. We go down another 18 inches we’re back to sort of the background levels of sulfate in this particular aquifer, and the benzene more or less disappears. So the benzene instead of being uniformly distributed through the aquifer, it’s a little scam or scan right underneath the LNAPL that’s producing the source of contamination.

So we went down to the toe of the LNAPL object and did the same thing. So again, this is the vertical distribution of TPH as analyzed in core samples and hydraulic conductivity. Down at the toe of the aquifer you notice there’s sort of a deep attractor down about 18 feet, very highly conductive layer that would tend to pull the groundwater down deeper into the aquifer. This is a vertical extent of benzene and sulfate but we see the same pattern. The benzene is confined to the interval around the water table, it contains the LNAPL. Where we have benzene, there’s low or no sulfate, and where we have sulfate there’s little or no benzene.

So, we took that concept of how the electron acceptors like sulfate, nitrogen, and oxygen are distributed in an aquifer and the relationship between the source of the contaminant and the vertical distribution of the contaminant and did another case study. I was invited to go into a site where the cleanup was finished, at least the site owner and the contractor claimed it was, and the region wanted to know if that they truly were finished with it. This particular site, it was owned by a power utility, an electrical utility that used to service these big line trucks.

And they had a dry well underneath the garage where they just disposed of oil and gasoline and radiator fluid and whatever. When RCRA came in and they put on the monitoring wells they discovered a plume of contamination, and they chose to clean it up using aerobic in-situ bioremediation. So what they did is they installed two galleries pictured there, those lines at the bottom of the well. These are just trenches full of gravel where they injected groundwater amended with nutrients, phosphate, and hydrogen peroxide to supply oxygen.

And then that was chased across the side with a recharge gallery below it. And so you have a movement of oxygen and phosphate and then the groundwater living crosses the spill. You can see the work pit, and there’s a well that was actually in the work pit when contamination occurred. Then the water was collected in a recovery well at the very top of the diagram and then recirculated back through the groundwater recharge gallery and the nutrient gallery.

So these are data on the distribution of concentrations, of BTEX compounds in five wells that extend from the leading edge of the flow of remedial groundwater that’s MW1. And then as we go up MW2 is in the work pit where the highest concentrations were. MW8 and MW2 is… and MW3 are further down the flow path and then RW1 is recovered well, that recirculates the water. So this looked almost like a gasoline spill when they started to clean it up. And after several years of work, they got it down to the concentrations in the right-hand column.

Now, these are data for benzene, which is a risk driver and unfortunately, MW8 didn’t reach the MCO for benzene. So based on the definition the site wasn’t clean and could still impose a threat to groundwater quality in this aquifer as a water supply aquifer. So I was invited to see if it was clean. The approach that we took was to install a series of… we didn’t install well, we used push technology to take core samples and transect on the down-gradient side of flushing of the amended water. The black dots are locations where we took core samples. And then the triangle is the most contaminated location where we did a vertical evaluation of the concentration to contaminants in the groundwater underneath the on LNAPL object. So this is what the LNAPL object looks like, that’s the red figure. And it was still there, there was plenty of LNAPL after they’d done the cleanup.

And so at the most contaminated location, we went through and we did the same, we’re taking water samples. And so this figure shows the vertical extent of TPH as seen from analysis of core samples. And then each of those dots is the upper limit and the lower limit of the screen on the push tool. And then the blue thing figure is the distribution the hydraulic conductivity. And so this fits a little pattern that I’ve been showing you that the TPH was in silt and sand layer and that the effective part of the aquifer such as this in this case, it’s only about two feet thick, maybe a little bit more than that, was underneath the LNAPL.

So these are data that compared the measured hydraulic conductivity, the concentrations of MTBE benzene and BTEX. And it’s no surprise that the appreciable concentrations are in that first order sample at 18 to 20 feet. And you’ll notice that the hydraulic conductivity in that interval is actually quite low compared to the deeper material, in the true part of the aquifer.

So I used a concept that is well represented and well explained in a recent paper by Murray Einarson. Now Murray’s paper actually looks at a two-dimensional view and transect of groundwater moving away from the source. I’m gonna reduce his concepts to a one-dimensional view. And do some calculations using Murray’s approach and see if we can understand the importance of that high concentration in the shallow zone. So, there, in red, the hydraulic conductivity was 0.39 feet per day. So what I did is I took an average of the hydraulic conductivity across that entire interval, including the transmissive aquifer moved a little bit of less, transmissive material below it. And I calculated the fraction of the hydraulic conductivity that was represented by the particular depth interval.

That simply measured hydraulic conductivity divided by the average and then divided by the number of samples. In this case, there was six layers, so I divided by six. So I get a way of weighting the benzene concentration by the proportion of flow that would move through that particular depth interval. So that’s the column on the extreme right. Those are weighted, the measured benzene concentration multiplied by the fraction of the hydraulic connectivity that’s represented by that interval.

And then I took an average of the weighted concentrations which would represent the concentration would actually be delivered to water supply well down-gradient, and in fact, that weighted average concentration is much less than the MCO. So this is approach that I offer to you, you can use some calculations, if you bother to measure hydraulic conductivity to understand the contribution that a particular concentration contamination and a particular depth interval would make to the entire flow in an aquifer that would go to a monitoring well. If you compare the measured benzene concentration of 11.3 to the weighted concentration of 0.01, you can see that that 11.3 micrograms per liter that was above the MCL represented 1 part of 10,000. Or the water would actually be getting to a monitoring well.

And wait there’s even more good news on this because this particular aquifer had measurable concentrations of a nitrate and cyclic sulfate electron acceptors are capable of destroying the BTEX contamination through fermentation reactions. And so I went back and I looked at the original data, and if you’ll notice that RW1 that pumped well, the recovery well they installed for their remedy, actually has a pretty good surrogate for a water supply well. Each screened across the whole interval that was pumped, and that was never contaminated. Even at the very beginning before they started the remedy, the concentration of BTEX never exceeded the MCL for benzene.

So what could have been happening there? I surmise that the sulfate dissolved oxygen and nitrate in the true part of the aquifer was diffusing up into the silts and clays allowing the bacteria to degrade the BTEX compounds before they ever found a way into the aquifer. And that’s why they never showed up in the recovered well.

So these attenuation processes are consuming the contamination as fast as it leaves the source in the silts and clay. They’re not gonna move away from the spill, and in fact, a receptor down-gradient is protected. And so I really think what we need to do is evaluate whether, in fact, the distribution contamination and the benefit of the natural processes are protecting the aquifer as a source of drinking water. If it is, it’s not necessary to clean up all the contamination, all the monitoring wells to the drinking water standard. You only need to clean up your site to the point where your drinking water… the groundwater that leaves a spill meets the drinking water standards.

To do that, you need information on the vertical distribution of hydraulic conductivity. How do you get that information? Well, one way is as a more conventional approach, and it’s paper “Cho et. al.” I’ve written a fair number of papers that have received several hundred citations in the literature. I don’t think anybody ever read this paper, and nobody uses this approach but me.” But Geoprobe systems, my friend West Mackol [SP] put together a little system that allowed you to do a conventional traditional slug test on the temporary push tools. And so you can use conventional groundwater practice, do a slug test on a push tool, and get the same number that I got using a very standard approach.

Another thing you can do, they’ve developed very neat technique called electrical conductivity testing that allows you to recognize and distinguish the silts and clay from the sand and gravels. And these electrodes can be mounted on push tools and introduced into the Earth to do vertical profiling. And the way it works, silts and clays have a lot of exchange capacity, the ions in exchange capacity associated with the surfaces. And so the electrical conductivity of silts and clays are higher than the electrical conductivity of sands and gravel . And so the contrast between the two can be used to index whether the probe at that instance is in a silt and clay or in sand and gravel.

And Geoprobe has actually adapt to that and extended it, they also have come up with what they call a hydraulic profiling tool. What this thing does is it pushes water out into the aquifer as the tool penetrates, and the resistance to flow is an indication of the local hydraulic conductivity. So, the red line there is the pressure that develops in the tool as it tries to push water out into the formation [SP]. You can see in the first 10 feet of this case study, those are pressures are high, that’s because it was penetrating silts and clays, and then below about 12 feet than the pressure above the pressure that’s the natural way to the groundwater and the atmosphere is minimal, and that’s associated with sands and gravel. That’s the red line.

And you’ll see that that’s also confirmed by the blue line, which is the estimate of electrical conductivity. So these tools together can allow you to resolve intervals where water is moving from intervals for water is not moving. From the clay and silt overburden and the effective part of the aquifer. This is something I pulled off of Geoprobe’s web page, so they can actually take that difference in the pressure and estimate K in feet per day, that’s the right-hand column. If you compare the blue to high values of K on the right-hand side you’ll notice that corresponds to a minimum of electrical conductivity and the column on the left-hand side. So the two tools, the two measures together.

Let me give you a very quick way of figuring out where you are in terms of vertical extent of the effective part of the aquifer. I had this tool on one of my sites, they can produce this information at a particular location in less than an hour that includes set up and clean up. And they’re not the only ones that do it to be fair, there’s other approaches that are very efficacious. The Waterloo profiler now upgraded to the advanced profile system produces similar information using a very effective system. So there are people in the marketplace that can give you these numbers that I use in the calculation I showed you.

So what I would like people to start thinking about is installing monitoring systems that monitor the aquifer. The conventional screens at UST spills the well on the left and the well on the center, the real purpose of that is to try to find NAPL, so they know where the spill is to clean it up. They’re really designed to map the spill, they’re not designed to evaluate the threat to the water supply. And I think that we’re making a mistake using wells that are designed for one purpose for the other purpose of evaluating the threat to water supply.

I think when you’re doing spills install special wells that are screened across just the interval that’s gonna act as the aquifer down-gradient and source contamination. So it’s gonna be more than just throwing in wells and taking water samples and sending it out to the chemistry. You’re going to have to invest in a geophysical site characterization and understand your geology. And then install monitoring wells that are truly down-gradient of the NAPL and I recommend that you check the OVM data on the well construction logs to make sure that in fact, they are down-gradient LNAPL.

And then interpret concentration data on wells that are a faithful representation of the behavior of the aquifer as a way of evaluating whether in fact you’ve achieved clean up and it’s now ready to transition to the MNA or other passive approaches. So thank you for your attention today.

Dane: Okay, thank you very much, John. And now we will go to Todd Herrington of Regenesis.

Todd: Thank you. Thank you, John, for that talk, was great sitting here next to you and just learning from you and you know, really good stuff that you had there. Today, I wanna transition into some slides that talk about a new product that we have called PetroFix, which is a remediation technology designed to treat petroleum and fuel spills, restoring groundwater. I think it segues well into some concepts that John presented today, and I’d like to get in a few of those. And then we’ll get into some Q&A.

Just real quick, as I started in the industry many years ago, I started with consulting firm that we studied natural attenuation. So back then John was actually at the EPA, we spent a lot of time with John. It was just a lot of fun to do that. So I would say today it’s great to be here with him again today, you know, working on remediation.

One of the things that resonates with me on John’s talk is obviously great site characterization is gonna be really needed to do effective remediation. But one of the concepts also is really trying to control flux and trying to control bioremediation. You know, the concept of contamination being bound in say clay, overburden sites, LNAPL that, you know, goes from that or is in high K zones. You know, we as remediation practitioners and sites that I look all day long, you know, how do we control that? How do we minimize that?

And I think one of the questions, you know, to kind of transition from this talk into PetroFix is that what if we could, in these high K zones, where contaminant flux from LNAPL or clay overburden is moving quickly and there is risk to a down-gradient well there is risk the off-site migration. What can we do? What if we could make that high K zone act like clay or act like a tight formation? That’s actually something that we’re able to do with PetroFix this new product. So I wanna get into that a little bit.

PetroFix actually was released last year at the UST Tanks Conference, it’s only been out for a couple months, we haven’t spent a lot of time discussing it. So that’s one of the exciting things to go over this today. What is it? What is the mode of action and what’s special? First of all, it is an activated carbon-based remedial fluid. It is a carbon that’s milled down to one to two micrometers in size, and it’s an activated carbon. That picture shows really what it does look like diluted when you put it in an aquifer and it goes in easily with low pressure. Once it does go in, it does literally cut the soil and provides a layer on that swell for contaminants to swerve to. So once PlumeStop goes in it does that, it is positionally stable after say a few days you know, close to after the injection. The contaminants will swerve to that and you get that immediate removal of dissolved-phase contamination out of groundwater.

What we also do is once they’re swerved in place, is we do provide beneficial electron acceptors, typically in a form of sulfate and nitrate that give a great blend that stimulates anaerobic bioremediation, and permanent destruction in situ, and on the PetroFix, which actually also creates a regenerative effect freeing absorption sites for this material. It comes in 55-gallon drums. It’s really easy to apply. It shifts as a liquid. Some of the electron acceptors are mixed actually in the drums, but we also provide a separate mix in a bucket of an electron acceptors blend that’s added just before injection.

It’s very safe to use, it’s easy to handle, no special equipment really required just to be able to do… have [inaudible 00:31:02] you’re able to handle low to moderate pressures and high volumes. It is safe to use around existing infrastructure. And as we get into this, I’m starting to get a lot of calls and inquiries and there’s probably three main areas that we see most likely, you know, applications for you, you know, more common.

One would be excavations, you know, when you remove those tanks, when you’re digging out that contamination and getting into the smear zone, you know, do you wanna put the clean backfill in or can you put something in there to sort of mop up any residual contamination. This is a common approach in the industry and it’s something that PetroFix would work really, really well for. Probably the biggest area we see this being used and most common designs that we’re seeing is a grid approach. And that is attacking the source areas through direct push injection with Geoprobe.

We also believe that the use of this material say in a barrier formation on a property boundary or road where you need to minimize contaminant migration is also a certainly within the realm of being able to use this material. There are other carbon-based injectate on the market or CBIs. Some of you might be sitting there thinking we’re aware of those or have used carbon before. I wanted to make some important distinctions with what you’re able to use with PetroFix.

There’s probably three different categories carbon on the market, most common a granular activated carbon. That’s typically in a 400 to 1,000-micron diameter size, looks like sand. Typically, if you hold it in your hand, and that is the top left picture. When trying to get into this the ground it does take high pressure, it is larger than the pore throat size of most soils and it does result in aquifer fracturing to get it in. Similarly, a pattern activated carbon is much smaller, it is 50 to 250 microns in diameter. And when you put in a liquid to build, it’s a bit easier to apply but still, the diameter of that material is larger than a typical pore space, size of soil.

This chart that just came up is a textbook values derived for the average pore throat diameter for soils, medium sand, fine sand, and silt. What’s interesting with PetroFix… and we think that’s gonna give you a lot of options is that it’s milled down to one to two microns in size, which means that when injected as a liquid it can go and does go into soils down to silt, what has a pore throat diameter of 3 to 8 micrometers. And that’s why you’re able to use much lower pressures, high volumes. We think you’re going to experience much better delivery of this material of the CBIs out there.

When it goes into the ground when you inject PetroFix, it looks like you’re spray painting the soil. It really does. You’re able to coat the high K zones from floor to ceiling, so to speak, is one way to say it at the site. One interesting point I wanna point out kind of related to what John said in his presentation is the importance of that interface, that LNAPL interface very often between, say, clay overburden or low k parts of the aquifer that are going into say sand. That often is the most severe location, you have the highest contaminant concentrations, you have the highest levels of back to fusion, you have the highest flux rates, and how do you deal with that?

When you put PetroFix, in it does coat the soil it actually will coat that interval that interface, and does a great job of helping stop and prevent any sort of flux or back diffusion coming through there. So this is a picture that I just showed on the right of an actual soil core taken from a PetroFix application that’s performing really well. What you’ll notice there’s that where we put in a PetroFix, you just get a nice even distribution of the liquid activated carbon across that interval. So I think it really helps…it’ll help you be successful in trying to get the product where you need to get and get the results you need to get.

Let me move on. I meant to say this a little bit earlier, but we’re really excited about one feature of this technology, and that is this is the first time that we’ve done an online design assistant and calculator for you. This is something that we want you to be able to play with and access. And so we have a website called petrofix.com, and if you go there, there’s gonna be a lot of helpful resources, such as an online design assistant. There’ll be application guidance. There are technical resources and technical bulletins, including a great YouTube video or training videos on YouTube, that’s less than about 10 minutes long that shows you how to use the software.

Once you set up an online account, you can play around whenever you want as much as you want for your site to come up with what you need… you know, the dosing concentrations and volumes that you have. It does walk you through. You put in say depth of the groundwater, vertical injection, interval soil type, contaminant concentration. It will guide you, it will let you know if you’re out of balance or certain things will get certain indicators or flags. But eventually, when your design is complete, you’ll get your output, you will get a design application summary. In fact, you’ll be able to download this information as a PDF, which is really useful because you can send this off to a drilling firm, a direct push operator that can give you bid. And you can turn key, this technology yourself. So it’s really, really great, we’re really excited about this, and just giving you control, allowing you access to do this when you need. And be able to get… quite frankly, generate estimates in less than 30 minutes or sooner.

So with that, just keeping it short and sweet, and just giving you an overview. I’d be happy to take any questions as we come up either today or offline or if you need any other information or any sort of kind of help or training apps, we have this set that up for you. But with that, I’ll just transition over to Q&A period, if that’s okay.

Dane: Okay. Great. Thank you very much, Todd. That concludes the formal session of our presentation and at this point, we’d like to shift into the question and answer portion of the webcast. Before we do this, just a couple of quick reminders. First, you’ll receive a follow-up email with a brief survey. We really appreciate your feedback, so please take a minute to let us know how we did. And also after the webinar, you’re going to receive a link to the recording as soon as it is available. All right, so let’s circle back to the questions if we do not address your question we’ll make an effort to follow up with you after the webinar. All right, so our first question here is for John, and the question is with regard to your second case study that you presented, what was the completion interval of RW1 versus the monitoring wells?

Dr. Wilson: It was done 20 years ago and I don’t remember.

Dane: Okay. Fair enough, all right. So next question here is also for John, and the question is what about spills with shallow overburden and a fractured bedrock aquifer beneath?

Dr. Wilson: They might behave similarly to clay over sand aquifer, it just depends on the distribution of porosity and the hydraulic conductivity of the fractured rock. So you really can’t extrapolate what I’ve told you about and consolidate with aquifers situation you just described.

Dane: All right, okay, so next question here, this is a question for Todd, and the question is PetroFix different from PlumeStop? And if so, how?

Todd: Yeah, that’s a great question. It is different in that it is specifically formulated for petroleum hydrocarbons sites. It does have electron acceptor blended in. And it also is formulated somewhat differently, it transports differently. It is injected at higher concentration so it does need tighter spacing than PlumeStop. So yeah, there are some important differences in that aspect.

Dane: Okay, let’s see here, next question is another question for Todd, and the question is has PetroFix been used in bedrock situations?

Todd: That’s a good question. I am not aware that…has it? Okay. Yes, so PetroFix has been used in bedrock situations. So I’m working with Paul, our Senior Research Scientist who is assuring me of that. Yeah, so I don’t have that information in front of me, so for the person who asked that question, I’d be happy to follow up on that information.

Dane: All right. Okay. So next question. Another question for you, Todd. And the question is PlumeStop has been advertised as being limited to about 10 ppm. How can PetroFix be used in source areas?

Todd: Great. That’s another great question. So you know, I’ve got quite a bit of experience with PlumeStop you know, excellent solvent treatment technology and other really lower level hydrocarbon plumes, that’s a rule of thumb and it’s generally turn a lot of sites. PetroFix is specifically formulated to handle up to moderately contaminated sites. And what does that mean? We actually have a flag on the PetroFix design assistant software that if you have observed continuous three phase LNAPL that you’re probably in a phase beyond the use of PetroFix at that point. You probably need to do some sort of you know, ISCO injection, to do some sort of as a treatment knock down.But we certainly can go much higher than 10 milligrams per liter to treat this. Some of our case studies have done quite well treating, you know, 50 milligrams per liter in total BTEX and TPH contamination. So this is a much more robust treatment technology for petroleum hydrocarbons.

Dane: All right, excellent. Let’s see here. We have another question, this is another question for you, Todd. The question is, is PetroFix service available in Europe?

Todd: Yes.

Dane: All right, easily enough. All right, so the next question here is another question for you, Todd, and it is, can PetroFix apply for other VOC impacts, for example, TCE, PCE, etc?

Todd: Yeah, that’s a great question. No, it can’t be. It is not designed for that because since it’s formulated petroleum hydrocarbon, it is pre-blended with electron acceptors so it would not be appropriate for those situations.

Dane: All right. Okay, so we have another question here. This is a question for John. And the question is… it’s more of a statement here. Direct push smearing may close off borehole pores so that actual K is affected. Do you have a response to that?

Dr. Wilson: I have done one study that evaluated that. In the paper the “Cho et. al., 2000 Paper” we compared our direct push K estimates to the value of hydraulic conductivity from a slug test of a convectional well and the numbers were compatible. So on the one case where we did apples to apples comparison when we were penetrating are pretty sticky clay, we didn’t see that, but yes, there’s always a possibility. The newer technology tries to prevent that by gently pressing water through the pores as a tool as advanced prevent geological material from floating off the pore. So if you have an advanced profiling tool from the [inaudible 00:44:18] if you use a Geoprobe hydraulic profile tool, they take precautions to prevent that from happening.

Dane: All right. Okay, great. So next question here is another question for you, John. And the question says… this is a little bit lengthy, so please bear with me. He says, “Recent research suggests that TPH, as well as TPH related degradation compounds, could drive health risk over BTEX in some cases. If this is true, would this have any impact on estimates of impacts to a down-gradient drinking water well in your example of an impacted low hydraulic conductivity unit that overlies a drinking water aquifer?”

Dr. Wilson: The concept would apply to any contaminant. The answer to that is measure everything that you think could have an effect on human health, and run the calculations and evaluate the impact. I think that’s a general carry on, a general warning. There’s a lot of things in fuel besides petroleum hydrocarbons and they all should be evaluated. And all petroleum hydrocarbon should be evaluated not just that favors the BTEX compounds.

Dane: All right. Okay. So here’s another question this is a question for Todd. The question is has PetroFix been used for sites with petroleum NAPL?

Todd: Yes, it has. Like I said we need to just distinguish you know, the levels of LNAPL that we have. Like, it’s a rule of thumb we realize that, but we are concerned that’s, continuous several inches of standing pre-product or NALP, LNALP would probably, you know, send you into areas where you probably not gonna get the results that you want by PetroFix application.

But I do you wanna use this as an opportunity to clarify this in a prior question on that is that you know, you can use ISCO or other means to get rid of this LNAPL. Regenesis does have technologies to do that, and it could be a sequential approach, it’s possible to do ISCO or even a product called Petro cleanse to do this. And I just wanna make sure that people realize that you know, doing this one two sequential combination is completely viable, and just because we’re saying that yeah, if you’ve got heavy NAPL we’re not saying that eliminates PetroFix entirely from an equation, you just may need to use it down the road after you remove some mass.

Dane: All right, okay here’s another question for John, and please bear with me there’s a lots of acronyms on this one, so I’ll try to get through it clearly. The question is did MIHPT/LIF survey at a truck stop in Piedmont with surfacial soils. This person said that’s what they did. What kind of geology or soils would give high MIHPT pressures and low EC at depth well below the groundwater table level? If that question makes sense to you.

Dr. Wilson: The EC is related to exchangeable cations, so if you had a silica sand, very tiny, very fine sand that would not have a lot of electrical conductivity but it still will have a much lower hydraulic conductivity. So the people that actually do this at sites, many of them will cover their beds by doing a continuous core sample, or continuous core sample to the Earth and the geological engineer will feel it with their hands and send it off for analysis and confirm and validate [inaudible 00:48:27]. And that sounds like a situation where the EC was misleading.

Dane: All right. Okay, so next question here is a question for Todd, and the question is, does Regenesis get as heavily involved with the application of PetroFix as you do with PlumeStop?

Todd: That’s another great question. Obviously, this is a really new approach for us. We feel that there’s a part of the market that don’t always fit our typical clientele, where we’re pretty heavily involved with the design process. We feel that there’s… a lot of our customers understand remedial conceptual model development well, and this is for those customers that feel they can dig into this design assistant and come up with those solutions.

Now, that being said, there are resources… if you have questions or need help, please call me, you know we’re there for you. But I guess the answer is no, you know, this is sort of you take control, you design and then if you need any help, we’re gonna be there to help you out.

Dane: All right. I have another question here. This question is another one for you, Todd. And it is can you customize which electron acceptors are included with PetroFix or is it a standard pre-defined mix?

Todd: Yeah, that’s a really good question, too. So the sulfate is blended in with… let’s see here a calcium sulfate a hydrate is pre-blended in with PetroFix, so that’s just baked in. You have the option of in the buckets to order either additional sulfate as ammonium sulfate, and you can also have ammonium nitrate put in. And that is a choice that we give you, for instance, a secondary drinking water quality standards you might have issues with putting nitrate in, that may or may not be the case. So you have the choice of… we recommend a nitrate sulfate blend or you can go all sulfate. Hopefully, that answers that question.

Dane: Okay, great. Let’s see here. Next question, this is a question for John. And it’s also regarding the second case study. And it is, how was the hydraulic conductivity determined for each interval?

Dr. Wilson: The hydraulic conductivity was determined from the yielded water from the Geoprobe tools using the equations that are published in “Cho et. al. 2000.” So basically what we were doing is a miniature well capacity test. If I were doing that again I would probably use the Geoprobe Pneumatic Slug test, but I really think that it would produce equivalent numbers.

Dane: Okay great. Well, thank you very much. That’s gonna be the end of our chat questions. If you would like more information about environmental consulting services from Scissortail Environmental Solutions, please visit scissortailenv.com. If you’d like more information about PetroFix, please visit petrofix.com. Thanks again very much to Dr. John Wilson and to Todd Herrington. And thanks to everyone who could join us. Have a great day.