Hello and welcome everyone. My name is Dane Menke. I am the digital marketing manager here at Regenesis and Land Science. Before we get started, I have just a few administrative items to cover. Since we’re trying to keep this under an hour, today’s presentation will be conducted with the audience audio settings on mute. This will minimize unwanted background noise from the large number of participants joining us today. If the webinar or audio quality degrades, please try refreshing your browser. If that does not fix the issue, please disconnect and repeat the original login steps to rejoin the webcast. If you have a question, we encourage you to ask it using the question feature located on the webinar panel. We’ll collect your questions and do our best to answer them at the end of the presentation. If we don’t address your question within the time permitting, we’ll make an effort to follow up with after the webinar. We are recording this webinar, and a link to the recording will be emailed to you once it is available. In order to continue to sponsor events that are of value and worthy of your time, we will be sending out a brief survey following the webinar to get your feedback.

Today’s presentation will discuss adapting remedies to achieve site closure for challenging brownfield sites. With that, I’d like to introduce our presenters for today. We’re pleased to have with us Lori Riker, Senior Project Manager at Benchmark Civil Environmental Engineering and Geology. Lori Riker has over 27 years of environmental and civil engineering experience, focusing on industrial regulatory compliance and permitting, as well as remedial investigation, design, and implementation under various state and federal cleanup programs, with an emphasis on brownfield cleanup program sites. She has been a registered professional engineer in the state of New York since 1999.

We’re also pleased to have with us today Alana Miller, senior Northeast District technical manager at Regenesis. Alana has seven years of experience in the environmental industry and holds a Bachelor of Science in civil and environmental engineering from Princeton University. Her experience includes field and laboratory research with the Princeton Environmental Institute. Alana has also worked as an environmental consultant for Langan on ground-filled projects across New York City. In her current role at Regenesis, Alana works with environmental consulting and engineering firms to develop remedial approaches by offering design, application, and performance review services for in-situ groundwater and soil remediation. All right, that concludes our introduction. So now I will hand things over to Lori Riker to get us started.

Hello everyone, and thank you for joining us. It’s an honor to be speaking with you today. I want to thank Regenesis and my co-presenter, Alana, for the opportunity to share this remedial success story. Our case study covers the former Brainerd manufacturing facility, which is located in a mixed residential, commercial, and light industrial area in East Rochester, New York, which is approximately 85 miles east of Buffalo, which is where our office is located. The historic mixed use surrounding this three-acre site added a layer of difficulty to the remediation. Metal manufacturing occurred for nearly 100 years on this site, and the contaminated soil and groundwater is likely from improper disposal of degreasing solvents. Brainerd manufacturing relocated here in 1998, and in 2002, they signed up with the New York Department of Environmental Conservation under the voluntary cleanup program.

More recently, the building was leased to a company reconditioning and selling office furniture. As you can see from this timeline, site investigation began over 20 years ago. The progression is interesting as the initial phase two results don’t look too bad. However, Whereas the number of investigations locations increased, so did the soil and groundwater concentrations showing the importance of collecting enough samples until a source is located. Eventually we found the culprit, tetrachloroethylene or PCE and its breakdown product, trichloroethylene PCE. To give you an idea of how quickly groundwater flows across the site, the hydraulic conductivity of 7.9 x 10-4 cm per second is equivalent to about 2.2 feet per day. The problem at this site was that the downgradient property boundary was only 150 feet from the source area with residential properties bordering the site. So a release of PCE beneath the building would reach the offsite residential properties in just over two months.

Benchmark became involved in 2003 at the interim remedial measure investigation stage. Since it was established that the chlorinated volatile organic compound contamination originated in the former plating area, likely solvents being discharged into a sump, we installed an interior pumping well to mitigate off-site migration of the groundwater plume. Based on boring logs from earlier investigations, the subsurface was separated into upper and lower hydraulically connected units, but the vertical gradient was unknown. The pump test revealed very low hydraulic gradients, which is a shallow slope, and high hydraulic conductivity, indicating groundwater flows easily through the soil. The vertical gradient was low, so groundwater flow was essentially horizontal. The findings of the pump test supported construction of a groundwater pump and treat system with air stripping as a treatment technology to mitigate off-site migration while the remainder of the site was investigated.

The groundwater collected from pumping well PW1 was treated with low-profile air stripping and discharged to the sanitary sewer by gravity. The system operated nearly continuously from August of 2004 until May of 2018 when the New York State DEC instructed us to temporarily shut down the pumping wells while the progress of additional groundwater cleanup efforts was evaluated. Here are just a few photographs showing the pumping well, the day tank, and the air stripper. Another component of the remedial investigation was a limited sub slab vapor investigation. At the time, results were compared to OSHA permissible exposure limits and there were no exceedances. Too good to be true. Once the Department of Health guidance was released in 2006, the results indicated mitigation was required for those three compounds of concern. In 2010, a sub slab depressurization system was designed and installed by MitigationTech. The system continues to operate and is effective at creating a low-pressure zone beneath the slab and preventing VOCs from entering the building.

This figure shows the 28 extraction points and the six fans and manometers that are read on a monthly basis. There were many rounds of groundwater investigations over a three-year period to get a handle on the extent of contamination within the building and downgrading of the site. Well MW-6 installed near a floor drain in the former maintenance shop was determined to be in the source area. Floor drains used to be a very handy way to get rid of waste chemicals in the past. Offsite wells were installed further and further from the site until eventually we found the extents of this very narrow contaminant plume. We also sampled the small area not covered by buildings or hardscape and found barium and lead above commercial soil cleanup objectives, which wasn’t a surprise given the historical use. We ended up covering this 500 square foot area with one foot of stone.

Due to the risk of chlorinated solvent vapors finding their way into nearby homes, we performed numerous rounds of residential indoor air sampling and surprisingly only two homes warranted follow-up monitoring. We also found that these two residents were not even near the groundwater monitoring wells with elevated VOC concentrations, which was interesting. The offsite soil vapor sampling only revealed PCE at a low level in one sample. At the end of the monitoring, we concluded that the offsite groundwater to vapor migration pathway is complete, but thankfully minimal. This plan view shows the source area in the building, as well as the downgradient edge the contaminant plume with groundwater flowing in a northwest direction. This is a cross-section along the centerline of the plume from the source to the downgrading edge. After operating this pump-and-treat system for almost 10 years, we determined additional source area remediation was necessary to expedite cleanup.

So to summarize the findings of the remedial investigation, The uppermost water-bearing zone consists of mostly sand contaminated with chlorinated VOCs from these degreasing or plating operations released into the sump. Primarily we found PCE and TCE. The groundwater plume traveled northwest off the site and was fairly narrow. We continued operation of this pump and treat system during the RI. However, the source area groundwater remediation was warranted to reduce the VOC concentrations in the soil and groundwater beneath the building to expedite cleanup and shorten the required duration of the pump and treat system. On-site sub slab vapor migration mitigation was necessary, as was retesting of off-site residences. So, to enhance the pump and treat system, we worked with Inventures Technologies who designed a hydrogen gas infusion system to promote anaerobic reductive dichlorination. We added a second pumping well to increase the collection area.

After the groundwater went through the air stripper, we sent a portion to the sewer and diverted a portion to the GPRO system, which is short for Groundwater Pressurized Remediation optimizer system. Before the GPRO system, we added sodium bisulfite to reduce the dissolved oxygen, since we wanted anaerobic degradation to occur. This plan view just shows the basic layout of the pumping wells, PW1R and PW2, where the day tank is, the air stripper, and then the discharge of the sewer, as well as the diverted flow to the new treatment system. This is just showing the profile with the original pump and treat system, again, the gravity flow to the G-Pro system, and the hydrogen-rich groundwater flow to the reinjection wells at the upgrading edge of the contaminant plume. Just to give you an idea of this G-Pro system, we used standard equipment. We have the hydrogen gas cylinder storage, which was just placed next to the treatment shed for the GPRO system. The GPRO modules just sit inside the gas infusion tank and infuse saturated levels of dissolved hydrogen into the groundwater.

As the water contacts, the microporous hollow fibers hydrogen gas is rapidly transferred to the dissolved phase without sparging. Once reinjected into the subsurface through the three injection wells, the hydrogen acted as an electron donor and the chlorinated compounds acted as electronic sceptres and were thereby reduced. Here’s a plan view showing the treatment shed and the three reinjection wells. One of the most challenging parts of this system was installing the piping in the building so the water would flow by gravity. This is a summary of the remedial time frame showing a 10-year period from installation of the initial pump and treat system to the release and covenant not to sue. which is similar to a certificate of completion in the Brownfield cleanup program. The first periodic review report was submitted in August of 2016. This chart shows the trend of chlorinated VOC concentrations with time. You can see that the VOC concentrations fluctuated even after installation of the GPRO system.

The GPRO system operated well from 2012 to sometime in 2014, but then required continual maintenance due to biological growth and clogging of the reinjection wells. The wells were redeveloped in 2014, but improved reinjection rates decreased within a few months. The 2016 Periodic Review Report recommended a corrective action plan to evaluate alternate in situ groundwater treatment. Benchmark had been working with Regenesis for many years and heard about a new amendment that basically stops the movement of and destroys chlorinated VOCs. Our client was anxious to reach a remedial endpoint. So we reached out to Regenesis. They designed an injection program with this new product called PlumeStop, as well as other amendments to stimulate rapid biologically mediated anaerobic destruction of the chlorinated solvents. At this point, I’m going to hand over the explanation of how PlumeStop works to Alana.

Great. Thanks so much, Lori. PlumeStop, liquid or colloidal activated carbon, we inject this into the subsurface and due to the specific properties of the PlumeStop itself, it will distribute really widely in the subsurface. Then at this point, contaminants actually will absorb onto the surface of the activated carbon. At this point we get some increased biological degradation to occur due to those other amendments that we added along with the colloidal activated carbon. So if you remember Lori mentioned that previously they were injecting hydrogen to serve as the electron donor for biological degradation. Here in this case we injected plume stop along with our HRC releasing compound to instead act as this fermentable hydrogen source. Then as that biological degradation continues on and that dechlorination process is completed, we actually see regeneration of the sorption sites on the surface of the activated carbon.

This then allows the sort of cycle to continue where if there’s further contamination present either farther up gradient that is coming into the area where we’ve applied this treatment, or if there’s any material of contamination that is diffusing back out from the aquifer matrix, we now have the sorption sites available and ready to take on that further influx of contamination and the cycle can continue on. So what exactly is this colloidal activated carbon? We’re talking about it a little bit now. Essentially, we’ve milled down activated carbon to be about one to two microns in size and then mix it with some proprietary additives. So the colloidal activated carbon was initially designed to distribute widely through the aquifer upon injection and absorb a variety of organic contaminants. We really, in these early days, were allowing for this biodegradation of these organic contaminants so that all of these sorption sites could be regenerated.

More recently though, we’ve demonstrated on a whole bunch of sites that this can also be a really compatible approach with some abiotic reduction mechanisms like with our micron scale, zero-valent iron as well. Ultimately, what we’re trying to achieve here with these types of treatment is a long-term control over the mass flux of these contaminants. Like I said, the actual size of these particles of activated carbon is really critical to its success here. We’re milling it down to about one to two microns in size. This means its orders of magnitude smaller than your standard granular activated carbon and is actually about the size a red blood cell. And with that extremely small particle size, we actually get a proportionally huge surface area. That means there’s lots of readily available adsorption sites on the activated carbon surface. And due to that, we get extremely fast and extremely favorable sorption kinetics. So Lori, I’ll pass it back over to you to sort of finish up our story here on this really great case study.

All right, thank you. This is a plan view showing the plume stop injection plan. So we, together with Regenesis Remediation Services and a driller who had a geoprobe, we drilled a whole bunch of borings around MW6, which was the source area. And then also down gradient around MW5 just before the plume left the property boundary. We also directly injected into pumping well 1R. Here are some photos showing the equipment. And the first one is Regenesis Remediation Services injection trailer. The second is the geoprobe unit next to the injection points. And the third one there is a view of three of the injection point locations. We were very lucky that these areas were open because most of the building was just full of furniture. So I’m assuming that somebody had to come in and move all that. So thankfully it wasn’t us.

This next one is a close-up of the well packer set up where they directly injected into the pumping well. Then the pumping system that had to be removed prior to that injection. And then the geo probe G300 unit used to inject the HRC as the final amendment. So the plume stop injection program, the injections occurred in October of 2017. We performed post-injection sampling at the two on-site wells as well as the pumping well, the three different sampling events. In May of 2018, the DEC suggested we discontinue pumping and treating the system, discontinued the pump-and-treat system until we saw the effect of the plume stop. In January of In 2019, we reinjected into Monitoring Well 6 with plume stop due to a slight rebound in the concentrations. We performed on and off-site monitoring in 2019 and then reduced to semi-annual monitoring of the two on-site wells and then a downgrading off-site well, MW12.

This graph shows the VOC concentrations over time. So prior to operation of the GPRO system, total VOCs in the source area well were decreasing, but downgradient levels were increasing. Once the GPRO system was operational, concentrations dropped, but then they fluctuated. After the plume stop injection, we saw immediate reductions in chlorinated VOCs. We then observed that rebound at MW6, but after the re-injection in 2019, only trace levels were detected. As of December 2020, no VOCs were detected in MW5 and trace levels were detected in MW6 but they were below the groundwater quality standards. So we had to submit annual periodic review reports in December 2018, February 2020, March 2021. In April of 2020, the DEC approved the three final semi-annual events for those wells and allowed us to grout the unused wells in place. So on June 2nd of 2021, this was to be our final groundwater sampling event. And we found no on-site concentrations above groundwater quality standards.

Off-site PCE and TCE concentrations were slightly above groundwater quality standards, but reduced by at least 90% compared to historic 2008 results. And on August 17th, the request to terminate groundwater sampling and grout all wells was granted. So after a mere 21 years of investigations and remedial activities, the site received approval to discontinue the monitoring. Needless to say, we and our client were thrilled. Well that is it for my case study and I’m going to hand things over to Alana. All right thanks so much Lori.

That was a really great presentation on this really interesting site and I think to me what’s so great about a case study like this one is that we get to see the whole remediation story and how ultimately we can best utilize these different methods all the way to their point of completion and then at the end how we can get into an actual closure scenario. So now of course there are lots of different remediation strategies and Lori presented on quite a few of them that were implemented at this site here and for quite a while certainly pump-and-treat was sort of the gold standard for groundwater treatment but of course times have changed and there other methods out there and things like plume stop or other in situ methods, maybe a targeted excavation to take out some grossly contaminated material. Maybe at the site you’re dealing with, there’s no real time constraint and maybe just a super passive approach like a monitor natural attenuation scheme actually makes sense.

Point being there are lots of options and all of these strategies have their place and where they essentially are going to fit in most effectively depending on site conditions and the timelines needed to ultimately get to closure. But where do all these methods actually really best fit in? Graph here I’m showing obviously is not particularly precise or anything but demonstrates an important concept. When we’re dealing with extremely high levels of contamination or maybe free phase product is present out there, that’s where a physical removal strategy like maybe a pump and treat or an excavation or something to that effect is going to be the most effective here. Then as concentrations drop down either maybe because you did some mass reduction treatment or maybe enough time has passed for the plume to attenuate a bit or maybe the plume from the get-go was just never quite as heavily contaminated.

Regardless, as you get sort of farther down in concentration levels, that’s where other methods really start coming into play. Maybe that’s a chemical approach with a chemical oxidant or maybe, you know, as we’re starting to get into some of these really low-level concentrations and get toward the levels you need for regulatory closure. That’s where these biological mechanisms or in-situ sorption-based approaches really start to shine. Of course, all these differences in efficiency and effectiveness have some cost implications to them. And since the bulk of the treatment that Laurie was talking about on this Brainerd site involved a pump and treat system, I thought it would be helpful to maybe take a really generic look at what the relative kind of life cycle costs might be for a pump and treat system versus an in situ approach.

Again, this is a generic graph. There aren’t any actual costs listed out here, but just wanted to kind of convey the message that you’re going to see really large cumulative costs in pump and treat systems. And this is due to the long-term operation and maintenance needed to run these systems. And ultimately, too, these pump-and-treat systems often reach these asymptotic levels that are still exceeding regulatory standards. And the reason that you observe this asymptotic behavior is due to what we call back diffusion from the Aquifer matrix. So to display that for you here a little bit, I just wanted to kind of briefly run through what the stages of back to fusion look like for a contaminant release. So this graphic here is depicting sort of the initial stage of a contaminant release, where on the left here is our source area, this red indicating areas of increased and elevated concentrations in groundwater.

And we have these different lithological units present here as well, where these more transmissive sandy lenses are going to advance the plume farther down gradient. And then you’ve got these lower permeability zones around it. Then sort of over time, as the plume has really generated and come to its own, you get this expansion out from those more transmissive zones into some of that more stagnant and finer grain material. And this is what we call the loading stage, where you see the expansion of the plume not only sort of along the flow path, but also into some of those finer grain material lenses. Then as we really bring ourselves into the final evolution of this plume, maybe you did some bulk treatment out here or maybe the plume has already sort of advanced and attenuated somewhat. In any case, now we’re in a situation where the contamination that is present is located in some of this finer grain material and is actually going to diffuse back into these transmissive zones.

And this back-diffusion stage can last for an extremely long amount of time. And that’s why these pump-and-treat systems often fail to get down to those low-level targets and why they end up needing to be run for years and years unless another treatment approach is pursued, like at the site Lori discussed. So how is plume stop able to manage these situations with back to fusion? Well, the plume stop itself, due to the fine particle size of the activated carbon itself, can actually get into some of that finer grained material. But more importantly, is that it can actually be applied in such a way that it’s coating the interface of these different zones and is able to capture the contamination as it diffuses out from that finer grain material. So with this type of colloidal carbon application, we’re able to quickly achieve results to these low-level targets, but also, really importantly, able to do that and minimize that rebounding effect.

Now, if we’re talking about needing to reach some of these low-level standards, for me at least these days, PFAS comes to mind since the targets we’re trying to treat down to are just so low at that extremely low part per trillion level. So I wanted to briefly touch on another site here that we worked on in partnership with Benchmark. This was another New York State brownfield site, but this time instead of chlorinated solvent impacts, this site was impacted with PFAS. And we implemented a pretty robust plume stop barrier and Benchmark also addressed the source of the soil in the vadose soils utilizing activated carbon as well. Not to get into the details on that but just to say that activated carbon was sort of used in multiple ways on this site to combat the PFAS contamination. So we implemented a plume stop barrier at this site sort of near the property boundary with the intention of cutting off the plume and preventing any further migration offsite.

The PFAS concentrations were quite elevated, certainly above the New York standards with the PFOS especially over a thousand parts per trillion. So we applied the Plume Stop in three rows here, pretty tight application here. And we did this application in the summer of 2021 in August. And by the end of the year in December, New York State issued the Certificate of Completion for this site. So it was a really nice and quick way to ultimately get to closure on a site like this. Today, Lori spoke in detail about one Brownfield site in New York, and I just touched on another one that we worked on with her and her team. but New York State in particular has a very robust brownfield cleanup program and we’ve been involved with many of these sites. The map here is showing just New York sites where PlumeStop has been applied. We over the past few years have implemented 22 PlumeStop treatments across the state of New York. 14 of those were actually enrolled in either the brownfield or voluntary cleanup programs. The others on the map here were either state superfund sites or a handful were responses to open spills.

But ultimately, just trying to show here really how well-suited this type of remediation method can be for these brownfield sites where you want to quickly achieve results and have the confidence that the application will you down to these low-level targets. And of course there’s lots of things to consider for a potential plume stop application. Of course we need to be understanding what the actual target contaminants of concern are on the site and make sure that we have all the information on that. We also though do need to understand what else is out there that is going to compete for sorption sites on the plume stop itself, whether that be other organic contaminants that are just for whatever reason not a regulatory concern or just other sources of organic carbon that might pose a demand on the carbon. With these barrier type setups that we often employ, we also like to get a really good handle on groundwater velocities and contaminant fluxes.

I’ll touch on this in a bit more detail on the next slide, but suffice it to say, this is a key component of our modeling and how we actually put these designs together. Then during the application itself, we like to perform real-time distribution monitoring. We need to make sure that as we’re doing this application, we’re actually building a sort of strong enough underground fence that doesn’t have any holes in it and isn’t going to let anything pass through. So, we’ll do that in the field through either confirmation soil cores or sometimes we’ll install temporary wells or use the existing well network to make sure we’re getting our intended radius of influence and the desired coverage. All right, so jumping back in here to understanding these contaminant fluxes. Over the past few years of doing now hundreds of plume stop applications, we found that on most sites the plume itself is usually pretty well delineated in terms of you know the actual impacted areas, but there’s often data gaps in terms of what the actual groundwater velocities are and in turn what those fluxes are across an area.

And when we’re designing something to essentially be a long-term permeable barrier, understanding what is fluxing into that zone is hugely important. So we developed a tool called flux tracers to essentially map what the contaminant fluxes across a monitoring well screened and how this works is we would ship out these flux tracers to you to install in a groundwater monitoring well. They’re deployed in the well and they reside in there for about two weeks. They’re retrieved. The device itself is sent back to Regenesis for sample analysis. Then we run our analytical on that and we a report that contains information on both the contaminant mass flux itself and the groundwater Darcy flux. And what’s really nice about this versus doing, you know, a pumping test or something is that we can actually get information on both of these different fluxes at discrete depth intervals. So we can really hone in on which vertical zones we need to actually focus our treatment.