Today’s webinar will focus on case studies that demonstrate turning challenging CVOC sites into remediation success stories. With that, I’d like to introduce our presenters for today.

We’re pleased to have with us Stephen Sherman, consultant at Integral. Stephen Sherman is a California licensed professional geologist with over 17 years of experience in soil, air, and groundwater investigation and soil and groundwater remediation, primarily focused on CVOC and PFAS contaminated sites. His experience includes leading air, soil, and groundwater site investigations, managing monitoring and sampling programs, overseeing various drilling technologies and in-situ remedial injections, and designing and overseeing the installation of groundwater monitoring, injection, and extraction wells.

He also has experience in environmental site assessments, construction management, remedial costing, and remedial performance evaluations.

We’re also pleased to have with us today Todd Herrington, Director of Product Management for Regenesis. Todd Herrington has 25 years’ experience in the remediation industry and an in-depth understanding of the complexities of in-situ remediation, having evaluated or implemented mechanical, biological, and non-biological in-situ remedial technologies at over a thousand sites.

At Regenesis, he collaborates with industry experts to generate innovative approaches to site remediation problems with a particular interest in colloidal technologies. All right, that concludes our introduction.

So now I will hand things over to Stephen Sherman to get us started.

Hello, everyone. Welcome to my presentation. It’s going to cover two case studies that both used in situ remediation to address chlorinated compounds in groundwater.

So every project has its own challenges. And these cases had their share. Many of the topics discussed are probably be familiar to the audience but I’m hoping there’s something in here that inspires a different approach maybe for your project sites.

We start with a former dry cleaner located in South San Francisco, California. You can see the site location marked on the regional map of the Bay Area on the right. Commercial cleaning operations specializing in large fabrics like drapes and curtains span from 1965 until the early 1990s in the two most northern units of the property warehouse building.

Site investigation activities took place over approximately two decades. The general groundwater flow direction is to the southwest and the depth of groundwater ranges from 12 to 22 feet.

A dual phase extraction system was operated from 2007 to 2015 and it removed a significant amount of contaminant mass from the source property and neighboring property. A diagram of this DPE system can be seen at the top of the slide.

The system operated down to 40 feet and removed approximately 118 pounds of either vapor phase or dissolved phase tetrachloroethylene.

While it was very effective, that DPE system performance had asymptotic returns as they typically do. And in the chlorinated compounds primarily, PCE remained in groundwater beyond that lateral and vertical influence of this technology.

So we need another solution and we need one that was cost effective to address the remaining contamination. And they get the site on a path to closure around pretty rapid redevelopment schedules. So when contemplating the next steps for the site, we set forth the following goals.

We want to combine all the historical data and utilize all the historical data quickly, efficiently, build a new, more adaptable conceptual site model. We want to address data gaps and further delineate chlorinated solvents in groundwater.

And then we want to finally target those optimal and accessible locations for in situ remediation. The prior conceptual site model consisted of only 2D representations such as cross sections.

These are very useful and standard for reporting but they’re less optimal for planning as it takes some imagination to understand the bigger picture enough to make really important decisions with the investigation and designs.

So we like to use 3D implicit modeling. We like to combine the historical site data into a new conceptual site model that then can be updated periodically throughout the whole rest of the project.

It’s implicit meaning that the site chemistry is being projected in an implied manner or interpolated between limited data points. On the slide are some examples of the projected groundwater chemistry in the soil lithology data. The upper right image shows the well screens that are shaded corresponding to concentration, in this case, PCE, but we can also cycle through the other primary chemicals concerned for this site, such as TCE, cis-DCE, and 1 ,1-DCE.

For working purposes, we usually sum the chemicals concerned together and call it total CBOCs.

The yellow circles on the left map show some of our selected investigation points to fill the lateral and vertical data gaps that we’re after. And the various shades of blue and contour lines represent the approximate extent of the plume at the time.

The historical concentration highs and general groundwater conditions are also displayed here and these will later be used for remedial design input parameters. So the pre-design investigation consists of a whole bunch of familiar technologies.

Cone penetrometer, membrane interface probe, hydraulic profiling tool, we also have discrete groundwater sampling, mostly the confirmed responses from the MIP logs.

Of course, we had installation of new groundwater monitoring wells, and we also had deployed passive flux meters to measure groundwater velocity and mass flux. For those who are not familiar with passive flux meters or PFMs, you’re hanging absorbent material across your well screen, and over time, VOCs absorb to the PFM while simultaneously releasing a tracer compound.

You then segment and analyze the PFMs measure absorbed mass and the mass of the remaining tracer over that exposure period. This allows you to calculate groundwater velocity and mass flux for customizable segments lengths along your well screens.

PFMs are great as a complement to other groundwater velocity data obtained, like from traditional slug testing, which usually represents an average across an entire well screen.

PFMs help you verify those high flow zones that you may have expected from seeing sands and gravels in your soil logging, but there are often many surprises zones that were not identified by logging.

You can see deployment of a PFM into a well in the center picture there and bar charts the Darcy velocity and mass flux results on the bottom. The PFM study results indicated that our site had an average linear velocity of about 0.4 feet per day or around 150 feet per year, but there are also frequently small zones as fast as one foot per day and as slow as two inches per day.

The conceptual site model was updated with the new investigation data. The CSM combined various soil data qualitatively into three categories of relative hydraulic conductivity to conceptualize this.

The goal is to conceptualize these primary flow zones. For example, soil that was logged mostly as clean sands was categorized as relatively high conductivity, and it’s shown in pink here, and the soil log is predominantly fine grained, was categorized as low conductivity, shown in gray.

The big caveat with this grouping method, which is not unique in any way, is that it’s not a guarantee that you have the highest flow zone in where you would expect, especially if the source information is only from soil logging, CPT logs, electrical conductivity logs, et cetera.

So, what I find really helpful for this is the hydraulic profiling tool results and the PFM results.

They’re more reliable sources for predicting flow because they’re actually measuring flow instead of just implying flow.

So, here on the log, we see two semi-confining fine-grain layers interpreted at the site shown by the dashed lines, and then we also see flow within the site’s three interpreted water-bearing zones. HPT pushes are especially useful for in-situ injection projects.

Why is this so good? As HPT is being advanced, it’s attempting to force water out in the formation under pressure. It then measures flow if it succeeds in forcing that water out.

It’s basically a tiny injection test continually implemented as you advance in depth. This log shows that our conditions are pretty tight at this site. With much of the tool that bright red line maxing out 115 PSI when the soil logging indicated that this was a bunch of silty sands where you would expect flow.

Well now we have an updated interpretation of the plume extent. Here you can see our slice view along the groundwater flow direction. We find that the bulk of the CVOCs reside in that middle B zone, and we found that the plume extent is further downgrading the site, but it’s relatively narrow.

Here’s a cross section generated from our 3D model and printed up with Adobe Illustrator. It’s showing roughly parallel with groundwater flow direction along the center line of the plume. Total CVOC concentrations are shown next to the corresponding well screens.

Again, this figure is showing similarly the bulk of the remaining contaminant masses in that B zone. At this point, we sufficiently defined the plume extent for the purposes of remedial design. So, what are those remedial objectives for this site?

First, we have a remedial goal of 100 micrograms per liter, or PBB. Total chemical is a concern, which is primarily PCE. We want to implement a remedy that allows groundwater concentrations to eventually attenuate to maximum containment levels, contaminant levels, in a reasonable timeframe.

Second, we want to meet no further action criteria to qualify for case closure while conducting the work under voluntary cleanup.

These criteria are based on the San Francisco Water Board’s low threat criteria.

It should be noted that these remedial goals were all developed considering that there are no downgradient production wells and the soil vapor sampling conducted on the surrounding commercial properties indicated concentrations are below applicable screening criteria, which is great.

Lastly, we are treating groundwater where it’s actually accessible and then letting things attenuate downgradient. As it turns out, the properties in the further downgradient direction completely refuse access for injections, so the plan was just treat where we could.

The remedial approach selected this site was enhanced reductive dechlorinization in the accessible areas and then monitor natural attenuation. The injection fluids were a mixture of ERD reagents and anaerobic water supplemented with ferrous gluconate to further reduce oxygen and promote some measure of abiotic reduction.

Regenesis provided the reagent dosing for the products based on our design inputs and the Regenesis products included 3DME, CRS, and BDI+.

In the pictures, you can see the milky white totes containing the 3DME, the blue drums containing the CRS, and one of the BDI kegs in the center.

Todd will further discuss these products after my presentation. The updated plume model was used to assist in injection placement within the estimated plume extent in terms of that remedial goal of 100 PBB.

These dots represent the planned injection locations within the A and B zones. The injections would have a target race influence of 10 and 12.5 ROI, and the injection spacing was at least two times ROI with additional spacing to account for groundwater velocities carrying the reagent further down gradient.

Due to access constraints from tenants and the redevelopment, the challenge here was to treat the site all in one go.

With a single injection event, there were going to be many areas that would no longer to be available for additional investigations, really had limited time to get these done.

Here’s a side view of the planned injection locations. The injection interval lengths conservatively target the plume in the zones that we interpreted earlier as moderate, the high hydraulic conductivity.

The injections within the A zone were planned for around the water table to as deep as 30 feet. And then for the B zone, we were going as deep as 70 feet.

With injection intervals, lengths ranging from 15 to 40 feet long, so pretty long. The reagent was delivered through two to four foot retractable screens going from bottom to top of the injection intervals. The tooling was advanced to depth using limited access rigs and CPT trucks.

Due to the site’s many intermittent layers of clays and silts and the relatively max pressure responses you saw on the HPT logs earlier, it was very much anticipated that the reagent would not be delivered over the entirety of those injection intervals.

How it would work is the crew would first start at the deepest bottom interval and pressures would be held for some time with no or little flow before pulling up to the next interval to confirm that that zone was not injectable, ideally without fracking the formation.

It required a lot of patience while initiating flow to minimize short-circuiting reagent to shallower intervals, which is more likely to occur under higher pressure situations.

We would generally start with just above hydrostatic pressure and increase incrementally from there. This allowed us to deliver reagent at relatively low pressures, usually between 15 and 60 PSI. This approach helped us save a lot of reagent and that we place other places while also not missing key injection intervals.

This approach doesn’t work unless you do continuous injection monitoring.

We evaluate the SUMROIs with injection volumes, target injection pressures, and delivery times. We moderate changes in baseline conditions and install temporary biometers near the injections. Some of the changes we were looking for would include things like increasing water levels, i.e. mounding, and increasing temperature due to the above-ground mixing tanks being warmer than groundwater, though this obviously can be opposite for your sites in colder climates.

We were also looking for increasing specific conductivity because the reagent mixture itself It was around 2,500 microsiemens per centimeter, and you’re injecting the freshwater like this. It’s very easy to see that kind of change.

We’re looking for decreasing oxidation reduction potential and decreasing dissolved oxygen because we’re injecting anaerobic water. We’re also advancing soil cores near the injection locations and inspecting those cores to better understand where that reagent actually went in the soil columns.

We collected groundwater and soil samples and submitted them for rush testing of total organic carbon to verify ROIs in the target reagent dosing.

There were areas that indicated we placed the reagent shallower than desired, unfortunately, or the reagent just didn’t make it to the desired ROI.

And so what we would do is we’d go back and re-inject during the same mobilization once we realized that from the monitoring data. So, this would not have been possible without continuous field monitoring.

Here’s a summary of all our injections shown by the brown dots. In total, approximately 418 ,000 gallons of reagent mix was injected beneath the source property, neighboring property, and the street, so quite a lot. Let’s just discuss more challenges we’ve had.

First off, as mentioned in the program, we’re shooting for one continuous event.

But unfortunately, we had to wait for tenants to move out of the source property in stages, and we had to wait on the redevelopment on the neighboring property, as you can see from aerial photo, all the construction activities happening. So I had to break it up into several mobilizations over two years, unfortunately.

Another big challenge was the difficult drilling conditions. Quite a few of the injection locations you see on this map are actually clusters, because it generally took several attempts to get the target depth and confirm the injection response.

There was significant tip resistance, and unfortunately some of the drill pipe was sacrificed permanently to this job while exceeding the limits of direct push technology this site.

In other applications, like when you’re advancing CPT, you can lift the drill string up a bit as you go down to reduce the sleeve friction, but with their tractable tool, you can’t lift very much without damaging or clogging a screen when pushing back down.

Also in other applications, you can use friction reducers, but for injections, the last thing you want is a widen hole above your injection.

Sometimes Vennite can be used as a borehole plug, but there can be a lot of uncertainty with doing that, one driller trick that did help us tremendously for drilling on this project was simply sharpening the end of the injection tooling.

The injection tools typically come with a very shallow cone, kind of blunt, and sharpening it to a deep point made a huge difference for us. The injections in the street going as deep as 70 feet were particularly challenging.

And if we did it again, we may have considered using injection wells on just straight portion, though injection wells bring their own set of challenges, including cost and fixed position.

Now, I’d like to show some of our performance monitoring results, and I’m also happy to say that this site received case closure last year.

The image at the top shows the baseline concentrations from just the wells in early 2019, so it doesn’t have any of the grab groundwater sampling chemistry. The image at the bottom shows concentrations in those wells in December 2022.

The last batch of injections were completed in August 2021, so this is showing more than a year following our completion of the injections. In general, we see significant reductions.

There were some stubborn areas, notably in the more challenging depths beneath the street, that didn’t appear to receive the full dosage of reagent, either because of delivery issues or from washout. Here’s the concentration charts for the performance monitoring wells.

These charts are way too small for you to read, but the takeaway here is comparing the black total CVOCs line to the purple dashed line on each chart. That purple dashed line is showing the 100 ppb remedial goal. As you can see, the majority of these wells met our goal, but a few did not.

Since most of these would, these remaining wells, only a handful were underneath the street, the risk was considered pretty low in terms of potential receptors.

So this didn’t inhibit our case closure at all. Now let’s talk about our second site in Felton. For this site, we partnered closely with Trinity Source Group located in Santa Cruz, California, who handles most of the bulk of the environmental consulting and field work for this site, whereas integral is mostly focused the in situ remedial design portion.

Removing down south from the Bay Area is indicated by the arrow on the satellite image on the right. The small town in Felton is about 15 minutes from Santa Cruz along Highway 9 in the Santa Cruz Mountains.

In the mid 1980s, PC was detected in the spring coming out of a steep bluff along the San Lorenzo River, pictured here on the left. Here we can also see some pictures of the site looking at Highway 9. Strip Mall is located about 300 feet from the Lorenzo River and it was flagged as the likely source property due to the operation of various dry cleaner businesses over the years.

It included things like a laundry mat that had a do-it-yourself coin-operated dry cleaning machines in the early 1960s. You can see the strip mall in the area on the right and the San Lorenzo River at the bottom.

As the topo image implies, the rear of the strip mall is abutted by a steep cliff and the river is about 45 feet lower than the site because it’s sitting on a terrace. You can see the steep drop-off to the river in the center photo. Spent solvents were likely disposed to and spread through the site’s septic system.

And here’s some pictures of the septic system removal, which included a really nice redwood septic tank, unfortunately.

You can see the former tank and the leach field on the site map view below in between the buildings there. Here’s another site plan with utilities. In general, the site is split up between the on-site portion west of Highway 9 and the offsite portion east of Highway 9.

A soil vapor extraction system had been in periodic operation since 2009, and it’s done a really good job at VADO sown mass removal and controlling on-site vapor intrusion.

The SVE system and trenching is shown on purple on this aerial map, and the drawing on the left shows the close-up of the SVE trenching connected to the vapor extraction wells. Let’s talk about groundwater.

This map is overlaid with the implied total CBOCs in groundwater. The boundaries of the outer blob represents five parts per billion, which is the primary MCL for PCE. The inner greenish blob represents the 100 ppb, which is where we’re going to eventually target our remedial design.

Groundwater velocities are generally between half a foot to a foot per day based on a variety of estimation methods over the years, including slug testing, tracer testing, release timing calculations, and of course, passive flux meters, which we talked about previously.

Site groundwater flows to the river, not surprisingly, but oddly in a northeast direction when you would expect a southeast direction due to the river flowing south.

Well, why is that? Older studies focus heavily on their interpretation of the bedrock interface to explain this odd groundwater flow direction.

As seen from the initial conceptual site model picture, the site is located on that river terrace consisting of an unconsolidated alluvium underlain by this Lampico sandstone, which is a thick bedded to massive shallow marine deposit.

The Lampico sandstone outcrops on a cliff that flanks the strip mall, and it’s also going to be found at the bottom of the river channel.

The idea is that the PCE impact of groundwater rides along the top of this sandstone bedrock interface as shallow as 18 feet below ground surface, leading to the springs.

And it doesn’t really penetrate past the bedrock because it’s considered non-transmissive. It’s a cool idea. Unfortunately, this leads to one of our lessons learned. You should use multiple lines of evidence for interpretations.

Here’s a picture of an auger head after drilling just one borehole for a well installation at this site. All the teeth have been grinded right off.

If you recovered a few chunks of consolidated sandstone and met progressively drier and denser conditions before you encounter refusal, you may be tempted to call it bedrock. And you may want to argue that the joint sets are non-transmissive.

But as you can see with the HPT data, there are areas clearly with flow zones that previously were interpreted as bedrock. Also, the fact that we’re using HPT, a direct push technology, going into what was called bedrock, that’s also suspect.

With better recovery technologies from sonic drilling, we see sandy water-bearing zones beyond the depths that were previously called bedrock. We see both rounded and angular gravels underlain by these unconsolidated sands.

Further, some of the descriptions of the La Pico sandstone include things like pebble conglomerates and locally friable, meaning that the degree it becomes brittle is highly variable depending on where you are. The sandstone is also described as not entirely indurated, in other words, not being strongly cemented throughout.

So even if this is something like bedrock, it shouldn’t be considered non-transmissive. Okay, that was too much geology. We have a new conceptual site model now, which shows that we have deeper contamination in the deeper flow zones than we previously thought.

This cross section is looking perpendicular to the groundwater flow to the river, to those springs at the end there on the right. Here, you can see our CBOC mass on the cross section in purple. This is our target for remediation.

We plug the soil lithology and the applied flow zones into our model. Bright yellow columns are poorly graded sands, and the blue columns are gravels. The gray plane is the interpreted continuous gravel layer that goes across the site. It connects classifications of rounded gravels with other mentions of gravels, such as so-and-so soil some gravels, or gravelly sands.

The red plane at the bottom is connecting where angular sandstone clasts were logged close to the 40 foot below ground surface. Again, as we discussed in part one of the presentation, it’s important to confirm our implied flow zone hypotheses using other evidence.

We were able to confirm these zones using a combination of HPT and the passive flux meters. Here’s a view of the well screens in red, and the water table at the site represented by the blue plane.

The green contour lines, they’re a little faint, but you can see that they’re showing the 100 ppb total CVOCs in relation to the wells and the water table.

Here’s a head-on view, like if you’re pleasantly floating in the river looking up at the strip mall. Well, you can see that the gray gravel layer has that trough going northeast, and this is the structural driver for that odd groundwater flow direction we talked about earlier and where the CBOCs are also going.

So the original site conceptual model wasn’t completely wrong. It just wasn’t bedrock. Here’s a side view of the implied plume and the soil lithology combined with some useful labels. The green 100 ppb plume outline is about 30 feet thick and it thins out to about 25 feet thick off-site.

These are going to be our target treatment zone thicknesses. The most orange central blobs are the zones implied to be over 1 ,000 ppb. Note that it’s expected these orange blobs are actually in connection underneath Highway 9, but we don’t have a lot of data points there, so that’s why they look separated.

There’s also a lot of flattening that we’re doing with the model of the plume extents. So you see it’s probably going further than reality in both the upgrade and downgradient direction. So this is an important reminder to remember this is a qualitative tool that you’re using to assist with the design, it’s not definitively telling you where the concentrations are.

This is a top view of the implied plume with the outside again representing 100 ppb. This map has our injection pilot test well arrays for both the onsite and offsite. The arrays are set up for a radius of 10 feet and they’re placed near existing wells so we can do this 15-foot stretch goal.

On the right, you can see drawings of the injection and monitoring well screen depths drawn on the previous cross-section, and they’re really designed to target that upper and lower zones with the most CVOCs. Here’s our injection testing steps for both the onsite and offsite.

Water was mixed with colloidal activated carbon, a product named PlumeStop, before feeding the injection wells with a pump. The colloidal activated carbon, or CAC, was used both as a visual tracer and for judging remedial performance.

A relatively small amount of CAC was added to the onsite test just to be able to perform visual tracer tests, while the offsite received close to a full treatment dose.

The CAC visual test is performed by comparing purge water from a well to a 50 milligrams per liter standard and diluting it with water until it looks about the same.

The amount of water that you add is then multiplied by a conversion factor to get that estimated concentration of CAC. We also added salt as a conductivity tracer to our tests, and we monitor for the same parameters as covered during part one of the presentation.

So the pilot test results were really promising.

We were able to confirm volumes and time needed to make reasonable ROI targets, and as a bonus, we saw how effective colloidal activated carbon can be when applying a treatment dose as the CBOC concentrations offsite dropped significantly.

We also drilled soil borings to inspect for cac in the soil column in directions perpendicular to groundwater flow to really understand the lateral coverage between future injection wells.

We want to know how well does it travel in between the wells? What are our remedial objectives for this full-scale remedy of this site?

First, we want to remediate the onsite groundwater to 100 parts per billion for the total chemicals of concern, which will further result in an eventual attenuation to water quality objectives, which are, again, the MCLs.

Again, we propose them meet no further action criteria based on low threat closure of our CBOCs that may linger below the remedial goal, but above the WQOs.

Second, we wanna remediate this offsite groundwater underneath the highway and up gradient to the plan of Permanent Reactive Barrier or PRB.

Third, we wanna cease flux of CBOCs down gradient of that PRB to the extent practical.

To begin that process attenuation from the PRB to the springs going to the river.

Another important consideration from this design is the potential vapor intrusion concerns down gradient from the treatment areas. You can see on the maps, there’s a business and a residence between the PRB and the river. This means that we want to both reduce degeneration of and increase the capture of degradation daughter products such as dichloroethylene and vinyl chloride.

To meet these objectives, re-recommended onsite remedial action for onsite includes a combination of in-situ ERD with in-situ chemical reduction, ISCR, while the offsite remedy is going to include that downgradient PRB using ISCR and colloidal activated carbon.

This model image conceptually shows the placement of the injection wells to deliver the reagents. The tool helped immensely with deciding on target depths and an injection wells design, dramatically reducing the amount of time spent on doing this exercise.

Note that these are for working purposes only and the injection wells do not actually go up to as shallow as shown, which are going to the surface and as deep as shown. These are just being used as a tool.

Here’s the layout of where the actual injection wells ended up, shown by the green and black circles. The wells needed to be shifted a the fit around many above ground and underground obstacles, especially as you can tell for the offsite PRB, which really wanted to be a straight line, but it just was not going to happen.

It couldn’t be a straight line. There’s just too many things in the way. Zooming in on those injection wells, here’s the design treat target minimum ROIs for the reagents that we’re using. Again, Regenesis provided the reagents and the recommended dosing based on our design inputs.

So, the ISCA reagent used was the sulfidated zero valent iron or SMZVI, and the colloidal activated carbon product, of course, is PlumeStop, just like the pilot testing. The onsite ERD reagents are 3DME and BDI.

We also placed BDI in the PRV wells to boost microbial populations down gradient. So, we basically put BDI everywhere. Even though we technically met that 15-foot ROI stretch goal during pilot testing, we considerably went with higher density of wells with the spacing, and we selected eight, 10, and 12-foot ROIs.

As you can see from the blue circles, the design places the ZVI in the center, more concentrated portions of the plume, and we correspondingly have tighter well spacing, especially for the PRB. We don’t want anything slipping past it.

The pilot test wells are being used again for the full scale, but they’re broken out into the A and B clusters because the treatment zone thickness is so large. We have a 30-foot thick on-site and a 25-foot deep off-site.

And you might ask, well, what are we doing with these new injection wells then? Are we also doing clusters? Are we doing A and B? Or do they all have this crazy 30 foot and 25 foot long screens? The answer is that we’re using dual screen injection wells with about six feet of blank casing in between the upper and lower screens.

This approach saves a tremendous amount of footprint on an already very congested site, and it broke up the target treatment zone thicknesses to more precisely deliver the reagent to higher flow zones crossing over those upper and lower screens.

As shown on the two diagrams, we used inflatable packers to plug up the wells while we’re delivering reagent to force it to one particular screen. Here are the pictures from the injection well installations.

You can see the stainless steel wire wrap screens, the well sump, the middle blank casing, and the schedule 80 PVC in the distance there used for the casing to the surface. You can see both the construction from bottom up or top down.

For the full scale remedy, we injected approximately 63 ,000 gallons of reagent mixture into the onsite wells, and then 32 ,000 gallons into the offsite wells. We wanted to install durable wells that could hold up to injection pressures and this much work, and also last if you wanted to come back and have to re-inject down the road.

So we really wanted these nice long lasting durable wells. Here’s some photos of the injection field work. You can see an example of the packer assembly I was talking about on the top left and what the packer looks like when it’s inflated the seal off the inside of the well casing.

The drilling rig had to be used and set up between points because these packer setups, the manifolds, they’re several hundred pounds for safety reasons. We had these drilling rigs to kind of set them up and lift them out and put them down.

In these photos, everywhere you see a nitrogen tank is effectively an active injection with the packers deployed. During the field effort, we continued with fuel monitoring similar to the pilot testing to confirm our ROIs were met.

Luckily, we only had a couple of well screens that needed to be gravity fed, do low flow conditions, but the rest were fed around two to five GPM. One big challenge was the water source for reagent mixing. A permit for a hydrant was just not possible at this site.

So water trucks had to be used the whole time. There was some added benefit to that. So we basically used the water truck as an external extra mixing tank because we can make it anaerobic water or we can add our salt to the mix before it goes to the trailer. So that was kind of nice.

The strip mall had several businesses that remained busy throughout the onsite injection. So managing the parking lot traffic along the highway was quite the chore at times. And yes, that’s a picture of a banana peel safety cone protecting some of our injection hosing.

That was the most popular traffic cone at the site. I had to include that. Here are early sampling results about a month after finishing the injections. They’re being compared to baseline concentrations from 2025 shaded in gray.

In general, we’ve already seen significant reductions, but we also see signs that things are very, very early in the onsite dechlorinization process, everything’s still ongoing.

Looking at MW12 and MW4, for example, we see the mass continues to enter the PRB from up gradient and the highway, but we also see the PRB is working pretty effectively down gradient of the PRB, but eventually we want to hope to see that the influent concentrations reduce coming from the onsite to below the remedial goal, so the PRB can do less of the heavy lifting over time.

Here are charts showing baseline in a single sampling event since completing the injections. Again, the purple dashed line here marks that 100 ppb remedial goal for total CBOCs. Some of these charts indicate, just like the last slide, that we’re very early in the dechlorinization process.

For example, if you look at MW3, if you can even find it on this grid, it has a large amount of DCE from dechlorinization of the PCE mass, so it’s still undergoing its process. But 13 of the 22 wells here are already under the 100 PBB goal, so we’re off to a good start.

Thank you very much, and feel free to reach out to the project team for more information. Todd will now take a deeper dive into the reagents we used.

Yeah, thanks for that, Stephen. That was really great. That was a great presentation on two challenging sites. I love the amount of site investigation and reformulating the remedial conceptual models and focus on delivery, all great stuff.

As Stephen said, I’d like to get into more of some of the technicals about the remedial technologies that were used. So I’m going to do an abbreviated overview of the colloidal solutions that that integral Stephen used many of, not all, but I’m going to point out the CBO suite that we have for treating solvents.

I want to backdrop that first, though, by talking about our philosophy for research here with Regenesis. We do indeed go for, when we develop products like the S-micro-ZVI, the plume-stop-chloro-lactobacarbon, we’re really focusing on distribution a lot.

When we develop technologies, certainly reactivity or speed. We feel like if we can overcome some of these challenges of distribution of, you know, can we get meaningful reactivity? Can we achieve a persistence or longevity with a product?

Can we just make it simply easy to apply, combine it together? You know, that would be ideal for that with a goal of a single application.

Certainly when we work with integral other clients, we’d love to go out with the amount of work that’s been done in the field to try to get in with the cost of some of these wells and the complexity to do a single application to achieve cleanup goals.

I think everybody would like to do that to get to those cleanup goals sooner, single applications easier than multiple applications.

And that reduces total project cost. And with that, the reason I titled this as colloidal development is for the last 10 years or so, Regenesis has spent a significant amount of research on very small amendments. I’m going to show you what I mean by that.

So the first that Stephen mentioned is PlumeStop colloidal activated carbon.

This material is one to two micrometers in diameter, and it is a colloidal technology. And what does that mean? I’m not a chemist. I remember when we first started talking about that, I didn’t really know what it meant.

There’s a lot of really complex definitions for what a colloidal technology is, but for what we’re talking about today, it’s a homogeneous mixture of micron-sized particles dispersed in a liquid. So it’s not a solution, and it’s not something that settles that you’ve got to frack in. So on the left, we actually have PlumeStop that’s been diluted.

And on the right, you have a patterned activated carbon that hasn’t been treated or doesn’t have an ability, or even another colloidal product that doesn’t have an ability or the polymers or dispersants to stay as a colloidal solution will settle, and that makes it much harder to inject.

And you can see that, and that we’ve spent a lot of time showing that colloids improve distribution. So when you get down and say you use a packer system and you want to inject this material, the PlumeStop and all the colloidal materials that we’re talking about today will go through equally as well.

And you don’t have to fracture under high pressure. And we feel that that doesn’t leave gaps, you know, during the injection.

So, that’s a core area of research that we spent a lot of time doing, certainly then getting the persistence and the reaction speed out of it.

So, this has spanned about 19 years. The development of R&D of the material started about 2007. PlumeStop came out in roughly 2014, and it’s really spawned about five colloidal technologies.

Most people don’t know that. But we have five, not all are used for solvents. We have one for hydrocarbons. We have one for exclusively for PFAS.

PlumeStop’s also used for PFAS, but today, and we also actually, let’s say we have 3D micro emulsion, which is another colloidal technology. I’ll get into why you can call it that.

And that preceded the R&D development of today’s focus of the colonial amendments.

So we really feel that the use of these gives a lot of design flexibility to be able to put them in injection wells, as you see on Stephen’s sites, into direct push if you can get the depth and other innovative applications that way.

But you know, the first thing, the attraction to using an activated carbon and using in-situ absorption is a couple things. One is tackling back diffusion, persistence, speed.

The idea is I think most people understand if you use an activated carbon, you can get pretty fast results. If you put enough in, you can get a lot of longevity, but there’s a limit to that and then you’re going to want to regenerate it.

But in terms of focusing on just the sorption, PlumeStop itself is a one to two micrometer colloidal suspension of inactivated carbon suspended in water.

It does have dispersants and polymers so that when you ship it to the site, it stays suspended. When you dilute it, it stays suspended. You can inject it to get that wide air distribution, extremely fast sorption. And we’ve been saying for years, turning the aquifer into a purifying filter.

So for those of you who may be new to this, who haven’t seen some of our presentations before, on the left is a close-up image of sand. And this is pre-colloidal activated carbon application.

And after that is where PlumeStop has been adhered to the surface. Notice it doesn’t occlude it. Water can go through just fine. This is a surface adsorption sequestration type approach.

And then once you hold it in place, that allows you to spend a lot of extra time reacting and destroying or supplying chemistry to destroy contaminants, regenerate that carbon, extend the lifespan of that carbon.

So you get the speed and longevity this way. And one way that I like to show this is an earlier site that we did. And this actually is, I think I can add a couple more years of performance on this, but when I put this together, or we did, this is PlumeStop that used an old donor that we had called Aquifer, or HRC, excuse me.

And what we saw is eight years of performance of non-detect or near non-detect over that time.

So that’s what I mean by longevity of a colloidal activated carbon. And then we can increase that time if we can regenerate in situ. And so the way we do that is to regenerate in situ is we have to destroy the contaminants on the colloidal activated carbon itself.

And we use two different approaches, Stephen used two different approaches for recommendations on this site. One is biological or biotic and one is abiotic.

The biotic destruction is what many of you are probably familiar with, is reductive or enhanced reductive dechlorination where you supply an electron donor and that’s able to bio-stimulate the dechlorination of contaminants like PC and TC towards the right as chlorine is removed and replaced by hydrogen all the way to ethane.

One of the interests of biotic destruction and the use of zero-valent iron and today talking about S-micro-ZBI, which is a microscale ZBI, is that there can be a buildup or concern about buildup when doing reductive dechlorination on the top row at cis-DC and vinyl chloride.

S-micro-ZVI is special in the fact that it has a long lifespan and it can sidestep that abiotically and go to acetylene, to ethene in a process and not produce anywhere near the amount of cis-DC or vinyl chloride.

So that’s very attractive to a lot of people and really actually using them both together kind of gives the best of both roads if needed.

So in terms of enhanced reductive dechlorination, you know, 3DMicromulsion is a fantastic donor in the sense that we’ve used it on many, many sites. We have a lot of case study evidence for it. And what it is and what makes it distinct is that it is an engineered molecule of glycerol polylactate and fatty acids.

So it’s essentially a sterified chains of lactate acid on the right of the molecule if you’re looking at the diagram on the upper right. And on the left, you’ve got two more fatty acid chains. And because of that, the molecule itself has a different affinities for water on the right to the left.

The right side is more hydrophilic or water loving and the left side is more hydrophobic.

When you put it in water, Anything above 300 micrograms, let me say 300 milligrams per liter, it does a spontaneous micelle formulation which is, or micelle formation on the lower left.

What that does is that micelle is similar to surfactant chemistry where the hydrophobic tails point inward and the polar heads of the molecule point outward into the water and allows it to start to propagate widely through the aquifer, it self-distributes.

And then when it starts to dilute through distribution and drops below 300 milligrams per liter, it does attach and sorb, ferment in the aquifer and produce the effect that we’re looking for to stimulate reductive dechlorination for a lifespan of up to five years.

So we use this a lot.

One of the things that we don’t use it with is we’re not able to directly inject with PlumeStop because it will adsorb to the carbon, kind of like oils, you’re not able to use emulsified oils or oils with anything like a PlumeStop.

So we would look towards something else like AquiFix.

Now this was not something that was used on Stephen’s products.

This came out about three years ago and it was with the need primarily through the creation of barriers for solvents where we have a need to do a single-row or double-row injection where we want to put PlumeStop and an electron donor in the same spot.

We don’t have a lot of room and we also want a lot of longevity.

So this AquiFix is unique in that it’s a 0.5 micrometer colloidal material created out of solid waxy organic particles.

They do not ferment quickly.

You have low fermentation rates.

very small size but they last a very long time and so we can actually inject those just like our other products so far under low pressure get wider distribution and you know establish that reductive dechlorination that we want to see.

Now in the lab what we’re seeing is now this has been out for three years we haven’t had a case study that goes to 10 but we’re predicting on release rates in lab that this would go as high as 10 years on a single application.

As you can imagine, achieving that can be very beneficial for any sort of barrier system.

Right now, the longest case study that we have is probably around 40 months with continuous donor output.

We’re still seeing effect on that, so we’ll be publishing more on that in the future.

In terms of the iron, the iron, as I mentioned earlier, is attractive because it you know, this is one of the reasons that we did use S-microZVI in some of the jobs that Stephen highlighted, the second opportunity. The thing with iron is that it’s a really good reductant.

It’s very fast. It has a lot of electrons. But the challenge is that primarily is that it rusts.

And when it rusts, it forms an iron hydroxide rind, which prevents, that rust layer prevents the electrons from moving out and to where they need to go to the contaminant.

So there’s been a lot of research in the field.

It’s not research that Regenesis had funded, but we are the first to commercialize this product.

And it’s possible to passivate the outside of say a colloidal size molecule of iron is what I’m trying to say, using an iron sulfide layer. So that’s what sulfidating means is using an iron sulfide layer.

And what happens is that iron sulfide layer is very hydrophobic. It repels water.

It prevents actually the activity between the iron and the water.

And I know some research papers that are out there that are indicating probably upwards of plus 95% more efficiency of those electrons going to the contaminant than actually going to the water.

So it’s very, very effective, has a very long lifespan.

We’re seeing up to four years on this and it’s very fast.

So one of the graphs I like to show It is a laboratory column study that we did that shows the destruction of TCE in a lab at 150 micromoles, you know, in a laboratory experiment.

And we ran that with S-micro-ZVI for about two weeks, and you can see near complete removal in that jar compared to bare non-sulfidated ZVI.

It’s pretty slow.

It took actually close to a year to even get to the reductions in the lab.

So you’re getting the speed as high as 30 times more reactive when you put that in the subsurface.

So when we put these together, there’s a lot of different combinations.

We don’t always put SMZVI in the surface.

We don’t always put a donor in.

A lot of times in the source area, we’ll put say an electron donor and SMZVI.

That’s what Integral did on the Southern site.

and then if we have a barrier that we want to really perform, we might put all the substrates in there so that we get the synergistic effects of everything together.

And this is what this illustration is showing. Let’s say we have the pore space in an aquifer.

We go in and we can inject PlumeStop simultaneously.

Say with AquiFix, we start to get the adsorption of the solvents to to the colloidal activated carbon.

We have, I said AquiFix earlier, I meant to say S-micro-ZVI.

We start to get the direct reduction, biotic reduction of the contaminants through S-micro-ZVI.

We also, we need, we can put an AquiFix.

That AquiFix will also attach, it will immobilize in the presence of the PlumeStop and S-micro-ZVI, enhance that reductive chlorination as well.

And so, if we’re able to get these products lasting for that long, even up to 10 years, it can have a lot of gradient back diffusion that comes in, you know, for treatment.

And again, particularly important for property line barriers and things of that nature.

I’m actually going to go by this slide just for time because I want to get to the questions for everybody. Stephen mentioned flux tracers. We do carry those.

If people are interested, We do, you can go to our website and research some or even place an order for them, but very helpful in determining mass flux rates and groundwater flow velocities by depth in an aquifer.

So I wanted to put a plug out for that.

And then one of the things that we can do, and this is, we’re building more units, it’s more broadly available, is an inline blending system.

So it’s possible to come out and minimize the number of injection tanks and pull product right from a PlumeStop, S-MicroZVR container and vary doses by foot or by location, which is really unique.

So we can do up to six injection points simultaneously, up to four amendments applied, real-time data.

They can come right to the desk of our clients.

Reduces a lot of the variability in human error.

And I think really is the point I want to make is that we can take the benefits of colloidal technology, the ease of handling, the low pressure injections, combine them together to get a myriad of different various configurations or grid configurations that meet the needs of our client.

So with that, I’m believing we still have five or 10 minutes for some Q &A, and I wanted to stop there.