Hello and welcome everyone. My name is Dane Menke. I’m the digital marketing manager here at Regenesis and LandScience. 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 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 you after the webinar. We are recording this webinar and a link to the recording will be emailed 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 a case study in air quality data control. With that, I’d like to introduce our presenters for today. We are pleased to have with us Dr. Sigrida Reinis, Senior Associate at Langan. Dr. Reinis is a professional engineer in the state of California and a licensed general engineering contractor in California with over 25 years of design and construction oversight experience. Dr. Reinis the technical leader of the gas and vapor intrusion mitigation and monitoring practice for Langan in California supporting projects ranging from quarter acre brownfield redevelopments for affordable housing to landfill redevelopments for multi-tower life science campuses. In addition she leads the probabilistic cost estimating and decision analysis practice for Lange and Nationwide.
We’re also pleased to have with us today Hieu Nguyen, Principal Engineer at LandScience. In this role, Hugh oversees product implementation at construction sites and provides technical support to regional and district managers, as well as LandScience clients. He has over 15 years of experience supporting vapor intrusion mitigation system designs, specifications, and installations across the United States, Canada, and Australia. He’s also an active member of the ITRC Petroleum Vapor Intrusion Task Group. All right, so that concludes our introduction, and now I will hand things over to Sigrida Reinis to get us started. All right, thank you, Dane. And with that, we will just launch right in. So what I’ve prepared today is a presentation that looks at a project that Langan has been working on for a number of years. We designed a vapor intrusion mitigation system.We oversaw the construction of that system, and then subsequently we’re engaged by the client to conduct post-construction performance monitoring.

And the focus of this presentation will be the data set that we’ve collected over time and some of the challenges that we encountered in interpreting that data. So just a quick overview of what I’ll be covering in this talk. Provide a bit of a site history, including a description of the environmental conditions of the site prior to redevelopment. Then the contaminants of concern that were identified, and then subsequently the vapor mitigation system that was installed. And then looking at the post-construction monitoring data, talking about how we first started thinking that perhaps we had some anomalous data and what that did to the project in terms of data interpretation and resampling and all of those kinds of things. And then how we ended up coming up with an approach to actually identify those anomalies and changes to the monitoring program that we’ve subsequently implemented. And just a quick disclaimer, I do want to mention that all of the data that is presented here is available to the public.

However, the opinions expressed are mine alone, and the mention of any products by name does not necessarily constitute an endorsement by Langan Engineering. All right, so this site is located in the famous Silicon Valley in Northern California. And this site has various uses that go back to the 1930s. And a phase one environmental site assessment conducted by another consultant a number of years ago did not identify anything that you would consider to be a smoking gun. Yes, there were some industrial uses, but really nothing that would constitute any kind of cause for major concerns. However, the site is located within a regional VOC or volatile organic chloride plume. And the regional plumes contaminants of concern are PCE and TCE or perchloroethylene and trichloroethylene. And as you can see from this figure of the three sites that are associated with this regional plume, our client site is literally across the street from one of them. So not only is it across the street, but historically somewhat down gradient, more recently a little bit also cross gradient as there is a series of extraction wells located a little bit north of our client site.

So, we believe that the historical gradient might have been more directly towards our client site, but we know over the last 10, 15 years, that gradient has shifted a little bit to the north. And this site has been redeveloped as a mixed-use complex, which includes ground-level commercial space, two stories then above that of residential apartments, and the entire development is lane by a single-story underground garage. And here’s a photo of the early installation of the vapor mitigation system barrier, some of the elevator pits you can see there. But prior to this redevelopment, the PCE and TCE concentrations found in the site groundwater were generally consistent with those of the regional plume. And the soil had no evidence of contamination and certainly none was found by visual oral factory cues during excavation all the way down to 15 feet. And then some localized areas, you can see even deeper than that. And the environmental consultant at the time, which I should mention was not Langen, but they certainly did very good work.

Seven out of their eight bottom confirmation samples were non-detect for the contaminants of concern. And one of the samples did have some detections of PCE and TCE, but they were below not only the environmental screening levels of the time, but also the updated water boards, environmental screening levels. so relatively low detections in soil. And the soil gas investigation though did find some elevated concentrations, TCE up to 150 ,000 micrograms per cubic meter and PCE as high as 40 ,000 micrograms per cubic meter. Interestingly, our staff has back calculated that what looked like the high concentrations of VOCs can actually be attributed simply to these low-level residuals that are below the environmental screening levels for soil. So kind of a quick take-home note here is that just because your soil concentrations are below environmental screening levels doesn’t mean that you won’t find these constituents in soil gas and still at relatively high concentrations potentially.

So we were engaged by the client then to design a vapor mitigation system and in keeping with our standard of practice, this is a fully passive vapor mitigation system, very simple components, so it’s three inch diameter perforated pipe, PVC pipe inside of the four inch gravel layer and the system has just four risers, one in each quadrant and nine perimeter inlet vents that allow fresh air to enter that subslab. I should mention this is a little bit of an older design at this point. If we were to design it today we’d probably have you know twice as many risers but otherwise it would be broadly similar to what you see here. And the original installation was a very, at the time, you know, was kind of the standard. It was a 60 mil spray applied vapor barrier membrane with a carrier geotextile fabric and a protection geotextile fabric. And I should also mention that subsequently, because of the challenges that we had with our data, we did later post-construction apply a retro coat in selected areas, those being the four elevator pits and the four stairwells, just the floor slab of those stairwells.

And I can touch on that a little bit later, but RetroCoat did end up being applied post-construction. It was one of the ramifications to this project of having challenges interpreting the data. Post-construction, of course, the basic concept behind a vapor mitigation system is to provide a preferential pathway for VOC vapors to vent to the atmosphere so that they don’t accumulate beneath the slab. Our performance showed that we had approximately one air exchange rate per day in that gravel layer under the slab, which is, you know, on par with what we see for our other passive vapor mitigation systems. And what you have graphed here is the results of the Mann-Kendall trend test. And the TCE concentrations over the time since we started monitoring in the fall of 2016, We have gotten, or what we have seen by riser monitoring, which we take to be broadly indicative of what’s happening in the gravel layer of the venting system. We see TCE concentrations have increased, or I’m sorry, decreased by approximately 80%. So going from a value of about 1 ,000 in the beginning to 200 towards the ends of the cycle.

And of course, there’s a lot of variation, a lot of ups and downs in that graph. And my personal interpretation of that is that what this reflects is that when the groundwater table fluctuates seasonally, you know, in California, we have a wet season and a dry season. And we’ve just now in October started a new water year. And over the winter is when we’ll see the majority of our rainfall and then by about the end of April, that comes to an end and then we have a number of dry months. And we see that reflected, of course, in the groundwater table elevations. And because the groundwater table is kind of right beneath the slab, conceptually, what I think is happening is that as the groundwater table rises, it pushes, if you will, the vapors that are present underneath the slab up towards the underside of the slab and into the venting system. And then as the groundwater table eventually then falls again, that soil vapor space expands and so the concentrations become a little bit more dilute.

So, to my mind, you know, that explains a lot the pattern that you see in the graph. The peaks are essentially our winter sampling event, and not necessarily every winter because of course we’ve had quite a number of years of drought by now. But nevertheless, you see this quasi-seasonal variation in the NVOC concentrations underneath the slab. All right, so just looking at how we do this monitoring. So this involves quite a lot of SUMA canisters, and I should note that all of the canisters that we receive from the labs are individually certified. This is a rather expansive monitoring program. So we’ve got, I mentioned earlier, a garage and then commercial space and then two floors of residential. So, in the garage alone, we’ve got four elevator pit samples, we have two, we have four samples that are collected in the, loosely speaking, four quadrants of the garage. Then we collect samples at the basement level of each of the four stairwells, and then also up at the second floor, so the first residential floor, we’re also collecting four riser samples at the roof, and then three ambient air samples.

And then, because we quickly figured out that we probably had an indoor source issue, we added some additional sampling locations. So a sample set of approximately 30 samples initially collected on a quarterly basis, then on a semi-annual basis, but then because we had these data anomalies that we were trying to figure out, we ended up also conducting more limited sampling events in between. And what we’ve seen over time is that our TCE concentrations at the 95% upper confidence level have been consistently at approximately half of the 50% of the residential environmental screening level. So, you know, very low. A lot of non-detects and a few detections, again, on average, at the 95% UCL were still well below the environmental screening level. The PCE concentrations, on the other hand, were highly variable, and we started to suspect very very early on that we had an indoor source issue specifically with PCE and over time what we’ve ultimately believe we’ve determined is that after contacting the elevator maintenance company and obtaining the MSDS sheets for all of the products that they carry on their maintenance vans or trucks that one of the lubricants that’s used during elevator maintenance has as a precursor PCE.

And so it’s not uncommon to find these low level residual concentrations of PCE in that product, even though PCE is not listed on the label. So the PCE concentrations, what we found would vary widely over time, there would be times when we had just very, very low PCE concentrations and then other monitoring events where we had concentrations that were above the ESL. So we were a little bit chasing our tails for a while until we figured out this this elevator maintenance product. All right, so now taking a dive into what I mentioned, these data anomalies that were so confounding. So as I noted in an earlier slide, we started monitoring in the fall of 2018, and we first started noticing these odd results you know, in a data sample of 30 samples distributed throughout a four-story building, we were getting hits of TCE and PCE that just, they just looked like outliers. They just did not in any way kind of fit the distribution and certainly did not fit what you would think would be a vapor intrusion mechanism.

So, we then started to place our duplicates in sampling locations that we thought would be most likely to have detections so that we could do some sort of, whether it was relative percent difference or percent difference analysis, but be able to do some calculations. Then, as we struggled, continued to struggle with these anomalies or outliers, we then added two what we called co-located duplicate samples. So they were essentially triplicates, and so the way that setup worked was you had the customary primary and duplicate sample where the same, you know, stream of air is connected through a splitter and then right next to it, a third canister with its own regulator, no splitter, it just was its own sort of sample setup. So we had these co-located duplicates or otherwise could call them triplicates. And then because of the frustration that we were experiencing at one point, we changed labs altogether. And I should say that both of the labs that we’ve used are very reputable air labs. And then, again, because of the continuing challenges with these data anomalies, we then began what ended up being three trial runs of using passive sorbit samplers.

So these were kind of additional duplicates, if you will. So we didn’t replace the canisters with sorbit samplers. We just put sorbit samplers out there in addition to the canisters. And then looking at it more closely, began to look at various numerical approaches to trying to really pinpoint these anomalies or being able to say that these are anomalous results. And what we settled on was a percent difference calculation. The relative percent difference kind of had its challenges, Whereas, the percent difference kind of gave us a nicer data set to work with. And I can circle back on that and just a little bit what we mean by that. But at any rate, here’s just one example of the, you know, just one set of primary and duplex sample from one monitoring event. This happens to be from October of 2019, where you see, we had PCE and TCE are our contaminants of concern. And then I suggested that we add benzene to this data quality analysis because it’s pretty much present everywhere.

No surprise with a subterranean or a garage at the basement floor level, The vehicles act as a source of benzene. Benzene is virtually non-existent in the subsurface, so it was not only not a COC, but is present at either not detectable or at very, very low levels in pre-construction solid gas samples. But it’s definitely present in the building, thanks to just the vehicles that are parked in the garage. So, that’s a third constituent that we added to this data quality process. And so, you can see here, there’s the calculation for percent difference, and for this one pair of samples, our percent difference for PCE was well over 1 ,000%, so 0.321 versus 5.34. For TCE, 0.32 versus 1.22, so that’s a percent difference of nearly 300%. Benzene was a little closer, 1.24 versus 1.2, so just a few percent difference. So this is the type of thing where we’re struggling.

We have an environmental screening level for PCE of 0.46, for TCE of 0.48, and we have you know, a sample where we have exceedances of the ESL for both constituents. So this is just the one example of the, you know, kind of the challenges that we were facing. And, you know, we of course have a regulator who’s concerned about vapor intrusion. And we’re saying, well, not only do we have an indoor source of PCE, but there’s also something else, you know, going on with our data. And so we kind of went a little bit back in time and went all the way back to May of 2019. As I mentioned, we first started seeing these anomalous results in October of 2019. So going back just a little bit further, here’s just a summary of how many duplicates we collected on each occasion and how many of those were rejected through this data review quality control process. And then just for illustration, what the maximum percent difference was in these data sets. And then based on these percent differences, how many of these duplicate data were rejected. And I should mention in the previous slide, I noted that benzene was brought in as a third compound to look at. And I would say that our rejection criteria are slightly conservative because we would reject a sample’s results if two out of the three analytes had a percent difference of greater than 100%.

And just by comparison, in lab review data, often a relative percent difference of 25% is considered tolerable for a lab standard. And here we have 100% difference. And as you can see from the table, our maximum percent difference was in the many hundreds and even thousands of percent. And I should also mention, this is just the duplicates. There were, of course, many other samples that were just single samples. And there were cases where we had data points that looked anomalous, but because there’s no duplicate, we had no way of really rejecting it. So we kept them in the data that we reported. And just in summary, looking at the percent rejection, on average, you’re looking at a 23% rejection rate in comparing just primary versus duplicate samples. So by extrapolation, what I think this points to is that during any given sampling event, maybe a quarter of your data could be suspect.

So to close out this presentation, just a few takeaways and the potential exploration of a path forward or multiple paths forward. So what I did not know, I wish I had known, but I didn’t know at the time that I was grappling with these data anomalies. There’s a really excellent publication by Thomas McHugh and others that was published in 2018 that’s titled, Evidence of Canister Contamination Causing False Positive Detections in vapor intrusion investigation results. And it’s in the Journal of Soil and Sediment Contamination. And there’s the full reference there. And what’s interesting is that our results, just for this one, this case study that I presented, our results are really quite similar to the results that this team came to. They essentially data mine the California environmental databases. So again, publicly available data and compared percent, they also use the percent difference calculation. And they looked at the percent difference in groundwater samples and duplicates versus soil gas samples and their duplicates. And what they found was that the groundwater samples had a percent difference that exceeded their criteria of about 3%, whereas where soil gas, they were at approximately 25%.

So very similar, slightly different approaches, both they and we used a percent difference calculation. Their data set is thousands of samples, ours across many sites, across many labs. Ours is just one site, just two labs, and yet the results are very comparable. And I would say in our case too, I think we’ve concluded that our data anomalies are very likely related to canister contamination. And in our trial runs using sorbent sampler, sorbent samplers, we’ve not seen those types of anomalies. And again, anomalous looking data points might actually be anomalies, but if you don’t have a duplicate, It’s really difficult to say, well, that this result is problematic other than just looking strange and not fitting the data set.

So the question in my mind is, you know, is it perhaps time to, if not move away entirely from canister sampling, at least incorporate other sampling methodologies? And again, this would be, you know, dependent upon the situation and what the objectives of the monitoring are. For this particular site, we’ll be moving to a combination of passive sorbent samplers and canisters. We’ll continue to use canisters for grab samples such as from the elevator pits. There are situations where it’s difficult to deploy a passive sorbent sampler. So, you know, a combination approach, I think, is where we’re headed. And of course, there’s also what’s called a continuous sampling approach and where essentially a sample is collected through tubing and analyzed in a kind of a miniaturized GCMS setup, let’s say every 10 minutes or every five minutes and that approach, it still uses the same analytical approach, but it doesn’t use a canister. It just pulls the sample right into the analytical machine, so that too does away with the canister.

So that concludes my prepared presentation. And with that, I will hand it off to Hieu Nguyen with Land Science. All right, so I’ll start.nThank you for attending and your time to listen to our best practices on QAQCs that would apply for both passive barriers at existing and new construction buildings. Just a quick agenda here, we will be looking at the existing building assessment, evaluating different types of concrete testings along with profiling and typical application procedures and best practices in how to get the coatings to properly adhere to the surface. With that, looking at various applications, either for retrocode or other coatings that will be applied directly on top of concrete. Then we’re looking at jump to a different segment for a new building constructions where QAQC of passive barriers will be discussed, and evaluations on its performance, and barrier choice to the appropriate site conditions. Then we’re looking at various QAQC measures and best practices to evaluate, and also to consider when building any new constructions.

Looking at vapor intrusion at existing structures, first thing to understand is that pervious concrete slab is porous, In majority of the cases that we consist of cement, coarse aggregate, sands, water, and maybe other polymers are added onto the mix. And notice that concrete can be very absorptive materials, so permeability would increase when the aggregate size increase when the concrete mix is made. With that, concrete has ability to absorb and dissolve both moisture and contaminants when exposed to extended time or at high concentrations. What we’re looking at here is typical thin concrete slab, not necessarily a thick, matte footing scenarios, but for thin concrete slab, for a typical mix ratio water to cement ratio of 0.28, 2.4, most likely will contain about 15 to 25% voids. These voids will act as a, I wouldn’t call it a path of the least resistant, but are catalysts and potential voids that vapor can accumulate and also diffuse through over time.

So when we understand the concrete compositions, give us some other ideas in terms of if there is calcium water soluble that’s in the concrete, these pores actually would expand and increase over time when concretes either erode away or dissolve away over time. So understandably that concrete is porous, we’re looking at two different types of scenarios. One is new concrete. When looking at new concrete, first thing we want to look at is their latencies. If there’s a lot we need to remove and evaluate also the cure time of the concrete slab. Was it properly cured and have adequate cure time? Typically, concrete would cure between 10 to 28 days, depending on the admixt and the water content. When applicators walk the site, we will typically recommend the grid profiles or the concrete surface profile to be able to get good adhesion on that concrete and evaluate the integrity and the structural of that concrete before application.

For all concrete, various assessment that we make will be researching what type of material has been exposed to that concrete’s floor, Potentially, it could be oil, chemicals, grease, fat, others, releasing agents. A core sample of the concrete slab may be required to evaluate the exact compound that it’s supposed to. So understand the material that has been contaminated in that concrete materials, allow us to evaluate the compatibility of the coatings, and also the ability to get good adhesion onto that floor. The other is to evaluate the structural integrity of that concrete slab by various methods. The crude and effective method is using a metal chain. We can run that across the floor to identify different sounds reflected from that contact. If there is a hit between the chain and the floor, we can identify if there’s a hollow spot. And that’s an area that could be delaminated over time. Potentially it might need to be repaired or patched prior to the application.

As a rule of thumb, most manufacturers want to make sure that the coating is firmly bond onto the existing concrete surface rather than bond and relying that adhesion onto the existing coating. So if there is an existing coating, we recommend it to be removed and or confirmed with the client that there’s a liability if there is a potential delamination from that coating if they insisted to be left in place. Once evaluate the condition of that concrete slab, we then test that concrete slab for potential exposure to moisture and other chemical. Two of the tests that are required by land science and many other manufacturers is the relative humidity test, which is in the SDM F2170, which measure the actual moisture content in the slab at a specific time. Notice that the relative humidity test and calcium chloride tests are specific to the time it is tested. We want to make sure that is consistent to the condition that the building will be operating under.

I would not recommend testing it if the building was not fully operational, meaning if there’s a roof was not installed and or if the building is not under an HVAC system. What we want to be able to identify these in the scenario that will be occupied and operating in that condition, both temperature and humidity would be considered. The calcium chloride test is what below there is actually a calcium chloride disk that has been placed inside of a cap and then sealed together on the outside. The calcium chloride tests measure the moisture drive across the slab, measuring in pounds per 1 ,000 square feet. This typically would be done between 60 to 72 hours duration. What that does, we evaluate how porous the slab is and ability of moisture and other contaminant to diffuse through over time. Notice that since this is an ASDM standard test, these test kits and methods are available commercially. Applicators and design engineers are welcome to use different manufacturer as they see fit.

One recommendation is as long as they follow the two ASDMs methods that we’d recommend, most likely would give more consistent data and results. Once the results have been received, the manufacturer, either land science or other manufacturer will evaluate this data and recommend the right barriers and our primer for that application. The next QA that we wanna look at is be able to profile the concrete once we identify the moisture drive and the moisture content in the concrete slab. The best way is grind the floor, As you can see the picture on the top right-hand side, this floor has been grind where you see a tooth shape in terms of the surface to be able to gain double the amount of surface area for the coating to adhere to. The same area now with the tooth configuration, it would give that much better adhesion over time.

In the bottom right-hand side picture show a typical adhesion of retro-coater other coating materials apply directly onto the pieces of a tile and what the test we want to evaluate is the ability of the coatings to break away the tile before it breaks apart from that adhesion. So both the surface profile and the chemical makeup of the coatings plays important role in terms of the adhesion that the coating will have on that concrete slab. In terms of values, we recommend having an SP3 or an 80 grid surface for a typical thin mill coatings. There are cases where we recommend go through a concrete surface profile SP4, which is a 60 grid. If you’re not familiar with what types of grid that would look like, there are various sandpaper that’s commercially available that you can evaluate the texture. And that’s easier to identify if you can run your fingers across it to get how that feels like.

There are many ways to achieve that surface profile. The one that’s most commonly used is shot blasters. You can see in the photo here, a gentleman’s run the shot blaster. What that does is runs a high speed, different size of the shot, hitting surface profile to achieve the exact concrete texture. You can see the color difference between where the shot blaster ran versus not ran is substantial especially when that is done. There’s also a vacuum line that’s connected to that sharp blaster to be able to remove the shot and also vacuum the area to a very nice clean prep surface. Other methods are handheld grinders which are designed to be achieving and profiling the surface to the right specification.

The picture on the left shows the gentleman connected the handheld grinder with the right diamond blade and connected to a shop vac or a different vacuum to be able to not allowing the particulates to disperse into the air. Same goes for the gentleman on the right hand side where the diamond grinder would be able to grind and remove and profile the floor to the right specification. There are other equipments. As we know, the right tools improve the job and the efficiency the projects. Other mixing tools that we highly recommend and in many cases required for applicators to use is the high-speed adjustable drill using the jiffy mixing blade. This allows the product to be thoroughly mixed and be able to mix to the right ratio prior to application. Other is the thermometer or different types of equipment to measure the temperature of the straight prior to that application. What that does is with the right tools we provide a more efficient and the best applications over the course of the installation.

For most applications, either retro coat or others, squeegee and back roll is the ideal and the most typical techniques. Very straightforward where the applicator had using a notch squeegee to spread out the materials directly onto the floor. This could be starting with the primer and or other coatings on top of that. Crew of thumbs always review the product technical data sheets and on the buckets and or on the technical literature to make sure the mixing ratio is correct. Oftentimes that would give you the best result. Additionally, working temperature, most coatings have a range of temperature where the coating will be able to cure. So that plays a critical role in terms of maintaining the consistent temperature over time.

Evaluating membrane thicknesses using a wet meal gauge, either offered by LandScience or others, to be able to measure the coatings based on the wet volume that’s being installed here. And then cure time, reading that documents, the TDS and all the buckets that the material comes in from. Understand when the coating will be cured to the point where you can apply the second coat. Either it’s tag-free and all other methods within that recoding window so applicators can apply the second code with no delaminations issue. As a rule of thumb, communicate with your clients, managing that expectations in terms of the barrier coatings, the time it takes to install, the commitment that they’re putting in in terms of removing clients and other machinery to allow application to be continued in a timely manner, and also communicate the number of mobilization that the applicators would be needed to get the coding done in time.

And lastly is aesthetic. This is a critical part of the codings when applicators and the clients communicate with there’s going to be a texture surface versus would there be a color paint chips or other types of profiles or aesthetic that’s required. So do have that communication with your clients to make sure the right colors and the right aesthetic has been applied correctly. And the last piece of the puzzle is the workmanship. Crew of firm is what we recommend is having the right applicator has been trained, certified to perform the installation. All that does is ensure that the consistency of the coating has been applied, the efficiency done within a timely manner and be able to stand behind the warranty that most manufacturers would offer. Other QAQC methods that we require is using that wet mill gauge. We know most coatings are either 100% solid or 75% or whichever the solid content is. We can always use a simple math of the total volume that the product comes in divided by the area and you typically get the thickness overall.

Assuming there’s no waste product disposed in somewhere else, but as long as the product has been applied directly and used on site, you can definitely get the right thickness from that overall volume. So brew of thumb, you know, use a wet meal gauge to measure thicknesses on each lift or each coat that’s been applied. So starting with the primer, then your barrier, then your sealer, make sure that it’s the right thickness is in accordance to your manufacturer specification. So the very important aspect of any application is improving its existing condition. So you see the photos on the left-hand side here, the coatings before the coating has been applied, there’s a lot of damages, there’s a lot of cracks and imperfects on the floor. There are also oil stains that you’re looking at the very top right hand side of the picture. There are also other stains that the floor has.

The goal is, at the end, you have a nice clean floor and a durable, improved, low permeabilities, very strong floor in terms of tensile strength that the coating would provide and improve that condition substantially. Next, I want to lead to the vapor mitigation for a barrier that will be used on new construction building and looking at various evaluation criteria. Number one, if we are dealing with contaminated vapors, which could be from methane gases to radon to other petroleum, hydrocarbon or chlorinated solvents, and much more. Rule of thumb is want to make sure that the chemical resistant property of the barriers is resistant to the contaminants that we’re dealing with on site. As always, evaluate the concentration of the contaminants underneath your building and also the source if possible. then evaluate the constructability of the barrier itself.

Understandably, site could be specified to have gravels, sand, native soil, you name it. It could vary from site to site. Constructability plays important roles in terms of preventing barriers from damages, and durability and longevity of the barriers one is installed. So quality of the applications is very important, and in terms of the right barriers for the right job. Some of that we will discuss in the later slides, but others is looking at the installer, the experience of the applicator where they train. Do they have the proper tools and equipments in the training to perform the installation timely and efficiently? Next is the cost perspective of the barrier considerations. Budgetary number is great. We want to make sure that we set the expectation to the clients. If this is the scenarios where it’s a warehouse scenarios, single layers versus three layers, we want to make sure we have the right recommendation for that particular site condition.

As I mentioned before, various barriers have their own pros and cons for site that has a lot of penetration, irregular shapes, foundation, contours, waffle slab scenarios. So in sites like that condition, a single layer system can be very challenging in terms of conform and shape the right foundation without any fish mouth or concern or damage, especially if the barrier is too rigid to install, it could pose a challenge. So the right system and the right barriers will be ideal in terms of selection and how well the barriers will perform. So, consider the amount of penetrations, the irregularities of the shape of the foundation, and how difficult it is to form. There are cases where spray apply barriers could be more beneficial compared to a fully welded system versus a single layer system. This is something that oftentimes consult with your design engineers or manufacturer to get the best results. This is the bread and butter in terms of how they recommend the right systems. So don’t hesitate at all to pick their brain on it and see what works the best. They’ll give you their opinions in terms of what has been installed and provide various case studies to back that up.

Next is QAQC measure. Different manufacturers would have their own QAQCs. We will speak directly for land science alone with that all of our below grade barrier will required certified applicator. What that means was the group of applicators that has been trained by our technicians to be able to perform the work, understand the products, understand the process, and having the right equipment and tools to perform the work in timely manner and efficiently. They can also provide various thickness verifications and testing logs and QAQC on their end and inspection logs for clients if need to. We highly recommend the use of third-party inspectors, which impartial to the install, they would be coordinating with the applicators to perform the inspection once this is commencing. Documentations in terms of inspection checklists and inspection logs could be daily, could be weekly, depends on the client’s expectation.

As a rule of thumb, we’d recommend having pre-construction meetings with the clients, with the generals and other trades where a barrier will be installed. Understand that the coatings or the barriers that will be installed and the importance of having that and the carefulness that’s working around these barriers. Understand that there can be sequence where concrete contractor would be coordinating with the plumbing contractor and our applicators to be able to get the job done in a timely fashion. And then last but not least, I want to have any plan for monitoring locations. We want to make sure that those are being outlined and labeled properly. Our applicator can assist with that, fan things and other kind of inspection purposes and other plans to make sure that the active system would be installed properly and maintained. Those would be outlined in the meetings as well.

So, with that, I mean, we want to make sure that the kind of quick recap on the quality control measure. On a QAQA perspective, we want to make sure we get the right installer for the work. They will provide an ease of installation, bring in the wealth of experience in terms of site conditions, and be able to install based on the manufacturer specification. Third-party inspections, land science do provide an online inspection and all in-person inspection training for various inspectors to be able to confidently walk on site to perform inspections. Others are thickness verifications. We want to make sure that the barriers install based on the right thickness. Both thickness verification on concrete versus caliper cutting out coupons and wet mill gauge are all available, either commercially or from LandScience.

Lastly, smoke tests and fuel inspection reports. Smoke testing, as you can see the photos on the right-hand side there, most likely we’ll find leaks through the areas that’s weakest from the install, and that will be around the penetration or termination points. It’s critical that these areas will be patched by either spray application or other means to make sure that the barriers have been fully sealed prior to concrete application. And then last is the in-field inspections, inspector are expected to perform inspection both visual and provide reports to the client to make sure the coatings and the barriers has been installed properly. And with that, we have these contact information here for both Sakrita and myself, feel free to reach out to us with any questions. And I think I open up to Fordane for any question that you might have.