WEBVTT 00:00:00.000 --> 00:00:08.000 On behalf of the Interstate Technology and Regulatory Council. Welcome to today's training. Itrc. Sediment cap chemical isolation. 00:00:08.000 --> 00:00:18.000 which is an introduction to the ITRC online resources produced by itrc. In 2023. My name is Taylor Vogel, and I will be your moderator for today. 00:00:18.000 --> 00:00:40.000 I now have the pleasure of introducing our trainers. All of them served as members of the team and volunteered to support the training offered today. Before we get started, just a quick note, some of the links presented in today's training may be broken or out of date. If you run into any issues accessing a link, you can always navigate directly to the main guidance document and use the table of contents to find the specific sections we're referencing. 00:00:40.000 --> 00:00:48.000 At this time I will hand it off to Ashley from the Michigan Department of Environment, Great Lakes and Energy. 00:00:48.000 --> 00:00:57.000 Thank you. I'm excited to welcome you all to our webinar today about the sediment cap chemical isolation Guidance that was published in 2023. 00:00:57.000 --> 00:01:06.000 There are a number of technical references that are available that discuss different sediment remediation approaches and sediment capping specifically. 00:01:06.000 --> 00:01:13.000 One of those is our 2014 Contaminated Sediment Remediation Guidance that ITRC previously developed. 00:01:13.000 --> 00:01:21.000 Many of these technical reference materials remain valid and are helpful for understanding sediment capping, but they tend to have a higher level focus. 00:01:21.000 --> 00:01:34.000 For example, the 2014 ITRC guidance provides a high-level overview of sediment remediation technologies, and it summarizes the key factors that should be considered when evaluating different cleanup options. 00:01:34.000 --> 00:01:46.000 One of the chapters of the 2014 ITRC guidance is dedicated to capping, and it provides useful information for deciding whether or not capping could be an effective remedial approach for any given site. 00:01:46.000 --> 00:01:58.000 Our team supports the information in the 2014 guidance, and we believe it's a valuable resource for projects that are in the Alternatives Analysis and Remedy selection process. 00:01:58.000 --> 00:02:13.000 Our 2023 sediment cap chemical isolation guidance was developed to expand upon ITRC's 2014 guidance, with the goal of improving consistency in the project phases that follow remedy selection. 00:02:13.000 --> 00:02:28.000 Our goal for the guidance was to go into detail about the design, construction, and performance monitoring for the chemical isolation function of CAPS, and to create a framework that encourages more consistent designs and performance outcomes for CAPS. 00:02:28.000 --> 00:02:35.000 I'll let Bordek continue with an overview of our training for today. 00:02:35.000 --> 00:02:49.000 Thanks, Ashi. I'll start by going over the roadmap for today's training. I'll briefly cover the introduction from Section 1 of the guidance document and trainers speaking after me will cover content from the remaining sections of the guidance. 00:02:49.000 --> 00:03:04.000 Listed here. Um, as Ashley mentioned, the 2014 guidance covered remedy selection for contaminated sediment sites in great detail, and the graphic shown here on the right outlines the general process to be followed when capping has been selected as part of your remedy. 00:03:04.000 --> 00:03:25.000 You will see this graphic throughout the training, as each trainer will use this graphic to identify where we are in the process and which sections of the guidance are related to a particular step in the process. 00:03:25.000 --> 00:03:41.000 Okay, you may have noted that Section 4 was missing from the previous slide. This training will not specifically cover Section 4 of the guidance. However, data needs from Section 4 will be touched on throughout the training as they inform all aspects of our discussion today. Section 4 mainly consists of. 00:03:41.000 --> 00:04:01.000 Table 4-1, a snapshot of which is shown here on this slide, which summarizes data needs to support chemical isolation layer design, modeling, construction, and monitoring. And you can access this table and the associated data needs in the online guidance. 00:04:01.000 --> 00:04:11.000 So, sediment capping objectives shown here include physical stabilization to provide physical isolation and prevent particulate transport. 00:04:11.000 --> 00:04:22.000 chemical isolation to limit migration and release of dissolved contaminants from underlying sediment, and the protection of benthic communities by preventing direct contact with underlying contaminated sediments. 00:04:22.000 --> 00:04:33.000 These objectives are the same as the 2014 guidance. However, today's training and the accompanying 2023 guidance focus on the chemical isolation function of CAHPS specifically. 00:04:33.000 --> 00:04:40.000 And with that, I'll give it over to Bhavna. 00:04:40.000 --> 00:04:45.000 Alright, thanks, Vanda. 00:04:45.000 --> 00:05:01.000 All right, Section 2 capping overview. This section basically provide details on capping objectives and particularly the chemical isolation function of the calf. 00:05:01.000 --> 00:05:21.000 So gapping can be a single layer or a multi-layer system of clean materials or a combination of materials or amendments to meet the objectives that has just described. The 3 primary objectives of physical destabilization, chemical isolation and protection of benthic community. 00:05:21.000 --> 00:05:38.000 And these objectives are generally interrelated and can be combined to achieve the site-specific performance objectives. Now, if site conditions are conducive, then a single-layer cap may serve multiple functions and achieve all these performance objectives. 00:05:38.000 --> 00:05:54.000 But in some cases, a series of layers may be required. And in this slide, we have a multi-layer cap system, and we'll go through the function of each of these cap layers. Now, although this guidance is mainly focused on the design of chemical isolation layer. 00:05:54.000 --> 00:06:10.000 It is important to understand the entire cap configuration because these different cap layers, they do contribute to the design of chemical isolation layer. And Deidre will elaborate further in the following section as well. 00:06:10.000 --> 00:06:26.000 So, let's take a look at the configuration of this multi-layer cap system here. The first layer that is placed right on top of contaminated sediment. We are mixing or consolidation can occur is the base or leveling layer. 00:06:26.000 --> 00:06:33.000 This layer creates an even or stable base on which rest of the cap layers can be placed. 00:06:33.000 --> 00:06:45.000 And it basically prevents mixing of chemical isolation layer with the contaminated sediment. It adds geotechnical stability and improves cap constructability. 00:06:45.000 --> 00:06:54.000 Uh, then chemical isolation layer, uh, this layer is designed to inhibit migration of contaminants from underlying sediment. 00:06:54.000 --> 00:07:08.000 Uh, and that can generally occur via adjection, diffusion, dispersion, myoturbation, or gas ablation. And design of this layer depends on the nature of contamination and hydrodynamic conditions. 00:07:08.000 --> 00:07:18.000 Then filter layer. This layer is intended to mitigate any mixing of chemical isolation layer from the upper erosion protection layer. 00:07:18.000 --> 00:07:33.000 And this layer is typically used when there is a difference in grain size between these two layers, and is typically constructed with medium-sized grain material or geosynthetics that serves as a transition layer. 00:07:33.000 --> 00:07:49.000 Then erosion protection layer. It's also known as armor layer. This layer is intended to protect physical integrity of the chemical isolation layer from the anticipated erosive forces that can be caused by hydrodynamic conditions or. 00:07:49.000 --> 00:08:04.000 navigational traffic. Now, it is important for the sites where there is a potential for cap disturbance due to these high erosive forces. Even for the low energy environment, a minimal protection or cover may be required. 00:08:04.000 --> 00:08:20.000 And this layer can be constructed from a range of coarse-grade material or some manufactured materials. Now, design of this layer is not a part of this guidance, but there are some references provided where you can find that information. 00:08:20.000 --> 00:08:36.000 Habitat restoration layer. This is the uppermost layer that accommodates benthic community after recolonization. The requirements for this layer is project specific and could be driven by permits and errors. 00:08:36.000 --> 00:08:58.000 This layer may require suitable stone size or a particular grain size, or even addition of some substrate to promote benthic life composition and thickness of this layer could be project specific. If fines are used, then we might need to consider a thicker layer to account for any losses or of sacrificial material. 00:08:58.000 --> 00:09:06.000 And there is a possibility that we might even need to replenish this layer based on the project-specific requirements. 00:09:06.000 --> 00:09:22.000 Um, now, I'll just emphasize this surface layer of surface of the cap constitutes BAZ, which is biologically active zone, and it will be referred throughout the training. 00:09:22.000 --> 00:09:47.000 Now, a range of cap configurations and materials can be used to accomplish performance objectives depending on the site conditions. The first column is same as the previous slide showing all the cap layers. Second column represents a scenario where a base layer may not be required, for example, for some of the dredge and cap projects. This layer may be required to stabilize drench residuals. 00:09:47.000 --> 00:09:59.000 decapping. But in some cases, we may decide to place amendments directly after dredging to address any residual contamination, and a separate base layer may not be required. 00:09:59.000 --> 00:10:19.000 Then third column shows a separate habitat restoration layer may not be required, and this could be the case if the erosion protection layer material provides a suitable habitat for recolonization, or even if the site is depositional, then a distinct habitat layer may not be required. 00:10:19.000 --> 00:10:24.000 unless there is a project-specific requirement for this layer. 00:10:24.000 --> 00:10:36.000 Fourth column represents a scenario where a filter layer may not be required, and this can be evaluated based on the material we select for the chemical isolation and erosion protection layer. 00:10:36.000 --> 00:10:52.000 Then this last column, this represents a single layer cap system where a single layer may serve multiple functions and can achieve more than one objective. This could be for the sites where there is a low potential for chemical migration. 00:10:52.000 --> 00:11:07.000 And in that case, a layer of clean materials such as sand or gravel can be used to basically create a physical barrier that can prevent direct contact for potential receptors from the contaminated sediment. 00:11:07.000 --> 00:11:17.000 And in that case, a multi-layered CAP system may not be required. 00:11:17.000 --> 00:11:37.000 So in the previous slides, we reviewed single layer cap single cat layer or a combination of cat layers that can be designed to meet the specific site specific performance objectives. The 3 most commonly referenced cap types are unamended granular caps, low permeability caps and amended caps. 00:11:37.000 --> 00:11:46.000 And these are basically based on the type of material we use for the chemical isolation function of the cap. 00:11:46.000 --> 00:12:05.000 Unamended granular caps, uh, they are typically constructed with inert materials such as sand, stone, or other natural materials. These gaps are permeable in nature, and they are generally intended to provide physical separation and increase the attenuation thickness. 00:12:05.000 --> 00:12:19.000 I select contaminants by preventing any direct contact of benthic organisms with the contaminated sediment. 00:12:19.000 --> 00:12:36.000 Low permeability caps. These are typically constructed of clay-based materials or geosynthetic liners, and these materials are designed to provide relatively impermeable or low permeability barrier that reduces the advective flux of contaminants. 00:12:36.000 --> 00:12:48.000 And these cats also provide physical separation and impedes upward flow of cool water and migration of contaminants. 00:12:48.000 --> 00:13:02.000 Now, amended caps. These caps have consist of wide range of reactive amendments. These caps are typically permeable. That allows upward flow of pool water and returned chemical migration. 00:13:02.000 --> 00:13:22.000 Uh, selection of amendment, that depends on the site's specific conditions and contaminants. For organic contaminants, typically activated carbon and organophilic clay-based amendments are used. If navel is present, then a combination of amendments could be used, uh, where organophilic clay could be used to address that. 00:13:22.000 --> 00:13:40.000 and activated carbon to address any dissolved phase contaminants. For sites with heavy metals, amendments such as appetite, zeolite, or siderite are typically used. And in Section 2 of this guidance, there is a table that summarizes all these different amendments. 00:13:40.000 --> 00:13:57.000 Then there are different placement techniques. These amendments can be either mixed with granular materials, such as sand, or they can be applied in bulk, in formulations that are commercially available, or they can be placed even in mat-based forms. 00:13:57.000 --> 00:14:12.000 We also have CAP models that have capability to evaluate these different amendments and commercially available formulations, and that will be covered in this training as well. 00:14:12.000 --> 00:14:20.000 Cap design considerations. So this slide illustrates 4 critical design factors that will be covered throughout the training. 00:14:20.000 --> 00:14:36.000 Chemical design criteria, it is important for the evaluation of chemical isolation layer thickness and selection of amendments that depends on type of contamination, level of contamination, and hydrodynamic conditions. 00:14:36.000 --> 00:14:53.000 Uh, physical design constraints. It's important for us to understand for the design and constructability of cats, how the site settings are, what the navigational requirements are, any geotechnical concerns, any presence of debris or a structure. 00:14:53.000 --> 00:15:04.000 Any particular habitat requirement. Then we need to have an understanding of hydrodynamic conditions and erosion potential or any slope stability concerns. 00:15:04.000 --> 00:15:20.000 Then permitting, it is important to understand permitting requirements and errors in the initial planning phase, as this there could be some requirements that may need to be considered during the design as well as at the time of cap construction. 00:15:20.000 --> 00:15:39.000 Then, lastly, constructability. It is important to understand constructability requirements from the initial design phase, and to understand how the gap will be constructed, and if there will be any construction constraints so that cap can be constructed as designed and specified. 00:15:39.000 --> 00:15:45.000 And with that, I'll pass it over to Deirdre. 00:15:45.000 --> 00:15:59.000 Thanks, Baba! Um, so as Bhamna was just showing, there are different types of capped configurations, different amendments that may be needed to meet your site goals. 00:15:59.000 --> 00:16:15.000 And when in designing a chemical isolation layer and defining what that thickness is going to be, or whether amendments are needed. We often turn to models. And Danny Reibel is going to get into the modeling later in this training. 00:16:15.000 --> 00:16:22.000 But before we dive into the modeling, we first need to understand what we're designing the cap to protect. 00:16:22.000 --> 00:16:31.000 And also what other considerations need to be taken into account. So in this section, which corresponds to section 3 of the guidance document. 00:16:31.000 --> 00:16:38.000 We're going to cover design criteria and other key considerations. 00:16:38.000 --> 00:16:53.000 So when we talk about performance targets. The goal is to reduce risk to human health and ecological receptors, and we've referred to these as remedial action objectives, or RAOs. 00:16:53.000 --> 00:17:03.000 And as you can see from these examples, REOs are broad in nature. So, for example, I'll take the first one, which is human health. 00:17:03.000 --> 00:17:12.000 Reduce risks to adults and children from incidental ingestion and dermal exposure and consuming contaminated fish and shellfish. 00:17:12.000 --> 00:17:23.000 Um, so you can see these are broad, but when we design a cap, we need our criteria to be more specific, and we need it to be quantitative. 00:17:23.000 --> 00:17:33.000 So that's where the design criteria come into play. The design criteria are requirements that the cap must satisfy. 00:17:33.000 --> 00:17:39.000 And we can break those down into the questions of what, where, and when. 00:17:39.000 --> 00:17:56.000 So when we talk about the what we're talking about either concentrations that we need to meet or a flux reduction we need to meet. When we get into the where we're talking about the depth of compliance or point of compliance. So the depth within the chemical. 00:17:56.000 --> 00:18:01.000 or the depths of the chemical isolation performance targets apply. 00:18:01.000 --> 00:18:15.000 The where is also spatial scales. So surface weighted average concentrations or swack basis over the specified area, or maybe you have to meet your criteria on a point by point basis. 00:18:15.000 --> 00:18:28.000 And then finally we get into the when. And so the when is the timeframe that the chemical isolation performance targets apply, and we refer to that as our design life. 00:18:28.000 --> 00:18:40.000 So, here's a few examples. When you read each one, you'll see that each of these has components to it that answer those questions of what, where, and when. 00:18:40.000 --> 00:18:46.000 So if I take the first one, the pore water concentration of contaminant X. 00:18:46.000 --> 00:18:50.000 shall not exceed one nanogram per liter. So that's the what? 00:18:50.000 --> 00:19:01.000 It shouldn't exceed that at a depth of 10 centimeters. That's the where and then over 100 years, and that's the when. 00:19:01.000 --> 00:19:10.000 And so if you look at each of these examples, each of them have those components of the what, the where, and the when. 00:19:10.000 --> 00:19:16.000 And so that allows us a quantitative way of evaluating the cat performance. 00:19:16.000 --> 00:19:26.000 So here I'd like you to think about potential issues you've encountered when establishing the remedial goals at your site. 00:19:26.000 --> 00:19:38.000 One example that I'm going to get into is uncertainty when the design criteria are based on a solid phase concentration. And that's particularly true for organic compounds. 00:19:38.000 --> 00:19:45.000 And on the next slide i'll show you what I mean. 00:19:45.000 --> 00:19:55.000 So here we're talking about the what. and, as I mentioned, the what could be a specific concentration or a flux that needs to be met. 00:19:55.000 --> 00:20:04.000 So, in the case, if we're designing. The design criteria are based on concentration. We have 2 options. 00:20:04.000 --> 00:20:11.000 The criteria could be on a pore water basis, or it could be on a solid phase basis. 00:20:11.000 --> 00:20:24.000 And so, when evaluating the performance of a cap, either during design or later in monitoring after it's constructed, it's really helpful for the design criteria to be on a pore water basis. 00:20:24.000 --> 00:20:33.000 And that's because the presence of organic carbon in the cap itself will influence the concentrations on a solid phase basis. 00:20:33.000 --> 00:20:45.000 And so, it's just easier to understand if a cap is performing as expected if the criteria is on a pore water basis, and I'll I'll show you what I mean with this example. 00:20:45.000 --> 00:20:58.000 So on the left, this is you can see a graphic of the CAP profile. So we have our sediment. Above that we have a layer of sand, and above that we have what we call a biologically active zone. 00:20:58.000 --> 00:21:13.000 Then there's a graph. This is output from a capson model on the y-axis, we have depth, so that's corresponds to like the depth of those cap components. And on the x-axis, we have concentration, um, and it's pore water concentration, micrograms. 00:21:13.000 --> 00:21:26.000 per liter. And so you can see, as you move from the sediment to the sand to the biologically active zone, concentrations are decreasing as you move towards the surface. 00:21:26.000 --> 00:21:36.000 And there's a little call-out that shows you, um, that Zoom's in on that biologically active zone. So you can see the concentrations decreasing. 00:21:36.000 --> 00:21:41.000 Now, the graph on the right is the same exact model simulation. 00:21:41.000 --> 00:21:46.000 But the results are unabsorbed phase basis, or a solid phase basis. 00:21:46.000 --> 00:22:00.000 And again, using that little zoomed-in circle to the right, you can see that the concentrations in the biologically active zone, that BAZ, are affected by what we assumed. 00:22:00.000 --> 00:22:11.000 The total organic carbon would be. And so… The higher the total organic carbon is in that layer, the more absorption that's going to happen, and then that concentration becomes higher. 00:22:11.000 --> 00:22:20.000 And… Also, if we assume the Toc is lower, then the concentration is lower. Right? So. 00:22:20.000 --> 00:22:39.000 Knowing what that TOSC is and what it's going to be in the future is really important if you're going to look at things on a sorbed phase basis. So by setting your design criteria to a pore water concentration, you can avoid that effect. 00:22:39.000 --> 00:22:56.000 So another complicating factor for designing a cap and you're and defining your design criteria. Our background concentrations. So in dynamic environments, the background concentrations affect the surface sediment. 00:22:56.000 --> 00:23:00.000 And hence, they affect the surface of the cap. 00:23:00.000 --> 00:23:08.000 So this graphic on the left shows a cap on top of sediments with no deposition. 00:23:08.000 --> 00:23:20.000 Um, I've overlaid an X and Y axis on top of this graph, and so the pink line at the bottom represents the concentrations in the sediment to pore water. 00:23:20.000 --> 00:23:27.000 So, if I click here, you'll start to see that the concentrations. 00:23:27.000 --> 00:23:34.000 Yeah. Sorry. Yep, you'll see that the concentrations are moving up. 00:23:34.000 --> 00:23:44.000 Through the cap. as… And then on the right… Yeah, I'm sorry. 00:23:44.000 --> 00:24:03.000 This example is now showing how deposition. will affect that. And so this is where we have deposition and the depositing particle particles have an elevated CoC concentrations. 00:24:03.000 --> 00:24:09.000 So, as I move through this. You'll see that the concentrations at the surface. 00:24:09.000 --> 00:24:18.000 are being affected. by the concentrations in that depositing particles. 00:24:18.000 --> 00:24:26.000 So, knowing what your background concentrations are may help you define realistic criteria. 00:24:26.000 --> 00:24:45.000 And these graphics also highlight the difference between cap effectiveness and remedy effectiveness. So in both cases, the cap may be working as intended, and that's what we refer to as cap effectiveness. In both cases, the cap is resulting in concentrations decreasing. 00:24:45.000 --> 00:24:56.000 As they're migrating up through the cap. But in the case on the right, although the cap is performing as expected, the remedy may not be. 00:24:56.000 --> 00:25:00.000 performing, and you may not have cut off the source. 00:25:00.000 --> 00:25:11.000 And so remedy effectiveness versus cap effectiveness is an important distinction, particularly during long-term monitoring after the cap is constructed. 00:25:11.000 --> 00:25:18.000 And Tamara, we'll get into that later in this training. 00:25:18.000 --> 00:25:29.000 So the next question that we want to answer is the where. So we can talk about the where as the point of compliance. 00:25:29.000 --> 00:25:49.000 And the point of compliance is directly related to our remedial goals. So this is a graph that shows a cap with a chemical isolation layer and an erosion protection layer or habitat layer. And in this case the same layer is serving both those functions, both habitat and erosion protection. 00:25:49.000 --> 00:25:55.000 So for remedial goals that are established to be protective of benthic organisms. 00:25:55.000 --> 00:26:08.000 The point of compliance is within or at the bottom of that biologically active zone, because this is the zone where benthic organisms are going to live and feed. 00:26:08.000 --> 00:26:17.000 Now, for remedial goals that are established to be protective of ambient water quality criteria or fish at higher trophic levels. 00:26:17.000 --> 00:26:34.000 Uh, representative surface water conditions. The point of compliance is near the cap surface where the chemicals will flux to the surface water, or in the surface water itself. 00:26:34.000 --> 00:26:42.000 Now, a concept that is discussed in the 2023 guidance is the design evaluation depth, and. 00:26:42.000 --> 00:26:47.000 This is the depth at which you will design the cap to meet the target criteria. 00:26:47.000 --> 00:26:59.000 So this is an example of a cab designed to be protective of benthic organisms, and therefore the point of compliance is again in that biologically active zone. 00:26:59.000 --> 00:27:05.000 The design evaluation depth may be the same as that point of compliance. 00:27:05.000 --> 00:27:21.000 But depending on the capped environment, there may be reasons to design to design the cap to assess performance at depths other than your point of compliance, and some of these reasons include the presence of large armistone. 00:27:21.000 --> 00:27:30.000 or confounding effects from deposition. And I'm going to get to some examples in the next few slides. 00:27:30.000 --> 00:27:35.000 So this is an example of a cap with large armor stone. 00:27:35.000 --> 00:27:47.000 You can see that large armor stone at the top of the cap. You can, you know, I mean, this is for illustration purposes, but you can see that there's lots of void space, and the void space has a lot of surface water in it. 00:27:47.000 --> 00:28:01.000 So, the large armor stone is therefore not likely to provide attenuation of your chemicals. The large pore space is more representative of surface water, unless it fills in from depositing material. 00:28:01.000 --> 00:28:18.000 So, in this case, we have large armor stone that's not filled in. It may be more appropriate to evaluate cap effectiveness below that armor stone. So in this case it would be like in that filter layer. 00:28:18.000 --> 00:28:33.000 So continuing with that same example of a cap that's designed to be protective of benthic organisms. So once the cap is placed, the benthic organisms will start to reoccupy the top of the cap, so that biologically active zone is at the top of the cap. 00:28:33.000 --> 00:28:38.000 And the point of compliance is again in that biologically active zone. 00:28:38.000 --> 00:28:47.000 So now we're going to consider deposition. So with deposition over time. So in this graphic we're looking from. 00:28:47.000 --> 00:28:59.000 left to right on the graphic. The point of compliance rises as that biologically active zone continues to transition into that newly deposited material. 00:28:59.000 --> 00:29:07.000 So, if the deposit material is clean, it may contribute to natural recovery, and then provide that additional attenuation. 00:29:07.000 --> 00:29:14.000 So in this case, you may choose this as your design evaluation depth as well. 00:29:14.000 --> 00:29:30.000 However, you also may choose a design evaluation depth that is deeper, avoiding the influence of those depositing particles or that depositing material. And so by doing this, you would be assessing the effectiveness of the chemical isolation layer alone. 00:29:30.000 --> 00:29:42.000 to provide your attendees. So, even if designing a cap to meet criteria at this deeper depth, you could also understand the anticipated. 00:29:42.000 --> 00:29:55.000 concentrations in your biologically active zone, and that will just help to set expectations for later, perhaps like during monitoring. 00:29:55.000 --> 00:30:13.000 So now this is an example that combines the last 2 concepts. So it's large armor stone, but it's also filled in from deposition. And so in this case, with the infilling, it'll behave similar to the the deposition example that I just showed on that last slide. 00:30:13.000 --> 00:30:33.000 So again, you can, you know, set your design evaluation depth to either the point of compliance or to a to a deeper depth. That deeper depth B, which avoids the influence of the depositing particles and evaluates the effectiveness of the chemical isolation layer. 00:30:33.000 --> 00:30:43.000 All right. So now we move on to the question of when. And the design life answers the question, when or for how long? 00:30:43.000 --> 00:30:53.000 The design life is the minimum period over which the cap is designed to meet the target criteria. 00:30:53.000 --> 00:31:04.000 So caps are designed to provide long-term risk reduction. So a typical design life that is widely accepted is 100 years. Could be shorter depending on your circumstances. 00:31:04.000 --> 00:31:08.000 So this graph shows an example output from CAPSIM. 00:31:08.000 --> 00:31:20.000 The blue line shows the predicted concentrations at a depth of 5 centimeters from the surface of the cap, and it shows this over a 100 year simulation. 00:31:20.000 --> 00:31:28.000 In this example, the cap was designed to meet the criteria, which is shown as the pink horizontal line. 00:31:28.000 --> 00:31:44.000 and is doing that for 100 years, and you'll see that the concentrations at 100 years. So that blue line are still less than the criteria and are expected to remain less than the criteria for more than 100 years. 00:31:44.000 --> 00:31:59.000 So although we designed a cap for 100 years, which is its design life, its performance life may be longer, especially when you take conservativism into the design process. And there's a number of factors that. 00:31:59.000 --> 00:32:07.000 add conservativism to a cap design. And I'll get to those here. 00:32:07.000 --> 00:32:24.000 And so there's a number of ways that conservativism is built into the design a lot throughout the entire process. We'll start with the design criteria. A lot of times we perform risk assessments, and there's conservativism built into those risk assessments. 00:32:24.000 --> 00:32:40.000 When we do the modeling, the input parameters we build conservativism in there. Some of the inputs to the models that have the largest influence on results are the groundwater seepage rates and the contaminant concentrations. 00:32:40.000 --> 00:32:51.000 Again, we may try to be more conservative with those inputs. Again, partitioning characteristics have a big impact on the results, and deposition rates. 00:32:51.000 --> 00:33:12.000 If you have deposition at your site. Um, then we move on to the material specifications during the design. So this is where we would specify a minimum thickness and an amendment dose to meet the criteria. Again, we can be conservative there. And then, when we get into the actual construction. 00:33:12.000 --> 00:33:30.000 And the placement of these materials, the contractor may place more than what's specified just to ensure that they meet the criteria for or the specs for the construction and the placement of those materials. 00:33:30.000 --> 00:33:40.000 Alright, so now that we've gone through the process of defining the design criteria. We want to consider other factors that may impact the design of a cap. 00:33:40.000 --> 00:33:56.000 So we want to know if there are any constraints on cap thickness. Some examples might be that you need to, you know, keep the cap thin for flood control, or you may have navigation requirements. 00:33:56.000 --> 00:34:02.000 In this example, I'm going to use navigation as the example. And so. 00:34:02.000 --> 00:34:07.000 Due to navigation purposes, we may have to maintain a minimum water depth. 00:34:07.000 --> 00:34:24.000 Right, so that means that we're only left with a certain… height or thickness remaining for the cap placement. So let's just zoom in now on that, on that what's left, or what's remaining for the cap. 00:34:24.000 --> 00:34:37.000 So now consider that other layers are needed, and how much room we have left for the chemical isolation layer. And this is referred to in the 2023 guidance as the top down approach. 00:34:37.000 --> 00:34:45.000 So we may need a base layer right? If we need to create an even surface. I think Babna talked about that in the last section. 00:34:45.000 --> 00:34:50.000 Um, we want to protect the chemical isolation layer. So we need armor layer. 00:34:50.000 --> 00:35:02.000 Um, depending on the difference in size of what our chemical isolation layer is going to be, and the size of the armor layer, we might also need a filter layer. 00:35:02.000 --> 00:35:09.000 And so then that leaves us with how much room is remaining for that chemical isolation layer. 00:35:09.000 --> 00:35:19.000 And so if that thickness isn't sufficient, we may need an amendment, or, you know, to maintain that thinner. 00:35:19.000 --> 00:35:28.000 thickness, or we might need to dredge to, you know, create more room. 00:35:28.000 --> 00:35:40.000 So in talking about the amendments. So CAC amendments are often required to meet the performance targets. Amendment types depend on your chemicals of concern. 00:35:40.000 --> 00:35:57.000 Um, you can have a combination of amendments that may be needed. It really depends on what chemicals are at your site. Um, you know, you might have an amendment that's needed for an organic chemical, and then you might also need a different amendment that works for, like, a metal, for example. 00:35:57.000 --> 00:36:06.000 Um, these amendments can be placed in discrete layers, they can be mixed with other materials, or they can be added directly to the sediment. 00:36:06.000 --> 00:36:23.000 We do recommend data collection to support the modeling for the the cap design. And then also when when considering these amendments and and where they're going to be placed. You also want to consider the benthic community impacts. 00:36:23.000 --> 00:36:38.000 Um, there are… there are some literature that may indicate some toxicity, again, depending on where the amendment is in relationship to where the benefit of organisms will be. 00:36:38.000 --> 00:36:56.000 All right. So section 3.4 of the guidance document provides a comprehensive list of like other considerations listed. Here are just a few of the fundamental characteristics to consider. But I encourage you to read Section 3.4 for more information. 00:36:56.000 --> 00:37:06.000 Um, so when designing a cap and kind of setting up, you know how how you're going to design it, you might want to understand the spatial differences at the site. 00:37:06.000 --> 00:37:22.000 that can affect your chemical isolation layer. This might help you to optimize your cap design, particularly if you, like, need a very robust cap, maybe you can limit the area which that robust cap will need to be designed. 00:37:22.000 --> 00:37:35.000 Um, based on maybe differences in chemical concentrations, the contaminant distribution. And this includes geochemistry, which can also be important for some chemicals. 00:37:35.000 --> 00:37:52.000 Maybe there's a spatial difference in Navel presence. You can have differences in your seepage rates. Again, that seepage rate is a key parameter for cap design. And then you might have different parts of the site which have deposition and erosion erosion potential. 00:37:52.000 --> 00:38:14.000 And then finally, we want to think about the benefit community structure and the bioturbation. So bioturbation depths of 5 to 10 centimeters are common. But site specific data may be needed from benthic surveys to inform the model, and also the depth over which said bioaturbation occurs and where those benthic organisms are living and feeding. 00:38:14.000 --> 00:38:35.000 may also inform that point of compliance. So to wrap up this section, we talked in detail about the design criteria. And with each question of the what, the where, and the when we discussed complicating factors, and how we might handle those. 00:38:35.000 --> 00:38:51.000 We also spoke about design constraints with an example of that top down approach with that navigation limitation example. And then, finally, we gave a few examples of other site characteristics that should be considered for the chemical isolation layer design. 00:38:51.000 --> 00:38:59.000 And again, there's a lot of information there in Section 3. So I do encourage you reading that. 00:38:59.000 --> 00:39:08.000 And with that, I'll introduce Danny Reibel, who is going to talk about the chemical isolation layer modeling. 00:39:08.000 --> 00:39:24.000 Thank you, Deirdre. I appreciate the opportunity to to build on the topics that she's been discussing, and that the other team members have been discussing, and and say, Well, okay, we've talked about models and various aspects. 00:39:24.000 --> 00:39:38.000 How are we going to make that work? And… Make sure that I'm… yeah, I am controlling the slides. So how are we going to make that work with an actual. 00:39:38.000 --> 00:39:49.000 design modeling. So we're going to talk about some of the aspects of translating this conceptual model, the conceptualizations that we've been talking about into a model. 00:39:49.000 --> 00:39:56.000 And without a lot of the details, but to give you at least an overview of that process. 00:39:56.000 --> 00:40:13.000 Uh, we're going to address, well, why are we using a CAP model as opposed to some other sort of model? What models are available? What are the key things that we should be focused on to ensure that our results are valid, and that is related as well to. 00:40:13.000 --> 00:40:20.000 What is the model most sensitive to? What are the most uncertain parameters? 00:40:20.000 --> 00:40:24.000 So some of the things that we might do with the model is. 00:40:24.000 --> 00:40:32.000 you know, we have a design criteria, we have a location that we're going to use to evaluate our design. 00:40:32.000 --> 00:40:49.000 Well, how thick of a contaminant isolation layer do we need to be able to achieve those goals? What are the composition of that? We're going to add an amendment like activated carbon. How much carbon are we going to need? And again, evaluate some of the sensitivity to these. 00:40:49.000 --> 00:40:58.000 Is that if we miss that carbon match, or if we end up with. 00:40:58.000 --> 00:41:14.000 is our results, are our results sensitive to that composition or that thickness? Or perhaps it's not very important at all, and that makes give us more comfort in how we apply the model and and ultimately. 00:41:14.000 --> 00:41:33.000 design and build the chemical isolation layer. We can also use a model in the, you know, we're obviously trying to predict forward in time. We're trying to evaluate, say, at 100 years of a lifetime of a cap, what sort of performance do we expect? Well, during that interim period. 00:41:33.000 --> 00:41:38.000 We have an opportunity to then evaluate how well is the. 00:41:38.000 --> 00:41:55.000 The monitoring data we're collecting compared to what we were predicting. And so those are all effective uses of a model, and we'll talk about, you know, how to do some of those. So first of all, why CAP models? 00:41:55.000 --> 00:42:05.000 There are surface water models, there are groundwater models, but neither of them focus a lot of attention on the sediment. 00:42:05.000 --> 00:42:23.000 near surface sediment environment itself, which is where the cap is operating. It's where contaminants are migrating. Where we're worried about benthic organisms, it's just that 10 to 20 centimeters, sometimes as much as a meter. 00:42:23.000 --> 00:42:27.000 Where we're focusing all of attention with our CAP model. 00:42:27.000 --> 00:42:45.000 Groundwater models can tell us a lot about the water that's coming to our surface water interface or sediment water interface. The river models or the water surface water models can tell us a lot about the behavior, the processes in the surface water. 00:42:45.000 --> 00:43:00.000 But if we're looking at detail at that sediment-water interface where a lot of processes are going on, it's a perfect storm of physics, chemistry, and biology that are occurring in those upper tens of centimeters in sediments. 00:43:00.000 --> 00:43:04.000 And that's where a CAP model comes into play. 00:43:04.000 --> 00:43:15.000 Some of those processes. Certainly, there's a potential for erosion and evaluating that. That does go into the domain of the surface water modeling. 00:43:15.000 --> 00:43:30.000 But in general, we try hard not to have erosion. We try to design, say, an armoring layer that you saw some examples of in a way that it will be protective even under high flow events. 00:43:30.000 --> 00:43:50.000 And if there's one thing that we can describe pretty well, it's the… erodibility of non-cohesive sediments, and that's what we make our armor layers from. We don't do it out of cohesive sediments. We're making them out of materials that are non-cohesive, and we understand when they're going to erode. 00:43:50.000 --> 00:44:06.000 So we're going to ultimately our purpose there, and we don't need a CAP model to do that, is just to ensure that our armoring layer is protective into the max flow. Often the bigger challenge is figuring out what might what type of flow should we? 00:44:06.000 --> 00:44:19.000 Protect against. But once we have a stable layer, that's where all the processes of the chemical isolation layer and the the modeling for of that chemical isolation layer come into play. 00:44:19.000 --> 00:44:36.000 The mobile phrase of the contaminants or the pore water. There's a lot of redox changes that occur in the near surface that could affect chemistry. We have the organisms that really dominate behavior in the upper few centimeters, and they're often the object of. 00:44:36.000 --> 00:44:55.000 What we're trying to protect as well. The benthic boundary layer, which does relate what's happening at the surface to the overlying water, and there's some other processes like hypereach exchange. So there's just a few of the processes that occur at the sediment-water interface, and those are what CAP models are designed to describe. 00:44:55.000 --> 00:45:12.000 Recovery is one of those models. It's from the Corps of Engineers, and it breaks our sediment up into various layers. The surface layer, because of bioturbation activity, is generally assumed to be well mixed, and then there are other layers. 00:45:12.000 --> 00:45:25.000 That have a variety of processes, transport between dissolved and particular fractions, advection, diffusion, deposition, erosion, all of these things. 00:45:25.000 --> 00:45:39.000 can affect the recovery model. We also have CAPSIM, which is the model that we've been working on for a number of years at Texas Tech, and. 00:45:39.000 --> 00:45:54.000 It interacts through a graphical user interface, and a lot of people find that pretty helpful. And so it's probably the most widely used model at this point for describing the future behavior of a cap and the effectiveness of a chemical isolation layer. 00:45:54.000 --> 00:46:12.000 Again, it breaks up the sediments into different layers that have different functions and different processes, and tries to describe the chemical behavior in each of those systems. Capsim actually has an awful lot of. 00:46:12.000 --> 00:46:26.000 capability that most people don't really use, such as the ability to model multiple reactions simultaneously that are coupled. So, for example, you could use it to model biogeochemical conditions. You could… we've used it to model. 00:46:26.000 --> 00:46:44.000 Perhaps 15 simultaneous coupled relationships that relate the various redox sensitive species and contaminants that respond to those. But again, most people don't really make use of that. It can model sorption kinetics or. 00:46:44.000 --> 00:46:55.000 equilibrium. Most people buy… only deal with equilibrium. But there is that opportunity if you're worried about, for example, whether the activated carbon you added. 00:46:55.000 --> 00:47:05.000 is going to have significant limitations because you use granular carbon versus powder. You can assess those sort of issues within the capsim. 00:47:05.000 --> 00:47:14.000 It also includes some typical properties of some commercial materials like Aquagade or. 00:47:14.000 --> 00:47:22.000 some reactive core mat, for example, those are available there, and it has a lot of built-in. 00:47:22.000 --> 00:47:43.000 default values that are useful as well. But it is ultimately a tool to try to predict the rate and movement of contaminant migration, the behavior long term of these contaminants through chemical isolation layer. 00:47:43.000 --> 00:48:00.000 So one of the most important questions is what contaminants or what processes are the most important? Where should you focus your attention if you're trying to define and refine parameters? Certainly identifying which contaminants you want to try to simulate. 00:48:00.000 --> 00:48:16.000 Those that are strongly sorbing versus those that are not as sorbing certainly have very different behavior. So identifying that contaminant, what is going to control both exposure and risk, and what's going to control the design of your cap is pretty critical. 00:48:16.000 --> 00:48:31.000 What concentration should we design against? Is it perhaps a maximum, or perhaps a 85% tile in the concentration distribution defining and getting agreement. 00:48:31.000 --> 00:48:40.000 with stakeholders as to what you're going to employ for your contaminant and the concentrations you're trying to protect against are key. 00:48:40.000 --> 00:48:52.000 Certainly, the absorption coefficients of those contaminants in the chemical isolation layer are key. In general, we rarely try to design caps that are actually reactive. 00:48:52.000 --> 00:49:09.000 Instead, they're slowing migration primarily through sorption, so understanding the sorption coefficients are key, as well as relating our sediment concentrations to what's in the interstitial water, which is where it's mobile and moving through a cap. 00:49:09.000 --> 00:49:20.000 Because the movement through the water is the key, those groundwater upwelling rates are a very important model input, and one of the most difficult to assess. 00:49:20.000 --> 00:49:36.000 If we have a strongly upwelling groundwater system, moving into the water, a gaining stream at very high rates, it's going to have a completely different effect on the contaminants in the chemical isolation layer than if that is. 00:49:36.000 --> 00:49:42.000 negligible. Sediment deposition is something that we often don't take into account. 00:49:42.000 --> 00:49:55.000 Because we're unsure how well it will work far into the future. But if there's any significant deposition, it can very much enhance the performance of a chemical isolation layer. 00:49:55.000 --> 00:50:08.000 recognize that much of the recovery we often see at settlement sites are associated with natural deposition and natural recovery. And of course, that's just isolating over time the contaminants with a natural cap. 00:50:08.000 --> 00:50:26.000 And so knowing what those might be could be very beneficial. Again, we often don't make use of that because we're a little uncertain as to how well they be or we're trying to do a conservative design. And of course, where we're going to evaluate the cap design is also extremely important. 00:50:26.000 --> 00:50:36.000 And one of the issues is not necessarily evaluating our design right at the sediment water interface. 00:50:36.000 --> 00:50:56.000 The, uh, at the sediment-water interface. those concentrations that we see there are strongly controlled by how fast we move contaminants from the surface to the overlying water. So that benthic boundary layer. And so I can modify the performance. 00:50:56.000 --> 00:51:08.000 of my cap a lot by changing the performance… movement in the water. Well, that's not designing our chemical isolation layer. That's why we don't necessarily use that to estimate. 00:51:08.000 --> 00:51:24.000 and evaluate our designs. So we… it can be important that intensity, the sediment water exchange, but in general, it's not very important, and it's especially not very important where we're often set our compliance point. 00:51:24.000 --> 00:51:40.000 The kinetics absorption onto strongly sorbing phase. This is the granular versus powdered activated carbon can be important, but only in those systems where there is a very dynamic, that is, high upwelling. 00:51:40.000 --> 00:51:50.000 very thin layers, low amounts of carbon. Like, if I'm trying to put 1% activated carbon into a thin layer of sediment with. 00:51:50.000 --> 00:52:02.000 pretty high upwelling rates. Kinetics of that sorption could be important. If I'm looking at a thick layer or a lot of carbon, not so important. 00:52:02.000 --> 00:52:19.000 If we are dealing with non-conservative contaminants where there is some reaction, it'd often be important. It will be useful, at least, to identify what those kinetics of those reactions are, and certainly capsa can take that into play. 00:52:19.000 --> 00:52:28.000 We often assume that these compounds are long-lived, and they don't react, and that's just a measure of conservatism. 00:52:28.000 --> 00:52:47.000 Uh, but when we're looking at. decadal or even longer time scales, a lot of these contaminants will, in fact, react over time and taking that into account, at least in a sensitivity analysis, could be useful and important. 00:52:47.000 --> 00:53:07.000 I think it's always important to recognize when we're using a model, we're looking at. We break in the capping modeling effort. We tend to break up areas into sub areas. That is, we're looking at specific areas where a particular design of a cap might be appropriate, and we're worried about. 00:53:07.000 --> 00:53:27.000 how an area is going to respond. basically dealing with contaminant information, maybe at a few points within that area. But the overall performance is about capping as an aerial remedy. We're trying to protect the waterway, and it's. 00:53:27.000 --> 00:53:44.000 not a a point by point remedy, even though we often design it and model it as such. It's also important to recognize that a cap is not like a balloon. If we core it, for example, to see how it's behaving after 10 years, it's not going to let all the contaminants out. 00:53:44.000 --> 00:53:55.000 In general. So, you know, again, we're looking at performance over an overall area, and as a result, statistical measures, for example, a. 00:53:55.000 --> 00:54:14.000 85th percentile of a contaminant concentration as a design remedy is often quite appropriate, not necessarily design the entire site for the worst case. I mentioned before being careful of interpreting concentrations of the cap water interface right at the interface. 00:54:14.000 --> 00:54:24.000 What happens there is often controlled by what happens in the water. And so we're designing to that, not necessarily designing the chemical isolation layer. 00:54:24.000 --> 00:54:33.000 The flux can be a little better than concentration, and that's the point that the last box on this slide is trying to get at. 00:54:33.000 --> 00:54:48.000 Now, the question of model uncertainty and sensitivity. Certainly, we don't know all the model parameters. Some of them are more important than others. And how do we determine that? And how did I identify which were the most important parameters is through. 00:54:48.000 --> 00:55:04.000 It's one of the most important and most useful aspects of the model. We can evaluate the sensitivity of the results to the specific parameters, and then we can focus our attention on those parameters that always that. 00:55:04.000 --> 00:55:20.000 will… are boast uncertain, but also because of their uncertainty, the results are sensitive to their values. And those are the values in the upper right. Things that are uncertain, but don't really affect our conclusions. 00:55:20.000 --> 00:55:32.000 aren't very important things that are. That we know very well, obviously, they don't hurt our conclusions very well. But again, those that we. 00:55:32.000 --> 00:55:45.000 are both uncertain, and that affect our results is where we need to focus our attention. And the model is a perfect tool to play what-if games to evaluate that. 00:55:45.000 --> 00:56:00.000 Oops, I was gonna show one slide and you've seen some others, but just as an illustration, this sort of things that you get out of CAPSIM or recovery is predictions of concentrations, for example, over time. 00:56:00.000 --> 00:56:16.000 But you could also use it to predict fluxes in a given cap environment. You could get it to different contaminants. You could look at solid concentrations. You could look at solid mixing. There's a variety of outputs that it can. 00:56:16.000 --> 00:56:27.000 calculate for you. And again, you can use this to evaluate sensitivity. How long is it going to take to to migrate through my cap? 00:56:27.000 --> 00:56:43.000 What if I change that mixture that's in that cap, the amendment? How is that going to affect the results? These are all games that you can play with the modeling with that. Let's stop and open it up for a round of questions. 00:56:43.000 --> 00:57:01.000 All right. Thanks, Danny. As Danny mentioned, we have reached our 1st Q&A break of the training. We do have a couple questions I can ask the trainers at this break. Just a reminder, you can use the Q&A pod at any time during today's training, and we will have one more chance to. 00:57:01.000 --> 00:57:19.000 Answer your questions at the end of the training today. So the first question we have, what type of monitoring is required once taps are in place? What are the cost estimates for continued monitoring? Sorry. 00:57:19.000 --> 00:57:23.000 Actually, we have a monitoring section at the end. 00:57:23.000 --> 00:57:35.000 So, maybe hold that question? 00:57:35.000 --> 00:58:02.000 Sure, yeah, I was going to mention that we were probably going to get into this later in the training. We'll see if that question does get answered. If not, we will return to it at the end of the training. Another question I have for the trainers is the goal of a sediment cap designed to perform significantly better than natural recovery? 00:58:02.000 --> 00:58:07.000 Well, this is Danny, and I guess I might just suggest that. 00:58:07.000 --> 00:58:37.000 If you are trying to manage the risks at a site, and you find that natural recovery is insufficient or not moving fast enough. I mean, that's exactly why we pursue some sort of remedy, such as capping. 00:58:40.000 --> 00:58:46.000 All right. Thanks, Danny. I'm just going to ask one more question before we continue with the training. 00:58:46.000 --> 00:59:03.000 How much does the type of climate affect the type of cap that is used at a particular site? 00:59:03.000 --> 00:59:13.000 Well, it doesn't seem like anybody's jumping on that one. So again, I will have some comments, and there certainly are some. 00:59:13.000 --> 00:59:25.000 regional issues, and I'm… but when you're talking about climate in this context, I'm assuming you're referring to conditions such as in the north, where you might have. 00:59:25.000 --> 00:59:37.000 Uh, icing over in the winter. That's an issue that in some specific areas, the formation of ice dams can compromise the cap. 00:59:37.000 --> 00:59:45.000 In general, I would say that with a few specific exceptions such as that. 00:59:45.000 --> 01:00:00.000 that regional climate has pretty minimal impact on the cap design. But there are some specific examples, and I just alluded to one. 01:00:00.000 --> 01:00:12.000 All right. Thanks, Danny. I don't see any other. Oh, there was one more question that came in once again. 01:00:12.000 --> 01:00:29.000 should cap still be used whenever there is cleanup that meets required State levels for an Mfa. But there is still contaminant within the material. 01:00:29.000 --> 01:00:41.000 Don't know if the trainers have any response to that question just came in. 01:00:41.000 --> 01:00:46.000 Um, I think this is Deirdre. I think that. 01:00:46.000 --> 01:00:56.000 Typically, like, when we're designing a cap, we we generally try to design it to meet a certain criteria. So if. 01:00:56.000 --> 01:01:09.000 If the cleanup already addressed. the concentrations and concentrations in your sediment are already less than your targets, then a cap is probably not needed. 01:01:09.000 --> 01:01:18.000 But if if there is still contaminant in your material, you would. You would just, and you want to address it. You would just need to to know what. 01:01:18.000 --> 01:01:27.000 concentration is acceptable. Maybe from a risk perspective. Um, and then design the cap to meet that criteria. 01:01:27.000 --> 01:01:35.000 I'm not sure if that answered the question or not. 01:01:35.000 --> 01:01:55.000 Great. Thanks, Deirdre. Emily, I think asked that question. If you have any follow up questions, just continue to use that Q. And a pod, and we will hopefully get to them. All right. I will go ahead and continue on with the training. So thank you all for interacting with the Q. And a pod, and we will. 01:01:55.000 --> 01:02:10.000 Like I mentioned, have one more opportunity at the end to answer more questions. So I will now turn this over to Mike Ellis from Barr Engineering to get us into the next module. 01:02:10.000 --> 01:02:18.000 Thank you, Taylor. So this next module will discuss constructability considerations for. 01:02:18.000 --> 01:02:26.000 the cap, or I should say the chemical isolation layer. So far we've discussed, um. 01:02:26.000 --> 01:02:31.000 How do we design a cap and important considerations when evaluating an appropriate cap. 01:02:31.000 --> 01:02:40.000 In this section, we'll focus on, um, how to… kind of incorporate that design into construction specifications, and how. 01:02:40.000 --> 01:02:51.000 to conduct appropriate quality control during construction. Uh, next slide, please. 01:02:51.000 --> 01:03:05.000 Um, so just this kind of sequence reiterates what I mentioned on the previous slide. So important things that we'll discuss from this module are construction, quality assurance, quality control. 01:03:05.000 --> 01:03:17.000 Um, and things to document, uh, during the construction of a cap that would be important to incorporate in a construction completion report, um, or as-built drawings for the project. 01:03:17.000 --> 01:03:28.000 Next slide, please. Um, so the figure on this slide is one that we've shown previously, um, conceptual figure. 01:03:28.000 --> 01:03:39.000 of sediment cap with a chemical isolation layer. And some of the most important constructability considerations are listed here regarding material placement. 01:03:39.000 --> 01:03:54.000 And, um, mixing. And if you could just imagine, you know, a sediment cap with multiple layers like the conceptual figure has here. If each of those layers is not placed in accordance with. 01:03:54.000 --> 01:04:01.000 What the design calls for, either because of mixing with an underlying layer, or placement spread. 01:04:01.000 --> 01:04:11.000 Um, that issue kind of gets compounded and can lead to implementation of sediment caps that don't behave as designed, because they weren't constructed as designed. 01:04:11.000 --> 01:04:27.000 Um, so really the important considerations we're laying out here are just to ensure that the constructed cap is consistent with the intention of the design, and that it's going to perform as designed. 01:04:27.000 --> 01:04:37.000 So, in regards to material placement, a couple things to keep in mind and we'll go into in a little bit more detail are material spread, and that can be. 01:04:37.000 --> 01:04:49.000 Um, upstream to downstream, but also, um, you know, riverboard to shoreward, or various directions, depending on the flow environment that material is being placed. 01:04:49.000 --> 01:04:58.000 And then consolidation or mixing of materials with underlying layers can reduce the effective concentration of. 01:04:58.000 --> 01:05:07.000 cap layers, so that's an important consideration to evaluate looking at placement methods for each layer. 01:05:07.000 --> 01:05:12.000 Next slide, please. 01:05:12.000 --> 01:05:22.000 Um, the image on this slide, um. shows what you would want to see in an amended. 01:05:22.000 --> 01:05:37.000 amended material for chemical isolation layers. So there's. materials that we would typically amend. So this example is sand amended with a granular activated carbon particles, and as you can see in the conceptual image. 01:05:37.000 --> 01:05:47.000 Um, the sand particles are well mixed with the activated carbon particles and the activated carbon particles are well distributed within the sand. 01:05:47.000 --> 01:05:55.000 And that's ideally, um, what we want to see when the material is placed, but getting there can be difficult. 01:05:55.000 --> 01:06:02.000 Some important things to consider, both in the design and implementation are the dose requirements. 01:06:02.000 --> 01:06:14.000 And that dosing requirements, um, while important to make sure that the amendment is the sufficient mass or volume of the amendment that will. 01:06:14.000 --> 01:06:18.000 meet the intent of the design. The specifications also need to be. 01:06:18.000 --> 01:06:28.000 Written such that, um, verifying that amendment dose in the field is plausible or feasible to do. 01:06:28.000 --> 01:06:35.000 And then the amendment also needs to be well mixed and distributed like is shown in the conceptual image. 01:06:35.000 --> 01:06:44.000 And there are amendments that can be affected by mixing or placement, either by separation or. 01:06:44.000 --> 01:06:48.000 Um, actually impacting the integrity of the amendment itself. 01:06:48.000 --> 01:06:55.000 So being able to verify that the place material is consistent with the integrity you want to see. 01:06:55.000 --> 01:07:00.000 Um, as per the design is an important consideration, um, both. 01:07:00.000 --> 01:07:08.000 in specifying placement methods and in developing a construction quality assurance plan. 01:07:08.000 --> 01:07:20.000 Uh, next slide, please. So there's a number of different placement methods contractors can utilize for placement of sediment cap material. 01:07:20.000 --> 01:07:31.000 Um, this slide, and then the following slide will highlight a few of the common and then proprietary placement methods that you may see in the field. 01:07:31.000 --> 01:07:40.000 Um, so first, starting to the far left on the slide is a concrete bucket. So this is a fairly low cost. 01:07:40.000 --> 01:07:51.000 Method using commonly available equipment, and… It can be placed from shoreline or barge, which is helps for. 01:07:51.000 --> 01:07:56.000 Uh, site access. But the disadvantages are that accrue. 01:07:56.000 --> 01:08:05.000 needs to access the bucket, and then there's some limitations when it comes to lift control. 01:08:05.000 --> 01:08:17.000 Another common placement method is use of an excavator that's shown on the second image from the left. So this is obviously a fairly common. 01:08:17.000 --> 01:08:24.000 commonly available piece of equipment that can be utilized from shoreline or from a barge. 01:08:24.000 --> 01:08:34.000 disadvantages associated with excavator placement are that there is difficulty in controlling the lift. 01:08:34.000 --> 01:08:39.000 And then fairly low production rates compared to some other methods. 01:08:39.000 --> 01:08:52.000 Um, a clamshell bucket, um, is another… potential placement method. This is very common in the marine industry and can have higher production rates. 01:08:52.000 --> 01:09:06.000 But as you can see on the image for this option, it typically would… utilize a crane, and then a barge for transporting material closer to the clamshell and crane. 01:09:06.000 --> 01:09:13.000 Um, so there are challenges associated with overhead obstructions and just being able to get. 01:09:13.000 --> 01:09:25.000 um, that equipment into tight areas. On the far right-hand side, there's an image of a conveyor delivery. So this can be a really. 01:09:25.000 --> 01:09:37.000 efficient method with high production rates. It also allows you to have some pretty good control over the lift because the material is being spread out or you can kind of spread it out with. 01:09:37.000 --> 01:09:41.000 Um, by varying where the conveyor is being placed. 01:09:41.000 --> 01:09:59.000 Um, the disadvantage is that it can be difficult to actually get material into the hopper for the conveyor, um, and… For sites with tight access or longer, I guess, placement areas, um, that can be difficult. 01:09:59.000 --> 01:10:15.000 Next slide, please. So there's a number of proprietary placement methods that marine contractors who commonly do this work have. We've included examples from JF Brennan. 01:10:15.000 --> 01:10:21.000 Ian Sevenson on this slide on the left-hand side of the slide is the example from. 01:10:21.000 --> 01:10:31.000 JF Brennan. Um, so in both of these examples, they're using hydraulic delivery of cap materials to. 01:10:31.000 --> 01:10:36.000 A barge, um, and that just allows for various efficient. 01:10:36.000 --> 01:10:42.000 Delivery of those materials to the capping barge and limits downtime. 01:10:42.000 --> 01:10:57.000 Um, so the advantages here, uh… or that you get a higher production rate, and then also, um… or evenly distributed placement of materials, so the material is spread out. 01:10:57.000 --> 01:11:06.000 As shown in the curtain on the left-hand side of the the figure there. 01:11:06.000 --> 01:11:15.000 The equipment itself can be hard to get into, um… Tiger project locations. So that's a limitation. 01:11:15.000 --> 01:11:24.000 In the example on the right-hand side of the slide is a similar setup from Sevenson. 01:11:24.000 --> 01:11:39.000 But they have hydraulic delivery. of the cat material, and then spreading the material as it's hydrated or wetted, whereas the Brennan example, uh, dries the material prior to placement. 01:11:39.000 --> 01:11:46.000 Um, so similar advantages and disadvantages for the Sevenson capping method, just slightly. 01:11:46.000 --> 01:11:54.000 Different based on contractor preferences. Next slide, please. 01:11:54.000 --> 01:12:03.000 So, we wanted to talk through some key considerations for placement, and then material loss as well. 01:12:03.000 --> 01:12:12.000 And if you there we go. Thank you. Um… So for placement accuracy and tracking, the equipment. 01:12:12.000 --> 01:12:26.000 an operator experience using that equipment are really important. Um… In being able to accurately place material, um, so evaluating, uh, contractors' proposed. 01:12:26.000 --> 01:12:33.000 Uh, personnel for the work, along with their proposed equipment and tracking methods is important to make sure they're. 01:12:33.000 --> 01:12:42.000 Thinking through, um, the steps and personnel needed to achieve the requirements of the design. 01:12:42.000 --> 01:12:52.000 And then there are, um, quality control measures that, as engineers and scientists, we want to implement to verify that the. 01:12:52.000 --> 01:12:59.000 CAP was built as designed. So we have those listed out here, and you want to consider. 01:12:59.000 --> 01:13:16.000 Where the lifts are placed, the quantity that's placed in the uniformity of the material placement. And some of the best practices that are commonly utilized to do that include RTK GPS bathymetric surveys, indirect measurements, and. 01:13:16.000 --> 01:13:24.000 I'll talk about those, um, in more detail on the next slide. 01:13:24.000 --> 01:13:35.000 And then key considerations to think about to evaluate material loss include the material properties, the equipment accuracy in the placement conditions. 01:13:35.000 --> 01:13:43.000 Um, some… for material properties, some things to consider are the. 01:13:43.000 --> 01:13:56.000 density of the material being placed, and. Whether it has a higher density and a tendency to sink fairly quickly, so less opportunity for the material to spread. 01:13:56.000 --> 01:14:07.000 or a lower density and a lower sinking rate, which could increase the spread of the material when it's being placed. 01:14:07.000 --> 01:14:17.000 And this can come into, I guess, more consideration when you have an amended cap. So the amendment. 01:14:17.000 --> 01:14:26.000 in the material that is being amended may have different densities, so the rate at which they fall out within the water column would be different. 01:14:26.000 --> 01:14:33.000 Um, and therefore, there could be some settling or separation that occurs during placement of the amended cap. 01:14:33.000 --> 01:14:47.000 And making sure… there's… well, I should say there's ways to make sure that that doesn't happen based on how it's placed, or… The state in which it is placed, but evaluating that the in-place. 01:14:47.000 --> 01:14:56.000 um, mixture is consistent with the design would be an important consideration if you do have an amended cap. 01:14:56.000 --> 01:15:03.000 Next slide, please. 01:15:03.000 --> 01:15:11.000 So this slide highlights some of the typical quality assurance methods for verifying cap placement. 01:15:11.000 --> 01:15:22.000 In one caveat that I wanted to mention before getting into each of these methods is that there really isn't a one-size-fits-all solution to projects. 01:15:22.000 --> 01:15:28.000 These are options to consider when developing a quality assurance plan. 01:15:28.000 --> 01:15:45.000 the quality assurance plan itself needs to be specific to the project objectives and how the cap is designed. So, um, these are… I guess can be considered a menu of options rather than a one size fits all. 01:15:45.000 --> 01:15:52.000 Um, bathymetric surveys are really common in capping projects. 01:15:52.000 --> 01:15:58.000 They are typically integrated into quality assurance plans in some way, shape, or form. 01:15:58.000 --> 01:16:05.000 Um, they allow for area-wide analysis, and then another benefit here is that, um. 01:16:05.000 --> 01:16:14.000 It's typical to have… contractors who have capabilities performing bathymetric surveys fairly local and readily available. 01:16:14.000 --> 01:16:33.000 Um, the disadvantage with this approach is that it gives you the segment surface, but does not tell you any information about settling or mixing, or if an amendment was used, whether that amendment separated out during placement. 01:16:33.000 --> 01:16:43.000 Another option is a sub bottom profile. And there's an example of a result from a sub bottom profile survey shown. 01:16:43.000 --> 01:16:52.000 On this slide, um, but that technique can provide a profile of sediment bed that allows you to differentiate. 01:16:52.000 --> 01:17:01.000 Where there are different materials, so depending on the material properties, you could be able to tell where the material type switches within the sediment profile. 01:17:01.000 --> 01:17:14.000 Um, it can be fairly approximate, it can be kind of tricky to… parse out accurate results depending on the environment that is being utilized in. 01:17:14.000 --> 01:17:23.000 And then, a disadvantage here is that it is location-specific, um, not kind of an area-wide analysis. 01:17:23.000 --> 01:17:34.000 Um, sediment profile imaging is another option where you actually take a visual image of the sediment profile, as it name alludes to. 01:17:34.000 --> 01:17:41.000 Um, and that allows you to get, you know, kind of a more accurate picture of what's happening within the sediment profile. 01:17:41.000 --> 01:17:50.000 Um, can allow you to evaluate whether the amendment used in the cap. 01:17:50.000 --> 01:18:05.000 was well mixed after placement, or if there was any separation of material. Um… Some disadvantages with this option are that it is location-specific, so this is, you know, one specific point and not an area-wide evaluation. 01:18:05.000 --> 01:18:11.000 Um, and depending on the materials used for the sediment cap, there could be limitations in. 01:18:11.000 --> 01:18:16.000 The thickness or depth that you're able to profile. 01:18:16.000 --> 01:18:26.000 The settling pans can be another option for evaluating placement. So this is a pan or bucket that's placed into. 01:18:26.000 --> 01:18:34.000 the area that is actively being capped, um, and then removed after capping, so that anything collected. 01:18:34.000 --> 01:18:41.000 In the pan or bucket, as shown in this photo, um, can be evaluated against the design requirements. 01:18:41.000 --> 01:18:49.000 So it does give you kind of a snapshot of what, um, the cap placement would look like without needing to. 01:18:49.000 --> 01:18:53.000 take a core or a profile through the cap. 01:18:53.000 --> 01:18:57.000 But some disadvantages, again, are that it's very location-specific. 01:18:57.000 --> 01:19:07.000 Um, and that it's not able to evaluate any mixing, um, because you're placing that pan over the underlying cap layer. 01:19:07.000 --> 01:19:18.000 And then finally, um, collection of cores is another way to verify place conditions of materials. So. 01:19:18.000 --> 01:19:31.000 Similar to the sediment profile imaging, you're getting an actual look at what the place cap material looks like and allows you to evaluate mixing, um. 01:19:31.000 --> 01:19:41.000 some disadvantages with it are that, um… It's subject to compression, um, as you're taking the course, so the actual. 01:19:41.000 --> 01:19:52.000 Um… thickness may be a little bit different than what it is in the water column, because it's getting compressed as the core is being collected. 01:19:52.000 --> 01:19:59.000 Um, and that, again, is another very location-specific option. 01:19:59.000 --> 01:20:19.000 Uh, next slide, please. So, kind of to wrap things up, we wanted to just highlight some of the important concepts and considerations related to constructability that need to be accounted for during design and construction of sediment caps. 01:20:19.000 --> 01:20:31.000 The first is to evaluate the proposed equipment. And as scientists and engineers, typically we don't like to get into means and methods for how things are constructed. 01:20:31.000 --> 01:20:42.000 And typically that is up to contractors to decide, but it is important in this scenario to look at what is being proposed. 01:20:42.000 --> 01:20:50.000 Um, and give it a truth check as to whether it is likely to meet the design requirements and ask the appropriate questions to make sure. 01:20:50.000 --> 01:20:59.000 Um, you don't get in a situation where during construction, there's back and forth about whether or not the design requirements, um. 01:20:59.000 --> 01:21:15.000 are reasonably achievable. Net control placement of layers can be really important to limit mixing of layers. As was highlighted earlier in this training, the layer thickness. 01:21:15.000 --> 01:21:22.000 is an important variable in modeling and designing sediment caps. So making sure. 01:21:22.000 --> 01:21:34.000 that the placed thickness meets the design is important, and you can do that by evaluating how placement of the layers is occurring. 01:21:34.000 --> 01:21:46.000 An amendment delivery, um, can be another tricky one when it comes to placement of sediment caps activated carbon being a common amendment does have. 01:21:46.000 --> 01:21:57.000 density that's typically different than the material that's being amended to so separate separation is a concern. And you want to make sure that. 01:21:57.000 --> 01:22:06.000 the delivery of that amendment to the as place sediment cap is consistent with your design requirements, and then building, uh. 01:22:06.000 --> 01:22:14.000 construction quality assurance plan that allows you to verify that dosage is achieved in the field, both. 01:22:14.000 --> 01:22:19.000 before and after mixing. Her after placement. 01:22:19.000 --> 01:22:34.000 And then finally, just a reminder that a robust quality assurance program is important for sediment cap construction. Most often these are constructed underwater, which just makes the. 01:22:34.000 --> 01:22:52.000 Verification of as-built conditions, more difficult than other… construction that occurs on land, so… Um, remember to evaluate options based on what your objectives are for the project, and kind of think about a. 01:22:52.000 --> 01:23:09.000 Multi-layered approach for construction quality assurance. And I think that's it for me. 01:23:09.000 --> 01:23:10.000 Okay, I think we're gonna. 01:23:10.000 --> 01:23:24.000 Okay, so we're gonna wrap up here to talk about the monitoring and maintenance. You've gone through this entire process, done all this modeling, all this evaluation, construction. 01:23:24.000 --> 01:23:41.000 You do want to make sure that everything is working the way it's supposed to. A cap is really like any other built infrastructure. It needs to be performing, and it needs to be in the location where you. 01:23:41.000 --> 01:23:48.000 Expected to be doing what you want it to do. 01:23:48.000 --> 01:24:00.000 So there's kind of a bunch of reasons why we monitor in order to assess the performance of the CAP. Obviously, we want to compare it to. 01:24:00.000 --> 01:24:13.000 You know, the dimensions and the quality of what was… designed. Theater went through a bunch of things that I'll touch on again briefly here to. 01:24:13.000 --> 01:24:28.000 see whether… what is going on in the surface of your sediment layer now is chemical migration coming up through the cap, which will be a performance concern, or whether it's deposition from background. 01:24:28.000 --> 01:24:40.000 What is your natural recovery? Which could be deposition of clean sediment. Do you need to maintain in any way, and what are your long-term. 01:24:40.000 --> 01:24:48.000 objectives. How long will your cap last? Do you need to do any repairs? That kind of thing. 01:24:48.000 --> 01:25:01.000 So obviously sampling is one way to look at your CAP performance. And this is sort of a basic. 01:25:01.000 --> 01:25:14.000 layers here, where you… under your water, you have your… biologically active zone, and then underneath it, your chemical isolation layer over the source. 01:25:14.000 --> 01:25:19.000 Material, and you do want to make sure that. 01:25:19.000 --> 01:25:25.000 You have… adequate thickness of your different. 01:25:25.000 --> 01:25:34.000 layers, and that they're approximately what you expect them to be and what you've modeled with that predicts successful CAP. 01:25:34.000 --> 01:25:56.000 performance, and if something is… a problem, if you're starting to see breakthrough, for example, in your chemical isolation layer, you can possibly take action before you have a problem with contamination moving up into your biologically active zone or discharging to your water. 01:25:56.000 --> 01:26:14.000 column. This is kind of what Deidre went over, so I won't belabor it, and it's kind of a hard thing to wrap your head around if you're looking at it really quickly, but the first one on the left is, yeah, as you get deeper, your concentration. 01:26:14.000 --> 01:26:31.000 Is… is getting higher, and then with your shallower, where you want to be protective, it's getting… lower if you are getting lower, but not lower enough, that could mean your isolation function is not. 01:26:31.000 --> 01:26:48.000 operating well, and if it's getting better, and then suddenly getting worse, as shown on the right, that tells you there's something coming from the other side, from the top, and with… and you have recontamination, and that is not necessarily cat performance. 01:26:48.000 --> 01:27:03.000 problem, but it could be an overall remedy performance problem if the background was not adequately characterized, and we've designed this cap that's doing its job, and then you're ending up with a… Same. 01:27:03.000 --> 01:27:11.000 type of problem. So how do we actually measure the chemical isolation performance? 01:27:11.000 --> 01:27:31.000 Deidre mentioned… or water, that's kind of your gold standard here. If you go into the you know isolation layer and your dissolved phase is clean of the contaminants that you are remediating for, that's a great indicator that. 01:27:31.000 --> 01:27:39.000 your… CAP is functioning, that you're not having breakthrough of soluble contamination. 01:27:39.000 --> 01:27:54.000 Sour phase, also pretty common, but it doesn't necessarily tell you how contamination is partitioning between solid and aqueous, so it's not… as useful. 01:27:54.000 --> 01:28:10.000 Surface water, honestly, most agencies really do want you to look at surface water, but because surface water tends to so rapidly dilute anything that might be coming up through your cap, it's unlikely to really. 01:28:10.000 --> 01:28:26.000 indicate whether there's a performance problem. I mean, maybe if you have a really lazy system like a wetland with very shallow water, and you have a big problem, you might see it. But in general, you wouldn't expect that to be. 01:28:26.000 --> 01:28:34.000 particularly useful. And then by Oda, that is also a very complicated thing to. 01:28:34.000 --> 01:28:53.000 evaluate. We had a lot of, uh, heated discussions in our team meetings about fish tissue sampling. Everyone loves fish tissue sampling, but the truth is that fish move around a lot, and in most systems it… anything you find in fish is not going to be reflective of what's coming up. 01:28:53.000 --> 01:29:10.000 through your cap, and even if it is, fish have typically such a slow half-life over which they will eliminate contaminants and with things like bioaccumulators, PCBs, pesticides, and so forth. 01:29:10.000 --> 01:29:29.000 You can have a very, very decade even before your system starts to show the benefits of remediation, so… I mean, you can look at that, certainly if you looked at biometric monitoring of your biological community on your cap rather than the chemical. 01:29:29.000 --> 01:29:45.000 Concentrations in biota, that might be a much more rapidly recovering criterion that you could look at, and that's… it's always nice to see those bugs, uh… Back hopping. 01:29:45.000 --> 01:30:03.000 So, like anything else, a cap can… need a little love over the years. Why would you do that? Well, a lot of reasons. First of all, as we first just discussed, you might have breakthrough. 01:30:03.000 --> 01:30:09.000 In which case, you need to kind of figure out, you know, which of your layers may not be optimally performing. 01:30:09.000 --> 01:30:27.000 things may start to consolidate and you know they're getting crushed, you get subsidence. We talked about bathymetric measurements, looking at the elevation of your sediment layer. And I can tell you a lot about what's going on on the bottom there. 01:30:27.000 --> 01:30:48.000 Maybe you have some kind of instability, and somebody asked about climate, and certainly, you know, your climate zone, as Danny said, is not really important, but if you have a marine environment, and you are subject to a lot of storm events, certainly that is something that could affect your. 01:30:48.000 --> 01:31:04.000 CAPS integrity, as can a lot of vehicular traffic going on around the area if you're close to navigational channel or for any other reason, there is physical disturbance, it can mess up the cab. 01:31:04.000 --> 01:31:17.000 Those are all reasons why maybe you might need to go in and do some repair, and that's fine. It is infrastructure, and it needs to be maintained. 01:31:17.000 --> 01:31:23.000 So, overall, the point here is just, it's not once and done. 01:31:23.000 --> 01:31:32.000 You should have a plan. for what you're going to monitor, why you're going to monitor it, and how your monitoring program. 01:31:32.000 --> 01:31:39.000 reflects your cat performance and its function within your larger remedial action objective for. 01:31:39.000 --> 01:31:46.000 your site area, and there's all kinds of things from monitoring to pore water to. 01:31:46.000 --> 01:32:05.000 Physical evaluation that can tell you how you're doing and you may need to change those over time. It can be somewhat of an adaptive management approach where you need to circle back or you just may have certain things built into your long-term plan that say we're going to go out every. 01:32:05.000 --> 01:32:15.000 X number of months or years, and look at A, B, and C. And then… As Deirdre talked about. 01:32:15.000 --> 01:32:37.000 Your cap is an area wide. solution. If you have a little bit of subsidence or some erosion right on an edge somewhere, or on a shoreline, that doesn't mean that your entire infrastructure is failing. So there's… there's no need for it to be absolutely perfect. You just want to make sure overall that it is. 01:32:37.000 --> 01:32:42.000 Functioning. 01:32:42.000 --> 01:32:55.000 And with that, um… We're ready to wrap this up. 01:32:55.000 --> 01:33:03.000 All right. 01:33:03.000 --> 01:33:19.000 I'd like to thank all of my fellow team members who presented today. Our goal for this sediment capping guidance was to expand on the 2014 sediment remediation guidance by developing a comprehensive understanding of the design. 01:33:19.000 --> 01:33:26.000 Construction and long-term monitoring and maintenance of CAPS, with a focus on the chemical isolation function. 01:33:26.000 --> 01:33:35.000 So, to recap, designing the chemical isolation function is an iterative process that begins with understanding remedial goals and objectives. 01:33:35.000 --> 01:33:43.000 We use those objectives to develop chemical design criteria specific to the contaminant fade and transport pathways within the CAP. 01:33:43.000 --> 01:33:54.000 Chemical design criteria are the what, the where, and the when, or for how long, that serve as the conditions that the design must meet to satisfy the remedial objectives. 01:33:54.000 --> 01:34:04.000 Once these design criteria are established, CAP design involves selecting appropriate capping materials and thicknesses that can achieve those design criteria. 01:34:04.000 --> 01:34:17.000 In addition to the chemical design criteria, it's important that the cap also satisfy other design factors, such as physical constraints, permitting, and other regulatory requirements, and it must remain constructible. 01:34:17.000 --> 01:34:32.000 Two modeling tools are available, and were discussed, that have been developed specifically to support capping design, and these modeling tools can be used to estimate how well various cap configurations and materials will fulfill the design criteria. 01:34:32.000 --> 01:34:46.000 After the design is completed, it's important to convey CAP construction requirements clearly to contractors, and to employ construction quality assurance measures to verify that the built cap is consistent with the design. 01:34:46.000 --> 01:34:56.000 Finally, it's important to factor in how CAP performance will be monitored, potentially in addition to other effectiveness monitoring approaches for the remedy. 01:34:56.000 --> 01:35:10.000 We recommend that CAP performance data be compared with predetermined maintenance triggers so that it's clear, upfront, when CAP maintenance should be considered in order to ensure the CAP will continue to meet its design objectives well into the future. 01:35:10.000 --> 01:35:18.000 With that, I'll hand it back to our moderator for another question and answer opportunity. 01:35:18.000 --> 01:35:48.000 All right. Thanks, Ashley. Yeah, we have reached our last Q&A of the training today. We do have a couple questions for the trainers. First question, how is a geomembrane layer cap typically repaired for animal burrows? 01:35:51.000 --> 01:36:02.000 I can… I'll just jump in. So the caps that we're talking about in this training are subaqueous, so they're underwater. 01:36:02.000 --> 01:36:14.000 So the burrowing organisms are going to be like benthic organisms, like hieronymids or worms, um, and they don't usually burrow that deep. 01:36:14.000 --> 01:36:31.000 Um, and we're burrowing does occur, you try to, you know, keep, um, maybe keep that layer deeper than the burrowing dust. 01:36:31.000 --> 01:36:50.000 Great. Thanks, Deirdre. A question I have here for Mike. If you use core collection for QA, Qc. How do you prevent contamination or mixing between layers? 01:36:50.000 --> 01:37:17.000 I'm guessing this question is referring to, um… Maybe, like, once you remove the core and that… portion of the cap of not being… constructed as design, but I think typically, um… Type core is considered incidental, like the actual core that's being removed from the cap. There may be… 01:37:17.000 --> 01:37:33.000 special considerations where removing even just that small of a piece of the cap wouldn't be acceptable, and if that's the case, you know, core collection wouldn't be a recommended approach for quality assurance. 01:37:33.000 --> 01:37:45.000 In… in that scenario. Um… I hope that answers the question, but let me know if not. 01:37:45.000 --> 01:37:57.000 All right. Thanks, Mike. I don't see any other open questions in the Q&A pod. So I'm going to go ahead and wrap up the training. If any more questions do enter, I will. 01:37:57.000 --> 01:38:16.000 ask our trainers before we completely wrap up. So thank you to our expert trainers for being here today and for their contribution to the itrc. Document. We would like to hear back from you, so please be sure to fill out the online feedback form that's linked on this last slide. And I'm also going to drop it in the chat now. 01:38:16.000 --> 01:38:23.000 Filling out the feedback form and certifying that you participated will allow you to receive a certificate of completion by email. 01:38:23.000 --> 01:38:34.000 If you need further clarification on the answers or would like to ask more questions, feel free to email us at itrc@itrcweb.org, and we will follow up with our trainers to get your questions answered. 01:38:34.000 --> 01:38:49.000 And then I do see one more question in here that I'll ask, and then I will officially say, Thank you. Goodbye. Who is usually responsible for monitoring? Does the job fall on public or private sectors? 01:38:49.000 --> 01:38:54.000 I assume that was the question asked. It says public slash private sectors. 01:38:54.000 --> 01:39:05.000 I mean, I think it's gonna be… it's gonna depend who the responsible party was for the remediation. I mean, my experience, it's been… Uh, private sector. 01:39:05.000 --> 01:39:19.000 But that's because that's most of the work I do. 01:39:19.000 --> 01:39:38.000 All right. Thanks, Tamara. And with that, I think that wraps up our training for today. So thanks again, everyone, for questions and interacting with the Q&A pod today. We hope to see you in the future at other itrc trainings, and thanks again to our expert trainers for being here and volunteering. 01:39:38.000 --> 01:40:08.000 The guidance document and in the training. Bye, everyone.