 All right. Good afternoon everybody. Thanks for showing up again after lunch. That's always good to see you come back So we're gonna talk about Rebecca if there's any Rebecca's in the in the audience today. I apologize We're not picking on you But Rebecca is the one of the great acronyms that we in government like to use. That's the RBC a and It stands for There we go Just want to leave you in suspense there Rebecca is risk-based Corrective action So what is risk-based corrective action? So conventionally when we're looking at a clean up remediation looking at how much mass of the contaminant can we remove? The risk-based corrective action kind of turns that around and instead of how much can we remove? The question is how much chemical mass can we safely leave behind and the key there is safely This is not just a way to leave more behind But a way to balance that with the safety of the environment and human health And how do we also ensure then that future generations know what we did and where we did it at? This isn't a new process the Rebecca process dates back to the Superfund program when it was adopted in 1986 It was part of that evaluation manual. That was the first reference to it. It's been modified over the years 1990 ASTM actually came up with a standard for risk-based corrective action and a specific one for petroleum sites And then in a couple of updates over the years They've also added the inclusion of vapor intrusion, which is one of the risk pathways into that standard So this isn't something new that we just came up with but in the past the department has used risk-based corrective action But we've not had a standardized policy or procedure on how to go about that We've done it on a site specific basis usually working with the consultant that's working on the site So this is an effort for us to try to standardize that So obviously in the pristine world we'd remove everything and turn it back to pristine conditions But that is not always the case still one of our goals when we can but often we do have limited resources We have limited technology to use to get to that point And in some cases we end up doing more harm to try to get to that endpoint than by leaving some acceptable level of contamination in place And this provides us a consistent scientifically defensible process for how do we determine where that line is And we want it scientifically based legally defensible So we can use that across our various different programs and and Still substantiate that if we're challenged on that That doesn't mean there's not some mechanism in there for Or decision-making. It's not a cookie cutter process by any means There are still decisions that have to be made both by the consultant proposing this and by the department So there there is a bit of an art to it as well as strictly the science But it does at least provide a framework to facilitate that discussion Based on this very basic level. This is the conceptual model of a risk-based corrective action You start with the source of contamination That source is linked by pathways To a receptor in a receptor something that could be harmed by that contamination The example I've used here is for underground storage tanks of petroleum products That would be the source Groundwater could be one of many different pathways And the domestic water well would also be a pathway to the end user of the consumer who's drinking or utilizing that water Who would be our receptor? There's many different pathways to receptors and a lot of the focus of of the discussion in the conceptual model of using a rebecca process is to think about those pathways Some examples ingestion of water or soil vapor intrusion into indoor space or Ambient air effects in the outdoor space Dermal contact with either water or soil ingestion of contaminated biota or even exposure to that biota Potential plant uptake and exposure Groundwater discharge of surface water systems ecological receptors, which is any of the biota that's out there that could be harmed A lot of the focus of the rebecca process is usually focused on the human health component that obviously is one of our Is our primary concern But the ecological receptors are as well and a lot of times those kind of get neglected Our process does include ecological risk and so that needs to be addressed as well Two different mechanisms that you can utilize the rebecca process This shows the forward risk assessment. So this is basically answering the question What is the risk or a given site condition? We have a site. We know what the current conditions are What is the risk? And this walks you through the process first you have the environmental media the concentration and the horizontal vertical extent The fate and transport of that media through the different pathways That creates an exposure to our receptors Which creates the toxicity and that then is calculated as the risk or the hazard That's the forward mechanism Example this would be we have a site. It has very low levels We think we could probably close the site based on the risk We'll go through this process and determine if the current risk at the site is acceptable The other way to use the rebecca process is the backward risk assessment And that is to answer the question. What site conditions Would meet the given risk conditions? So now we're working backwards Starting with a known risk acceptable risk level and working backwards to develop what those site conditions would be And this would be such that we have a site. We know there's no more work to be needed But we need to know what level do we need to clean clean up to And so this would end up giving you a site specific Condition or conditions that you would then need to meet in order to see closer to the site where there's other Other one is where you start with your current conditions and determine if that site can be closed at that So very similar. I mean the the math is the same Regardless, but there's two different ways of looking at that So some key components if you're going to do a risk based corrective action Here's some things that you have to start with upfront And I appreciate Brenda's talk this morning talking about site characterization. She was looking at it from a More uh reclamation side from remediation side It's every bit as important for for this without a good Site characterization You can't develop that risk because if you don't know what you got It's very difficult to tell what that risk is going to be And likewise, even if you are working backwards If you don't know some of those site conditions, it's very difficult to tell what would be an acceptable cleanup criteria So obviously full delineation. That's very important We want to have a stable plume so that and One of the particularly challenging parts is if you have utility corridors Then may cause it to be something different than your typical Pregnant pancake of a plume that's sitting there. So The more complex your subsurface geology gets With either fractures natural pathways preferential pathways or man-made ones through utility corridors The more complex it becomes And so the more you have to work on doing an adequate delineation That means it's not going to be simply three boring stand to identify the the farthest out perimeter of of the plume You're going to have to do a little more detailed work on that And that leads into the site conceptual model. How else what's going on there? What do you think which is what's happening on the groundwater groundwater is always going to be a Critical pathway to evaluate. So what's happening there? What's happening on the surface? What do you have nearby? This conceptual model of the site is going to be really important And then as part of that conceptual model identifying those potential receptors And the pathways to those receptors for both current and future land uses We have a tendency to look at the current land use and say well Nobody's living there. Nobody's built a house there at this point But we have to remember unless there's something that can close off that pathway From the future we're going to leave this contamination place We have to think of what could happen on that site in the future and we'll talk about a Few different ways we can do that The other question is what are your endpoints now as part of our process in developing this we have Pulled in a lot of the standard regulatory endpoints such as our water quality standards The public EP MCLs or state MCLs and the regional screening levels And so those are already incorporated into the calculator But if you're looking at something different that we haven't covered with that you're going to need to know what that end point is Sometimes that's not easy. For example, if we're dealing with emerging contaminants such as PFOS Right now we for only a couple of the PFOS compounds do we have good toxicity data So you would not be able to do a risk-based corrective action for most of those PFOS compounds Because we don't know what the toxicity is And so we need to know what that endpoint is We also have to identify the cumulative effects There is no one toxicity value for crude oil It is toxicity based on the individual components and for oil Particularly we're going to look at the B-tex components and the PAH Components and we're going to look at the cumulative toxicity of all those and so again that increases the complexity of analysis Because you have to look at each of those individual parts and then also them all combined And then finally this isn't as useful it can be used but it's not as useful if there's no degradation Part of what's so useful of this is you can use that time Before that contamination reaches receptors to account for natural degradation If you don't have that such as with salts, which we tend to deal with a fair bit You may have some dilution in there and if you can account for that You can use that but you're not going to have the degradation that you would with the petroleum product And so the benefits of using this aren't going to be as significant as if you were looking at Hydrocarbon or organic solvents would be another example that would degrade One of the best ways the consultants can Simplify this process as you start crossing off pathways You identify your receptors And you look at how does my contamination get from my source to my receptor And start crossing off ones that aren't there the incomplete pathway There's different ways you can do that Perhaps it's because the natural site conditions for example If you have a clay aqua card underlying source contamination That's going to restrict movement into drinking water aquifer Then you can close off that that pathway if you can show that that is a continuous layer And that's naturally occurring You can also use administrative controls these would be things such as the zoning that's in place or Ordinances if you're working in a city or a county Or environmental covenants on the property that restrict future uses of that property Now obviously because you're restricting future uses The landowner of that property is going to be integral into this process because they're going to have to be involved in that discussion The other option is to use engineering controls the common one for this is if you have Concerned with vapor mitigation There's things you can do to the building itself through an engineer system to close off that pathway or prevent that that movement. So That's the first thing you're going to look at is can we close off those pathways? If we can't close off a pathway, we have to calculate what that risk is And the only ones we've calculated all those different risks will know which one is really going to govern the the cleanup So this it's not a quick and easy process. I guess that's maybe the point I'm making here. Is this not something that's going to make it Sites just magically go away But if you can put in the legwork to make a good case Using this process They will be able to close some sites that would probably be very difficult to get to closure otherwise because of some of the restrictions we talked about So it's after lunch. So I'm going to be a little interactive here and we're going to talk through kind of an example of a site So picture the site It's next to some rail lines. I see I think I even got a Point right here picture site. Let's just say hydrocarbon contamination Got rail lines there We've got some residential areas there some roads kind of park there So let's start off thinking We've got our source What are some of our receptors and let's just not even worry about the ecological receptors Let's focus on human health receptors. What are human health receptors? Just shout them out Groundwater. Okay. Groundwater would be a good pathway to What would be our final receptor there? The residents yep the people living in those houses right there Most likely could be people recreating that park if there's wells there Those could also be potential receptors other potential receptors So if exposure people walking across the site walking around the site either Recreating the site or just walking through The other other potential receptor there could be people doing work on the site if if there's excavation or Things being done there. That would also be a potential receptor Anything else? What was that? Vapors. Yes. So that would be another pathway to a receptor People just being in the area or even outside the area the vapors could travel some distance. So yeah, let's talk about some of those pathways We've identified so when we got groundwater as a pathway to Water well either drinking or or exposure. We've got vapors both in the air potential vapors to the the structures itself Dermal contact from people Recreating on the site or people workers digging the site Why is the difference to differentiate between somebody that might just be walking and playing on the site and somebody that's working on the site Different toxicity because you have you could have little kids You could have at-risk people that are recreating their workers. We make some assumptions as to age and That can affect what we could use for a toxicity value there What would be one of the problematic pathways that I that you'd be worried about on this site And it may help you figure it out if I mentioned that this park here is called roundhouse park This actually used to be a roundhouse a railroad facility an industrial site So you could have lots of preferential pathways through utility corridors there some you may never Not even know about because of it was you know put in place long before one call was ever a thing And so you're really going to have to do your due diligence in the delineation of that in order to know that we don't have a preferential pathway running along right away here that could be actually causing a even a very slim finger of that contamination to move Move off in that direction And that'd be one and again Railroad right away a lot of times we've got other utilities using those as well. So that would be one of the problematic areas that I would be worried about That we didn't talk about who not to didn't touch on the ecological receptors But what about the consumption or human consumption of wildlife? Could that be a pathway? Yeah, that could be a pathway. How can we control that in this situation though? Considering that this is probably this is in town. We'll say this is in town That if there's an ordinance prohibiting hunting in town, which there may be we're hunting within a certain distance Of residences, which we know there is Then you could close that pathway because you would not be able to be hunting in that area So you can cross that off this fairly easily And that's kind of how the analysis go identifying the receptors the pathways to those receptors Crossing off the ones you can and then you look at what you have left And you make this a do we calculate them do we close those pathways through one of those control methods that we mentioned here Or do we do we calculate it and and determine what level we have to clean up to? Any questions or any other thoughts on this? On our little example site here Yes, future that good example a good good thought there is so that we kind of talk about current Current things but if you look here, there's some streets It looks like that may be an area for future development the way the city's planning there And so we would need to look at future uses as well So is there is there zoning restrictions? Or do we need environmental covenants to prevent say the house with a basement? or Other types of development. Maybe we want to restrict that area. So but There's not a school or or some other type of park or something placed over that contamination. And so that's A good thought where we have to look to those future uses as well other thoughts comments Little bit on the timeline. And so we've been working on this That's been Shannon a little over a year To develop this rebecca process we use a consultant with some familiarity developing these rebecca processes for many other states And so you might see some similarities with with other states, which is is fine. Again, there's a standard ASTM standard for the process of the process should be familiar if you've done this in other places We'll be publishing our Documents the the instructional documents the excel calculator that goes along with that on our website I'll say this week. It may not go up exactly right away tomorrow, but this week sometime and so those will be available for you to download and look at and Peruse and see what questions you may have We're still training on it. We're going to be doing some additional training with the at the deq in march as we're still learning as well And then I would like to hear feedback from those that may be using that as a tool what you feel is necessary for training Do you there may be a handful that want the deep dive getting right into the calculations others may want just a Shallower level to look at here's what it is And here's how you would take it to your in-house risk assessor and deal with and present them the information to do their magic So looking for feedback on training needs and what everybody would Appreciate on that after you've had a chance to look at it But we can really just begin discussing some of these sites at any time if you have ones that you've been Interested in waiting knowing we're developing this we can start talking about those now any time So bear with us as we work through the first few it will take a little longer as we're learning as well But we'll get up to speed and then that should simplify the process for everybody So again our goal with this Is to take a difficult problem And rather than finding a solution that really only makes things worse to find a good compromise that meets the needs of Being a reasonable cleanup and also being protective of public health and the environment. So But that are there any questions? Yes, sir Sure, we can certainly look at existing sites With that if the sites have obviously already been closed, they're closed We're not going to go back and reopen anything But if you have a site you're currently working on yes, we can look at utilizing this understanding that Yep, we've we may you may be backtracking a bit in order to Get the necessary information, but we can we can look at that For existing open sites We can yes Yeah, if we have sites that are still open We can apply this to that and keep in mind this this is not a requirement You do not have to use the rebecca process You can still basically the Well, you're kind of using the rebecca process, but the tier one levels are basically what we've utilized in the past if you reach Clean up for that level you you're done. You don't have to go through the calculations of that. So So that's still an option You don't have to use rebecca if you think there'd be a benefit in using that for a site that is remaining open Yes, we can we can have that discussion Look at that site and see if we can Utilize it for that