In this lecture, we're going to talk about some of the basic principles fordesigning an MNA monitoring program. Dave, what are some of the important components of an MNA system? >> Well, to start off, it's good to remember, there are a couple different types of monitoring that can be used at different times in the MNA process. We touched on this a little bit during our previous lecture. The first is that it's done to build a proper conceptual site model and ultimately support the selection of MNA as a remedy. >> Okay, and so it's usually in combination of historic monitoring data and perhaps some high resolution characterization techniques we discussed in the last lecture, all to collect this data. So you're collecting soil and ground water samples, maybe installing some new wells, monitoring points. Trying to get a better understanding of the site conditions. >> Yeah, you want to establish these lines of evidence using a combination of past and present data to establish that there's no current risk and that conditions in the future will support attenuation in a reasonable time frame. >> Okay, so I see the three lines of evidence there. Just a note, and we've talked before, that doing these rate calculations, some people put them in different lines of evidence, right? >> Yeah, sometimes people consider daughter product data maybe as a line of evidence one but the general goal at this stage is to sort of collect a lot of data, support a lot of different potential lines of evidence. >> Okay, and one key thing is that you got concentration versus time graph here. If you don't have much historical data, then maybe you need to collect more of that. >> Yeah. >> To sort of understand what's going on. >> But after you've settled on MNA, you're basically transitioning then to a different type of monitoring, this is long-term or performance monitoring. >> Okay, so we see here, we got a characterization remedy, then there's long-term performance. When we talked about this in the last lecture. >> Yeah. >> You think about these differently, right? >> Yeah, there's a lot of great guidance in terms of how to do this sort of monitoring. And one of the best resources that's out there is this EPA document from 2004. Title of this is Performance Monitoring of MNA Remedies for VOCs in Ground Water. >> Really nice document, lots of graphics, sort of lays all this stuff out. Very MNA-focused, right? >> Yeah, and so we'll go through some of the key points within that there. But one of the main things that this talks about, and these are memorialized in the earlier EPA protocols, is the objectives for MNA monitoring. So let's talk about a few of these. But basically your overall objective, demonstrate that natural attenuation is occurring, detect changes in conditions that reduce attenuation efficiency. A couple more, Chuck? >> Identify toxic mobile byproducts, verify that that plume is not expanding, that's sort of a key one, right? >> Yeah, and then critically, obviously, no impact to downgradient receptors, as well as identifying whether there might be new releases contributing to what you're seeing. >> And maybe just to confirm that if you have any institutional controls like d!on't drill in this area, make sure that they're working as you thought. And just verify attainment, that you're meeting your remedial objectives, right? >> Yeah, and so these are the overarching objectives, but then you have to decide which ones of these might be relevant for your particular site. So you have these site specific remedial action objectives, RAOs. So this is very common to sort of set these up specifically for the site that you're dealing with, that's what you gotta do. And so once you've basically decided on what these are, then you transition to another thing which is, Chuck? >> Preliminary remediation goals, or PRGs. >> Yeah, so these are the actual numeric criteria that you might be expected to meet in order to achieve those particular objectives. So the bottom line on this is that these are what you're expected to do, and then you've gotta design a modern program at your site to meet these objectives. So one way to look at this, and that EPA 2004 document had these great graphics, we're recreating them here. It's taking a look at a bird's eye view of a plume and then where you might monitor on it. >> And they've got six different panels of this. So we're going to build through six builds of this? >> Yeah, so imagine you're a bird looking down right here and trying to pinpoint where you might monitor. >> Okay, so this is a bird, again, that has X-ray vision that doesn't see soil or the earth worms but that's where the plume is, right? >> Yeah, some bird with special plume vision, I guess. >> Exactly. >> Okay, so first off we're going to look at, basically, monitoring in the source area. This is critical, you need to have an understanding whether you're seeing any attenuation in that source zone. Also, if there's any new releases, and you probably have some institutional controls as well. And then an overall assessment of your performance. >> Okay, so that's number one. Let's go to number two here. And that's where we're going to go to this high concentration plume core and right downgradient source zone and you're going to look at what's going on with this highly transmissive zones. Maybe you're going to draw that line on the sand, have that vertical transect and maybe do some mass flux mass discharge measurements. >> Okay, so then we might move a little bit further downgradient and look at more low concentration areas. Maybe the plume fringe, and there's a lot of different reasons you might do that. But one that's mentioned here is you might have earlier attainment of your remediation goals due to attenuation. So that can get you on board and maybe improve or optimize your long term monitoring. >> Hey Dave, this is really on the sides of the plume, it's not the edge yet, right? >> Well, we'll talk also then about the sides here into the next one because we'll move into plume boundaries. >> Okay. So, plume boundaries, you really want a monitor if that plume is expanding or hopefully it's shrinking at both the sidegradient and downgradient locations or this transects. And just confirm there's no risk with these receptors. >> Yeah, so these are pretty critical as well. And then, another interesting thing that's talked about the EPA document, this is the idea that there might be recalcitrant zones. And so, the one that's showing here is sort of near this source zone. And this is areas where you may not be seeing all that much progress towards your remedial goals. And a lot of potential reasons for maybe, why these would occur, things like matrix diffusion might be influencing, might be contributing to persistence. So in those areas, you may need to do some additional monitoring and maybe even high resolution monitoring to identify what's going on. >> Okay, a quick question, and time out maybe. So matrix diffusion has really been confined to the chlorinated solvent-type plumes. But is this guidance for any type of plume, or is it really just for chlorinated solvents? >> Well, I think that it could be tailored to pretty much anything that you're dealing with. But yeah, you're right, the chlorinated solvents has gotten a lot of the attention, but this is applicable to a lot of particular compounds. Last one, Chuck? >> We're going to go to the upgradient areas. And this is help to establish your background. Is it aerobic upgradient, how does that geochemical conditions change as you get into this plume, identify these conditions, is there any sources upgradient? Things like that. So you're going to monitor upgradient and that's that number six. >> So that's really what you going to be interested in terms of locations. What do you want to monitor for? Well, we've got a few of the ones that are typically called out in here. Obviously, the constituents of concern, they're your target containments that you're trying to attain some sort of clean up on are going to be on that list. >> Then geochemical indicators. These are classics. We want to know about that redox potential. Is it aerobic or anaerobic? Things like that. The whole suite of things, temperature, pH, things like methane, sulfate, nitrate, iron, these electron acceptors. >> Basically, trying to establish that the processes that you're relying on for MNA or actually working, right? >> That's right. >> And then transformation products. So things that might be byproducts of your target containment as well as maybe metals, things that might be actually being mobilized in terms of through-transformation processes. >> And then just finally these others, which are things like water level isotopes, biomarkers, minerals. Here's a question, Dave, about this, is if you're going to be monitoring for a long period, do you want to try to reduce in some ways your analytical list if you can? >> You definitely want to have it optimized because there can be a lot of financial liabilities associated with long term monitoring over the course of many years. So really making sure that you identify the most relevant parameters, matching them up to the program that you need to do. So this is sort of the analytes and we haven't really talked about how often you monitor. That's going to be a subject for the next lecture. So why don't we move on then to the key points for this particular lecture. So MNA monitoring program involves characterization to support the selection of MNA as a remedy, but also long-term performance monitoring to document that MNA is working. >> Okay, and you gotta design this MNA monitoring program to address specific RAOs of these remedial action objectives. >> Yeah, and then finally, MNA monitoring locations and analytes are selected to ensure that objectives like performance and plume stability can be adequately assessed.
