CHUCK NEWELL: This is our final lecture for the dilution as an attenuation process sometimes. Today we're going to wrap up our talk about dilution as an M&A process. So Dave, can you give us a quick update from the last lecture? DAVE ADAMSON: Sure, let's put this graphic up that we used in the last lecture. The way to visualize this is to have a vertical control plane perpendicular to your ground water flow. And then you use the combination and the concentrations, the groundwater darcy velocity, and the size of the plume. You get a mass discharge. That's a grams per day number. And mass discharge in this case, we're basically using that to describe the amount of loading. CHUCK NEWELL: That's right. And then our other term, mass flux is the mass per time per area. Such as grams per day per meter squared. Now just a quick note that many earlier publications, the mass flux was used instead of mass discharge for this grams per day number. So you just have to be careful. But now the convention is that the loading is called mass discharge, and that this-- the most common units are grams per day. And this mass flux is this loading per area, basically that goes on. So you can use this mass discharge as a first order approximation of the impact, or it could be used for prioritization. DAVE ADAMSON: And maybe let's spend a little bit of time talking about how this prioritization works. There's a lot of variability in the mass discharge numbers from site to site, right? CHUCK NEWELL: That's right. So let's first talk about ooms, or orders of magnitude. These are these factors of 10. And I think the main message is that our business is a order of magnitude type business. If you look on the left there, we have this plume, a plume map. And typically, we draw them using orders of magnitude. Like the outer contour is 1 microgram per liter, then 10 micrograms per liter, 100 and 1,000. They step up by factors of 10. And Dave, what's on the right hand side? DAVE ADAMSON: On the bottom right, we've got basically hydraulic conductivity value. So these are a bunch of values. The source here in this case is the biochlor manual, this modeling software. But basically describing that if we're talking about various types of geologic media, all the way from clays to gravels, you're talking about hydraulic conductivities in terms of these order of magnitude changes. You might use terms such as like a 10 to the minus 3 sand, or a 10 to the minus 6 clay. In this case, we're talking about the centimeters per second hydraulic conductivities. So a lot of times, we're dealing with concentrations or hydraulic conductivity terms in these order of magnitude type terms. CHUCK NEWELL: And so that sort of sparked some of that thinking on our part. So let's expand our discussion and think about other natural phenomenon that are based on this idea of orders of magnitude. So Dave, I want to give you a test here. I'm going to show you some pictures. Can you tell me what is a natural phenomenon, and what is the scale that describes it? So let's go to the first one here. What do you see? DAVE ADAMSON: Well, this is earthquakes. This one I know. So we're dealing with the Richter scale here. It goes from 1 to 9. Every time you go up a unit, you're talking about an increase in damages by a factor of 10. CHUCK NEWELL: Orders of magnitude. So let's do this next one. Next test. What is this phenomenon? And then what's the scale? DAVE ADAMSON: So these are photos of hurricanes or hurricane damage. And we use a Saffir Simpson scale to describe hurricanes or cyclones. You're going from Cat 1 to Cat 5. Basically, damage again, is going up by an order of magnitude as you go up this category scale. So I'm familiar with the pictures on the left. I believe that's Hurricane Ike, and the damage associated with that. Not so familiar with the photos on the right, Chuck? CHUCK NEWELL: Well, I was personally impacted by Hurricane Ike. Actually that's a picture of my well, old car. That was the tree, hit the chimney, and then it rolled down the roof, and went right into my car. So I was part of that factors of 10 damage in that category 3 type storm. But the key point is that there are these natural sort of classification systems out there. Richter scale, Saffir Simpson hurricane scale that are based on these factors of 10 orders of magnitude. And so we said, can we do this for groundwater? And so we started out by taking all the sites that we knew. And this was using data that I helped compile, along with Graham Carey from the ITRC report. And we put all of our sites together and came up with this table here. So here's I think about 40 sites. Ranked from the highest site to the lowest site. And Dave, what do you see when you look at this mass discharge table? DAVE ADAMSON: Let me count what I'm seeing in terms of the orders of magnitude. But I think I'm getting up to nine different orders of magnitude based just on the sites within these charts. CHUCK NEWELL: Going from 56,000 grams per day, which is our mega site. And then this one over here is 0.0078 grams per day. That's the smallest one. what would we call that site? DAVE ADAMSON: Well, that would be the piss ant site, correct? CHUCK NEWELL: Exactly. But then you see this scale here between the piss ant site the mega site, nine orders of magnitude. And so we said, hey, can we put these sites that are here, or any site, if you knew the mass discharge, into 10 different buckets. And let's see what we did here. So this is a paper we wrote with Doctor Shela Farhat you were co-author, Bryan Looney. But we say that if you know your mass discharge, you can go into one of these buckets. And if you look right here, if you're greater than 100,000 grams per day, what are you classified as? DAVE ADAMSON: Mag 10 plume, in this case. CHUCK NEWELL: And then a plume in the middle. 1 to 10 grams per day is a Mag 5 plume. And then this really small one, if you're less than .001 grams per day, a Mag 1 plume. So that's this idea that you can get this idea of what they were. So one other thing we asked ourselves is what was the sort of statistical distribution of this? So let's look at our 40 sites and see where they fall into this magnitude scale. And so we're looking at here. What's the x and y-axis here? DAVE ADAMSON: So we've got a plume magnitude category on your x-axis here. So how many different sites then is shown on the y-axis? So we've got a sort of a distribution across from 1 to 9 in this case. Kind of a plume magnitude and a few sites that fall into most of those different categories. CHUCK NEWELL: Sort of looks like a bell curve. Maybe a little bit? You can sort of see this distribution in here. But the idea is to try to come up with this universal nomenclature or this point of reference for people. We can talk about earthquakes or hurricanes. But for groundwater hydrologists working on these plumes. It's like if you and I were at a bar somewhere. And I said, Dave, I just got asked to work on a Mag 7 plume. What would you say? DAVE ADAMSON: Well, I've been working on a Mag 8 plume myself. CHUCK NEWELL: And then we're there. And then somebody we don't know is standing at the end of the bar. She says, you guys are slackers. I'm working on two Mag 10 plumes. DAVE ADAMSON: Sounds like a pretty good bar. Someplace I might want to hang out at. CHUCK NEWELL: Yeah, so if you had a bar with a groundwater focus, maybe you could do things like, instead of a Martini, you would have a darcitini. DAVE ADAMSON: They would play a lot of Talking Heads "Once in a Lifetime," water flowing underground. CHUCK NEWELL: And then you get your ice in different sizes, based on sieve size. So it sounds like a pretty good bar. DAVE ADAMSON: I think we can move on from that. CHUCK NEWELL: But the idea is you have this classification system. You can also get information about potential impacts. And you could think about what's going to happen if that magnitude plume impacts the water supply well, or does stream dilution. So if we look at this one here, and we have mass discharge on the left. And we could see what does it take to impact a domestic well that's pumping at about 600 liters per day? And it would take a Mag 2 plume to do that. And then a municipal well, pumping at 400 liters per minute. That's about 100 gallons per minute. DAVE ADAMSON: In this case, it'd be a Mag 5 plume. CHUCK NEWELL: And then for the stream with the mixing zone flowing at 4 cubic meters per second? DAVE ADAMSON: Mag 8 plume in this case, to impact that stream. CHUCK NEWELL: And so those are the examples of these different things about these different loadings that are out there. DAVE ADAMSON: So this sounds a lot like the TMDL concept. CHUCK NEWELL: That's right. So let's talk about that interesting point. I just have a slide about this, since there are this in the surface water, this whole program. Called TMDL, Total Maximum Daily Loads. And it's the amount of pollutant that a water body, or a water segment can assimilate without exceeding their water quality standards. So here are some examples, where they do some of these studies. What they really do is they say here's the safe water quality criteria that we want to have for, in this case, copper dioxin. And they figure out what loading won't exceed that level. So in the Copper River, it's 5,450 grams per day. And then there's dioxin in the Houston Ship Channel, about 0.04 grams per day. DAVE ADAMSON: So a lot of difference in these two different cases. I would like to point out that I do recognize one of the people in this picture on the right. CHUCK NEWELL: That's actually my wife, Doctor Hanadi Rifai, who runs a big TMDL program at the University of Houston at Galveston Bay. Looks like she's holding up one of those darcitinis at this bar we've been talking about. DAVE ADAMSON: You'd be willing to drink that? CHUCK NEWELL: Yeah, but she does a lot of work trying to calculate those loadings. So in some ways, we're talking about a concept that's very similar to this total maximum daily load idea that goes on in surface water. DAVE ADAMSON: Well, that's pretty neat stuff. I think we may want to take a little bit of a step back and address a few questions about mass flux and mass discharge in general. Sort of covering the last three lectures that we've dealt with. So what's the big advantage to using mass flux or mass discharge concepts? CHUCK NEWELL: Good question. Just think about waste water treatment plant discharges from waste water plants. What they want to know is the loading. The seminal capacity is based on these loadings. That's the mass per time, and not just concentration. Concentration in some ways is just one dimension, one factor that you might understand that you might need to know about to figure out the impact a contaminate may have. DAVE ADAMSON: Well, if you're worried about impacts, why don't you just measure the concentration in the well or in the surface water? CHUCK NEWELL: So you're talking about INRS Mackay paper. And the idea was to use this formula. But they were using more as a screening system for plumes. They were saying if this plume continues to migrate, could it cause a problem when it hit that water supply well or surface water? But if you had a plume that had already reached a water supply well, you wouldn't need to do that. The whole mass discharge, you'd just measure that well. DAVE ADAMSON: And then finally I think for an M&A course that we're dealing with, is it really OK to consider dilution when talking about M&A? CHUCK NEWELL: I think it really depends on the program and the contaminant. There are some ideas that the contaminant 1 4 dioxin has some pretty high aquatic levels. It's pretty safe in surface water, relatively. But these other per polyfluorinated substances, they're not. They would be much lower. So you have to think of those type things. Some ground remediation experts have wondered why dilution is relied upon for waste water and air discharges, but not ground water. So it's an interesting question, overall. DAVE ADAMSON: Well maybe let's go over the key points then for this lecture. CHUCK NEWELL: First, mass discharge can be used as a prioritization system for plumes and as a trip wire to estimate if your plume is relatively strong or relatively weak. And then secondly, dilution can be used as an M&A process, but really only under certain circumstances.