CHUCK NEWELL: Here is lecture five of our series, "Dilution as an Attenuation Process," sometimes. After talking about mass flux, mass discharge last lecture, in this lecture we're going to talk about the five methods to get those numbers. DAVE ADAMSON: But to start off with, Chuck, maybe we recap the key concept from the last lecture. CHUCK NEWELL: OK, so if you know the mass discharge in grams per day, you can estimate the potential impact of a water supply well or stream or stream mixing zone. DAVE ADAMSON: We've got an example here then. And so we can go through the units, basically. These are US units. Time gets canceled out, and gallons, we convert that to liters. And grams get converted to micrograms. Then you start with mass discharge and flow rate, and at the end, you end up with this concentration, micrograms per liter. And that's the concentration in the water, being pumped at the well. CHUCK NEWELL: That's right. And just to confirm, this is more for a case where the plume has not reached the well, but one where you want to get an idea of what would happen if it did. So more hypothetical, you're trying to estimate that potential risk. And this mass discharge concept, that 2 grams per day you're seeing on this slide, it's really coming from this idea of a vertical transect as one way to get this thing. So here's this transect. It's vertical to the ground, it's perpendicular to groundwater flow. DAVE ADAMSON: And the idea is essentially you're combining the plume size, the Darcy velocity, and then the concentration in that plume. CHUCK NEWELL: That's right. And to do some of that math, let's bring in my new best friend, Sir Isaac Newton on this. Let's look at here, we're going to define two key terms. The first is mass flux is the mass per time per unit area. And it's on the left. And you sort of see different areas have higher mass flux and lower mass flux. Now if you integrate this over this entire area, you're left with a mass discharge, mass per time. And so in terms of integration, it wasn't one of my strong courses in there, I asked Sir Isaac Newton to do this. So he integrates it, and he says, hey this plume has a mass discharge of 1.5 grams per day. DAVE ADAMSON: Well, you know you've told me stories about your struggles with calculus. So I'm glad you asked Newton to do this for you in this case. CHUCK NEWELL: That's right. So one thing is I've learned two amazing things about Newton, as we went through trying to figure out some of the pictures for this. The first was his description. He didn't use the word calculus, but he called calculus the method of fluxions, which is really pertinent to our idea about mass flux here. So that's the first thing that I learned. DAVE ADAMSON: And the second thing is? CHUCK NEWELL: The guy had amazing hair, really good hair. DAVE ADAMSON: Amazing hair, well, better hair than you? CHUCK NEWELL: Certainly. DAVE ADAMSON: OK, well let's move on. CHUCK NEWELL: OK. So then the ITRC-- Interstate Technology and Regulatory Council's DNAPL team, and I was on that team, put together a great guide on how to get mass flux and mass discharge numbers. You can read the guidance, you can sign up for online training or see some recorded training sessions, be a clue-in. One of the key things we did in that guidance was to say you can get the mass discharge values using one of five different methods. DAVE ADAMSON: One of the things that I recall, when you're going through this is that you sort of say there's five different personality types that might be associated with each of these individual mass discharge methods. CHUCK NEWELL: That's right. You remind me, and I'll tell you the secret of finding the right mass flux method for you. So we're going to start, and this is the first, method number one. It's the transect method. And you basically draw this line in the sand, and that's this vertical plane that's going perpendicular to groundwater. And then you set up these window panes. In the bottom right panel, we have two of these window panes that are in there. You determine the area, that's the width. And b is that thickness in the saturated zone. And then you're going to do this calculation. We're going to take mass discharge times the concentration times the area times the Darcy velocity all together and then get this mass discharge, or sum up each window pane to get the total mass discharge for the plume. Let's list an example of this. So if you do this example in this slide, it's just a couple of these different polygons. But if you take data like this, you can get some very high resolution ideas of what that mass discharge is. DAVE ADAMSON: OK, and this is the 2005 paper, the Guilbault, PCE site, right? CHUCK NEWELL: That's right. And so looking at all this stuff, you can integrate this. And that's what they did in this really great paper. In the end of day, they said the mass discharge at the site is about 56 grams per day or what we call a mag 6 plume. DAVE ADAMSON: Well, I understand the 56 grams per day. And then the mag 6 plume we may need to explain a little bit more. CHUCK NEWELL: We'll do that in the next lecture. How's that? DAVE ADAMSON: OK. CHUCK NEWELL: So plume magnitude, that's something new. But we'll go into that in more detail. But that's the first method. That's the transect method. DAVE ADAMSON: OK, well what personality type should use this method then? CHUCK NEWELL: The way I talk about it is that if you're a real outdoors type, you like putting on those steel toed boots, you like wearing that hard hat, you like going out there and collecting all those 40 mil VOAs and put in the ice chest, you like to belly up to that FedEx and mail those things out. If you like to take groundwater samples, this is for you. Because as you can see in this graph, a lot of groundwater samples were taken. Let's go to the second method. And this is called well capture methods. And the idea that we're going to sort do something different here. There is a pumping well. Instead of measuring this contamination all for itself, we're going to draw to the surface and measure the flow and measure the concentration. And as you can see, the units here they cancel out, and you can get a mass discharge. You can't get a mass flux. And there's some cautions you have to take about when you apply it, like making sure you're at steady stay conditions. But this is the well capture method, a pretty easy way if you have an existing pump and treat system to get that mass discharge in grams per day. DAVE ADAMSON: And so what personality type would be associated with this method? CHUCK NEWELL: Well, the idea is that if you like pumps, if you like any type of pumps-- centrifugal pumps, bladder pumps, jet pumps, top drive pumps, Moineau screw pumps, any type of pumps-- you just like to put metal in the ground and corral it and lasso that groundwater plume and bring it to the surface, this is the method for you. DAVE ADAMSON: Well as much as I'd like to hear you list as many pumps as you know, maybe we'll move on to method three. CHUCK NEWELL: OK, this is a really neat one. This is passive flux meters, invented by two professors, Kirk Hatfield and Mike Annable at the University of Florida. You put this instrument down in a well, and water flows through the screen and through the instrument. Two things happened. There's a permeable sorbent, which will absorb your contaminant. And if that thing is down in the modern well for two weeks, you can get that flux that's sorbed on to the sorbent. They also have soluble tracers, to give you some idea of what that Darcy velocity is. Look at the top right hand panel. You see they used the dye, and it's sort of filling in. So as the time goes by, the sorbent will sorb more of that. Think of that being your contaminant-- TCE or benzene or whatever. And so at the end of the day, you get thess-- it will do you some convergence calculations. So a pretty neat method that you would use to do that. Let's look at some photos of this. It's really looking at some of the installations, some of the sampling. But there's the flux meters themselves. The water flows through there. Pretty easy to install, you just put them in there. DAVE ADAMSON: What personalities would be interested in this method? CHUCK NEWELL: Maybe the personalities of the two inventors, right there on the left, from the University of Florida. Anybody who likes new gizmos, likes exciting new concepts, integrating things together. If you're that type of personality, like these guys, then this is what you'd use. Let's go to method four. And this is using existing data, like transects based on isocontours. And this is the idea that you would take existing information you have in your site reports. And then instead of drilling wells to get this data, you're going to draw your line in the sand, as you see in the map there, just with a pen and paper, and sort of construct synthetic transects. And then you'll know the width, you know each window pane. You can use the groundwater contours as these places where you have an estimate of what that groundwater concentration is. At the end of the day, you can do the same thing as a transect method and then get this mass discharge. DAVE ADAMSON: This is a pretty neat method better. So whose personality does this one fit? CHUCK NEWELL: I'd say this is a person who really doesn't like to leave the office. You don't have to do any field work. So your office is in a cube, you're right next to the kitchen. There's coffee there, peanut butter. So that's the one for you. Sort of a controversial method. Because some people say without high resolution sampling you're going to miss some of this. But our group said, no, these plumes have information. You can extract it using this synthetic method. So that's method four. DAVE ADAMSON: OK, well what about method five, the last one? CHUCK NEWELL: The last one is using computer models. If you think about it Dave, these models, they're just built in a great flow and concentrations and source sizes and everything else. So here's an example from REMChlor, rewritten by Dr Ron Falta, a US EPA model. It's very mass discharge centric. That's the units, kilograms per year. This is like kilograms per year. You can sort of see here over time they've remediated the source, and the mass discharge goes down. But there's a little bit of that slug going down the snake. But we list a lot of different computer models that will give this information. But this is this fifth method. DAVE ADAMSON: I feel like we've covered all possible personality types. But who's left? Who would want this method? CHUCK NEWELL: I think it's people who like computers for anything, like gaming, music, movies, dating, whatever. If you're into using computers, that's the method for you. DAVE ADAMSON: OK, well I'm thankful there's only five methods. But it covers a lot of bases in this case. CHUCK NEWELL: OK, well let's wrap up. The idea is that if you know the mass discharge somewhere upgradient of a water supply well or a receiving stream, you can estimate its potential impact. DAVE ADAMSON: And we went through the five different methods, basically to get these mass flux or mass discharge measurements. And there's a lot of guidance provided through that ITRC mass flux, mass discharge document.
