 The basic concepts and design aids that you might run into if you're looking to design tile drainage systems, and so we'll start off with, and I'm sure a lot of you have seen this picture before, Gary Sands group at the University of Minnesota created this years ago, but basically it gets across to the right idea that drainage pipes are tile buried in the ground to control the water table, got saturated water soil, and you're trying to control the water table so the crop can grow at its maximum mobility. And you've probably seen this one before, but this just illustrates it, and Hansel hit more on this later, but really you want to keep that water table at a level where the crop has the opportunity to fully develop its root zone, get access to all the nutrients and water that's available in that area, and then be able to grow better, and that's the whole purpose of surface drainage is to alleviate these problems of high water table. So just to give everybody a basic idea, elevated water tables are due to some kind of restricted layer down here, water will sit on top of it, but there is always some seepage through that layer. It's very slow, but what happens if it starts to rain, obviously you get runoff, but you get infiltration, and the water table will start rising because the amount infiltrating exceeds the amount that's slow seepage underneath, so that water table can rise up to near the surface depending on how much rain you get and over how much time, and so that's where the problems come in. So I just wanted to show you how water flows in the tile, at least up here in the Red River Valley, what we've noticed. And where this comes from is that Hans and his research plot says observation wells, and quite often in late July, August and September, the water table is well below the tile drains. Those two black dots you see there are tile, and we've had other research sites up and down the valley which show the same thing. So typically what we see is that by early September, the water table, because a crop uses so much water, is well below the tile, and there's no flow. But if it starts to rain, like it did in 2019, the fall of 2019, pretty soon the water table starts rising, and you see that kind of light blue what I've got above the dark blue, that's what we call a capillary fringe. It's not quite saturated soil and water doesn't quite flow into the tile. It's only one that actually saturated water table rises up above the into the tile that it starts flowing. And then the tile starts flowing and you get a mound between them obviously because water is draining out the water. Water table is still rising from the infiltration. And actually if you look at the flow from the center here over to the tile, it flows into the tile. Research has shown that over 70% of the water that enters tile comes in through the lower half of the tile. So that's what's happening. And then if it keeps raining and infiltrating, the mound can grow up and get up near the surface. So from a design point of view, what we're trying to do is for a given amount of water that may infiltrate, we want to set this distance so that during if you ever get those high flow conditions that the water table doesn't get up right up to the surface and drown out the roots of the crops that might be between the tile. Of course, if you stop raining, stop infiltrating, water table drops down. And in 2019, as we went into the winter into December, this is where the water table was sitting because it was down even with the tile and there was no crop using water. So it was all primed for the next growing season for the next spring. So that gives you kind of a broad cartoonish view of how water might flow in the tile as we see it here. And so just to give you an example, I pulled this diagram out of a Iowa State Bulletin, Experiment Station Bulletin from 1911 showing a point up here that got two transects that they put across this field. System one, system two. And these black lines here are all observation wells in between. They had quite a few. And then the tile is here. The tile lines and you can see there. So on April 13th, the water table was at where the blue line is showing. And then on April 14th and April 18th, they got rain, a total of about 1.65 inches on this site. And on April 19th, when they measured it, the red line shows you where the water table is at. So you can see in system two up here where the tile is quite a ways away, the water table is almost near the surface. But here in between it grows up to within a foot, within a foot. And you can even see that here's a road and there's a ditch and there's some drainage off here. So when you went back the next day on April 20th, that's the green line, you can see that almost all the way across it had dropped almost a foot except over here by the ditch. Excuse me. So that's kind of backs up what I just showed you that that's kind of how tile responds to rainfall events. And that's what we see here, too, is that tile generally responds to rainfall events. There's some exceptions to that. But generally, that's true for almost all systems. So if you look at the water balance, I got a pie chart here. If you took a field and measured all the water into it over the year, you know, this would be the total amount of rainfall and soil moisture that had been there. The green is the amount that you would lose with a crop during the summer, during the evaporation and transpiration. The yellow would be surface runoff from rainfall events. And then you'd always have some seepage down below. But if you tile that same field, what we've noticed is that the evaporation and transpiration actually increases a little bit, takes a little bit bigger part of the pie. And now you can see the subsurface drainage is lots of times it's almost equal to the surface runoff. Of course, that depends on the severity of the storm and so forth. But generally, what we found is that if you say you got 20 inches of rain, you might lose an inch to deep seep reach, you might have during the course of the growing season, you might, you might see 17, 18 inches go up through the crop, and then you might see two inches go out, surface runoff, two go out through the subsurface drainage. That's what we've observed in some of our monitoring up here. And I'm going to show you what happens with tile and surface runoff. This was a field that we'd monitored for four years. And this is in October 25. Now the crops dead. I mean, it's been frozen. It's not using any water. So the red here kind of shows the rainfall amounts as it received over a 30 hour period. So you can see the surface runoff parallel along. And then when we got this second spike here, it really took off and dropped off. So a couple days later, surface runoff had off from the field that is had basically go down gone down to zero. That doesn't mean the ditch receiving it is is is going down because lots of times you got more than one field feeding a drainage ditch. But but look at where the tile this is actually measured values here. The runoff was modeled. But this is actually measured tile flow. You can see about the time the surface runoff started to tile flow peak. From that rainfall amount. But it never did get above. I think it was 700 gallon a minute was coming out of that tile and this 142 acre field. And if I look out over all the way to thanks almost to Thanksgiving, the tile kept flowing. We didn't receive any more rain. But you can see it kept flowing and flowing, flowing all the way out to for quite a bit. And so when I add up all that flow compared to the surface runoff turns out they're both about the same. Quite an interesting fact. But again, tile, the flow coming out is very low compared to what runs off the field. So that kind of sets us up to at least understand tile drainage. So the procedures and tools that you would go through is you would what I'd say for any design is you you got to do preliminary site evaluation. Unfortunately, we have a lot of online tools available to allow us to do this in our office. And there's also paper resources. Primarily what I'm talking about there is you got published so county soil surveys. But you could look at the soils. You can determine what drainage coefficient you want. And why I put that in there is say you're out west of Jamestown, you might use a quarter of an inch drainage coefficient and I'll explain that in more detail later. But in the Red River Valley, you might use three eighths. If you're in Southern Minnesota, or parts of Wisconsin, you might use a half an inch. It all depends on much rain you get. So that drainage coefficient is something that you can select and you can play with in in setting up some of the how to go about designing it. Then of course you can get topographic features. Some of that is available online. And then I always say that you can't do tile right unless you get a field and site visit visit with the land owners. And there you develop more detailed topographic maps in particular the the drains, the outlet, the actual elevation of the outlet may not be what shows up on your paper topographic maps, especially using LiDAR. And then once you have all that information, then you can start looking around at how you do a tile layout on that field, selecting your tile grades, your tile spacing, tile sizing. I got to tell you right up front, it's been our experiences no one right way to tile a field. There are many different ways to tackle it. Some ways are better than others. It all depends on on the field situation and and some of the installation requirements. So so let's start with soils. And I don't know how many of you have ever seen this is called a USDA soil triangle. Across here we have the percent sand going from zero to 100%. The percent clay going from zero to 100% and then the percent silt. So if you take any of these percentages and you can come up with these soil types. So you can see we got sand, lomi sand, sandy loams, and they might have over 50% sand, 20% clay. It's sandy clay loams, sandy clays. And the reason I bring this up is that in tile what we're really afraid of is with standard plastic tile that's perforated, it can handle clay soils. And the rule of thumb is 30% clay, anything more than 30% clay at the depth that you put the tile is you could probably you can use normally perforated pipe. But if you get less than 30% and you got a higher clay content or sand content and sand is the real fine sand is the real culprit here, that can pose problems and you might have to specify using a sock or a fine slot in those areas. Now all fuels are created equal and they're not the same all over. So that's why the soils information is extremely important. So I usually look at this triangle here is this is where you would definitely need sock. And as you get farther out here you that would really depend on on the soils in that field. But anytime you get a lot of you got a tile sand, you're probably going to have to have some kind of a blockage on the fine slot or a sock on the tile. It's an added expense for the sock. But it may in order for this thing to be a long term investment that needs it's needed. So I think Hans will talk a little more about this. But basically, if you took a soil column, and you filled it all up with water, it would be totally saturated, everything all the pores near it be full of water. And then if you could pull a slot here and let it drain naturally, it would drain down to what we call fuel capacity. That's the ability of the soil to hold water against polar gravity. And that is primarily the water that crops use for for their production. And they it's as you can see in the picture here is a combination of water being held by soil, but you also got openings in here where you might have oxygen and soil air is as a soil scientist might call it. And that's what the crop needs both air and water in order to grow. Ideally, if you were to let it drain all if if the crop sucked all the water out, you'd eventually get down to a wilting point. That's the point at which the crop can't pull any more out. But there's still water in there. And the only way you get rid of that is to dry it out in an oven or in a desert, you might say. So that would be oven dry. So this is plant available water. And that's not what we're draining. What we're after what that gravitational water where after it goes out to a drain tile is this water is from saturation down to field capacity. And that can change on soil type. But this is we're not affecting the plants growing condition. What we're doing is taking out this excess water that takes away that soil air and just causes problems for plants to grow properly. So Hans has made a real nice water holding demo on YouTube. I'm not going to go to that. I don't think we have enough time. But basically uses a sponge, Hans uses a sponge to kind of show that you can wear that you can fill the sponge up with water and then it won't drain down a certain point. But then we squeeze it to let what's left over. So we will we will share this link on the resource material that we will give. Just quickly want to know how many of you we have about a third of you that have voted. So wait a little bit who we have the majority. So we know that's good. We have a lot of active farmers with us crop consultants, employees, others. All right, that helps us to to understand kind of what audience we have today. Great. I'm seeing we have about 70 voted so I will just end the polling here. And so the results are that we have at least 50% active farmer. We have some farm operators that have retired agribusiness, public employee, wonderful. So the majority of you are not working for a company. So we will kind of keep that in mind as we continue. So thank you for sharing Tom you can continue. Okay, I want to cover some of the important soil parameters that affect the flow of water through the soil to the tile. And one of them is the saturated hydraulic connectivity. In the old days, some people would have known might have been introduced to this as permeability. But really, it's a we use a term called case that and you'll see this in publications and everything. And case, the there's an old Frenchman named Darcy, who was the first one to really develop this equation showing what that saturated hydraulic conductivity is. And what it is is a measure of how well the water can flow through the soil in a horizontal direction under a different head. So in this case, this is kind of a picture of his of his early experiment. He had a horizontal cylinder, they filled up with soil. And he had added water here, it flowed through. And then it would flow through here. And then based on the different, he could adjust the elevation, he could then he knew the area in here, and he knew the length of this thing. And then based on that, he could calculate the flow rate, and he could measure the flow rate. So based on a number of experiments, he came up with this case that value, which is intrinsic to the soil that you have in there. And this is very important, because this is what helps. We have to have this value to determine what spacing we want to use for a given soil type in the field. So if you look at a picture of like a following what I showed earlier about water in between the tile, you might have water up here. And the water level might be here. So you got a head differential from here to here. So the water is going to flow downhill just like it does anywhere else any difference in head. So it's flowing this way and then enters the tile. So you can see how the Darcy's law is related to tile flow. So we're dealing with horizontal flow and believe me, Darcy's law is also used in a lot of groundwater modeling for wells and other things. That's case set. And what I did is I went through the literature to find out what these values are over a range of soil type. So if we start up here, we got core sand. The bar shows the range of values that I found. It's usually around 50 feet per day that will go through core sands. And if you go as you go down through lomi sands, you can see that by time you get down here, it's about one foot per day that the water will flow through on a silt loam. And silt clay loams all have about that same value somewhere around one or a little less than one. And then when you get to the real fine, sandy clays or the silty clays, or even the clays, you can see now you're down about 0.06 feet per day, which is pretty slow. So the slower the water moves, probably the closer together your tile have to be in order to drain out the same amount of water given all other things being equal. So this kind of gives you a range of these case set values based on soil type. And down to the very bottom, I don't know why I put it in here, but peat and muck have a wide, wide range in designing a tile system for peat or muck. There's a whole different activity and we don't have time to cover it here. So I'm going to just stay talking about mineral soils and not these organic soils. So you can get fuel level soils information off the web now. As I mentioned, we got county soil survey books. A lot of them are getting pretty old, but more, you can go to NRCS. In the US, you can go to a web soil survey and you can go to any field and you can get the latest information. You can zoom right down to your field and get a whole lot of soils information. I tend to I use that sometimes for more detail, but I use a Google Earth overlay called Soil Web. Google Earth Pro is free. You can download it and you can then get a file, an overlay called SoilWeb.KMZ from the California Soil Resources website. I've got the website here. And this is in that list of links that Hans mentioned that we have that on a separate sheet that will be sent to you. And then for Ag Canada, I found that they have soil surveys, but they haven't digitized them that I know of. And but you can go to the site and you can get their access to these paper copies and PDF form and a Manitoba. You can you can get them there. So just to show you the Canadian version, here's for the Morden-Winkler area, straight north of Walhalla. You can go into there and then within this book, they have a table of estimated engineering properties of soil. So over here, you can see the soil series name like a Winkler clay. And if you look over here, here's the disturbed hydraulic conductivity and inches per hour. You can see it varies by depth from 0.05 to 0.1. If we were to put the tile down at this level, you know, you might use a case at of 0.03 or something like that. If this is all the information you got in contrast to that, you can look up here, this is Flanfield loam. You can see the estimated down this 48 inches. So down if you were down in this range, you'd be two to three. So you got different case sets for different soil types. And that would then affect what spacing you might have. So that information is available. And like I said, I really had this up once before. What I'm going to do is share my screen again and then I'll bring up an example here. This is a site south of Fargo. A gentleman actually contacted me, but he had, as you can see, he has some water problems on here. And so if this were a site that you were doing some preliminary investigation, this is on Google Earth Pro. Here's over here is that soil web. If I click it on, it'll turn on. And this is exactly the same information that you would get from WebSoil Survey because they're tapped into exactly the same database. So one of the nice things, the reason I like Google Earth Pro for some of this evaluation. So let's see, I click on this soil here. It shows that it's a Glendon loam, slightly saline stratified. And 75 percent is Glendon, but you got some Mantador Tiffany in here. So if I click on here. It'll bring up this and then I can look at this Glendon, since that's the majority of the soil in there. And it gives you a lot of information that you can look at. But if you go down here, what they've done real nicely is they showed the variation by depth down to 200 centimeters or two meters. A little over six feet. Although the NRCS usually only samples down to about five. But you can quickly see here, the percent sand case that you can see that it varies, it's above 10 and then it increases. And this might be the depth that you put the tile. So this is where you might be interested in looking at. You can see the percent sand content goes way up. And the clay content goes way down. So if you're putting a tile in at three feet, which is about 100 centimeters, you probably have to have sock in this part of the field. Now, the nice thing is, you can click on this and you can get a table that shows all of those. So here I've got the depth and range. And I can look at the percent sand. And you can see from 71, it's about 81 percent. It's less than that underneath percent clay. And then you can look at the case that values. So here you definitely have two different cases, one up here and one down here. Yeah, so it's to me, it's a really nice feature. So I'll go back to that and then you click on this button up here and we'll go back to Google Earth. So if we wanted to look at this soil real quick, you can do the same thing. It's a coven silty clay loam. It's about 84 percent of this coven. I bring that up and look at the coven. Now you see that percent sand is pretty standard. It's seven all the way down, percent clay is 28. Case that is very low. So quite a difference just in that one field. And that's one of the reasons I kind of like this is that you can quickly look at fields and soils and get a pretty good idea of what the variation is across that field and with depth. So let's go on with this drainage coefficient. I talked about this earlier. The drainage coefficient is a design. It's a depth of water that you remove from the soil in 24 hours. So typically with field crops, we talk about good surface drainage. You might it might be a quarter to a half an inch for field crops, high value crops that might be a higher. Just because you want to vegetables and other things are more sensitive to excess water, you might want to get it out of there faster. But the drainage coefficient is a design point. What I mean by that is it's going to be used to design the carrying capacity of the tile to remove a certain amount of water and a certain amount of time. And that doesn't mean that the tile always flows at that amount. This is the maximum design point. So to give you some idea, maximum flow from tile outlet. If you designed at a quarter inch drainage coefficient. That would be a quarter inch per acre. That would remove about in a 24 hour period about if it was flowing at maximum capacity at about 6,800 gallons a minute, 6,800 gallons total or about 4.7 gallons per minute per acre. So if you had 100 acres, you could expect that the flow coming out would be about 470 gallons a minute. If you designed at 3 eighths of an inch drainage coefficient, then you would be about 10,000 gallons would flow out. And that'd be about seven gallons a minute. A half inch drainage coefficient. Would be about nine and a half gallons per minute. And this, the drainage coefficient is very important because if you have to put in a lift station, this is one of the basics of design for lift stations. So whatever drainage coefficient you select, based on a lot of it is based on how much rain you get in your area as to which one you would pick to design on. Just to give you some idea, this is a site in Richmond County, 142 acres. This was in 2010, a very wet year. I think between April 22nd and November 18th, we received 25 inches, over 25 inches of rain, almost 26. And you can see the fall, we had a lot of rain. And that's when we had our maximum flow coming out. But it peaked at about 500,000 gallons a day, coming out of the tile. But if you looked at it in terms of what's the drainage coefficient and a quarter inch drainage coefficient, this 142 acre field should have been draining about 966,000 gallons. So we didn't even get, we were probably draining out about an eighth of an inch drainage coefficient. And three eighths, this system was designed for a three eighths drainage coefficient and was actually one and a half million gallons a day would come out if it flowed at that. Over four years, we never saw this site do that. And this is exactly the same graph. But just to give you some idea of this is the estimated daily water use removed out of that 4200 acre, 142 acres by corn over the growing season. So started pulling it. They were able that year planted in April, harvested in. And you can see in this one day, it pulled out almost 1.4 million gallons of water and a crop did. It's a real good growing day. And of course, you can see some of the weather patterns coming in here. You had days when it goes real low and this is not unusual. But just backs up that pie graph I showed you earlier where most of the water removed out of the soil is going up through a transpiration and evaporation. So LiDAR is light detection and ranging more and more places basically describe it. They fly over an area, usually this time of year where there's no leaves on the trees and they shoot millions of laser pulses at the ground and then they reflect back and they're able to record them. And then based on that, they can make topographic maps for large areas. So in the Red River Basin, they have a LiDAR viewer where you could go to to look at fields, Minnesota has their site. You can also download their files in North Dakota. A lot of theirs is on the State Water Commission website in the LiDAR and again, I'm not real from, I know that Canada has some available. I'm just not familiar enough to know where you would find that but this is a, almost as soon as this became available a lot of our tile installers started downloading this and fitting it right into their software packages so that they could superimpose this on top of their as part of their design guides. Welcome to us, one question. How does drainage coefficient relate to KSAT? Oh, there's, the drainage coefficient is an engineering design point and it is used to size the tile, the carrying capacity of the tile of the pipe. The KSAT is a measure of how water moves through the soil to the tile. So they're not related really in any way. But both of them are used as part of the design process. Is that good? So I would say KSAT is more intrinsic to the soil types are in the field. The drainage coefficient is the value you select for your area and rainfall patterns to use to size the tile so that the water flows in and carries it away. I hope that. Anyway, so to go on, here's a topographic map of an area, actually one of our former county agents. It's one of his fields, but I went to the Red River Valley site and I was able to pull this up and you can see that, well, let's take the top of his field here. You can see the drainage patterns going down and go down this way. Up at the top, it's, take that over, it's 1,490 feet. This is 1,488, so those are two foot increments. So you can see it gets down to 1,480, 78, 76 and it pretty much flattens out right in here. You can see a holding. So this is the type of information you can get to quickly look at topographical information, access to LIDAR. And again, working with LIDAR, that would be a whole separate workshop that might take a whole day. So I always say that you, from after this point, after you're doing the paper one, you got to do to your field reconnaissance. Basically you're meeting with the landowner or renter, you'll get a whole location services in case there's any very electric lines, gas, oil, rural water, et cetera. Identify wetlands. If there are identify wetlands and then you're in the farm program, the NRCS would have to calculate a lateral effect distance so far you'd have to stay away from them. And then just note basic boundary conditions, roads, culverts, so forth. Current surface drainage system, soil types, we already went over that, whether there may be salinity or sodium issues, where the high and low spots are. And then the big important one is where's that water gonna go if you drain the field. Usually it's gonna go the same place that the surface runoff goes, but this becomes a very, very important part of drainage layout and design. So in this case, this is a Red River Valley field, hardly any slope at all, 2000 feet. You can see it's at 10.6 there, 10 there. So you got about a six tenths of a foot drop across this field and the outlets over here. So, and there's a ditch there and note, and you measure the bottom elevation so you know how much of a depth you got to work with if you're gonna put a system on here. If you got a field like this, you gotta quickly identify the outlet. Look at these topographic maps. First thing off, if you look over here, the ones close together, you know that steep. So you don't have to go very far to go from 48 to 47. So this is a steep area of the field. And on top of graphic maps, anything pointing downhill is a ridge. Anything pointing uphill is a swale. So you got a ridge here, a swale here. Yeah, kind of a swale up through here. And that's one of the secrets of looking at topographic maps. Just remember that ridges point downhill, swales point uphill or ditches point uphill. So I recommend measuring a lot of these particular points, you know, potholes, outlet elevations using our TKGPS is one way. You could do it the old fashioned way by surveying, but this works out pretty good. This several years ago, we had a couple of students do a project with us and they were out surveying one of the fields on campus here for some of the weed researchers. But they have a base station here and then the portable unit. And of course, this thing is the one that gets the accuracy and then feeds into this one, but you need that kind of accuracy in order to determine, especially on flatter fields, how much elevation you actually have to work with. And when we talk about elevation, we talk about rise over run or tile grade. So if this was the main and you're putting in a lateral, if there's a rise over the run, we talk about tile grade and percent. So typically, for example, 1.1% grade would be a one foot rise or drop in 1,000 feet. We don't go by just a slope. We go by the grade, 0.5% grade would be a five foot rise or drop in 1,000 feet. And you can run into both of those in the valley and that affects how fast water moves down the tile. And this is where the question about the drainage coefficient, the size of the main would be affected and by the flow of that. So can you change grade? Obviously, a lot of the newer systems on the tile plows allow you to measure the elevation and then a lot of them have software that will automatically adjust the grade as long as you're continually going up. So you got a flatter grade here, steeper grade here. What we don't want is these kinds of things because this is where sand accumulates, this is where water sits. This affects the drainage. So if you hit a rock or something else that's buried and it changes the grade, you have to or something affects it. Even I've been told that your GPS can actually vary from day to day and be kind of off if you were plowing in from one day to an X. So this type of situation is we don't want. So grade control is extremely important to make sure if you want a long lasting tile system. And spacing, and this is where the case that comes in is it's gonna allow us to calculate the correct spacing so that we have a situation like this. Like I showed you earlier, we don't want this where it doesn't drain in between. And so this crop gets flooded for a period of time and affects its growth. So just to give you some general idea, if you look over here, you got clay loam, silty clay, silt loam, sandy loams. The drainage coefficient of a quarter inch, you might have your tile spacing combined with your case that is gonna be wider because the case that the sandy loam, the water is gonna move through the soil a lot faster to remove the same amount of water under given conditions of a selected drainage coefficient. Three eighths, you can see there's a range from clay loam to sandy loams. And if you went to half inch, you can see that you're getting closer together because you're removing more water in a 20, we're usually working on a one day idea of removing that amount of water. So this is an interesting looking formula I'm sure Latia, you don't have to worry about it. I put it up here because I wanna show you that the drainage coefficient is the amount of water we expect to infiltrate to drain out of the system. And the case at is this value. So one of them is for below the tile and one of them is for above the tile. Although a lot of people just assume that it can be uniform between them, but you can calculate the spacing once you have this and you have this from your soils. And fortunately, our colleague, when he was with South Dakota State University, Dr. Chris Hay developed this real nice drainage calculator that will calculate a number of processes for you. I would suggest everybody attending today, go to this website and just check it out. But I'm gonna stop sharing and actually go there and we'll look at, this is the actual website. So if I wanna, if you see you got drain spacing, you can average hydraulic conductivity if you got two different, like I showed you in the one soil earlier. So let's go to the drain spacing. Oop, there we are. So let me pull this out again. Okay, I think everybody can see that. So up here, you got your drainage coefficient and you can put in anything you want. I'm gonna put in, just for the heck of it, we'll put in 0.375, which is three eighths of an inch. I'm gonna go with, in this case, four inch tile. And we're gonna put it in at 3.5 feet. Now there's depth of restrictive layer. If you don't know, and it's usually really hard to determine, but we usually just assume that that clay layer that's keeping that water from going down is about 10 feet down. If you have better information, you can put in whatever it is. So if I put in 10, the minimum water table depth, I don't want, when we're in full flow condition, I don't want that water table coming up between the tile to within the foot of the surface. So I'm gonna put in, that's the minimum water table depth between the tile. I put one there. And then hydraulic conductivity units, you can select whatever they come in. Let's look at feet per day. And so from looking this up in the soil, let's say we got one. You know, calculate and say for these conditions, the tile has to be 49 feet apart. Can it be 50? Well, of course. Where these are all, you know, we're kind of approximating some of these things that hydraulic conductivity value could be higher or lower, but generally this gets you into the ballpark. And it's also it's very handy. You can change these values. If I went to three inch tile, it would be 48 feet. It doesn't, you can see it doesn't make a big, a lot of difference. What happens if you had this restrictive layer at four feet though? Let's say it was just below your tile depth. I have to go closer together. Why? Because there's no flow underneath the tile. So it has to flow horizontally. So you have to be closer together to remove that amount of water, that three point, this amount of water in a day. Again, this is a design point. So, this is a very, very handy. I'd encourage everybody to go there and just kind of check out the different ones. Chris did a nice job all the way down. You can fall the grade, the grade to fall, area drain, pipe sizes. If I go back to here, just showing you that as you go deeper in depth, the spacing gets wider. Why is that? Well, assuming that the area between a tile, you want to keep it level. The head differential gets greater as you get down deeper. So therefore the water can push through faster so you can go wider. So you can four foot 62, all things, all else being equal. So the shallower you are at a close, you got to be together and so forth. So to finish this up, tile sizing. So we use, there's an equation called Manning's. And I put the formula up here because you can calculate the flow rate in tile, the maximum flow rate using this formula. And I wanted to point out that N here is a roughness factor. And so the, this is the diameter of the tile, inside diameter, of course divided by 12 compared to feet. And this will calculate the flow rate in cubic feet per second. So this can be, there's a number of normal graphs and other things out there that will calculate this for you for a given amount of area, how much, this is used to help size the monotile, size tile you need to move the water over from a given size field. So in a class, we use a principle slide rule, but all the manufacturers have a slide rule like this. And basically solves that equation for you. And the nice thing about it is, you can see the slide sticking out over here. And what I've done is I've set three eighths of an inch drainage coefficient of 80 acres. The drainage coefficient is here. I put 80 acres in there. And then if you're using single wall, it would tell you for what grade, what size pipe you could use. So of course as the percent grade increases, the pipe size decreases because it can handle more flow. So if you're on a 0.1% grade, you would need a 15 inch pipe to handle that maximum design flow out of 80 acres at a 0.1%. So we also have a spacing calculator spreadsheet from Iowa State that we can send people, does the same thing, although you can just, it's a Excel file, so you wouldn't have to go online. You can do it on your computer. But in the interest of time, I've already, you heard me talk it. I apologize for that. On my screen, it looks the same, but anyway, so the deeper you go, the wider you can go on drain spacing for given, all things being equal because you got more head to work with to push water into deeper. So as you go deeper, you can go wider. That's just a fact of tile flow through soil. So, and this is the equation I was talking about. It's Manning's equation. You can calculate the flow rate through a tile at different diameters based on grade and roughness coefficient. So, and you can see this good, right, Hans? Yes. So anyway, here's the drainage coefficient. I got three, seven inch up here. You can see the slide out here and the slide rule. I set it at 80 and then down here, you got 0.1% slope and you need a 15 inch tile, although we have to 0.2%. But once you got up to 0.3, you could use 12 inch. If you're using dual wall for a portion on this 80 acres near the outlet, you can see that 0.1% slope or just above it, you could get by with a 12 inch. So why is that? Because dual wall inside is plastic. It's not furl so it doesn't present as much resistance to water flow. We also have down here, they put on there that you got four inch pipe size. You got 10 rows on it, coil lengths, 3,000 feet. So that's a handy feature to determine how many feet of tile you got by inch. And this is, of course, that's Prince Co. I don't know if all the manufacturers follow that same, but that's, it gives you a pretty good idea, a quick idea of how much is in a coil. This is the backside of the slide where you can put in the percent grade and then just look across here and pick off real quickly what the flow rates are. So at 0.1% grade when the tile's flowing full, the, it would be about 0.452 cubic feet per second. There's 450 gallons a minute in a cubic foot per second. So I don't know why they didn't put gallons on here, but you can see that the carrying capacity, of course, increases with the size of the tile. And again, this is calculated for full tile flow. And if you have dual wall, you can look at the same thing and see what the flow rate is for that. You can also pick off the velocities down here. So too bad we aren't in class, I could. So the topics and tools we covered today was, that was a real quick run through is how water enters tile. That preliminary site evaluation, really looking at the soils, trying to get an idea what the quayset values are, a drainable amount, clay sand fractions. So there is a question on that one, Tom. So the question is, if you have a lot of variability in quayset values within a field, would that then affect your design? Yes, it would. As I showed on that example, when I went to Google Earth, that middle of the field, the quaysets there were pretty sandy. So in that part, you probably could have, the quaysets, if I remember right, were somewhere around 33 of the units that they had. And then when you went over in the far right next to the road there in that soil type, the quayset was three. So that would definitely, in those areas, it would change your spacing. If you had variable quaysets like that, and that's why you need to do that preliminary check. That okay? Yeah. Then of course, the topographic features are the biggest thing. You can get them online, but you still have to go out and survey some of these, like the outlet and ditch bottoms and so forth to make sure that you have a pretty accurate evaluation. And then once you go to the field site, you can take a paper copy of the map with you or whatever, or on an iPad and mark up these topographic maps to note these where there might be things that don't show up on the paper. And then we talked about tile grades, spacing and sizing. So those are the tools you might use.