Get your notepad ready because Pivvot is taking you back to school. Joining Terracon means we have new coworkers to not only brag about, but learn from, and because our parents taught us sharing is caring, we’re inviting you to join the fun! For the cherry on top, we’re handing out AIA credits to those that attend the live event.
Our Geotechnical 101 Series begins with industry leaders, Ryan Feist and Levi Denton. Ryan is our National Director of Geotechnical Services, overseeing the quality, growth, and development of over 550 Geotechnical Engineers and Levi leads the quality, safety, and operations of the largest drilling fleet in the country.
Ryan and Levi will walk you through their roles during the geotechnical phase of the project lifecycle. Learn how these subject matter experts evaluate subsurface conditions, characterize a site, and provide engineering recommendations and consultation services in order to align design elements and site mitigation techniques to the owner’s needs and risk tolerances. Also, learn how Pivvot’s solution can be utilized to save time and budget during the site selection process, determine the slope of the terrain, depth of bedrock and other geological factors that are useful for geotechnical experts to be aware of.
Webinar Main Topics:
- Geotechnical Engineering and the Project Lifecycle
- Site Characterization
- Typical field and laboratory testing
- How subsurface conditions impact your projects
This first webinar will set the foundation (pun intended ;) ) for part two, “Solar Site Characterization and Engineering” where we’ll have Jimmy Jackson, P.E., aka Solar Geotechnical Engineering King. Jimmy will walk you through what every geotechnical engineer wishes you knew during solar site selection. How does the depth of bedrock, soft clays and other factors impact project site configurations, schedules, and budgets.
- Levi Denton, P.E., National Director of Site Characterization
- Ryan Feist, P.E., National Director of Geotechnical Services
Moderator: Jessica Turner, Client Development Manager, Pivvot | Stage1
If you are interested in speaking with an expert, please fill out the form below!
Background Music - Speaker 1 (00:00:28):
Jessica Turner - Speaker 2 (00:00:57):
Welcome everyone. Thanks for, we will go ahead and get started are in the right place. Both also sit back and enjoy the music. Get started here. All right. Welcome the webinar we are hop on and make sure they're all set up.
All right. So we are going to go ahead and get started. I am Jessica Turner and I am just here to kick us off and hand it over to some of our awesome guest speakers that we have today. Just a quick couple of things that we need to go over before we jump in all attendees have been muted. However, there is a Q and a feature that you can use, and you can use that throughout. However, just note we'll, we'll try to keep track of it. And, and there may some responses that are happening in there, but we will have about five to 10 minutes at the end, as we're wrapping up to go through those Q and as in more detail, there is a recording that we will send out to all registered attendees and it will be available on our website as well. And then if you are here and you are hoping to receive AIA credits for this presentation, we will be kind of tracking who's coming in and out. And then at the end of the AIA portion, we will actually give you a link so that you can just give us your name and your AIA number and let us know if you actually want a certificate or not. And we'll provide that at the end.
So, with Terracon, we always like to start every meeting with a safety moment. And today is that it would be good timing to talk about mosquitoes. And as the temperatures are kind of hitting their peak here in north America, and we're working outside more and playing outside, and it just enjoying where we, we are living and working insect safety is a topic that is often forgotten. So besides the annoyance of basic insects by insect bites, it's also important to think about the diseases that are transmitted, transmitted by mosquitoes in particular. So obviously they've got a wide range of viruses, including Zika, dengue fever, and west Nile virus. So just make sure that you're kind of keeping that front of mind as you're outside hanging out and enjoying the weather.
All right, this is our first of our series that we're, we're starting here. So we've got the geotechnical 1 0 1 series that is this AIA credits, and that is the basics of what a geotechnical engineer does. And we really like to highlight that it's not dirt it's soil. The next one in our series is actually the solar site, characterization and engineering. So we've got Jimmy Jackson, one of our solar SMEs that will be leading us through that. And then we've got the geotechnical perspective for electric transmission routing as well. When we wrap up that Geotech 1 0 1, we'll head over to environmental 1 0 1 and kick that off a little later in the fall.
All right. So the project life cycle, we wanted to just give you a high level overview of this before we, we took a dive into the geotechnical pieces of that. So this is a client centered approach to how we work at Terracon and, and now pivot. So you can see here, we've got flex site design and mitigation, then construction, and then managing your assets. So in today's presentation, we have some awesome speakers that will be going through the design and mitigate side, and that's the geotechnical services, but they'll also hit on how you can get information a lot earlier in that project life cycle process, to make sure that you're, you're making the most out of that project process.
So this is, is the portion that we're heading into the, the a I a credits. We are registered provider, and here's all the, the information we need to provide on this. This is the SGC 0 0 1 presentation. And you are really lucky because we have some awesome, awesome speakers that have joined us. And we're very, very thankful that they are here today. We maybe had to put a couple of our, our pivot employees. Next paycheck rep is collateral to try and get these folks in here. They are just awesome. So we did manage to convince them to come on. They are famous and not to boast, but we've even got one. I'm not going to tell you which one that has a street named after him and his family in Ohio. So we've got Ryan Feist, who is our national director of geotechnical services. So he oversees the quality, the growth and the development of over 700 geotechnical engineers throughout the country, an organization. And then we have Levi who is our national director of the geotechnical site characterization. So he oversees the quality safety and the operations of one of the countries, or actually the country's largest drilling fleet. So now I'm going to hand it over to Ryan and he's going to go through our learning objectives,
Ryan Fiest - Speaker 3 (00:10:13):
Jessica you're too kind. Thank you for the introduction. Yes. The, the purpose of, of this presentation, some of those learning objectives behind it is just a, a general overview of what is geotechnical engineering. We will spend some time going through different collection methods on site characterization. How do we collect those soil and bedrock samples out in the field? And then how do we analyze those for different soil, characteristics and properties? And then we'll get a little bit into what some of that engineering analysis and consulting looks like in a traditional geotechnical engineering report.
So what, what is geotechnical engineering? And I must say when, when I'm out and about, and people ask me, oh, what do you do for a living? I, they usually start with civil engineering. Why? Because when you say geotechnical engineering, a lot of people don't know what that is. And if they start probing a little bit, then, then perhaps I'll, I'll tell them, I'm a geotechnical engineer, but the fundamental of it, the foundation pun intended is that geotechnical engineers interface between the earth, the soil and the bedrock and structures, and that the structures can be pavements, retaining walls, buildings, solar, arrays, whatever we're putting on top of it. How does, how do those structures interact with the soil they're, they're resting on?
Right? So this is all relative. Tell you a little bit of a story. As we get started, my parents have a greenhouse and I say, I grew up in a greenhouse that's. That was my first job as oh, mid teenager. And I recall when I was working at the greenhouse, I was filling pots with what I thought was dirt. And at the end of end of the shift, I went up to the grower and I was like, Hey, I I've got some extra dirt. What, what would you like me to do with it? And this person just shook their head and said, Ryan, it's not dirt. This is soil. Dirt is the stuff that you see outside you plant in soil. It's like, got it. So next five years, I was working with soil in the greenhouse fast forward. I'm now in college and I'm in my soil's lab.
And we're, we're doing a Proctor, which is one of the lab tests to see what the density moisture relationship is and get done with the test, working in my group. And I go up to my professor who eventually ended up being my graduate advisor. I said, Dr. Bowers, we're finished with the test. What should we do at the extra dirt? He just shook his head. Didn't say anything until the end of the class. And he says, some of you may call this dirt, but I will tell you, dirt is what you plant in. This is soil where we have engineering properties of it. So, the point of the story is it's all relative and its soil to different people. It's important to different organizations.
So, for this presentation, we're going to talk more about those soil properties. How do we think of it? Like steel that I beam, we know what the properties are. We have specific manufacturing, qualities and procedures to get the, the right tensile strength of that steel. Well, soil's got a lot of different components to it and it acts differently depending on what the ratios of those different soil types are within it. So it's our job to figure out what the properties are of that particular soil and how that will impact whatever structure we're putting on top of it. So, with that, I think we're going to switch over to Levi and he's going to walk us through the site characterization. What are some of the, the equipment that we use to collect the, the soil and bedrock samples? And then what type of tests do we do to identify what those engineering of the soil are? Levi.
Levi Denton - Speaker 4 (00:14:55):
Thanks, Ryan. Can you give me an audio check?
Ryan Fiest - Speaker 3 (00:15:01):
You got it.
Levi Denton - Speaker 4 (00:15:03):
Okay. Thanks. You're seeing the drill R here.
Ryan Fiest - Speaker 3 (00:15:05):
Levi Denton - Speaker 4 (00:15:06):
All right. Great. Thanks. Thanks Ryan. Like Ryan was saying, we're going to get into now, you know, how do we go out and, and, and grab those soul samples and evaluate it. And, you know, as, as Ryan indicated, you know, we don't have a, we don't have a manual for that. So we can't grab a book and figure out what the, you know, what the compressive strength or the you don't stress, or that is. So, we have to actually go out and get these, collect these samples and, and bring them back and test them and look at them, touch them stress them to their limits so we can, so we can learn about them. And so, the first thing is geotechnical engineers, we have to do is actually go out and, and, and meet it and meet it where it's at. And that's in the field where you're going to be doing the, doing the projects.
And so when we talk about doing geo site characterization, a lot of the first thing people think about is, is a drill rig or soul sampling, some type of soul sampling apparatus. And so that's kind of what you're seeing here. And that's, that's primarily what we might, might engage you out there and do something like that. But there's also, there's lots of other ways you can do it too. And I just thought, you know, and, and we'll probably focus on drill rigs and those more typical ways, but I just wanted to point out that there's, there's lots of things you can do to go characterize a site. You know, first off you can go, just visit a site. You can look around, you can look at, you can look at natural rock cuts, you can see what's going on out there, how things are behaving, natural, you know, just natural features of the land.
So there's a lot to gain just by going out and taking a look when you're exploring. So from a site visit, there's also you standard penetration test boards, which you'll talk in more detail about kinda like from like this machine you're looking at here, drill rig. We can go out and do test pits with like excavators or backhoes. We can do geophysics types of explorations. We can look at groundwater monitoring, well, data, install, Wells, and then we can also do more, more advanced testing, what we call tests or like comp penetration, testing, some other, some other methods like that. That we'll talk more about in terms of going out with exploratory equipment. There's lots of different kinds of, of equipment. So the, the first, the first one you saw on that previous screen was a, was a track manager rig, but there's also numerous types of exploratory rigs.
And one of the things you got to think about when you're going out are the conditions you're going to be encountering, and that'll dictate to a large extent what type of drilling rig, for instance, you might take out there. And, and then also it depends on what kind of test you're going to be trying to do, whether you're going to be doing some AER drilling or with some rotary work or pouring, or whether you're going to be trying to push a cone or, or some other type of device. And so there's, there's lots of different options. There's these track mounted pieces of equipment, truck mounted. So if you're a, you know, smooth, flat pavement type services, a truck might work well, but if you're in a, a more rugged landscape, something like an ATV or a track might work might work better. So depending on what you're, what you're going to encounter, you know, we'd select the different type of piece of equipment.
And then with those different pieces of equipment, we can do different, different kinds of tests. And so, and, and this by far isn't is an exhaustive list, but you can do standard penetration test. That's a pretty basic test com penetration test Delto modules, testing pressure, meter testing, ban testing. And we're going to talk about, we're going to mainly focus on S PT and CCPT today. Cause that's probably the most common and these tests have been some have been around for quite a long time and, and others were developed later, but you can see you, the S PT is by far been around the longest. Probably the only thing that's been around longer than that is a test bit.
The next thing up would've been the vein shear. And then, and then C P T and then pressure meter tested and diner came along. The, the S P T is what I would call kind of the standard. And then everything to the right would be what I would call a little more, a little more special, what we call specialized in situ capabilities in the, in the vein shear and the pump and trimer and the pressure meter and different things. And we'll, we'll get into that here in just a little bit, but first thing we'll get into today is the, is the standard penetration test. This is probably by far sort of the industry standard it's, it's tried and true. It's proven it's been around for a long time, as I indicated. And you saw there on the screen, when you, when you do the standard penetration test, when you talk, when you hear, you know, kind of the jargon, it would be like, what, what are the blow counts of the soul?
The end values that that's what you're getting with the standard penetration test. It's, you're basically pounding a pounding, a piece of pipe into the ground with 140 pound hammer in a split sleeve. And when you get that sample out, you have a disturbed sample. Cause obviously you counted a piece of pipe through it and, and you get something that you can look at, you pull it out of the ground and you can see it. You can, you can get a sample out of that. And you've got that amount of resistance that it took to pound that, to pound that sampler into the, into the earth. So when you look at that, at that first drill rig, that, that we put in there, that this has taken a, an SBT test. So you would advance a, an auger hole that makes this open cavity. Then you send that sampler down in the ground. And then this, this hammered device on the machine has a, a apparatus. And it's just continue pounding that spoon. And you're getting the blow counts.
And basic from that, we're going to get, we're get those blow counts. And then we're going to start creating the field log and, and start, start defining the, what we're seeing as we, as we explore the soul and we're going to make that field log. And then we're going to start, start creating this log. So really it paints a picture of what's below the ground so that we can understand what's going on. When you get a geotechnical report from, from an engineer, from someone like us, you're, it's going to contain a lot of information and we'll go through a little bit of that today. This is pretty, pretty standard, boring log it's been scrub. So it's, you know, it's pretty sanitized if you will. But if you look in here, there's lots of information on this log. And if we zoom in zoom in a little bit closer here about what's, what's in a boring log on that standard penetration test, those blow counts, you know, that we're driving that sampler in.
That's what you're going to see in this result. So we've counted and it took us two blow two, two hammer strikes to drive that sampler first six inches. And then the next six inches, it took us three blows. And the third six inches, it took us another three blows. And then when you add the last two that's, that gives you six and that's our end value. That's the, that's the standard penetration test. And, you know, it might show up in a different place on the log. Ours look like this, but you know, that's what you're looking for is the end value.
The next thing we'll talk about is the, the cone penetration test. It's a little more advanced, a little more sophisticated. The, the result of a, a CPT log is a, is a log that looks something like this. And it's going to give you a, a continuous profile of the tip resistance and the sleeve friction of that cone, the ratio, the friction ratio between those and then a poor pressures are going down. And you'll also get an indication of the soil, be behave of what the soil is based on ratios of those, of the tip and the sleeve friction. And we'll get into that here in a second. This is what a CT app rig looks like. It's can be a truck like this with a big box on the back and on the inside, you have a, a hydraulic press that is essentially pressing these rods down into the ground pretty much continuously.
So you'll, you'll push down one, one section of rod. You add another rod and you keep pressing that down and so on and so forth till you get to the depth where you're going, kind of works like this. So here's your column. It's a 10 square centimeter tip. That's not the only size. There's also another common size is a 15, 15 square centimeter tip. And it's pushed at a constant rate into the, into the ground at about two centimeters per second for the TM. There's a load cell. There's a load cell on that cone on the tip, and we're going to be measuring the, the penetration resistance, and we're going to be gathering up that tip resistance in sleeve, sleeve friction, as we indicated on the log there, there's another transducer behind the cone tip and it's measuring core pressure. So that's important. Cause as you're pushing through fine grain SOS, you're building the core pressures up.
And so to get that, to get that kind of normal stress out of there, you get a back those poor pressures out. And as these poor pressures, give us an idea also about, you know, the permeability of that soil as you build the pressures up, the soil is less permeable than say in a sand where it can dissipate more quickly. Another key thing to note about the, the penetration test is that it collects data pretty much continuously as you're pushing it down. So you, you know, with an S PT sample, you're general generally getting a sample or an indicator of what's going on every two and a half to five feet. And that's test is actually taking over an interval of a foot and a half. Whereas, you know, this, this C PT test, you're getting information at about, you know, every three quarters of an inch. And so for all intents and purposes, it's pretty much continuous directly. And then that information comes up through either a wire or through, through acoustic, up to your computer. And you're getting that data pretty much instantaneously.
The, the information on the, on the tip and the sleeve stress is going to give us an indication of a lot of different soil parameters. You can get correlations between the, the unre shear strength, the friction angle of the soil, the over consolidation ratio, the, the hydro collectivity, that's also permeability. And there's some empirical correlations of, of those parameters to actually what the soil is. So while you're not collecting a sample out of ground, we get something called the, the normalized soil behavior type. And that's what you're going to see in the log over here, where it's telling you, you know, this is a soil, this is a S silk or clay or sand or whatnot. And that's how we can, we can get an I idea of actually what's there without, without getting a physical sample of the, of, of the soil. And so here, you can see how that plots out.
This is the, I believe this is Roberts' chart, but you can have a, a, a friction ratio in, in the corn resistance and where that plots on the chart. That's what we're indicating there is the, is the sole behavior type on this area over here. And that's, that's how we indicate what the soil is without necessarily looking at it. So a lot of times, what, what you'll do on, on some sites is you would do this pump penetration test. And then with you need to collect physical soil samples, we would do the drilling and we'd get some confirmation actually by seeing the soil to correlate that with the C PT data. So a lot of times these tests are used in conjunction with one another, another test I'll just point out pretty quickly and then move on just so we can get through all this today.
But as the pressure meter test, this's another in situ method. So in this, you'd actually pre bore the soil boring, and then you lower this lower this device down into the, into the hole. And you're basically inflating that inflating that device against the bore hole wall. And you're getting an actual moist, a direct moist measurement down the bore hole. So you're getting a stress, you're getting a displacement and therefore you get this, you get this pressure and volume, and then that gives you a modular value directly. So it's a pretty neat test for if you're doing a something that's got a lateral load against, you know, like a pile for instance, or a, or foundation or something pressing laterally against the side, you can get that direct measurement down the hole. It's also pretty, pretty neat test.
So from there, we're out in the field. The next thing that we would do is we collected samples. We go back into the lab and then what we need to do is further characterize the soils that we collect in the laboratory. So we do some laboratory soil testing, and there's, there's lots of tests, way more than we're going to cover here today, but we are going to go through some common ones and I'm going to go back to the, go back to the boring log. And generally a lot of this information we'll put on the log. So I want, you know, put this in the context of how you, how you can see all this information if you're looking in report. So when you come back and we do some of those lab testing, a lot of this data that you see on the log has been developed where we've, we've logged the boring while we're out in the field, but we've also collected field data.
That's here. And then there's other lab data that shows up, and this is all in the boring log. And it's presented in, in the order in which, you know, in the Strato. So that's important if you look here in this log, we'll zoom, we'll zoom back in on this one particular part. And then over here on the right hand side of this log, you'll see, we've got some other data, some water content, something we call the, the plasticity or the Aaberg limits, these strength test a to a Tova test, that's she strength measure of shear strength. And so these are all things that we determine in the lab and then report back. Also, if here on the, on the, on the soil board, another thing just at a more basic level would just be, you know, verifying the soil types. We log this as we're out in the field, but when we get back to the lab, we actually run test these soils to determine what is the classification of that soil.
Exactly. So, you know, is it a clay, a silt sand? And you know, is it a, is it a plastic clay or a low plasticity clay? So we determine all that in the lab. And then we that on this log. So when you look at this boring log in its final form, it's been looked at by an engineer and then have laboratory tests that, that verify that, that what we logged in the field is in fact also what we, what we have in the lab. So that's important to note as well, as I mentioned, when you, when you bring that soil in, there's several different types of soil that, that you can encounter. And I'm going to talk about what those basic soil types are. And then we'll turn it back over in a second, about what that means in the context of what's going to happen on a project site.
So in general soil, when it's encountered the most elemental way, the soil ranges from large particle size down, the very small particle sizes and at the largest size is, is obviously like rock like bedrock. And then from there, it weathers down into other materials and as it gets smaller, it, the, the properties of that soil chain. So you have rock. And then as you, you know, screened out to finer to the finer souls, that rock then becomes like cobbles and then boulders and smaller, smaller rocks. And then it goes to sands and gravels, and then even finer than that, you have clays and clays. And silts when we get back into the lab and we run these tests, we, we perform these gradation tests, and this tells us a lot about the particle sizes of that material, but then also how that behaves. And so this is a typical grain size distribution curve.
You would see a Geotech report and it has, you can see the range here from cobbles, you know, just like we described before cobbles gravels sands down to place. And when you get down to, to, to even finer down to the silts and clays, there's, there's other parameters that we talk about, and that's the plasticity and that that has to do with how workable the soil is, will it shrink or swell, things like that. So, typical test that will perform to determine that plasticity of the fine grain soil is what we call an Atterberg limits test. And that's going to consist of a liquid limit test, a plastic limit test. And then as you take the difference of those that tells you what we will call the plasticity index, and that lets us know is at a low plasticity or a high plasticity. So I'm going to, to pull the curtains back on what that test looks like.
And it's pretty basic. Actually, you, you get this sample in and you to do this liquid limit test, you actually take the soil, you run it through a Sid, you mash it up, you add some water to it and turn it almost into like a put and you put it into this cup and you, you run a little trip hammer here, and this cup bangs down until, until this groove closes it, you cut in the soil. And if the water content and which that groove closes in a certain amount of blows is what we call that liquid limit.
Similarly, the plastic limit is going to be how, what the water content at which we can roll these threads down into this eight inch diameter thread before they start breaking into one eight inch pieces. So if that water content's too high, you're going to roll that down into a really thin thread. And it'll be on this, you know, thread like, and you'll have to lower that water content. So as imprecise as that sounds, that's the plasticity he, that we use. And we have been using it for a long time. And that gives us an indication of the, of the plasticity index. And all that is, is basically just the water content, the liquid minus the water content. That's what you reported the thing in of the classifying the soul. So if you, if, when we're talking about that liquid limit plastic limit, we run that through the TMS and through this, through this chart and based on how that soil behaves and the amount of silt soils, clay silts proportion of S silk clay with sand will give us that classification. And so if you take that, if you take that amount of soil passing the 200 and you get the liquid limit on that, and it's a, let's say it's a 60 liquid limit, and it's a, and it's a 20 P you plot that. And we determine that's a, that's a high plastic seal. So nothing magic about that, but that's how we do the classifications.
Another, another test that a typical test that we run in labs are strength tests. And I, and there's lots of strength tests. There's Trix strength tests, there's run confined compression test there's Toine shear test that we do pocket pins. There's lots of tests that we do. This is a pretty, a pretty typical UN confined compression tests set up. So basically that just means you're taking this, this sample, you're putting it into this, you're putting it into this device. You're noting it in any way. And you're just switching it on the top and bottom, and you're recording the stress that, that it can take before it fails. And then you plot that out. And this gives you like an UN confined compressive test. And you look over here and this gives you bone during the end, during cheer strength. So pretty basic, but there are lots of different tests that we do to, to determine sheer and soil strengths.
When we, when we go through that process of, of identifying all the stratigraphy and all the different types of soil and their, and their characteristics and properties, we can, we can then begin to get a, a visual picture of how that site's going to behave. And, you know, as we look at what, what types of soil we have, the, what you can expect from, from a granular soil is, you know, how, how they feel. They grainy, they transmit water pretty well. You know, water can flow from their well-drained. They have no plasticity. And when they're, when they're dry, there's, there's not really cohesion there. If you got to pile of sand, it kind of, it kinda SLS down at its if you think to like dry sand, what that's like clay on the other hand behaves quite a bit differently. The grains are really small, they're tight. They tend to attract water in between the particles. And as you get the water in there between the particles, it, it lubes 'them up. They become soft, not as strong, the more, the more wet they are. And as the plasticity increases, they have different challenges when you're using them.
Bedrock is, is the other extreme end of you know, soils, you know, intact rock. And there's all different kinds of rock here. And we won't go into all those different rock types today, but there's sandstones clay stones, stones, and those are more of like a depositional type of rock. And then you have the, the other harder rocks, like nicest granites, things like that, or Igni or metamorphic rocks. And they're more intact, have much higher compressor strength and support higher loads. Ryan's going to get into a little bit more about sole characteristics here in the next part and how they, how they impact projects. But in generally in general, here, these, these generally in, in terms of support and, and performance, the gravels are good. And as you go down, these, these kind of decrease in terms of desirability for, in all things considered, and Ron's going to go into that and, and quite a bit of detail and how these can impact your project in terms of, and foundations and support and, and things, project life that I'm, you
Ryan Fiest - Speaker 3 (00:37:29):
Just gimme a thumbs up, if you can see that. Thank you. Yeah. Just to dovetail into what Levi was saying, where we've identified, we've collected the samples, we've tested 'em in the lab. We've now got this engineering properties of it to go over a little bit more on this table. I mean, essentially the Coser grain materials, the gravels in the sands, they support structures better. I like to think of it like a sponge, your kitchen sink sponge. It's got all those little pores in it. It's the same structure that soils have in it. It's just usually filled with air or water, but as you get smaller and smaller, that water can't get out of those poor spaces nearly as fast. So where a, a sand may stay firm with that water in it, that clay, it, it just can't get out of it fast enough.
It's like a hydraulic press where you you're putting pressure on it and the water's squeezing out slowly, but it just can't outta that soil fast enough. Well, what does that mean? That means that when we apply pressure on the top of it, say a foundation for a building or other structures, it takes a while for that to normalize. And it may take months for that clay to allow that water, to get out, to support that new load. So generally more granular soils have better engineering properties, characteristics for support of structures. As you get smaller and smaller, it just takes a little bit longer. They have less strength to them, but they also have less stability.
One of those might be if you're on a really clay site and, and you've seen the construction equipment running over it, you almost get a water bed effect where you have too high, a water con in it content in there because the, the soil just can't get that water out of it fast enough, which results in that instability. So as we, so what do we do with all this information? We've collected all this stuff out in the field, how do we summarize it all? And that's where a typical geotechnical report would come in. So what, what the, the geotechnical engineering report, as I always say to all of our practitioners, this should only be a summary of what we've talked to the, the team and the clients about no surprises, but there's a couple of things that build the story. A geotechnical engineering report is a story.
First part of that story, what are we building? What's the project description. This is where that team aspect and the collaboration really comes into play. What type of building is it? How heavy are the loads? What do you anticipate the finished floor of that building being, or if there's proposed grades that helps us determine what the cuts and the fills are. What's your settlement tolerance for those buildings typically for, for buildings, it might be around an inch. Other aspects, as I had mentioned is really based around what's that grading plan look like, are we going to have retaining walls? Do we have below grade structures, fuel facilities with their, with their tanks that can be affected by groundwater and then pavements, it all comes down to what load are we applying to the soil over what type of area? And that load can be pavements. That load can be building foundations can be transmission tower foundations. It's just, how are we transferring those loads? And what do those loads look like?
Here's an example, just from a transmission line standpoint, what, what type of structures are we building in this particular example? It's around H structures and then direct embed poles. Typically on transmission lines, we don't have a lot of grading activities associated with it, but the loads, particularly the overturning loads on those towers can be quite large. Levi had talked about that pressure meter testing on, on really dialing in those lateral pressures down in the ground. This is where they come into play. Those, those towers. They may not have a lot of down pressure axial compression, but they have a lot of overturning, particularly in those, those wind storms. And that's where we can help design the most efficient foundation types by giving as much data as we can from the field collection. And then the, the lab testing site conditions. Another part of the equation, right? Yes.
Jessica Turner - Speaker 2 (00:42:27):
This seems like a good question to answer live here and not wait until the end. They are asking, do the soil characteristics evaluations apply for solar PV piles or is that a ranking specific to buildings?
Ryan Fiest - Speaker 3 (00:42:42):
Nope, that's a great question. So Jimmy Jackson is going to be presenting the next series in this really with respect to solar, haven't ignored it, but absolutely they may be lighter loads, but there's a, there's a huge cost savings for those H piles that hold up to solar arrays. Thousands, if not tens of thousands, hundreds of thousands of those piles that go in the ground, again, not heavy loads, but if we can dial in the, the properties of that soil and we can do some load testing out in the field and we can save even a foot of steel on each one of those piles, over a hundred thousand, 200,000 piles, it's an extreme cost savings to the project. So yes, it very much applies to solar arrays.
Great question. A lot more detail in, in the second part of the series, when we really dial into solar arrays and how we utilize the, the field collection, as well as the engineering side of it, the analysis. So other parts of this, this equation, so we've got, what are we, what load are we applying to the soil now, what do we have out there? Just from a ground surface perspective on this particular example, we've got it's undeveloped bar of vegetation, but then it says there's an apparent dry Creek bisecting, the site that keys you into, well, there's probably sediment down in that Creek. How is that going to impact things? What do we need to remove in order to, to give the performance to whatever structure might be going on top of that? So all of these things, and then down in the bottom there, even though it's under the geology, there was a highway built next to this particular site and there was BEMs. They had extra soil from a highway project 30 years ago. Well, now we've got old fill sitting on that site, and that's something else that we may need to address depending on where the building sits in relation to that fill. And I say, building, I'm just going to broaden that to structures, whether that's pavement, solar array, transmission lines.
So that site characterization Levi really spent a lot of time on this. We, we now take what we call a geo model and we, we dial in, what are the engineering properties associated with different layers on this particular example, we've got fill soils, we've got some native sands and clays. And then below that we get into some weathered sandstone and then some weekly cemented sandstone as it progressively gets harder as we go down into the, into the ground. So we use this as kind of that key, that legend as we go through the report. So we can talk about those native sands. And then we, we dial in the engineering properties for that kind of broader group. As you saw in those boring logs, we can, we can dissect it into a lot of different layers. This helps us generalize it, particularly for the structural engineers. So we can assign friction angles and cohesion and strength values to those particular layers.
We're going to spend a little bit of time on, on that site characterization. This is a, a building site, got some out parcels around it, lots of borings that we did around here. We want to make sure we've got a good understanding of what that profile looks like. We're going to focus in on this building down here. Each one of these crosshatched boring symbols is where we've, we've AED into the ground and collected those soil samples. And the squares are test pits. So we have this cross section through the building. We'll circle back to that in just a second. Those geo models, this specific layers that we had called out in that chart. We look at that kind, this is just all the borings for the building. It's kind of congested there, but it gives a good indication of where the finished floor of the building's going to be in relation to say that old fill that we encountered in those BES or where we're going to have to put new fill in there. Our borings, you see dip down the ground surfaces down here, but then we can start to see where the clays are and the sands, and then eventually getting down into that bedrock. And you can see here where the bedrock actually comes up into the finished floor elevation. This gives us a good indication where we may have some difficult excavations within portions of the building. Going back to that cross sectional view.
This gives us an indication of when we're in construction, where are we going to encounter those things specifically within that building footprint? And you can see that a lot of the fills are going to get removed as we cut down through it, but we will have to deal with some old material below the finished floor elevation in some particular areas. So again, we're building the story. What structures are we putting on it? What are those grades look like? What do those site conditions old, fill creeks, drainages, things of that. And then how are we going to address it with our recommendations?
One more, just from a, from a transmission line standpoint, I thought this was a, a good tie in, of not just using what we're collecting out in the field. We also want to tie it to available a publicly available information, geologic maps. So this was a several hundred mile long transmission line. This is the overview of that, that blue line is where that transmission line's going to go. And you can see that it crosses over a lot of different geology as it goes along that alignment dialed it in a little bit. So this guy is right up in here. The other screenshot is from over here. Well, we've taken select borings, although they may look closely space on this. They're probably about a mile apart. So that might represent five to 10 structures between borings. By combining these two things, we can better interpret what those conditions may be between the borings, another product that we have.
We, we have a product called stage one, which Jessica hit on a little bit later, but we that's a desktop review where we looking at those geologic maps and we can start to put together some predictive foundation parameters from, for some cost estimating. But for this purpose, this is really what can we do to get as much information from not only our borings, but the, the geology maps that we have available. Levi also hit on those, those other types of exploration over on the right here, perhaps there was a, a mountain, a hillside that we just could not get a rig in there practically. Perhaps our, our track rig couldn't get there would have to be helicoptered in well, instead of doing that, we can use geophysics to sound the ground and see how deep that bedrock is. And then we can also correlate that with that underlying geology. So we use a lot of tools in our tool belt to come up with what those recommendations are based on site constraints and even geologic constraints.
So now that we've gathered all that information, we need to apply it to our design recommendations. There's a lot more that we could get into. I wanted to just give a brief overview of several aspects of a project where we can provide those geotechnical design recommendations. We'll touch on a couple of these in a little bit more detail, but earthwork is always a big one, depending on what part of the country you're in that seismic or liquefaction. If you're on the coastal areas could play in foundations are a huge one. And that's where the structural engineers usually gravitate towards. And again, there's a ton of other ones in there just depending on the needs of that particular site, a couple of those different aspects, earthwork difficult excavations, this particular site. They had some huge chunks of, of bedrock that were in the soil profile.
I mean, those are big trucks and we've got some big boulders that, that were on this particular site. They ended up using this as fill they'd crush 'em essentially, but that shallow bedrock and we had talked about the solar. I'm sure Jimmy will get into this as well on the next one, shallow bedrock and pile driving for those solar arrays is a big deal. And if we get pile refusal early, it can cause a great cost increase where you may have to pre-drill those things, a ground water is another aspect. How do we dewater a site? How do we deal with that, that groundwater that might be on those particular sites.
We talk about that steel in the beginning, and it has specific properties because it's a manufactured element that we can incorporate into building construction. We're trying to do the same thing with soils. That's why we call it engineered soil. So after we dissect the properties of that, then we say, all right, how do we place fill? So it can support the structures that we need it to, to support. What does that density of that material need to be in order to get, say a 3000 pounds per square foot bearing capacity out of it. Other aspects that we provide guidance on would be the grading and the drainage.
Another aspect is settlement monitoring. This particular one was for a, a surcharge, the soils underneath. I had talked about those clays, not allowing the water to get out fast enough. We ended up placing gosh, 10 to 20 feet of fill extra fill on this building pad, because if we put the building straight on this, it would actually settle over time. Think of the leaning tower of Pisa, but not, not to that extent of time. So we we've accelerated. We want to compress those soils underneath. This allowed us to, to take that, that settlement. Instead of taking a couple of years, that would the building. We were able to accomplish that settlement within about three months. Then we take off this fill and then we can put the building on it. Now that it's been surcharged other aspects, you can see some water on that. Fill there. If that were on your subgrade, say over in the, the, the brown colored reddish brown colored area over here, we can chemically stabilize that soil to improve the, the characteristics of it.
Foundation design and recommendations, just a snapshot of shallow spread footings. In this particular case, I reference that 3000 pounds for square foot. These are the structural engineers. Usually come to find the information that they design their foundations, the concrete and the reinforcing steel around it. We, and we also give guidance on frost depth in this particular area at 60 inches. That is where the bottom of those foundations need to be in order to get outside of the frost zone must be up in Wisconsin or Minnesota, somewhere other aspects. And this is, this is an example from a transmission line where there's, again, information available for the structural engineers to design those drilled piers for those mega towers and that dials into what's that effective weight of the soil, those friction angles. How, how rough is that material? The adhesion, the cohesion values for the clays, lots of different values that the structural engineer can apply to the, the foundation design.
Other aspects would be wind turbines. We have a proprietary system that we use for wind turbines. It saves a lot on concrete costs and then other ground improvements. We talked about the surcharge there's other improvement methods that we can provide that might be cheaper than over excavating soil. And then bringing that back in is compacted fill. The last one that I wanted to touch on are pavements. Those are, are big for commercial developments, and it can make a huge difference for those solar arrays and, and wind projects. Particularly with the aggregate surface roads, I worked on a wind project where they really wanted to thin it up, said, wow, we don't really care. It's just a dirt road, dirt soil road. We just needed to, to work for us while we're putting the turbines in there. It's just going to be a support truck that goes out there and it's like, that's fine.
But I know schedule wise, these are very scheduled driven projects. And if you don't build the road well enough and you get a rainy season in there, you could have problems. This particular one, it and I, I live in Colorado. This was done down in Southern Colorado, dry 11 months out of the year, as they were bringing in the turbines, we got a freak snowstorm in April shut down the site for a month, though, all those turbines were sitting on the side of the road. They couldn't get in cuz it was a clay site and the road only had six inches of gravel on it and it just blew up on them. So they, they lost about three months’ worth of time, took a risk there on a, a lower grade road. But unfortunately it bit him on that one. So that's where we can help develop those recommendations to support the schedule and also keep cost in mind.
Last, last slide here got a little bit of an overrun there. Apologize geotechnical consulting. Please get us involved early in the project process. We'd love to collaborate with all the stakeholders and other team members, the design team members, just as I had talked about, what, what is that structure? What are the loads? What are the settlement tolerances? Our ultimate goal as a quality project that meets the clients and the clients and the owners, financial and risk expectations. We want that to be a long term project with the performance that's expected from that client. And I cannot emphasize enough communication, communication, communication. That's what, that's what we love. A consultant is an engineer that can communicate effectively so we can have that high quality project. I will turn it back over to Jessica to wrap things up.
Jessica Turner - Speaker 2 (00:58:05):
All right, well thank you, Ryan and Levi, this does wrap up our AI a portion. So if you do have additional questions about the AIA pieces of this, you can talk to Ryan or Levi. I will leave their information up here and then we will also provide it in a follow up email as well. If you wish to reach out to either of them, Frank, we do have it. We do need to get the link out to everyone. So please check your chat. If you do want to sign up for those AIA credits, just simply fill out this form. It's really quick. It's just first name, last name, your AIA member number. And then if you want that certificate or not, so we will move over here and right before we open it up for questions, I do just want to circle back to the topic of pivot and stage one.
So we pivot is the reason why we all signed up today. So we are really excited. Pivot joined the Terracon family a little over a year ago, and they are a software and technology firm really excited that as we're kind of merging these conversations and figuring out where pivot fits into the project life cycle. So if you are looking for software to aid you in cost, estimating, finding sites, making those go, no go decisions and getting some preliminary high level information before ever stepping foot on a site. Pivot is the tool for you. So after this, you'll have an opportunity to reach out to us to get more information on that. And then we have stage one. So stage one is where we take experts like Ryan and Levi that are situated all across the country. And we combine that with our over 55 years of historical project data. And we're able to provide you what we expect to find on that site. So pivot will help you narrow down the site. Stage one will get you some additional preliminary information with that expert enhanced opinion. And then we can move it over into that, the field exploration site, characterization and engineering and consulting. All right, so now we're going to open it up for questions and we do have a few minutes here. We'll head to the top. We've got Dylan and Levi having, having a quick discussion. Does any, do you want to add anything to that, Levi?
Levi Denton - Speaker 4 (01:00:49):
I don’t know if Dylan can chime in, if I kinda answer some of the questions in the chat, but he did have some questions related to the different types of exploration methods and when you would use certain methods over other methods and you know, we could the day course on that, but in general, the, when you're pushing C PT, you're, you're pushing that calm down and kind of forcing its way through the soil. So you're not removing soil out of the way as you're going. So you're limited on the C PT in some ways, once it reaches a certain density, it's hard to push that column. So we use that in soft deposits up. The kinda, you know, I'd say even up to pretty stiff deposits, but once you start hitting rocks and, and very stiff soil or bedrock or anything, that's going to refuse out your CPT.
And then you could supplement in with conventional drilling to where you're actually removing the soil as you go and take physically extracting the sample out along the way you would use those methods. And a lot of times we, we, we go in, we go in and a lot of times with a notion of what's already going to be there. So when we go out and explore a site, it's not like we're going out into an unknown land where we're, we're just randomly doing a grid of borings. And then like we're finding new things. We're not expecting a lot of those maps and things like Ryan show. We have a pretty good idea of what we're encountering when we get out there. And we like to really go in, in more of a confirmation mode and fighting a cold here, going into a mode of confirmation where we're, we're confirming what we think we already know versus, you know, we just don't know anything at all. What's going out there now that said, you always run the risk of, of encountering something that you're, you're not expecting in that case. You got to be nimble and change the course while you're out there. But in general, that's the way we approach that.
Jessica Turner - Speaker 2 (01:02:44):
Thanks Levi. We have. Would any of Terracon's databases be available on pivot for, for site analysis? So either Levi or Ryan, do you want to go into the, the SBC and the soil, parent material layers and things like that?
Ryan Fiest - Speaker 3 (01:03:01):
Yeah. As, as Jessica had mentioned, we've got 50 years plus of historical data and we are, there are publicly available GIS layers. We are developing our own internal GIS layers such as from all of our projects. What does pile embedment look like? Thermal resistivity values corrosion. So we're building some internal things based on all of the data that we have. Those will be rolled out in our pivot platform, particularly over the next year as we dial those in. So there are some available now, but more to come.
Jessica Turner - Speaker 2 (01:03:46):
Thanks, Ryan. All right, we have another one. Could you summarize the cost and benefits between ground screws for solar foundations and pre-drilling for piles? If bedrock is present?
Ryan Fiest - Speaker 3 (01:03:57):
No stay tuned for, for number two with Jimmy Jackson on our solar. I say that tongue in cheek there, the ground screws have a hard time penetrating that bedrock. And that's where that pre-drilling really comes into play. And this is where that site selection comes in. If we can identify areas where there's shallow bedrock, and that can be avoided before you even get too far on that site and you can shift it perhaps down the road to where that bedrock isn't as shallow, you may be better off, but I, I believe Jamie's going to be able to talk a little bit more about those ground screws versus pre-drilling
Jessica Turner - Speaker 2 (01:04:40):
All right, which is perfect. We do have another question on signing up for future sessions. So we will go ahead and get that scheduled. It'll probably be between three and four weeks out. So everybody that has registered today, you can, you will see that email to register for the second in the series. And it will also be posted on our social media channel. So go find us on LinkedIn and you will get that link to, to register. So Jimmy is, is getting all set up. I saw a sneak peek of his presentation and it'll be awesome. All right. Well, we are a couple minutes over. So I think we can wrap it up. Like I said, Ryan and Levi's contact information will be provided in the follow up email. So you can reach out to them if you have additional questions and then make sure that if you're looking for those AIA credits that you fill out that link for us. Other than that, we appreciate your time today and we will see you on the second series towards the end of August.
Ryan Fiest - Speaker 3 (01:05:53):
You thank you everybody.
Levi Denton - Speaker 4 (01:05:56):
And thanks a lot. Enjoyed the time. Everyone feel free to reach out to you have any
Ryan Fiest - Speaker 3 (01:06:00):
Questions? Absolutely. All right. I'm bail out.
Jessica Turner - Speaker 2 (01:06:48):
All right. Thank you.