- Commonly asked questions geotechnical engineers receive from development teams during site selection.
- Common misconceptions and constraints when it comes to solar site selection.
- What every geotechnical engineer wishes you knew during solar site selection.
- How depth of bedrock, soft clays, and other factors impact project site configurations, schedules, and budgets.
- Pile load, thermal resistivity, and geophysical testing, so you can stop saying, “what are they doing out there anyway?”
To wrap things up, Tamara walks you through the project development lifecycle, including where you can use Pivvot’s technology and Terracon’s Stage1.
- Tamara Hashimoto, P.E., Geotechnical Engineer & Development Manager, Terracon
- Scott Neely, P.E., Senior Consultant, Solar Subject Matter Expert, Terracon
- Rich Henry, Director, Customer Success, Pivvot
Moderator: Jessica Turner, Client Development Manager, Pivvot | Stage1
If you are interested in speaking with an expert, please fill out the form below!
Speaker 2: Jessica Turner (00:04:01):
All right. Well, thanks everyone for joining us on this Wednesday morning. Thank and for part two of our geotechnical 101 webinar series. So if you did miss part one, that's okay. We have a recording of it for you that you can go back and watch, and we'll be hitting on some of the highlights of that here in this presentation. So I am Jessica Turner. I am the client development and marketing manager for Terracon digital services, Stage1 and Pivvot, and I will be facilitating today, and I get the joy of introducing and setting up our awesome speakers for the rest of the webinar. So before we get started here, wanted you to know that we have muted everyone. However, we do have a Q and A function available, and you can see kind of where that is highlighted there. And you can feel free to ask questions throughout the webinar. However, we will be taking those questions and we may be able to answer them throughout the webinar, but we will save some of those that we need are experts to answer for the end. There will also be a recording that is sent out ahead of time, or sorry, sent out after the webinar is complete.
All right. So here at Terracon, one of our number one priorities is safety and August happens to be I safety month. So we like to start every meeting out with what we call an IIF moment, our incident and injury free moment. So it's often easier to remember your PPE and safety when you are clocked in and out on a job site. However, taking that back home with you, oftentimes those same reminders aren't in place. And so I just wanted to highlight the importance of making sure that you're wearing eye protection when you're doing some of those daily tasks like cleaning when you've got some harsh chemicals involved. And then when you're doing home improvement projects and then yard work is a really big one. I know I was mowing my lawn recently and there was just a little pebble that flew out and hit the windshield of my car and ended up damaging my windshield. So I can't imagine had that gone in my eye, how awful that would be. So just kind of keep that front of mind and where eye protection while you're out there doing household stuff too.
So this is part two, like I said, in the beginning, the first part was just the really basic foundation of what a geotechnical engineer does. We're taking that. And we're going on a deeper dive here today. And we're focusing specifically on what a geotechnical engineer does during solar site characterization and the engineering that is associated with that. The third part of the geotechnical service series will be the electric transmission routing. And that will be from the eyes of the geotechnical engineer as well. That will be next month and you will be able to register on our website. And then we'll also be sending out some email notifications and social media that will direct you to register as well. After we wrap up our geo series, we will have an environmental series as well, and that will start towards the end of the year and go into the beginning of the year.
All right. So when we're talking about Terracon, it is really hard to beat the footprint that we have across the nation when it comes to solar work, where we definitely have the experience here, and that's why these experts we're so looking forward to hearing from them today. So in the last four years, Terracon has completed over 4,000 solar projects across the nation with projects in all 50 states. And recently our E R rankings came out and we're really excited about a lot of these and we're number 12 for design firms. And then we're three with solar power.
So for our last webinar, here's some of the topics they ranged from all the way from going back to that very early. What is the definition of soil and bedrock into what is the type of equipment are field staff uses and they're out there doing field explorations and there's that site characterization with the laboratory data as well, and then all the way through how they take that information from their explorations. And they develop that engineering report that usually gets into your hands. So today we're going to hit on the importance of good siding and how we get information over to that geotechnical engineering team, so that they're set up for success. And then we've got Tamara, that's going to go through geologic hazards, current solar geotechnical practices, and then even get into a little bit of pile, load testing and analysis.
So I am so excited to introduce our speakers today. We have rich Henry who is my boss and the director of customer success for Pivvot. He brings over 15 years of consulting to product management and system implementation experience and experience in the energy sector. He's known to roll out the red carpet for his customers, and he is the go-to guide just to know what the customer experience is like and how to translate that back to make sure that the Pivvot product is enhanced to meet your needs. And then we have Tamara, Tamara began her career in our Terracon orange county office, and she now leads a team of about seven in our Las Vegas office with her nearly 10 years of experience in the industry. Her passion for solar energy projects has led her to the role of one of our solar subject matter experts. So she reviews and consults on subsurface conditions that impact solar projects throughout the United States.
All right. So at Terracon, we do have what we call the project life cycle, and it is a client centered approach to representing Terracon service in a more holistic way, the life cycle categorizes asset development into four different phases. As you see here on the screen. So we've got site selection, design and mitigation construction, and then managing those assets after they're developed in the next 40 ish minutes, or so we're going to walk through those top two. So the top left and the top. So the project life cycle, site selection phase, and then the design and mitigation phase. So we at Terracon want you to be able to learn as much as you possibly can about your site even earlier than you have before. So that includes talking about two of Terra, con's newest digital services. So we have Pivvot and Stage1 here, and we have an environmental expert on our team that has coined kind of the term pre diligence.
So Pivvot and Stage1 kind of fall under that category. And we have rich who will go through about a 10-minute demo of Pivvot, and we'll talk about Stage1 as well. And then we want to make sure that the design team is set up for success. So that's when Tamara will come in and show how we're going to use that Pivvot in Stage1 information to get you through the geotechnical services, the structural engineering services and the environmental services as well. So with that, I am going to hand it over to rich, and he's going to do a quick demo of pivvot.
Speaker 4: Tamara Hashimoto (00:13:10):
You are on mute rich.
Speaker 5: Rich Henry (00:13:17):
Thanks, Tamara, of course. All right. And thanks Jessica for the introduction and thanks everyone for being on the call. We're glad you're here. So as Jessica mentioned, this is kind of a demonstration. It's really what we want to start to presence with you all is how Terracon is starting to really push towards data and digital solutions to help inform you all, even ourselves as we move through the site selection conversation, and move through the life cycle of a particular site. So as we think about and talk about Pivvot, it's very much in the early stages. So this includes prospecting for opportunities and understanding the viability of the site and all the while we're leveraging the data to do that right, to inform us. So when we talk about Pivvot, we typically start with data. We think of ourselves as the data company. And when we think about our data, we think about that in three ways.
One we've gone out and curated a bajillion pieces of data that's publicly available, whether that's federal state, and sometimes county level data, we're getting that information, putting it inside our database, optimizing it. So it's performing and all the fun stuff to make it usable inside these applications. And we're also keeping that information up to date. So you can kind of check that off the list. You don't have to think about that part. The second way we think about data is sometimes we actually have to go out and license this information. So for example, we license the parcel data so that we can have nationwide coverage. And we can have that information in our system, which allows us to do cool things like aggregate properties that are adjacent to each other that are owned by the same property owner and get those really large opportunities. Another piece of data that we license is actually the energy infrastructure data.
So now we're talking about power lines and substations and existing pipelines, oil and gas pipelines that are out there. Why are we paying for that data? Well, given the activity and the focus on renewables right now, the publicly available data out there that represents particularly line information and substation information is just not sufficient. So based on our assessment and our experience and the experiences of our customers, we license information so that we can make it a much more robust data set. And I mean, in magnitudes of eight or nine times larger than some of the publicly available data. And then the last way we think about it is for us, this is super exciting. So I worked with a person that often would talk about beautiful collisions. And when I think about the Terracon purchasing, Pivvot, that relationship, that partnership is a beautiful collision. So you have Pivvot that walks in with deep bench strength and technology, understanding data.
How do we visualize that data? How do we analyze it? How do we produce reports, et cetera? We've got that right. It's our pocket. And then you've got Terracon. Who's been doing this for 50 years and has a bajillion boring locations out there to paint the picture of what's happening below the surface. So how do we bring those two stories together and walks that be beautiful collision. As we sit here today, there are several data sets that we already have available inside our platform, specifically cars and also soil behavior class, which I'll touch on a little bit, but we've got folks right now that are heads down between the Terracon side and the Pivvot side, those two teams coming together right now and talking about how we can take those 2 million boring locations and start thinking about new and innovative ways to flip the script a little bit on how we start to understand what's happening below the surface.
So more to come there. So that's the kind of three ways we often talk about data. What I'd like to do now is just use the siding application. This is one of two siding applications that we have inside our platform. This one's obviously going to go look for parcels out there typically for solar and wind opportunities. We also have a corridor siding application, which Jessica mentioned earlier that we'll talk about in the next part of the series. All right. So to kind of kick things off. So what we're looking at right now is our siding application. And on the screen, you'll notice that we've got all this huge magenta blob on there that represents areas that are around this feature here in the middle, where this paddle is, right. That's a substation. So I've said, look, I want to understand where within three miles of that substation could I potentially build.
So we're using our usable area calculator and has taken into account some of these constraints that you see over here on the left hand side. And I should mention to the folks that are on the call that are responsible for prospecting. This is just one way that you can approach it, understand the usable area front, then go start hand picking sites. We probably have 10 other ways that you can go in there and start finding opportunities. So we're just not spending time on that. Of course, we would love to take 30 minutes, 45 minutes with you to cover that and get into the details. But for the sake of this conversation, now at this point, we can start picking locations. And I have a couple of those right here. I'll go ahead and zoom to one of 'em. So when we talk about leveraging that data, we just did it.
We just used that to go understand the usable area around a three mile buffer around a substation. So we're doing some of those kind of special back flips to kind of figure out where we can and cannot build. All right. So to take that conversation a little bit further, another way that you all or we can utilize that data to help better inform you is just from that desktop analysis perspective. So everybody on this call, I am nearly a hundred percent certain that you all are using Google earth, at least once a week to go in and just kind of look at what's happening in particular area, totally buy into it. We're mapping folks, love maps, love satellite imagery, except that just having satellite imagery clearly is not sufficient enough. So what we've done is we've made all of the data sets that we've gathered.
We've made those layers that you can actually turn on the screen. So for example, here, we can turn on things like hydrologic group. I like to pick this one because I don't know it's pretty right. And it makes sense. So we can view these layers on the map, start to give this area a little bit more context. We can come down here for those that are doing some of that early site origination, we can start to identify, is there any prime farmland on this site? And of course, as we scroll down, you're going to see things like flow lines and water bodies and wetlands, all the typical constraints that's really valuable. Of course. And then we take it a step further when I was talking to you earlier about some of the data sets that Terracon is starting to provide or make available inside the platform.
So for example, we have this soil behavior class, and then this is something that Tamara could definitely nerd out on for quite some time. But you know, can see over here, the layer and the legend that starts to represent it's an approximation of soil and rock conditions that folks like Tamara or others can start to use to better understand kind of design conditions on that site. So there's that zero to two feet. We also have a layer that goes two to six feet. Is this engineering data? No, it's not right, but it gets us back to that pre diligence idea, which is get as much relevant information in front of us as quickly as possible. And by quickly as possible, although I've been yapping for a few minutes, a person could come in here, spin up a siding project, identify this site and understand the suitability of that site from a usable area perspective.
And also from an early preliminary design and engineering perspective, literally in minutes. So again, for the solar developers on this call, the name of the game is speed. Find those sites as quick as you can. Okay. So we've talked about having that data available to help find sites, understand usable area. In fact, why don't I come down here and we'll just look at the usable area for this particular site. So now we can see where we can build on this site and also where we can't build. So we've used the data to help us support that activity. We have those layers on the map that we can use for that kind of desktop review. And then here again, we want to be able to not only communicate where we can build, but what's happening in the areas where we can't. So, what I'm going to do is I'm going to come over here and turn off some of the noise.
I'm going to come over here and turn on the constraints. This is kind of like when you were in math class and the math teacher was like, don't bother giving me the answer. If you don't have the work, we don't want to be a black box. We want to show as much work as possible because understanding where those constraints are been to visualize those is important from a mitigative perspective. Are there opportunities here that we could take some mitigative actions to increase the buildable area on there, thus increasing the megawatts available on that particular site? So we can visualize that another way, of course, that we are leveraging the information here inside citing this from a reporting perspective, we have a federal level permitting punch list that kind of racks out some of the common federal level permits and lets based on the data, whether that particular permit has been triggered or not as much information as possible, green light, yellow light, red light a site, some of that's, some of that permitting, discussion's going to come into play as well.
And then we also have what we refer to as either the citing report or a constraint report. This is a pretty report. This means that now you can hand off this PDF to somebody and they can take a look at as opposed to jumping into the application and doing that particular work. So here's an example of that hydrologic group. Again, again, pretty colors, but you also get a summary down here of what the hydrologic groups are. And also the impacts on that site here again is that soil behavior class. And I got to tell you, I love this next one. That's what we're looking at now is zero to two feet. This next one is two to six feet and it's like red light doesn't even do it. Justice. There's a spot right there in the middle of our site that is going to cause us some sort of pain.
And that's the sort of information that we want to bring to light leverage our experiences with Terracon and their expertise to bring this information to light as soon as possible, right? No one's saying we need to necessarily can this particular site, but at least we have some visibility on what the type of activity on that particular site is. And to take that a step further, that was a pretty report. And now we're going to get into the nerdy Excel type reports, no offense, Tamara, but this is probably the type of data that you'd probably really dig into. So now we're looking at basically all of the data sets that we have in our inventory and basically taking all of that information and just kind of shoving it right through the site and of doing a cookie cutter to find out what are the impacts, particularly inside the usable area that you may encounter.
And also give you in terms of metrics, the impact, the acres impact on that site. So here, as we look at these two data sets around corrosivity right corrosivity as it relates to concrete and steel, you'll have that information available to you very early on in the process. And also as these sites mature, getting back to some of our solar developers, if you're able to mature these sites more and more, that that increases kind of the return on the investment. Also, when you start to hand these sites off to the designers and engineers, they're going to have this information available to 'em immediately, as opposed to getting to a situation where you put boots on the ground. And somebody's like, look, we have to change a configuration on this because of body blows on the particular site. So you'll have this level of information and to kind of take that a step further.
And I'm going to transition now over to Jessica, who's going to talk about the Stage1, a lot of this information is publicly available. You're not necessarily going to drive your engineering activities on this information. So, when we think about that life cycle, we have that preliminary sighting, what we're looking at right now, and then we're going to shift over to look. We want some more expertise on this. We want to get our SMEs involved and understand what's happening on this site. Make some recommendations, raise their hand to say there's some red flags here, which is how we transition into Stage1. And so from here, I'll pass the mic over to you, Jessica.
Speaker 2: Jessica Turner (00:26:22):
All right. Thanks. Rich. Just spend a couple minutes here with Pivvot. Rich showed you how you can not only identify a site, but actually come up with that usable area and those constraints associated with it. When you are ready to take that a step further and really drill down and refine those preliminary budgets and designs and schedules, then you can tap into Stage1. So with Stage1, we think of it in three parts. The first is all of Terra, con's historical data. So we have over 55 years and in some places like Cincinnati, we have over a hundred years of data that we are, have uploaded into our system and we have geo-referenced it. So within a matter of seconds, our practitioners can identify sites close by and pull up that historical, the boring logs as well as any lab, lab data associated with it.
So then we've taken that and we've paired it with a whole bunch of publicly available information, as well as some of the proprietary data sets that rich was talking about that are now included in Pivvot as well. And then the third piece, which is the most exciting piece for me is that we have experts across the nation who in some cases have 40, 45 years of experience. And they just know that area like the back of their hand. So we're combining all three of those into a report of anticipated site conditions for both geotechnical and environmental information. So we wrapped that all up and we have a team of dedicated client service managers and they turned these reports around fast. So what a preliminary desktop study was in the past, maybe taking three, four plus weeks to get into your hands. We are now turning around in a matter of days because we have a centralized team helping us get these out the door and work with those local experts to get their opinion.
So with S one, we have the geotechnical section, which is truly, if you were to take a drill rig out on site and drill a site, this is what we would expect to find. And we let you know if we have any concern about variation across the site and we let you know how confident we are in that information as well. And then with environmental, it is actually two different sections. We've got the subsurface environmental, which is really a high level phase one. And it's actually going to let you know if there's any sort of red flags or triggers or additional permitting processes that are going to take place when you do go through with an actual phase one, and then we have the natural and cultural resources. So with the cultural resources, we'll let you know if there's any sort of issues out on site where you may need an archeologist or your schedule's going to be delayed because of historical or public lands. We'll also go into the federally protected species. We'll go through what they are that are triggered on that site, as well as if any of them will actually cause any sort of issues for development. And then the last pieces, we'll start talking about any sort of wetlands or waters considerations that you need to keep in mind as you're doing those preliminary designs. So with that, all of these have been identified by an expert at this point. And that's when we get someone like Tamara involved. So, I'm going to hand it over to you.
Speaker 4: Tamara Hashimoto (00:30:17):
Thank you, Jessica. Okay. So this is the part where I get to nerd out about what a geotechnical engineer can do for you on a solar facility project. Thank you for that rich. So most, if not all the following hazards I'll go over can be identified with Pivvot or Stage1 and identification of these hazards early on. Not only help with site selection, but they also help SGO technical engineers to create a field exploration program and pile load testing program that is specifically tailored to your site. So if you remember that map that rich showed where it had the hard rock located at the very center of the site. So we would want to put some exploration points in that area, maybe utilizing different drilling methods to make sure we can break through the bedrock, maybe rock coring, as well as having alternative pile installation methods in order to make sure we can drive piles in that area.
So maybe pre-drilling before we install piles in that area or using alternative foundation types for that area of a solar site. So, starting out with frost and adfreeze, that's probably not a concern for me since I live in Las Vegas, but maybe for some others on the call, this is an issue. So these conditions will impact design of different foundations and the roadways, and it can also impact your pile embedment depth. So during our pile load testing program, we're going to want to either pre-drill or excavate oversized, pilot holes to that ad-free depth for two reasons mainly. So if you're doing a pile load testing program during the winter, you'll notice those upper soils will be frozen. So we want to remove those frozen soils that are providing higher capacities, then what those soils would have if they were not frozen. And then the other reason is that we would want to optimize the skin friction of the pile below that frost step.
So shallow bedrock. So again, like what rich showed us. If we have shallow bedrock on the site, that's a concern, right? So these conditions can impact the foundation type or installation procedures you might need to do pre-drilling before you install your piles. So, we then us geotechnical engineers can propose performing geophysics borings test pits to assist with determining those shallow bedrock ups on your site. Well, as I previously mentioned, we'll also want to make sure we're testing piles, utilizing those different alternative installation methods, such as pre-drilling prior to installing the piles in order to model those test and test those methods that you want to use during production previous mining. So, when you have this hazard on your site, we would want to do an in-depth settlement, evaluation of the deep fills. And we have two major questions that we want to figure out when we're doing our evaluation and that's how long ago was it backfilled and what was it backfilled with?
Liquefaction so shout out to my west coast people on this call. I'm sure you know what this phenomenon is, but this occurs where loose sand or non-plastic silt soils exist below groundwater, but it can also occur with sensitive plastic silt or clays below groundwater. So also known as cyclic softening. This is caused by an increase in poor pressure during seismic events, leading to a loss in sheer strength in soils. And it typically occurs in the upper 50 feet. So, when we do our geotechnical exploration, we want to make sure that we're performing a boring to the 50-foot depth, and then we're running some additional lab tests and performing our liquefaction analysis. So, when you have a site that has liquefaction hazard potential, especially on larger solar sites, there's not much we can do to mitigate these conditions. So it might be a risk to the owner, or you might decide to just to walk away from the site.
So if you have a small site, though, fiber columns can be a mitigation me measure, but I understand this can be pretty costly and sinkhole. So this occurs when limestone gradually erodes away with water over time informs these sinkhole features at the surface. So the way we evaluate these is we would perform a desktop review and also review LIDAR data and then perform a site reconnaissance. So, we typically recommend men that you want to stay at least 50 or a hundred feet away from these features, but if you wanted to get closer to them, when you're constructing the way we can evaluate the invest, the extent of these features is through geophysics and we do something called multiple electrode resistivity.
So another issue would be expansive soils. So what expansive soils do is they cause upward forces on your piles and that can require piles to be embedded deeper erosion. So this can impact pile embedment depths as well. We can collect some samples and run radiation tests on those near surface soils and surface soils. However, typically it's the civil engineer that handles erosion issues or figures out scour deaths and then corrosive soils. So this, the soils can deteriorate steel and concrete over time, which is something we identify in Pivvot reports that like rich went over earlier. So we can perform laboratory testing. We call it the corrosion suite of tests, which I'll go over later in the laboratory test slide, but corrosion engineers can utilize our lab test results and they can figure out how to mitigate this issue or see how much galvanization the piles will need.
Okay. Exploring subsurface conditions. So, on our previous geo 101 webinar, we went more in depth on some of these exploration methods. So if you would like to review that we go more in depth in that discussion, but some things we do for a typical solar facility project are site visits, borings cone, penetrometer test, test pits, geophysics, groundwater, monitoring, Wells field permeability, pile, load testing, electrical, resistivity testing, and thermal resistivity testing. So, Terracon has our own internal frequency like the exploration and testing frequency to prepare a design level report for you. So we use borings CPTs and test bits to do our field exploration. So as previously mentioned on our last geo 1 0 1 webinar, we go more in depth about what each of those types of exploration methods are. But CBTS typically are good for soil types that are lower I density and free of cobbles boulders, cemented deposits and bedrock.
But if you do have those type of soil conditions on your site, we can explore the site with borings and test pits. So borings, we just need to make sure we're using the correct drilling types so we can break through those harder soil conditions, or we might do rock pouring as well. And then test pits are really good for those soil conditions. So with cobbles boulders cemented deposits and bedrock, because then you can open up an entire excavation and see what it is you might be refusing on with your C P T or borings to determine if it was one of those soil types. So for solar arrays, we typically recommend one exploration for every 25 acres. And your borings will be between 15 and 20 feet test pits up to 10 feet or refusal for substations. We typically recommend two explorations sometimes more. And then for your battery energy storage system, that really depends on the size of the best and also the foundation types that will be utilized to support the structures in the best.
So this is what our typical boring logs look like that we present in the report. So on the far left boring log, if you look under the field test results, you can see that the blow counts are relatively low in the upper materials. So, whenever we see boring logs like this, we generally feel that it's going to be easy pile driving or pilot installation conditions. However, when you look at the middle and the boring log to the right, so for the middle boring log, you can see under the field test results column, there's a lot of 50 plus refusal blow counts. And you can also see that apparent cobles were logged out of depth of five feet below the ground surface. So when we see these conditions, we would recommend pre-drilling pile prior to installing piles on a site. Cause we think that's going to impede pile drivability. And again, on the right boring log, you can see that there's bedrock log. So that's another reason why we might recommend pre-drilling or some other alternative method for your, a pile load testing program and for production. So this is a typical C P T log. And so not going to in depth on this, because again, you can review the go 1 0 1 webinar previously, but you can see that we have tip resistance and sleeve friction values on this chart, which we utilize. We then utilize to correlate different soil parameters for our design. And you can also see based on this graph, there's you can see where the tip resistance or sleeve friction increases. So when you see those high jumps and values, that indicates stronger soil layers, which also may impede pile driving
Field electrical resistivity testing. So the electrical engineer will utilize our test results to help design their grounding systems. And what we do is we typically run it in general accordance with a S TM G 57, which is the winner for electrode method. And that consists of two mutually perpendicular arrays per test. And so for solar array areas, we typically test ACE spacings up to 200 feet. And then for the substation and best areas, we typically test ACE spacings up to 300 or 400 feet other unless otherwise specified by the electrical design team. So these are the typical geotechnical laboratory tests we perform for solar projects. However, it does depend on the soil conditions and project requirements as well. But as I mentioned before, we do a corrosive suite of corrosivity suite of tests to test the soils corrosivity. So we have pH minimum resistivity, sulfates chlorides redox, potential and sulfides that are included as that suite of testing
Thermal resistivity testing. So this can be used for design of cable or conductor sizes. You can measure the soil's ability to dissipate heat. So you can see from this graph, it does the thermal resistivity does vary significantly with moisture content. And then it forms what we call is this thermal dry out curve, which is included in your report. So if we are not provided specific testing requirements by the client, what we do is we typically run these tests, the samples at 85% of the maximum dry density determined by the standard Proctor. So a S TM D 6 98, and that's because this, it gives us a conservative value and models, trench backfill with little to no compaction effort. We also like to have generally at least three to four moisture points in order to create that dry out curve. And it usually ranges from dry condition to insitu or optimum moisture content depending which is higher. Okay. So now I'll go over pile, load testing and analysis, which includes pile installations, the three types of load testing that we perform when we're out in the field. So axial tension, axial compression and lateral, and then as well as the pile load, test results and analysis.
So when we install piles, we like to install the piles to the target embedment depths or refusal. And we like to install two piles at each, at least two piles at each test location with two different embedment depths. And we'll talk about why that's important later on in another side. So we install them to target embedment depth or refusal. And so our typical refusal criteria is less than one foot of embedment after 120 seconds, unless there's a different refusal, quite criteria that's specified by the client. And then we usually allow the piles to set for at least 72 hours before load testing. So to allow for soil setup so that our load test results are more accurate. And then the two test piles at each location are tested for axial tension and lateral load testing with the two different embedment depths. And then for compression load test locations, we'll install a third test pile at that shallower embedment depth of the two previous piles. So if you had a location with five foot embedment and eight foot embedment, we would install the compression pile at five foot embedment. So what we do on our pile drive time plots as we present the drive times per foot in a graphical format, such as this. And so this just presents what we typically include in our report.
So this is what it looks like in the field when we perform axial tension pile, load testing. So we're pulling the pile out of the ground and Terracon has their own proprietary low test system, this tripod. And because we strive to be innovative and due to our commitment to safety, we identified that our previous tripod system was really heavy and cumbersome to work with for our field crews when we're doing pile load testing. So what we did is we recently designed this tripod for safety reasons, and it's now called the Terra PODD 2100, and now it is much shorter and lighter for our field crews to maneuver. So our typical load test schedule when we're doing axial load testing is loading up an increments of 500 pounds up to 10,000 pounds or to the deflection criteria. Then unloading debt back down to zero pounds. And the deflection criteria is three quarter inches, which is average between the two deflection gauges on the pile. And of course we can adjust our load schedule and deflection criteria based on the design loads, if we're provided them or the client's request,
When we are analyzing axial tension load, test results, we are plotting them on graphs like this. And then we're checking what the ultimate load is at a quarter inch deflection. So on the left side, you have the five foot embedment test pile, which has a load of about 4,500 pounds at that quarter inch deflection. However, because we installed that second pile to a deeper embedment depth at the same test location, you'll see that the load did it didn't even reach the quarter inch deflection. So then what we utilize is the maximum test load, which was 10,000 pounds for that eight foot embedment test pile
For axial compression load testing. You can see, we use heavy equipment as a reaction force. So that way we can push down on the pile when we're doing our compression load testing. And our typical load test schedule is loading an increments of 500 pounds up to 13,000 pounds or the deflection criteria again, then back down to zero pounds. So again for compression, it's three quarter inch deflection average between the two deflection gauges on the test pile. So we can adjust that load schedule and deflection criteria, depending on the design loads and or the client's request as well, analyzing the data for the compression load test data. We, we look at a quarter inch deflection. So for this scenario for example, it was, they didn't achieve the quarter inch deflection. So we utilize the maximum test load, which was 13,000 pounds,
Lateral load testing. So here you can see, we have the two different test piles at a location. So those are the two piles with different embedment depths, and we test them concurrently such that they're reaction force to one another. So the typical Terra on load test schedule is loading up in increments of 500 pounds up to about 7,500 pounds and at least five cycles of loading. So what that means is we'll gradually load up and then go back down to zero and load up again in five cycles. So for example, 500 pounds, 1000 pounds, 1500 pounds back down to zero 1500 pounds, 2000 pounds, 2,500 pounds back down to zero and five cycles of loading. And then we go up to that, the max load or deflection criteria then unload down to zero at the very end. And the deflection criteria for lateral load testing is one inch deflection average between two gauges. So each test pile has two gauges attached to it and we're testing them at the same time. But if one fails, we can continue testing the other test pile. So the deflection gauges are situated approximately six inches above the ground surface. And that matters because as you go higher up on the pile, the pile is going to move more. The higher up you are. And then the lateral load is applied anywhere between 24 inches to 48 inches above the ground surface.
When we are analyzing lateral load test results, we are taking a look at half inch deflection. So for this example, we're at about 4,400 pounds at that half inch of deflection.
Okay. So why is having two different embedment depths important? So for instance, if we only installed that one five foot embedment pile at a test location, after all our skin friction calculations and analysis, we would come up with a required embedment depth of 10.2 feet. However, because Terracon has that additional data from that eight foot embedment pile, we're able to calculate skin frictions from that five to eight feet, and that helps us optimize the design. And then the required abandonment depth then becomes 7.6 feet. So by installing that deeper pile, that second pile at the test location, we save 2.6 feet of steel. So assuming we have a hundred thousand test piles that can equate to approximately 1.9 million in savings end bearing. So the way we calculate end bearing again. So we're taking our compressive load at a quarter inch deflection minus our tension load at a quarter inch deflection. And that will give us the end bearing value. And for the examples that I showed previously, that would be 8,500 pounds
Lateral analysis. So based on the results of our geotechnical exploration and our pile load testing program, we can then delineate your project site into different zones based on those different soil conditions at each exploration or test point. So this helps us to optimize the design for you. And then what we do is we prepare a pile soil input parameters based on those different soil zones, which are determined based on the field and load test data. And then we can provide you with a, we perform our LPI pile analysis and which we give P and Y multipliers in the report.
Now taking the results of skin friction analysis and bearing analysis that a pile analysis, and also giving consideration to adfreeze and expansive soil conditions. We can then determine the minimum required embedment depth for your project based on this pile in depth pile, embedment depth analysis that we perform. Another service that we offer is structural design for all the piles on your project as well, which we previously mentioned in that project life cycle slide. So we understand that our competitors also have a lot of solar experience, but what sets Terracon apart is our desire to lead an innovation by improving our processes like what we did with the safer and more efficient proprietary tripod system or the Terra PODD 2100. And also, with our visionary digital service solutions, those 4,000 plus solar projects that Jessica referenced in the beginning have expanded our data to include over 2.5 million subsurface data points across the nation.
So we're able to get this valuable information to you earlier to help you make go no-go decisions on your site and refine preliminary designs, budgets, and schedules. We also have an internal GIS database of all of our historical project data, which can be mine for soil's information and to help provide preliminary recommendations without ever having step foot on your site. By having this readily available data, we can also fine tune our services and tailor a specific scope of work that's unique to your project. So, we're here to help you from selecting a site and refining usable area with Pivvot to the start of early planning with Stage1. And then as you enter the design phase, we can provide geotechnical, environmental and structural engineering services that will lead you through to construction, where we can also provide you with construction material testing services. So with that, I just wanted to thank you all for your time today, but I would also like to end this presentation with a dad joke because I love dad jokes. So obviously you don't have to answer because you're on mute, but why doesn't the sun like clouds? Cause they're always throwing shade. And I know that wasn't funny, but I hope I at least brightened your day. Okay. Now I'll hand it over to Jessica to open it up for questions.
Speaker 2: Jessica Turner (00:52:50):
All right. Thanks camera. We have quite a few questions in queue. Alright. So the first one is from Kelsey. Is there much of a push to acquire geophysical geochemical data and near surface reports from oil and gas operations to better enhance the data sets
Speaker 4: Tamara Hashimoto (00:53:12):
Oil and gas operations? Maybe does that kind of sounds maybe like a Pivvot thing. If that's something we can
Speaker 5: Rich Henry (00:53:24):
Talking for my, maybe we could follow up. I don't have the person in front of you. I mean we could follow up and get a little more detail for me to understand that a little bit better.
Speaker 2: Jessica Turner (00:53:33):
Okay. Kelsey, we may reach out to you after to understand that a little more. We have Garrett who's asking in borings, what frequency of blow counts per foot would you typically recommend for pre-drilling assuming no full refusal.
Speaker 4: Tamara Hashimoto (00:54:57):
So what we typically do for our sample intervals, which gives you those field test results, the blow counts, SBT blow counts. We'll do every two and a half feet and the upper 10 feet and then every five feet after that. And then with when you have pre-drilling conditions, we don't really do different sampling methods. We just identify those areas of the site that we would likely want to pre-drill if not the entire site. And that's helped that what helps us is riches Pivvot report. So we are where we are able to identify those harder soil areas in advance of our exploration. So, we'll propose to do pre-drilling in those areas unless the client would like for us to do the entire site, because it depends on what's more cost effective and we want to do what they want to perform during production or construction.
Speaker 2: Jessica Turner (00:54:47):
Okay. We've got Neil, why is an ACE SPAC? Why is an ACE spacing of 200 feet required for winter?
Speaker 4: Tamara Hashimoto (00:54:57):
That's not what's required of us. That's just some the ACE typical ACE spacings we've seen requested by the electrical design team for solar arrays. We used to do 'em up to 50 feet, but we're now noticing that clients and electrical design teams are requesting larger ACE pacing’s in the solar arrays. So it depends on what they want for the project.
Speaker 2: Jessica Turner (00:55:21):
All right. Are the target embedment depths based on preliminary estimates using geotechnical parameters from exploration and the design modes?
Speaker 4: Tamara Hashimoto (00:55:31):
Yes. However, in certain areas we already have an idea of what our proposed embedment depths would be for a pile load testing program. We typically want to go shallower than what we think the recommended minimum recommended embedment would be for design.
Speaker 2: Jessica Turner (00:55:52):
All right. And then we have Kirsten, who's asking if we have a video that we can share of pile, load testing in action. And I do believe we have that and we might be able to add that into our follow up email with the recording of the webinar.
Speaker 4: Tamara Hashimoto (00:56:09):
Yeah, I think that would be really interesting because you guys probably don't know what it looks like when we go out and do our field exploration and pile load testing programs. And it would be cool to also see our new Terra PODD 2100 in action.
Speaker 2: Jessica Turner (00:56:24):
Definitely. All right. This one is from Kevin and it says one of the most common problems I run into is sites like in mid Texas, where there are variable soils, typically clay and limestone, some of the site has refusals. Some of the site has very low blow counts with bedrock. Is it typically hard to determine the exact areas where to pre-drill would be required? And then there's a second part, but I'll let you answer that first.
Speaker 4: Tamara Hashimoto (00:56:56):
Okay. Maybe I might get Scott, Neely's help with this one, what we're doing in order to delineate those different soil zones. But I feel like we could use a combination of methods, exploratory methods like borings as well as test bits and then with geophysics as well, possibly. But Scott Neely, do you want to chime in on that?
Speaker 6: Scott Neely (00:57:20):
Hey, thank thanks, Tamara. And good morning, everybody. I would say that it is difficult. We've done many projects in west and middle Texas. And though we have delineated, the sites with zones understood from our contractors that for the most part, it was helpful, but they still had piles that they had to remediate because they would hit shallow refusal. So without spending a great deal of money in geophysical approaches, I just don't know that there's any better way to estimate where you're going to encounter the refusal.
Speaker 4: Tamara Hashimoto (00:58:08):
Thanks, Scott. Sorry. I forgot to introduce Scott Neely, but he is like the ultimate solar subject matter expert for our company.
Speaker 2: Jessica Turner (00:58:19):
All right. So the second part of that question is have you considered adding multichannel analysis, surface wave analysis to your scope of work, to create better maps of the soil density?
Speaker 4: Tamara Hashimoto (00:58:30):
I feel like we've performed that in some areas of the site. Scott, has that been helpful in helping to delineate these types of projects, but differing soil conditions?
Speaker 6: Scott Neely (00:58:42):
Yes we have, but actually we tend to stay with the size of refraction only because it's a cheaper and quicker test and it's actually even better and more accurate, but either of those methods requires a great deal of time. And so it's a great deal of expense. So we have done it on a few projects, but I won't say that we do this routine.
Speaker 2: Jessica Turner (00:59:13):
All right, we've got from Dylan, how many piles are installed at each test location? I heard two, but is that for each type of test?
Speaker 4: Tamara Hashimoto (00:59:23):
I just realized I didn't go over the frequency that we perform pile load testing. So on your solar project, within the solar arrays, we perform, we have one pile load test location per 50 acres. And then at each test location, we'll have at least those two test piles for axial tension and lateral testing. And then depending on the soil conditions, test a certain number of those load test locations for compression load testing in which we'll install a third compression load test pile. So what was the second part of that question? I don't know if I covered everything.
Speaker 2: Jessica Turner (01:00:04):
Speaker 4: Tamara Hashimoto (01:00:05):
See, or did that cover it?
Speaker 2: Jessica Turner (01:00:08):
I think it covered it. Okay.
Speaker 4: Tamara Hashimoto (01:00:09):
Yeah, if it didn't let me know.
Speaker 2: Jessica Turner (01:00:13):
Okay. Next, has there been standardization applied in the pile drive time calculations to account for the different hammer, blow strength of the various pile driver brands and sizes?
Speaker 4: Tamara Hashimoto (01:00:29):
I don't know if we've done anything. How about you, Scott? Typically we're just presenting our we'll present on those plots, like our results, and then we'll give the pile driving or pile the pile rig type. And then some clients will request like the specs of that pile driving rig. But for us on our end geotechnical engineering end, we are not doing anything with that data. Do you know of anything, Scott?
Speaker 6: Scott Neely (01:00:57):
That's correct. Tamara. We know that different hammers deliver different energy, but in general, all the pod drivers that were aware, they're putting this at near 100% of the capacity and then they turn it on. And so that's generally what we understand contractors are actually doing as well in the field. So we're trying to emulate what the contractor is doing with that power driver.
Speaker 2: Jessica Turner (01:01:32):
Speaker 6: Scott Neely (01:01:33):
We just don’t know the difference between the hammers.
Speaker 2: Jessica Turner (01:01:38):
All right. Thanks Scott. We do have a lot more questions in the queue and we are kind of running out of time. So we'll get one more in there. And then if we did not answer your question, we will follow up with you in an email. So this next one is, can you discuss and compare ground screws versus piles from a geotechnical standpoint,
Speaker 4: Tamara Hashimoto (01:02:07):
I don't worked on a project with ground screws. I know that's a good alternative for harder soil conditions. What I have heard is it's pretty costly to install ground screws, but I know they get installed to a certain torque instead of a certain embedment depth sometimes. And that whoever the specialty contractor is that has those ground screws, they're the ones who are going to be installing and performing the load testing of those gr ground screws. And then Terracon will be present to document and record the results. But Scott, do you have any other feedback on ground screws?
Speaker 6: Scott Neely (01:02:48):
No. I think ground screws though, is we need to be careful of the term only in that ground screws. A lot of people might think of helical piers. And yet I do know that there are several proprietary screws out there. One is by TerraSmart. Another one is by Ojo. And so I don't think we know exactly what those costs are pile and how it compares with just a regular steel pile. So I think that would need to be farmed out by each of those suppliers and the actual costs.
Speaker 2: Jessica Turner (01:03:29):
All right. Very good. Well, we are at time and we do want to be respectful of the time that we set aside today. So like I said, if we did not answer your question, we will have one of our solar subject matter experts just respond to you in an email directly and we appreciate everyone for hopping on. And we definitely thank Tamara and rich and Scott for helping us with this as well. And we will be sending out that email with the recording of this. And we'll also go ahead and put the link for the first webinar in our follow up email as well. So with that hope you enjoy the rest of your Wednesday and take care everyone.
Speaker 4: Tamara Hashimoto (01:04:12):
Thank you. Take care.
Speaker 5: Rich Henry (01:04:14):
Speaker 6: Scott Neely (01:04:16):