Geotechnical Investigations for Large Solar Sites: Finding Hidden Costs
Greg: As a solar developer, you may have a rough knowledge of the geology in the area. And frankly, I have that knowledge because of conversations over the years with people like you, Arash. Having a general sort of a view on where your Geotech’s going to land is important, but then you have to get into the final points.
Whether it’s a driven pile or micropiles, I’m sure you’re going to get to further in this presentation, it’s finding those economies where a 5-megawatt site or a 50, or something larger. You need to be able to look at these sites and say, it’s driven piles for this section. It’s possibly helicals here. It’s possibly something else in this area.
Flexible Racking & Experienced Team Leads to Successful Solar Project Economics
And having a team, like the team that’s sitting at this table, where you all have a level of experience, you don’t have to reeducate people from day one. So, you don’t need to reinvent the wheel with discussions. With that team, you can accelerate your way to a solution much faster. And you can come up with a plan, where we put driven pile here and helicals here, maybe a combination.
For that you will need a flexible racking system. You need a contractor, a drilling contractor, who understands the nature of these types of projects to make them successful for a developer.
And if the developer’s not successful and the economics don’t pencil in and you can’t arrive at something that looks good in a spreadsheet, that you want to move forward and make the sizeable investments to get one of these things operational, none of us get to play at the end of the day.
The Cost Impact of One-Size-Fits-All Solar Foundation Design
Vishal: One other point, Dan, to pick up on your point about having driven piles in section A and then helical in section B. We have worked on a lot of projects, Arash and I, specifically where it was designed by others. They should have been driven piles in section A and helicals in B and then they just put helicals throughout the site because that was easy for them to design.
Dan: Yeah. A rubber stamp.
Vishal: Exactly.
Construction Impact of Poorly Designed Solar Sites
Dan: I have seen that with you, Vishal. That’s tough. As a construction contractor, we’re pulling our hair out. It just shapes the morale on the site. Everyone hates their lives and hates the job if the install is difficult due to the design. If the foundation works with the geology, it’s a happy, sunny day site, right?
So proper engineering, all starts right from the beginning, the preliminary site testing, the desktop study, geotechnical investigation, the pile load testing, and then the procurement. So, it’s in that order. That’s exactly what should happen to evaluate the site and evaluate your options.
Adapting Solar Racking to the Foundations: Cost-effective and Easy
Vishal: Some of the things that we’ve done, Arash and I, specifically on some of these sites is adapt the design to the foundations. For example, we know that there are driven piles in section A and a helicals in B. So, we’ll just design the rack to accommodate a round post. We’ll put a round-post driven in section B, and we’ll put a helical on A, so the top, the above-ground connection doesn’t change.
And then below ground, we’re putting in the right solution. That makes the most sense for the site and usually ends up being the most cost-effective and easy to put in the ground. That’s like one of the tricks in the toolbox. And I’m sure we’ll talk about a few more here, but I know that in those instances, that’s one solution we’ve generally done.
And then on other sites, we’ve seen a similar situation but with different foundation combinations. We’ve done ground screw in one section and a driven pile in another section or whatever makes the most sense. One of the advantages, we have with Polar Racking and our design is that we have a solution for ground screws, for driven piles, for helical piles, for ballast solutions. Our racking works with all foundation types.
We’re able to adapt to what the ground is telling us, rather than us saying, “Hey, put this in the ground because this is what we sell.”
Foundations Can Significantly Impact Construction Schedules
Greg: You’re both making me think about my little analogy about the funnel and the comment that the piles are the smaller things.
It’s the smaller things though that can become bigger issues. As you get further along in your development cycle and into construction, if you get some of those “small things” wrong, they can turn into some really big problems very quickly when you’re in the field. Because there’s no easier way to throw the wrench right in the proverbial spokes of a construction schedule, then to get your foundations wrong.
Dan: Absolutely.
Supply Chain and Foundation Issues
Greg: Because you have different lengths and different styles, getting those manufactured takes time. You don’t just go to Home Depot and pick them up. “I want the three-and-a-half-inch screw versus the four-inch screw.” You don’t have that, especially when you have challenging supply chains, like we have now, that just amplify, compound, pick whatever word you want, and make it a nightmare if you don’t get it right early on. You have to get it right.
You have to be as smart as you possibly can be going into it, and then you can deal with the smaller challenges that inevitably arrive. But at least those don’t cripple the schedule and then potentially screw up the project.
Cheaper Foundation Options May Run up Costs Later
Vishal: Well, we’ve seen a lot of people, who go for the cheaper option up front in the spreadsheet and then pay double to fix it afterward.
Greg: And lucky if it’s only double.
Vishal: And it’s usually much more though. We were working on a site recently where we proposed round posts because we knew that there were areas where you’re going to have to sleeve it. And that’s for sure, the right option. But like if you go with the W-section in that exact site, the sleeving becomes five times more or 10 times more. But people, they get caught with the shiny number upfront, so they just pay in the end. And that’s unfortunate – we see that happening way too much in our industry.
Greg: And you’re starting to sort of pull that thread there that maybe the cheaper solution will work. There’s a reason it shines. But if it’s got a 20% chance of working, you really got to think, do I want to go down to that?
So how much risk is there in that? How likely am I to succeed with that – with the lower cost solution versus what’s it going to cost me to pivot and switch gears down? So, if you have an intelligent plan, then you can take advantage of those cost savings. And that is my point.
The Right Team Supports Solar Design Risk Management
What you’re driving at, Vishal, is that if you have the right team, you can explore the minutiae of a project, the minutiae of your construction schedule, procurement, and all the rest of it to find those savings. But if you don’t have the right team and it’s across the board from Geotech to the major equipment supplier, your racking supplier, your foundation supplier – often part of that racking solution, and then your contract and if it’s on-site, it’s got to do the work.
Show up Monday morning and put the piles in the ground and put them in the ground at peaks. There’s a schedule and you got to put X number of hundreds of piles in the ground a day, or everything gets thrown off. That’s as I say, “You got to get it right.” And it can be right if you spend the time to figure it out.
Arash: And that’s the synthesis. I think like the message coming from the group is you need a team. If you have one out of four people at that table, saying, “This is the way,” and everybody else is saying something else. Chances are, it’s not going to work. And you need the developer’s buy-in, you need the racking company’s and the engineer’s.
The Limitations and Risk of One Foundation Type
You can’t have that one-trip pony. And in fact, too often or not, we’ve seen it. And both Vishal, all three of us, have brought it up where you have an install, or you have a designer that tries to design a site with one foundation type. The likelihood of you taking a 40–50-acre site and having homogeneous subsurface conditions is extremely unlikely.
Whether it’s 5%, 10%, 20%, 50%, it doesn’t matter, regardless of what that percentage of differences, if that hasn’t been accounted for in the design, you’re going to have 5%, 10% or 50% of the site, where those very large construction costs that both Vishal and Dan alluded to, throwing Greg’s spreadsheet out the window.
And suddenly, the financing of the project is that question because, what was originally financed, was, is not the reality. So, watch out for those spreadsheets.
The racking company should be able to accommodate the different foundation types. You need the engineer to be willing to look at designing different foundation types. And then you need a contractor that can accommodate installing different foundation types.
Different Foundation Types and Specialized Equipment
Greg: It goes without saying that as we rattle through these pile types, and you’ve got helical up now versus a driven. You got to know that when you show up at the site, whether you need a hammer or a screwdriver, they’re two very different tools.
And unfortunately, the types of hammers and the types of screwdriver equivalents that we use to construct these solar projects are not the kinds of things that, again, you can go pick up at Lowe’s or Home Depot. They’re specialized equipment that requires a specialized operator on top of everything else.
So just because you can jump in one of those excavators and dig a trench doesn’t mean you can jump in one of them and drive that pile in the ground, straight plumb, understand your torques, understand everything in that field to put that pile in the ground. That’s a whole another piece of the equation that sits with your contractor.
Quality Control on Solar Construction Sites
Dan: All that takes time to develop that team and the talents. We have been building a solar farm for 15 years. It took a while to get where we are – for people to truly appreciate the quality control that goes into it. As we’re installing these piles, whether it’s helical, driven or rock micro piles, you need to record the subsurface characteristics and relay that back to the engineers. Then they can look at that and say, “Okay, this is as per design.” If you don’t submit the quality control correctly, that pile never happened.
As with driven piles, we’re also recording time. We’re measuring every foot on the pile and literally there with a stopwatch, recording the time to determine penetration rates. With helical piles, we’re recording torque on a screen. So, for every pile, we will enter a pile ID number and the time we’d started installing that pile. As soon as that pile’s done, we hit stop and all of that gets relayed to the client afterward. So there’s a significant amount of quality control that can go into these projects. I am sure that people can truly appreciate what it is – countless nights, entering data into a spreadsheet.
Digitizing Quality Control for Solar Construction
Now that we’ve taken drilling into the 21st century, we’ve digitized everything. All our operators have iPads and they enter it all directly into their tablets. That way the client gets the information in real-time. The engineers get the information in real-time. They can assess that and evaluate the in-soil criteria right away and catch those, “These piles may need remediation before they get wrapped.” Often the racking crew is right on our tails. By digitizing everything, it works really well. I find it’s the way to go.
