McCarthy Improves Accuracy and Cuts Survey Costs by 80 Percent on Utility-Scale Solar Field Project
Established in 1864, McCarthy Building Companies has a long history of building across the United States in many different building and project types. The company has 3,700 employees and a number of craft employees, with offices across the country. McCarthy delivers building facilities that drive greater value for customers offering expertise in design, construction, post-construction, safety, quality, and technology. The company’s work spans several vertical industries, from advanced technology and manufacturing, aviation and commercial projects, to renewable energy, research labs, and water and wastewater management.
A Smarter Way to Build Solar Fields
McCarthy is expanding its work in the solar industry and has so far dedicated millions of man-hours to the efficient design, engineering and construction of solar plants across the U.S. To date, the company has completed over 35 utility solar plants, generating two gigawatts of solar power. Typical pile installation on a utility-scale solar project starts with a professional survey, usually completed by a two-person crew, marking tracker end pile points at the solar field.
The tracker device mechanically moves solar modules to an angle that aligns with the sun’s position throughout a day. The tracker system also includes the piles, torque tubes and the rack system. The tracker position is critical, and it requires mechanical installation with a pile driver for precision and stability.
Following traditional manual methods, after the survey crew marks the position of where the piles need to be installed, the layout team – typically consisting of three or four crew members – pulls the string lines and plants markers to indicate where the piles should go. The shakeout crew consists of another three or four people to distribute the materials required for install. The shakeout crew arranges the piles ensuring they’re facing the right way and that the correct-sized piles are “staged” at the proper location. They mark piles with a specific color by size for quicker distribution, according to the layout.
For pile installation, the machine operator walks beside the pile driver machine, operates the pile driver and logs data accordingly. From there, another crew member checks the pile type, moves the pile to the target, straps the pile to the machine, assures proper position and installs the pile. Josh Marriott, Senior Virtual Design Construction (VDC) Field Solutions Engineer for McCarthy, explains that the traditional process of pile installation is manual and extremely costly. Accuracy can also be an issue on a typical project. In fact, between 4 and 5 percent of piles need to be reworked on most projects, which adds up to significant costs.
“Before you even start to install piles on a solar project, you’re using eight to 10 people,” said Marriott. “We wanted to find ways to cut our labor needs, improve production and accuracy of the crew, and improve the quality of our work. Our SITECH Tri-Rivers dealer and Trimble were up to this challenge.”
Building a 3-D Pile Plan, New Workflow
Trimble and SITECH Tri-Rivers started by installing Trimble’s DPS900 Piling System on one GAYK Hydraulic Ram piling machine. They chose a 400-acre utility-scale solar field project in Millington, Tennessee, with 31,000 piles to install as their pilot project. To test the new equipment and process, they drove 40 piles to start. The results were impressive, with the worst pile being off target by only one-quarter inch. Pleased with the results, they installed the equipment on two additional machines next and started training their VDC team on the new workflow leveraging Civil 3-D and Trimble Business Center.
Trimble Business Center allows users to process and prepare geospatial data so it can be read by the DPS900 system. The operators access the pile plans from the on-board displays, line up the piling machine according to the design and drill for the pile. Operators can then view completed piles compared against planned piles in both 2-D and 3-D views.
3-D Guidance Delivers ROI
Jon Wieneke from SITECH Tri-Rivers helped the McCarthy team create a piling plan for the Millington solar project, assigning all 31,000 piles. Wieneke configured the piles and devised a pile plan leveraging the pile description that includes pile length, elevation, required embedment depth, and alignments. At the same time, he also created customized pile plan templates for McCarthy to use on additional solar projects as well. Wieneke utilized the feature code manager within Trimble Business Center for importing surface details and pile points into the software and then exported the plans to the Trimble DPS900 systems.
After a learning curve that lasted for approximately 2,000 piles, operators began to fine-tune issues and followed the pile plan to drive several hundred piles per day. After about one week, the foreman and operator became more comfortable with the Trimble DPS900 system and the team began to see positive results. They met tolerances of +/- ¾ to 1.5 inches north/south and three-quarters of an inch to 1-inch east/west. In total, the McCarthy team also succeeded in cutting rework required for pile placement to below 5 percent of total piles placed.
Using this 3-D machine-guided approach, McCarthy reduced the labor required for prep and pile installation by more than 50 percent, reducing the crew required from 12 people to a crew of three or four people. They were also able to install hundreds of piles per day, keeping pace with an aggressive schedule of three months, even with delays due to weather and waiting for the ground to thaw during colder months.
“We noticed that overall, our piles were straighter than they’ve ever been using more manual methods, and we were able to see significant advantages of reducing the labor required in the field,” said Marriott. “We also generally budget around $250,000 for survey costs for a solar project of this size, but now we’re minimizing those costs, too.”
Marriott adds that he sees the biggest benefit of leveraging the DPS900 system for solar projects where 10,000 or more piles need to be installed, or 20-plus megawatt sites.
While some of the survey budget was re-allocated for the VDC team to build out the pile plan, Marriott believes that overall, his team significantly reduced costs with this new process. “In other ways, we are also cutting time and money out of the schedule because we’re not waiting on the survey team, we do not have to stop work for layout tasks or to check our work because we’re confident it’s right,” he said.
Q/A Reporting Made Easier and Future Plans
Once the piles were installed, the team also created Q/A pile plan quality reports that track drive times and reports indicating if piles are leaning, for example. They also verify if the piles are within tolerance and placed correctly.
Looking ahead, McCarthy plans to use the Trimble DPS900 system on other large utility-scale solar projects. They’re also evaluating the possibility of leveraging an Unmanned Aircraft Vehicle (UAV), or drone, to quickly collect photogrammetry surface data for pile planning and tying that data directly into the machines for additional time savings.