The geotechnical side of solar installations

Under President Biden’s clean energy investment plan, the largest in U.S. history, the renewable energy sector is at a turning point. As part of the broad goal to reduce greenhouse gas emissions and work toward making the country carbon neutral, the Biden administration has allocated substantial federal funding to accelerate the development and transition toward renewable energy solutions.

In response to the national directive, development and construction companies have begun responding by diversifying their portfolios to take on more renewable energy projects. As a result, solar is one area that’s booming in terms of demand, scale and impact. In fact, according to the Department of Energy, it’s become the country’s fastest-growing and most affordable source of new electricity.

Industrial-scale solar power plants include solar panels, electrical substations, battery storage, inverters, high-voltage transmission lines (above and below ground), roads, grading, and environmental impacts. All of these components make industrial solar projects challenging and increase the need for a trusted geotechnical consultant. Due to the scale and complexity of developing large-scale solar projects, high-quality, performance-based geotechnical recommendations are essential.

Geotechnical engineering

It is best to integrate the geotechnical engineer(s) into the project’s development and design team project, rather than simply bringing on a geotechnical consultant who provides a report. Leveraging the geotechnical consultant as a member of the development team leads to a more holistic approach to the design and construction of the solar project and allows them to provide valuable cost-saving advice and recommendations.

The geotechnical work for a solar project begins during site selection and the due diligence period. Geotechnology experts conduct site investigations using a combination of traditional exploration techniques (e.g., exploratory borings, test pits) and geophysical methods (e.g., refraction microtremor and/or seismic refraction surveys, electrical resistivity) to identify geological hazards, characterize the near and subsurface soils, provide a corrosivity assessment, and provide design recommendations. Unlike most geotechnical projects where one or a few foundations are required, hundreds of thousands of individual foundations may be required for utility-scale solar projects. It is this scale of these projects that warrants, if not requires, the geotechnical consultant to develop performance-based recommendations, identify value engineering opportunities, and integrate quality control/assurance aspects into the design.

The more refined and accurate the geotechnical work, the more optimized the design recommendations are, creating the opportunity to decrease material quantities and installation time — reducing the project cost. A geotechnical consultant who provides robust evidence-based performance recommendations can save a project hundreds of thousands of dollars.

For instance, I recently spearheaded a value engineering effort for the inner array roads of a large solar project, where additional geotechnical services resulted in a cost savings of more than 10 times the geotechnical service fee. Through the collaborative value engineering efforts between the ownership group, general contractor, and geotechnical consultants, the design-build general contractor turned the geotechnical consultants into a profit center. On another solar project, through additional pile load testing and reanalysis of the preliminary design recommendations, we were able to provide updated performance-based recommendations that resulted in saving the project greater than $200K in materials alone.

While the geotechnical work is vitally important for any project, solar projects present a unique opportunity for geotechnical consultants to take a holistic approach to design and construction. Through a comprehensive investigation, the geotechnology experts can, and should, add value for both the ownership and construction teams.

As the solar market continues to rapidly grow, renewable energy developers need geotechnology experts as part of their core teams to optimize a project’s safety, quality, longevity, and cost-effectiveness for continued success.

For an industry that is projected to continue booming as much as solar, especially amid current legislation, you need more than a geotechnical report. You need a geotechnical consultant willing to take a collaborative, holistic, performance-based approach to any project.

Written by Nelson Pearson, P.E.is the geotechnical and construction services manager at Universal Engineering Sciences,, an engineering and consulting firm with nearly six decades of experience. Pearson spearheads all geotechnical work on UES’ solar industry projects, which includes site investigations, materials team support, ground and cable spacing, field design, installation specifications, and more. UES — and Nelson — recently worked on some large solar projects.