Geotechnical Services for Solar Foundations

Engineers Experienced in Cold Climate Design Considerations

PRI Engineering specializes in geotechnical services for solar foundations – designed, engineered, and constructed to withstand the pressures of any climate, especially the cold regions in the Northeast United States and Canada.

Our personnel have been involved in the full project delivery including permitting and planning, preliminary/detail design, and construction inspections.

With 200s of successful pile designs for solar projects ranging in size from 120kW to over 100MW, PRI Engineering has the experience and expertise in solar foundations to reduce your project risk and prevent increased capital outlays from scope creep and construction delays.



Listen to our webinar from September 10, 2020 which elaborates on PRI’s Geotechnical Engineering for Solar Foundations. Be sure to check out the Q&A session starting at 34:40.

Why Work with PRI Engineering?

We Design to Prevent Frost Uplift

Our Canadian-trained personnel are required to understand the dynamics of frost uplift and prevent foundation failure while adhering to strict design considerations. In contrast, the American design code and standards for civil engineering practices have no such requirement.

Cold Weather Experience

Not only are we trained by Canadian standards to design, engineer, and construct solar mounting systems in cold weather, we have over 50 years of combined experience doing just that. We have an extensive list of over 200 projects in cold regions of North America.

Minimize Your Project Risk

We de-risk your solar project, with your budget in mind. Our team is experienced in the design of solar foundations and alternative design to prevent costly construction delays and time overruns, when anticipated conditions are not encountered during construction.

Services for your Budget

We offer competitive rates because we tailor our budget to your risk profile. No matter the project type, we develop a work program to meet your exact project needs to ensure you are not paying excessively for information you do not need. Our rates include access to our highly experienced core team of engineers, who bring expertise to every project.


Solar Foundation Design Development

We can work with any racking manufacturer in the United States and Canada to consider racking loads from a multitude of products. Once we have identified the racking induced loads, we develop site-specific parameters based on the geographical area of the project.

Our design considerations for solar racking and foundation in cold climates includes:

1. Racking Induced Loads

  • Racking dead load
  • Wind load
  • Snow load
  • Seismic load

2. Geotechnical Considerations

  • Frost design depth
  • Adfreeze pressure
  • Wet/dry cycles

Geotechnical Investigation

Our unified geotechnical and structural engineering team provides an integrated foundation while considering racking design and constraints that can be further optimized via site-specific pile load testing programs at your request.

Our personnel’s involvement in the design of solar PV plants has included full design, QA/QC, peer reviews, Engineer of Record services, and acting as the Owner’s Engineer.

Specifically, we perform:

1. Subsurface Investigation

  • Preliminary site visits
  • Test pits, a superior method over boreholes
  • Subsurface profile for preliminary pile design

2. Pre-Production Testing

  • Test piles to verify design assumptions
  • Assessment of constructability
  • Understanding of subsurface consistency

Construction QA/QC Analysis for Solar Foundations

Our expertise and experience ensures efficient construction Quality Analysis (QA) and Quality Control (QC) of your solar array foundations. When designing a solar foundation for cold climates, QA/QC ensures your project is built to last.

In particular, we perform:

  1. QA/QC of pile erection in conjunction with the contractor
  2. Review of the racking erection
  3. General conformance letters at the completion of the project

Production Testing

PRI Engineering is one of the few geotechnical engineering firms in North America offering both pre- and post-production testing. Production testing assures you that our initial analysis and design recommendations are of the highest quality and result in durable structures that last throughout their intended lifespan.

Production testing involves:

  1. Verification of the solar foundation design
  2. Troubleshooting of non-conforming piles
  3. Testing deflection tolerances as required by the racking supplier

Solar Foundations Design: Report Summary

Solar Foundation Articles

January 5, 2024 in Case Studies, Civil Geotechnical, Construction Inspection, Solar Foundation Design

PRI Engineering’s Innovative Approach to Geotechnical Challenges at Blue Jay Lane Residential Development

PRI Engineering's innovative methods in geotechnics for Blue Jay Lane project - site investigation, grading, slope stabilization, and structural load verification.
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January 23, 2023 in Solar Foundation Design, Webinars

Webinar: Reducing Solar Foundation Risk

As solar generation systems become more economical and a significant source of green power globally, it’s crucial that we learn how to reduce the risks associated with constructing solar foundations.…
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Solar Geotechnical FAQ

We compiled a list of the most common questions about solar geotechnical services and the work we do here at PRI Engineering. Our solar geotechnical FAQ will answer your most pressing questions.

What are geotechnical services for solar?

Subsurface ground conditions are important to consider prior to and during the development of utility-scale and large commercial ground-mount solar arrays. Geotechnical engineers investigate solar sites to increase project safety and reliability while reducing project costs.

Ground conditions dictate which type of solar foundation should be used based on a combination of factors including soil type, subsurface obstructions, geographic location, groundwater levels, corrosion potential, topography, and local building code requirements.

What kinds of investigation work/testing do we need to develop a solar project?

Both geotechnical testing and pile testing are required to develop a solar project. Test pit excavations, test borings, in-situ field testing, and load testing are generally the most common practices prior to performing a geotechnical investigation for a solar project development.

Depending on the scope and budget of the project, the geotechnical investigation will consist of:

  1. Soil type classification
  2. Identifying Atterberg limits
  3. Particle size distribution of soil
  4. Friction angel or cohesion
  5. Resistance factors for the various layers of soil
  6. Corrosion considerations
  7. Adfreeze (frost heave) and frost penetration depth (including historic weather correlation studies, percolation, and water table)
  8. Pit excavation to find possible constraints during construction (soil stability, rocks, etc.)

A pile testing and design program is also necessary to determine how to best install the right solar racking foundation in the proposed site. The most important factors for a pre-production load testing and pile design testing program are the tension/pullout capacity and the lateral capacity. The parameters considered in a pile testing investigation include:

  1. Testing loads
  2. Testing piles
  3. Axial compression test (only needed in very large, heavy solar systems)
  4. Lateral test (not that necessary but optional)

Are there geotechnical investigation programs tailored to solar projects?

Yes, there are tailored geotechnical investigation programs for solar projects. This is because soil and subsurface conditions vary significantly based on geographic location. All civil engineering and public works projects require geotechnical investigations to ensure the safety and reliability of the structure. Depending on the size and other factors identified in the preliminary site survey and test plan, the scope of the geotechnical investigation program for the solar project will vary.

What should a geotechnical report for a solar project include?

A geotechnical report for a solar project usually includes results from the geotechnical investigation, the pile testing and design recommendations, and the pre-production load testing. The report begins with a basic background review of the site. It will then include information on the geotechnical investigation procedures such as the field investigation program, piezometer installation, laboratory testing program, and field resistivity testing.

Subsurface conditions are also detailed in length including information on the overburden, bedrock and other obstructions, and groundwater and borehole stability observations. Most if not all geotechnical reports conclude with a recommendations section which identifies general recommendations such as site preparation, excavations, groundwater control, and material reuse, backfill, and compaction.

The geotechnical recommendations section also includes frost considerations (such as soil frost susceptibility, frost penetration depths, and water availability), seismic site class, and recommendations for foundation design (including which pile is recommended such as driven piles or helical piles).

Other information that is found in a geotechnical report for a solar project includes the groundwater and soil stability, corrosivity analysis, thermal resistivity testing, liquefaction susceptibility, and other hydrogeological considerations such as an evaluation of impacts from sediment erosion control, contamination of aquifers, and/or the drawdown of water wells and water features. Construction monitoring and design review are also included.

Each geotechnical report will vary based on the scope of the project, which is why the initial site survey and test plan are so important. Depending on what is found in the initial screening, the geotechnical report will have different information and recommended designs.


Experienced Engineers for Solar-specific Geotechnical Services

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