The development phase for Saskatchewan’s newest 10MW solar facility is well underway. Usually one of the first to be onsite for solar projects, Bengeo Limited Engineering recently completed phase one of the geotechnical investigation: a preliminary site investigation for the solar foundation. Their recommendations and design will help ensure that the solar facility can handle the challenging conditions of the extreme temperature fluctuations and winter weather common in Saskatchewan.

The second of its kind in Saskatchewan, the 10MW Foxtail Grove Solar Project (nicknamed Foxtail Grove) will be developed, maintained, and managed by Kruger Energy and Saskatchewan L.P. Located just outside of Regina, the project will send power directly into SaskPower’s main electricity grid and will generate enough electricity for more than 2,600 homes.

What Tests Do Geotechnical Engineers Perform for Solar Developers?

As a general rule, geotechnical engineers test the physical and chemical qualities of the ground and soil at a site prior to construction. They do this to make sure the structure will be able to adequately resist design loads considering all potential conditions.

Geotechnical investigation and pile design testing for a solar project is vital to minimizing the construction costs of foundations, ensuring a durable foundation, and ultimately preventing costly repairs over the 25-year lifespan. The findings from these geotechnical reports provide valuable information for selecting suitable foundational designs and for determining any additional earthwork requirements. In the case of Foxtail Grove, Bengeo Limited Engineering reported their findings to Kruger Energy.

Many factors come into play when determining the most suitable foundations for a large utility-scale solar facility such as Foxtail Grove. For this geotechnical engineering report, Bengeo Limited conducted the preliminary design development, which can be broken down into two main questions:

• How deep does frost penetrate in the winter? (Frost penetration depth)
• How much resistance can the ground and installed foundation provide? (Load tests)

The answers to these two questions will have some of the greatest impact on the design of the solar racking system. Before going onsite for fieldwork, the team calculated the frost penetration depth, reviewed previous geotechnical reports, and developed the pile testing plan while considering a multitude of racking systems available for the project.

The onsite tests went into the specifics of foundation design and looked at how effectively two different pile types would perform:

• Helical pile tests
• Driven post tests

Helical and driven post represent the two most common types of piles for solar projects in northern climates. However, with over 3000 piles at a 10 MW facility ensuring alternative designs should be considered for anomalies which may arise when conditions varying from those encountered during the geotechnical investigation and pre-production testing occur. Production testing should be completed to verify anticipated resistance is provided on a small sample size of the final piles constructed for racking support.