- Over 95 ground-mount solar geotechnical studies since 2013
- Unlike borings, test pit excavations allow full observation of soil types, layering and potential for obstructions, such as boulders and/or bedrock
- Array areas vary from about 5 acres to nearly 100 acres; typical size is approximately 15 to 35 acres
Challenge
Preferred foundation systems for ground-mount solar projects are short driven or screw piles able to resist high lateral loads. The piles are typically designed by a design-build contractor based on multiple site-specific load tests. For bidding projects, designers need to know the soil type and potential for shallow obstructions, such as boulders and bedrock. Borrego and GZA needed to develop a cost-effective approach to characterize sites for pile foundations by addressing these design priorities.
Solution
GZA’s approach to field subsurface investigation for ground-mount solar projects uses test pits that allow boulder counts, and observation of ease of excavation, soil types and layering. Many test pits can be performed in a single day, compared to borings. Test pits also allow for collection of bulk samples for laboratory thermal resistivity and corrosivity testing. As GZA’s relationship developed with Borrego, we added report details related to equipment pads and site access roads.
Benefit
Over the course of numerous projects on many different site types, from open farmland to forested parcels, GZA has become a trusted partner on Borrego’s team. GZA efficiently delivers a report product that meets Borrego’s unique needs.
