Overcoming construction challenges in the Northeast for solar success
By Randy Smith, Director of Construction Management, Terrasmart
Finding the right balance between risks and rewards is at the heart of solar success. Ideal locations with flat, soft terrain come at a price premium, while rocky, rolling land can offer competitively priced leases and higher margins, but at a cost of time and development complexity.
EPCs and developers, especially in the Northeast, are constantly juggling complex construction risks on the ground that can easily derail margins and project schedules. Whether high winds, heavy snow loads, frost or extended muddy seasons, managing northeastern environments can be difficult. Undulating topography doesn’t help, with rock-strewn hills constantly threatening with refusals.
For PV success in the region, consider these actionable strategies to minimize risk, steer projects, and secure margins for the strongest possible return.
Northeast Building Risk No. 1: Refusals
Refusal is often the biggest unknown factor that can make a good project bad. They pose a threat for obvious reasons: you don’t see them coming.
There are a myriad of tests to quantify and measure a site’s decline risk, starting with geotech reports and pull tests. If the site has a constant ledge, then rejects are to be expected. Lands with predominantly paved ground contain rocks of different sizes and require more testing to make a foundation choice between piles and ground screws.
Five tests can help you make the right foundation decision. While not all tests are required for every site, consider doing thorough testing on difficult sites to better predict problems before installation.
- Tensile Test and Geotech Report: Tensile tests are done with screws and posts at different locations in a site. In order to prepare a geotechnical report, soil samples are analyzed to reveal the general properties of the site and gain insights about possible rejects.
- Compression testing: A compressive load is applied at various locations on the site to determine how the soil responds, especially to heavy snow loads.
- pull-out test: Also known as stress testing, this helps assess the anchoring or pullout capacity of the foundation, which is especially useful in regions with frost.
- Lateral Load Testing: Measuring the lateral capacity of a foundation is critical for high wind locations.
- Test Refusal: A geotech report limits insights only to the three or four areas assessed on a site, leaving room for risk during installation, especially on larger sites. Instead, denial testing in the site’s most challenging location — lowering a foundation to the denial limit — can better predict what problems may arise.
When evaluating a challenging site, pre-drilling the foundation can provide a risk-free solution. This is particularly relevant when year-end pressures are expected. Contractors should talk to the scaffolding partner about pre-drilling ground screws and piles to ensure projects stay on track.
In cases where larger rocks and boulders influence the design of a site, consider taking a new approach: a hybrid foundation model that combines a mix of screws and piles. Piles can be used in softer ground, while ground screws can eliminate the risk of failure on the rocky areas of the site. While this may complicate the test and design phases of the project, a hybrid model offers significant advantages during installation: the mixture takes advantage of the cost advantages of driven piles while taking advantage of the risk limitations inherent in using screw foundations. The goal is to optimize the profile of each unique site to formulate the winning risk/reward formula. Consider a partner who can provide both options and is well versed in such hybrid foundation systems.
Northeast Building Risk No. 2: Slopes
Shelf structures built on slopes require additional adjustability to accommodate the undulating terrain. For example, installation on a hard, straight ledge will take two to three minutes longer per foundation than installation on a soft location. With slopes of 30 to 36%, especially in areas with a lot of snow, the installation process is also slower.
When evaluating slope options, look for fixed and single-axis tracking solutions with high slope tolerances to reduce construction risks; the highest fixed tolerance we’ve seen on the market offers 36% in all directions.
The same consideration applies to trackers. Some systems are specifically designed for difficult soils and undulating terrain and can be used interchangeably with different foundation options. Flexible trackers with slope tolerances of up to 20% north-south can help with field misalignments. Look for systems that allow east-west and vertical adjustment to minimize land division and other civil work, keep construction costs down and schedule tight.
If you’re considering ground screws or a combination of screws and posts, look for adjustable shelving that works seamlessly with both.
Northeast Building Risk No. 3: Weather
While not a construction risk per se, weather factors are essential to ensure system performance and should be thoroughly evaluated at the design stage. Local codes for snow, wind and frost management can guide design parameters and component selection.
Snow: Racks must withstand heavy snow loads and be able to throw them off. Building codes written for roofs tend to ignore solar projects. Snow shed from a solar module only has about 3 ft to accumulate, while roofs can shed three times as much snow load. But adding height to the module forces crews to do trickier, higher construction work. In addition, to be able to bear additional snow loads on the modules, purlins must be larger or smaller. Racking partners must perform robust load tests with artificial snow in the winter or tons of rocks in the warmer months.
Wind: This is an important consideration on the coast and along larger inland lakes, where hurricane storms often blow through. Assess the various potential forces at the project site and ensure designers have conducted thorough wind tunnel testing to account for these stresses. Some scaffolding manufacturers use advanced software to simulate the most cost-effective design for a site’s unique wind profile.
Frost swell: Installers in the northern latitudes know firsthand the devastating impact frost can have on the long-term LCOE of a project. Remediation of raised foundations after installation is costly and can destroy the overall return on the project. Ground screws offer proven reliability against frost. Because their threads are embedded below the frost line depth, ground screws are most effective at resisting the buoyancy force of ice lenses. Their smaller diameter reduces frost load, while the threaded portion of the screw mobilizes significantly more tension against swell than a pile.
Bank on results in the Northeast with integrated, proven partner
Ultimately, developers and EPCs have a lot to gain from integrated partners who are ready to tackle the full range from foundation and scaffolding design to manufacturing, installation and electrical BOS. Choose manufacturers who do the entire build themselves with their own experienced installers and specialized equipment. Choose a partner who takes denial risks on your behalf. Ultimately, pave the way to project success with a team that offers proven experience and delivers results in the challenging and unpredictable Northeast.
As construction director for Terrasmart, Randy Smith leads a team of 180 field experts. With two-thirds of Terrasmart’s projects in the Northeast, Randy’s team has 12 years of installation experience in the region and has installed 1.1 GW in the last two years alone.