Construction projects that run smoothly and on schedule are certainly not free of obstacles. Working in the wind industry for nearly 20 years, we’ve come to expect challenges associated with unpredictable weather and wind conditions, uncertainty around equipment deliveries and difficult permitting processes–among other issues. Project planning and execution strategies have been affected by the evolution and growth of the industry. Today, turbines are engineered on an impressive scale, and with many preferred wind sites in use, developers are turning to low wind turbine technology to build on less desirable wind sites.. The changing industry is a source of new challenges, and it’s critical to project viability to address potential construction issues early in project planning that could equate to big dollars if encountered in the field.
Complex geotechnical conditions are often inherent to sites with good wind resources; i.e. close to lakes, wetlands, and rocky terrain. Understanding how environmental constraints translate into construction plans drives the approach to project execution. Our challenge during construction is to minimize areas of disturbance, while installing site infrastructure and safely and efficiently erecting turbines. Developers don’t always have the initial support to make decisions on balancing the construction footprint with the final wind farm footprint – which can vary greatly.
Comprehensive information on geotechnical conditions refines the project parameters and allows builders to deliver a price that will closely mirror the actual cost of construction. Contracts written with limited geotechnical information pose cost risks during engineering and construction, when true site conditions become known. Subsurface conditions dictate foundation, road, and electrical designs. Landowners, particularly farmers, want minimal disruption in their fields. Late identification of soft spots, warranting a thicker road profile, require greater excavations, therefore more soil to be spread or exported. This may conflict with expectations set in project development and can lead to time consuming negotiations.
Many of the projects that cross our desks involve turbines with tower heights of 100 meters. The construction process has grown more complex with the shift to taller turbines. As turbine size increases, they require larger, thicker foundations. Greater volumes of concrete challenge our material and schedule resources. On some projects, we now have to account for mass concrete heating and cooling treatments, required by code to prevent high internal to external temperature differentials from compromising the integrity of the foundation.
The crane market has responded with larger cranes to accommodate the growing turbines. During construction we prefer to move cranes fully assembled, as breakdowns are time consuming and costly. If optimal crane travel paths aren’t established early, allowing critical easements to be identified and secured, equipment costs escalate with each crane breakdown. Other logistics challenges arise when public infrastructure is unable to support turbine deliveries and construction traffic i.e. width of roads and turning radii, and robustness of existing structures. Confirming turbine transportation requirements and surveying roads early in project planning will facilitate necessary improvements before existing conditions impede deliveries.
Meeting challenges is part of our job. However, diligent research and adequate support during project planning can help developers and their construction partners circumvent challenges and increase project viability in this evolving industry.
By Brent Bergland, General Manager for Canadian Operations for Mortenson Construction-(Energy & Infrastructure)