Hawke's Bay Expressway
Project Overview
Following Cyclone Gabrielle in February 2023, significant volumes of silt were deposited in the Hawke’s Bay region. While reuse of this silt for infrastructure works on the State Highway 50 Expressway was an innovative approach, it introduced major challenges. The material was extremely fine, creating dust issues, and was highly erodible under both rainfall and wind. Left unmanaged, these conditions posed risks to environmental stability, public health, and the success of the expressway’s earthworks.
Scope
The project was part of the Road of National Significance Programme initiated under the new National Government. Fulton Hogan completed the major earthworks toward the end of 2024, preparing the site for stabilization. Two preload sites required urgent surface treatment, with dust suppression, erosion control, and vegetation establishment as the top priorities. The solution needed to withstand Hawke’s Bay’s hot, dry summers and unpredictable rainfall.
Our Solution
Stabi-Mulch
- Applied at 3,000 kg/ha to maximize dust control and surface binding.
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Seed Blend: Custom-designed, combining fast-germinating species for rapid coverage and deeper-rooted species for long-term stabilization.
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Stabi-mulch provided moisture retention and improved germination conditions, ensuring rapid strike despite challenging conditions.
Challenges
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The project faced significant climate extremes, with the threat of a hot, dry summer that could have compromised germination. Over the Christmas period, the site experienced approximately 80 millimeters of rainfall and periods of high winds, either of which could have caused serious erosion.
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=There was also the risk of dust and erosion affecting local communities and road users during construction.
Results
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Dust control was achieved immediately, protecting workers and nearby communities. Even under heavy rain and strong winds, the site showed no signs of erosion. After six weeks, the site demonstrated nearly 100 percent grass strike across both preload areas. The success of this stage provides a strong foundation for the next phases of work as construction continues toward the four-laning of the Hawke’s Bay Expressway.