While replacing the existing 15-ft-long concrete slab bridge for this $7.2-million project, the team faced challenges that included compressible soils and tidal conditions. Because a sealed cofferdam was not employed, all work was conducted during 8-ft tidal cycles.

Native tidal marsh marine sediments were removed and replaced with foam glass aggregate—a first for New England—when the causeway roadway was widened approximately 10 ft to the north.

These deep excavations beside the operating highway, along with use of the foam that is less dense than water, presented challenges, according to the team.

当团队意识到承包商的原始工作计划不可行时，它会与结构和岩土工程师进行头脑风暴，以制定最佳的行动计划。

最终，替代项目方法涉及让承包商采用一个创新的滑轨系统，其中包括钢制墙壁和驱动的钢桩，其中包括一系列可调节的沟渠盒。

When the tide receded, the trench boxes were lined with geotextile fabric that formed 20-ft by 10-ft cells into which the foam glass aggregate material was placed on the roadway slope. These were then wrapped and covered with steel plates or soil to prevent them from floating.

The team says it completed the project at budget and 50 days ahead of schedule.