The land bridge structures have three primary elements: the foundation, structure and headwalls. There are four overpass structures, with the two western structures extending 431 ft, 8 in., and the eastern structures measuring 277 ft, 8 in. The headwalls feature freestanding cantilever pieces connected by a structural beam. To support the overpass structures and headwalls, crews installed continuous strip footings the length of each structure.

Photo courtesy Ardurra Group LLC

To minimize environmental impacts, the project features a design that balances excavation and backfill so there was no dirt movement outside the project site. Excavated soil strategically backfills over the concrete structures, which served as the land bridges. When the contractor attempted to move soil with heavy equipment over the concrete structures, the team quickly realized that this level of heavy loading was not considered during the design process and took action to ensure that there were no detrimental effects on the concrete underpasses. Collaboration with structural engineers helped determine the appropriate load capacity for each haul over the installed concrete structures, ensuring both their integrity and safety.

Silt sand installed around the concrete precast structures serves both as a drainage system and a way to alleviate hydraulic pressure exerted on the segment walls.

However, the contractor faced a shortage of silt sand that adhered to the specified requirements and extensive lead times during the pandemic. To circumvent potential delays, the construction manager proposed mining silt from a proposed excavation area identified through boring logs within an accessible geotechnical report. This not only streamlined the excavation process, but also generated significant cost savings since the silt was found within the designated excavation zone.

To manage storm runoff in an efficient and visually pleasing manner, the team strategically built a channel running from north to south across the site. The channel subsequently enters an elliptical culvert measuring 20 ft in width and 7 ft 2 in. in height, which extends beneath Memorial Drive.