SFWMD C-23/24 South Reservoir - S-456 Structure Cofferdam

WGI teamed up with Ebsary Foundation Company to design a temporary cofferdam sheet piling wall as part of the Indian River Lagoon South C-23/24 South Reservoir Project for the South Florida Water Management District. WGI was tasked with the design of the temporary cofferdam and permanent sheet piling for the S-456 Spillway. As the specialty engineer responsible for the design and detailing of the cofferdam, WGI worked closely with the Contractor to complete the design allowing safe access to the dewatered construction area.

WGI’s design incorporated augercast concrete anchors and a tremie slab to resist the buoyant forces throughout construction. The cofferdam design relied on braced walers to resist lateral soil and hydraulic pressures during reinforcement and concrete placement 25 feet below ground level. Design was completed in accordance with the US Army Corps of Engineers (USACE) Engineer Manuals and Engineer Regulations.

WGI used SupportIT and the USACE CWALSHT design software to model the soil interaction of the retaining walls and RISA finite element software to model the braced walers through each stage of construction. Design models were developed for each stage sheet pile placement, partial excavation, waler installation, full excavation, augercast concrete and tremie placement, dewatering, permanent construction and backfilling, waler removal, and cofferdam removal.

WGI performed assessments of the cofferdam and waler installation during construction at the request of the Prime Contractor to confirm installation had been completed in accordance with the design conditions.