For the Herbert Hoover Dike, Thalle Construction Company is rehabilitating the C10 and C12 culverts. This project involves the demolition of the existing culverts and the construction of the new water control structures S-273 and S-275.
For each structure site, the demolition and construction require the installation of an earthen cofferdam within Lake Okeechobee and a landside steel sheet pile cofferdam in order to isolate and protect the work area during excavation, dewatering and construction. The earthen cofferdams require approximately 165,000 ton of select/embankment material and over 21,000 ton of imported granite rip rap armoring placed within Lake Okeechobee. The landside cofferdams are combination king pile and sheeting system 310 ft in length by 75 ft deep. While the existing structure is out of service, a bypass pumping system capable of operating 24/7 is installed providing irrigation water (lake to land 80 CFS) and flood protection (land to lake 401 CFS).
Construction of the new structure requires 65,000 CY of excavation, a dewatering system comprised of 30 deep wells along the perimeter and demolition of the existing culvert. The new structures will include steel sheet pile scour walls, CIP reinforced concrete foundations, headwalls, culvert barrels with steel liner pipe, and combination flap/slide gates. S-273 is two 10 ft diameter culverts and S-275 is three 10 ft diameter culverts each approximately 176 ft in length. A soil-mixed cutoff wall will also be installed in the centerline of the embankment and the embankment reconstructed to match the existing HHD dike. Final restoration will also include new rip rap armoring and control building.
Currently the project has completed the installation and testing of the bypass pumping system and is underway constructing the earthen and steel cofferdams.