Drake Associates performed the Underwater rehabilitation of sewage treatment plant ocean outfall in 60’ of seawater beneath the Cape Cod Bay. All work was performed by an 8-man team of surface-supplied commercial divers and crane operators, working from two barges (shown here) and a diving workboat 3,000 feet offshore. The project involved removal and rehandling of 1,500 tons of rip rap, placement of 1,000 tons of processed stone and the installation of 800 tons/15,000SF of articulated concrete block mattresses atop 700 LF of 30” outfall pipe and 12 individual outfall diffuser lines. Each diffuser line required internal cleaning, replacement of flanged flexible rubber couplings and the installation of new protective concrete arches. The work was successfully completed in October 1999 despite adverse weather and sea conditions. |
![]() ![]() The use of concrete mats in the intertidal and underwater environment is increasingly more commonplace. Drake Associates is a specialist in installing concrete mats underwater. The mats must be positioned precisely and then connected to create a continuous mat covering the entire area.
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