Ocean Outfall Submarine Pipeline

This project consisted of the procurement, fabrication and installation of a 1400 meter, 26 inch diameter, concrete weight coated, cement lined ocean outfall pipeline with an end diffuser section. The near shore portion of the pipeline required the installation of an access causeway and sheet pile cofferdam from the shore to facilitate the trench excavation and pipeline installation through the surf zone. A significant portion of the trench excavation was through limestone rock up to 10' deep, and was accomplished using extra heavy duty clamshell buckets and a barge mounted Maintowoc 4600. The pipeline was laid in 160' sections using the Weeks 540, a 45 ton derrick barge. The flanged connections and diffusers were connected underwater by divers working in a maximum water depth of 120'. The entire pipeline was backfilled with armor rock overlain by natural fill. The scope of work also included the installation of approximately 500' of 30" diameter HDPE pipeline onshore. The project was completed in 12 months.