Southwest Ocean Outfall 2024

The Southwest Ocean Outfall (SWOO) is a wastewater pipeline extending 4.5 miles offshore, reaching depths of 90 feet. It’s designed to distribute treated effluent into deep ocean currents for efficient dispersion.

Power’s in-house ADCI dive team completed their third project assisting San Francisco Public Utilities Commission (SFPUC) maintain operational standards of this hidden yet critical infrastructure that supports the City of San Francisco.

This recent scope of work involved inspection of the outfall pipeline and associated diffuser structures, clearing marine growth blockages, and assessing the condition of the Monel end gate and anchor bolts. With advancements in technology since our last visit, our dive crews achieved levels of precision and efficiency that redefine what’s possible for the client. Here are some examples:

• LARS (Launch and Recovery System): Provided controlled and safe deployment and retrieval of divers, even in rough sea conditions.  

• DP2 (Dynamic Positioning Class 2): Maintained the vessel's position without anchors or mooring, allowing precise station-keeping above the dive site and expedited relocation to adjacent worksites.  

• Dual-lock decompression chambers: Supported continuous surface decompression diving operations, extending work duration at depth and enhancing hyperbaric safety.  

• USBL acoustic systems: Enabled real-time diver positioning for seamless coordination between topside crews and divers.  

• Enhanced diver cameras: Equipped with high resolution, real-time depth sensors, and compass readings, facilitating underwater navigation and recording of workmanship.  

• ROVs: Conducted internal inspections of the last 1,000 feet of the pipeline, capturing sonar cross-sections

• 3D photogrammetry: Produced near-photographic as-built models of the end gate structure, even in low-visibility underwater conditions.

Despite strong currents and large Pacific swells, the project successfully met SFPUC’s objectives, ensuring the structural integrity of the SWOO pipeline and diffusers.

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