Fish Return System Outfall pipe

Project Description

Amentum assessed how to inspect and clear blockages in HPC's Fish Return System outfall pipe, where low flow velocity and sediment build-up could obstruct the return path. The study covered debris, silt and marine growth behaviour, use cases, deployment constraints, system architecture, work packages, schedule and a rough-order-of-magnitude estimate for delivery.

Challenges

The pipe is 628 m long and prone to heavy siltation, with predicted obstruction of about 41% in normal operation and up to 70% in extreme cases. Any solution had to work in salt water, tolerate low visibility, navigate flowing water, avoid damaging the concrete pipe, and be deployable safely from land through the transition structure rather than from the sea.

Solutions and Outcome

Amentum recommended a hybrid two-vehicle solution: a modified inspection ROV based on MarineROV for routine surveys, small-blockage removal and optional silt disturbance; plus a custom tracked clearing ROV with a shredder head, water-jet assistance and high-voltage tethered power for partial or full blockage removal. The concept also included a deployment cage, winch and ISO-container control station, with a planned 28-month development route to delivery. It combines low-cost routine inspection with a purpose-built intervention vehicle for severe blockages.

Future Work

Amentum has identified a clear pathway to deployment, beginning with detailed design, supplier engagement and subsystem prototyping. Initial focus would be on de-risking key elements such as locomotion, cutting/shredding and tethered power systems, followed by integrated testing and validation.