Prony Bay: installation of water intake and outfall infrastructure for transporting clarified effluent 

The main challenge was installing a 21 km long outfall in a highly environmentally-sensitive area (coral, whale breeding grounds, classified natural underwater formations, etc.) at a depth of up to 60 m along the pipe route.

This work required the development of new techniques for installing HDPE pipes. The pipes were laid without interruption using vessels equipped with dynamic positioning systems. This equipment, which uses thrusters and automated control systems, enables the vessels to maintain an exact position without anchoring. The method ensured that subsea pipelines were laid continuously and accurately, even in complex maritime conditions.

Construction and installation:

• Prefabrication of concrete collars for ballasting the HDPE pipes
• Welding the 800 mm and 710 mm HDPE pipes in 500-metre sections
• Towing 90km, connecting and installing the pipe in 500-metre sections, navigating through solid currents and narrow channels.
• Carrying out ports of the diffuser using an ROV