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Punaauia – Replacement of the seawater outfall in Tahiti

Located off the coast of the municipality of Punaauia, on the island of Tahiti in French Polynesia, this project involves replacing the seawater outfall from the wastewater treatment plant with a new HDPE structure that is more reliable and durable

  • Location

  • Solution Hydraulic and environment infrastructure

  • Key date

  • Customer

A new outfall to protect the Punaauia lagoon

The municipality of Punaauia is renewing its sea outfall to secure the wastewater treatment plant and protect a highly frequented lagoon. Crossing the Taapuna pass, the project must reconcile hydraulic performance, structural reliability and limited environmental impact.

The project is based on close collaboration with Polynesian companies and shipowners for civil engineering, diving, prefabrication of anchor blocks and maritime logistics, strengthening the local roots of the project. The QHSE approach is based on daily briefings, regular checks and marine environment protection measures, in order to combine team safety, structural reliability and preservation of the Punaauia lagoon

Engineering, procurement and marine works

Geocean is involved in the entire project chain: studies, supplies, prefabrication, logistics, maritime and underwater works. The detailed design studies include pipeline stability, ballast and anchor sizing, and the immersion and trenching strategy, based on recent Polynesian references.

The new outfall consists of a 560 mm diameter HDPE pipe over a length of 1,461 m, stabilised by ballast along its entire length, anchored in the most exposed areas, and protected at the landfall by an open marine trench backfilled. The pipes are manufactured and shipped from abroad, while the concrete blocks are produced locally. The sections are welded, and the welds are inspected before being towed to the installation area. Geocean has mobilised a modular pontoon equipped with a 40-tonne extractor to excavate the landing trench.