Mahe, Seychelles

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Multi-disciplinary marine scientific program to study nearshore areas around the main island, with the objective of updating wastewater processing infrastructure and extending WWTP outfall pipes into deeper water to improve dilution and move effluent away from the shoreline. Tasks completed included geophysics to map surface and subsurface conditions for pipeline installation, oceanography to map current flow direction and velocity to support dilution modeling, benthic habitat mapping and analysis to identify and avoid thriving reef communities, and shallow geotechnical sampling to examine soil characteristics for pipeline burial and support. Satellite drogue tracking employed for current mapping in the vicinity of prospective outfall diffuser locations.

Strict government policies and requirements, an abundance of ongoing coastal construction projects, and heavy political pressure to avoid areas to be dedicated as underwater national parks all contributed to make finding suitable locations for the outfalls a difficult task.

BELOW: View looking northeast from the island of Mahe, south of the capital Victoria, showing the coast before and after development. Saint Anne Island, home to a marine national park, in the background.