Buried Treasure in Berkshire Continued...
The combination of sewage water discharge and tourist beaches may seem as a contradiction in itself. However, this was exactly the challenging combination facing Montpellier and its surrounding municipalities when the old waste water treatment plant, at the tourist area on the Mediterranean coastline, Palavas les Flots, ran out of date in the 1990's.
The wastewater treatment plant was too old and in need of an extension. "In addition, it was clear that the plant needed a serious upgrade in order to answer forthcoming EU environmental requirements", says Jean-Pierre Magnat, from Montpellier Agglomération, who was in charge of the project for the municipality.
"We had the choice to continue leading the sewage water out into the river as we had done so far, or to lead it into the sea. And we found that the best solution was the sea. However, in order not to affect the quality of the water and the tourist life on the beaches, it was decided that the water should be led out at 11 kilometres offshore."
The Agglomération de Montpellier invited tenders to present solutions for the sea outfall. The choice felt on a plastic pipe solution because of its non-corrosive character and its concept of continuous extrusion.
"This meant a minimum of land work and reducing the disturbance that prolonged installation work could mean to the tourist life on the beaches. Other advantages of the pipe solution were that it was considered as one of the most reliable and safest of the solutions presented among the invited tenders," explains Jean-Pierre Magnat
The plastic pipes were delivered by tugboat in 515 and 550 metre long lengths from Norway to Montpellier.
The plastic pipes were fitted within concrete pipes to position it at the sea bed and to protect it from external damages e.g. anchors or fishing trawlers to give plastic pipes the required ballast weight.
The work was successfully concluded in 2004 and resulted in the longest sea outfall ever in Europe. The outfall is not only unique due to its length, it is also the first sea outfall pipeline completely made from non-corrodible materials.
The waste water which is led into to sea from the extended sewer plant is properly treated and all analyses of the quality of the water have been favourable. Tourists continue flocking to the beach at Montpellier as they have always done.
The project started in the early 1990's and was concluded in 2004
The project resulted in an expansion and up-grading of the existing treatment plant in the municipality of Lattes
In all a 9 km long land pipeline (DN 1600 mm) and the submersion of a 11 km long sea outfall pipeline (DN 1600 mm) were installed