Patra's Submarine Sewage Disposal Pipelines - Greece Western Region

The sewage of urban wastewater of the city of Patra was served, until 2001, by a large number of independent, universal flow, pipe networks through which untreated sewage was channeled at several sites along the coastline of the city. This uncontrolled disposal of waste created very serious environmental problems such as contamination of Patra’s Gulf, the downgrade of subsoil etc.

In 1999, as a part of the general requirement for environmental wastewater management and modernization of the sewage network of Patra, the local Municipal Water and Sewage Department conducted a contest for designing constructing, among other infrastructure, the submarine sewage disposal pipeline, in the so-called "Red Mill" region, south of the city.

The consultant engineer Albert Paul Yamin designed, on behalf of the offeror company "Perivallon SA", the protection works of the marine sewage disposal pipeline, including diffusion zone and overflow pipe and their off-shore laying process. The study was successfully completed in 1999 and the project was constructed in 2001.

Project details:

• Submarine disposal pipeline made out of high density polyethylene HDPE 4 ATM. The total length of the pipeline, including the diffuser, is 978m and the external diameter is 1,200 mm. In diffusion zone, the nominal pressure of the pipe is 6 ATM and of the diffusion pipes 10 ATM
• Submarine overflow pipe 140m long made of high density polyethylene HDPE, Helidur Spiral, having an inner diameter of 1,200 mm
• Covering with concrete of disposal and overflow pipelines, throughout their length, except diffusion zone
• Installation of continuous and uniform ballast, out of concrete 8cm thick, in order to permit to the pipeline to float, during the offshore laying process and to sink gradually while it fills with seawater
• Armoring the pipeline with rocks and rock fills into the wave breaking zone
• Protection of pipeline with concrete slabs, outside the wave breaking zone
• Protection of diffusion zone pipes with rock fills and concrete slabs, on top of them
• Placing of artificial concrete block, as obstacles, on both sides of the diffusion zone
• Placing floats, in order to mark the pipelines and secure maritime safety