WWPP and Submarine Outflow Pipeline at Matosinhos in Portugal

The submarine outflow pipeline, constructed by FCC, is located in the northwest zone of the Portuguese Atlantic coastline, between the River Miño and Leixoes

This is a construction and operation contract for the waste water purification plant and submarine outflow pipeline at Matosinhos.

It is located in an area exposed to severe wave forces and is divided into three sections, with the plant in the first two in an east-west direction and with the third at 45º towards the south with respect to the other two.

  • The first section is in the wave-breaking zone, with a length of 554 metres that is made up of a micro-tunnel that has a 1,600-mm inside diameter.
  • The central section is 1,890 metres long and executed with high-density polyethylene piping having a 1,200-mm diameter.
  • The diffusion section is 320 metres long and also made of high-density polyethylene piping, with a diameter of between 1,200 and 450 millimetres, fitted with 80 equidistant discharge nozzles.

By resolving the wave-breaking zone section by means of a tunnel, it was possible to make its execution independent of wave conditions and coastal transport and avoid interference with public use of the beach through works execution.

The tunnel has a straight-plan route, which in elevation, consists of a straight, 60-metre long section, a circular section with a 7,121-metre radius and 410 metres long and a final 84-metre long section with a 0.3% slope to its exit at the sandy bottom where it connects to the main outflow section.

It was executed using a TBM operated from a container on land, employing a laser guidance and verification system. The drilling diameter was 1,960 millimetres, with an inside diameter of 1,600 millimetres.

Intermediate thrust stations were installed every 100 metres and were intended to limit piping stress. 

Remarkable aspects

  • This was a highly complex submarine works because of the severe wave forces.
  • It was executed using a laser-guided TBM system.

Client: Matosinhos Municipal Services

Start date: 1996