ACCIONA has completed the construction of the wastewater mains on the left bank of the Mundaka estuary in the Basque Country, a project that will mean more efficient and sustainable management of the water resources in the Urdaibai area, declared a Biosphere Reserve by UNESCO in 1984.

The project has a final budget of almost 17 million euros and will benefit more than 26,000 people in the area and over 1,000 km² of industrial zones in the municipalities of Muxika, Gernika, Ajangiz, Forua, Murueta, Busturia (Gambe) and Kortezubi-Arteaga.

The new mains will collect wastewater from Gernika to Busturia and link up with other sections that have already been completed. The wastewater will then be sent to the Lamiarán plant in Bermeo for treatment before being discharged into the sea.

As well as the construction of the principal mains in the Mundaka estuary, ACCIONA has also built a number of other mains and secondary branches and four pumping stations.

The project also includes the installation of a supply pipe parallel to the mains, renewing the existing pipe between the WWTP at Gernika and Busturia which was in a poor state of repair. The route of this pipe was partially through the marshes in the estuary.

This completes the sections of the sanitation network between Gernika and the Lamiarán WWTP in a particular sensitive area in this respect. The Urdaibai estuary is a eutrophic (rich in nutrients) water body consisting of an estuary and a coastline that combines with the low regeneration capacity of the water in the Mundaka estuary.