Pumping solution for double-decker tunnel

In the city of Maastricht, at the southern tip of the Netherlands, work continues on the country’s first double-decker tunnel. The Willem Alexander tunnel will provide a better flow of traffic and free up more area for urban development. The first technical installation at the tunnel has now been commissioned, including an advanced pumping solution from Xylem.

The innovative tunnel is scheduled to open at the end of 2016. It will include an upper level for local traffic, and a lower level for through traffic. Above ground, the old highway will be replaced with a green area for cyclists, pedestrians and local traffic.

“The lower tunnel also includes two water basins, one on the north side and one on the south side, with a capacity of 120 m3 and 80 m3, respectively,” says Ronald Ruisch, Project Manager for Strukton, the contractor in charge of the project. “The basins will collect rainwater from the road surface, which will then be filtered and discharged.”

Pumping water between the basins

The road surface rainwater will pass through several ditches and a sand trap. Then it will enter the first basin through outlet pipes. The water is cleaned of sand before it reaches the first basin for dirty water. Two Flygt 3068 pumps ensure that the water is pumped first to the dirty water basin before being transported to the clean water basin.

“The final design for the Willem Alexander tunnel was developed in close consultation with Strukton, since in such a large project good cooperation about the design is absolutely necessary,” says Bas van den Berg, Team Manager for Public Utilities at Xylem. “The pumps in the north basin have a total capacity of 240 m3 per hour, while the pumps in the south have a total capacity of 135 m3 per hour.”

Clog-free pumping in the Willem Alexander tunnel

The installation in the basins consists of four pumps in the north, with one as a spare, and four pumps in the south basin, with one as a spare. The Flygt pumps used include Xylem’s clog-free N-range technology.

“If for any reason coarse particles end up in the basin, then the impeller of the N-range Flygt pumps automatically moves so that any larger solid particles or fibers can more easily pass through the pump and avoid a buildup,” Van den Berg says. “As soon as the object is discharged, the impeller is brought back to its starting position.”

Adapting the pumps to a higher voltage

The power supply in the tunnel is 690 volts, although normally for a tunnel it should be 400 volts.

“That did not work here, because of the large number of cables and pipelines entering the tunnel from the service buildings, which have to cover a long distance,” Van den Berg says. “If we operated with 400 volts, then the cables would have to be thicker, taking into account the voltage losses along the way, which is not exactly efficient. Therefore, we opted for 690 volts.”

This meant that Xylem had to adapt its pumps to the higher voltage. In addition to supplying and installing the pumps, Xylem also provided the piping and controls. Strukton provided the software, which will soon be integrated into the management system.

“This project requires optimal collaboration between Xylem and Strukton,” Ruisch says. “We are very satisfied with the quality of the engineering, the manner of execution and communication, as well as the delivered result.”

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