Three 'foundation projects' for construction of one pumping station

Already during the tender, Gebr. van 't Hek was approached by construction consortium Van Hattum en Blankevoort and Friso Civiel to participate in the implementation of the foundation design for Monnickendam pumping station. The foundation specialist comes from this region and is extremely familiar with the local foundation. The latter proved to be an absolute advantage for this special project, which is characterized by its many challenges and three different cofferdams.

Gebr. van 't Hek is responsible for the complete foundation package of the new pumping station. "At the end of 2019 we have already started with the design of the three construction pits, respectively the Outflow side, Inflow side and the Road pit," explains project leader Dennis Jonges. "The Road Pit is located exactly under the N247, the Inflow and Outflow sides are on both sides of the provincial road. Each construction pit is formed by driving precast concrete piles and installing a sheet pile pit with a 2-layer stamping frame. However, we started with the installation of temporary sheet piling due to the pre-loading on the Outflow and Inflow sides. This was partly performed from a pontoon."

Extensive weekend work

In order to realize the Wegkuip, it was first necessary to relocate a large number of cables and pipes. To this end, Gebr. van 't Hek installed 2 x 2 double sheet pile walls on both sides of the N247. "On these there is now a cable duct through which the relocated cables and pipes run," Jonges explains. "Then we drove the piles and sheet piles for the construction pit on the Outflow side. Then it was the turn of the Road Pit. Over two weekends, during which the N247 was closed, the sheet piles and piles were driven, the first layer of the strut frame was installed, as well as the edge purlins that are now under the temporary steel auxiliary bridge of the Road Pit. After this drastic but very smooth weekend work, we continued undisturbed on the Inlet side with the driving of the concrete piles and sheet piling. Initially scheduled for the end of 2021 was the installation of the second layer of the strut frame in
the three construction pits on the schedule, but that has been delayed due to the archaeological discovery in the dam. Remains of an old sea lock were found, pierced by the 'freshly' installed concrete piles."

Editable 

The archaeological find is currently being carefully mapped and documented. Gebr. van 't Hek is expected to be able to resume work at the end of February. "We will then proceed with the installation of the strut frames, obviously in close consultation and coordination with all parties involved including the archaeologists and earthworkers," Jonges explains. "It makes the work more laborious than initially conceived, but again we will find a mode in that. Once the strut frames are in place, the tubs can be excavated to depth and the combination can begin the concrete work. Once the concrete floor has cured, we come back again to remove the strut frames and pull the sheet piling." For Gebr. van 't Hek, the total project includes some 1,400 tons of sheet piling from AZ 18700 through AZ 36700 in plank lengths from 18 to 22 meters and also over 130 concrete piles square 45 and square 40 in lengths ranging from 18-20 meters. "All in all, a nice project with plenty of challenges and all that 'just' in our neighborhood. That makes it extra special."