Gaag Aqueduct

Project description

The A4 motorway crosses the Gaag river with an 600 angle. The 40 m wide roadtunnel is constructed as an aqueduct in the Gaag river. The aqueduct consists of a through shaped prestressed concrete structure. The approaches are open concrete structures. The total length is 380 m. The secondary roads along the Gaag river crossing the approaches are constructed as viaducts. The tunnelpart and the approaches are founded on tensile piles because of the high groundwaterlevel. The ship canal is temporary diverted and the aqueduct is constructed in phases. The buildingpits are partly surrounded by steel sheetpiles limiting the effects of the temporary lowering of the groundwaterlevel.

Scope of work

  • Final design, design report considering alternatives
  • Structural computation and design drawings
  • Review of tender documents
  • Detailed design comprising structural computations and detailed drawings
  • Review of contractors design documents
  • Design and contract specifications for the electromechanical installations
  • Advice upon construction
Specification sheet 2 page(s) - 253 kB


Ministry of Transport and Public Works, Tunnel Engineering Department

In co-operation with

Not applicable

Type of project

Other techniques


The Netherlands


Delft, Schipluiden

Project duration

1991 - 1998

Project phase

Design and tender preparation 1991

Construction cost

€ 15.882.000,= incl. M&E works (excl. VAT)

Consultancy fee

€ 1.135.000,= (excl. VAT)