Schiphol Group testing water storage systems at Schiphol Airport
The Schiphol Group airport management company is constructing a large aircraft parking area at Schiphol Airport: the U platform. The area will comprise a system of underground water storage facilities. The system is now being tested in a pilot project.
What has prompted this project?
Schiphol Airport is located in the Haarlemmermeer Polder. When paving, the surface area covered by pavement must be balanced out by creating additional open water. This is stipulated in the policy pursued by the Hoogheemraadschap van Rijnland district water control board, whose domain includes the Haarlemmermeer Polder. The project at hand involves the construction of three aircraft parking spaces and a runway. This requires the creation of a great deal of open water, which will cost Schiphol Group a great deal of valuable space and reduce the Group’s options for realising other future developments in the area. That is why Schiphol has launched a pilot project to explore several alternatives to open water. In the purview of this project, it has convened a working group in collaboration with the district water board, engineering offices, and the airport contractor.
Why does the district water board want open water next to pavement?
Additional pavement increases the risk of waterlogging in the polder. Such a risk can be reduced by creating open water. This adds to the capacity to collect rainwater from extreme downpours before the water from the polder is drained via the pumping stations. This keeps the polder water level from rising too steeply. The district water board requires developers to restore 15 per cent of the paved surface area as open water, for example, in the form of additional watercourses or ponds.
How has the working group set about the project?
The project working group has designed several water storage systems that may relieve the polder soil hydrology. First, it inventoried all the options for temporary rainwater storage in the vicinity of the aircraft parking spaces. Subsequently, it collected practical experience and devised system solutions that satisfied the requirements of the district water board. It also set down criteria to assess the various alternatives: How much will the solution cost? How much time will it take to implement the solution? Is the solution feasible? Can we apply it on a wider scale? What are the pros and cons?
Which solutions hold the most promise?
Of all the solutions devised by the working group, three met the requirements and criteria. The three water storage systems can be used individually or in combination. In the pilot project, they were connected as follows:
- Over-dimensioned gutter: Rainwater from the runways and the platform flows to a gutter that is much larger than the standard prescribes. This gutter is situated right next to the runway. Once the gutter is 70 per cent full, the water will flow on to a water-storing foundation or a crate system. These two systems are explained below.
- Water-storing foundation: From the gutter, rainwater flows to a foundation that is 40 per cent hollow spaces. Here it is temporarily stored. This foundation is situated underneath the outskirts of the runway, which, in principle, are not used by aircraft. The foundation thus serves an additional purpose: water storage.
- Underground crate system: Via the gutter, rainwater also flows to a crate system constructed underneath the green area next to the runway. The crate system provides temporary water storage, which means that the area underneath the green area also serves an additional purpose.
All three systems are connected to the surrounding watercourses by way of a narrowed drainpipe of approx. 30 mm. The narrow drainpipe causes an accumulation in the system, whereupon the systems fill with water. Over a prolonged period of time, the water now gradually flows to the watercourses, thus relieving the polder water system. By constructing these systems underneath and beside the runways, Schiphol Airport is making the most of the space available: the ground surface is used for multiple purposes and there is no need to create additional open water.
Special feature! Collectively looking for alternative policy
A special feature of this project is that the district water board was willing to assist in finding solutions. In the working group, all the key stakeholders involved in the project have explored the alternatives in concert. This has kindled enthusiasm and commitment among the members of the working group. Within the prevailing legislation, the working group has come up with an alternative to the existing standard.
How are the systems being tested?
In order to assess the performance of the water storage systems, the working group selected an appropriate testing location, where it has installed the three water storage systems and a monitoring system. The monitoring system comprises sensors that collect data on the performance of the system. This enables the working group to monitor rain intensity, the storage capacity, and the discharge rate.
How well do the systems perform?
The data from the monitoring system should demonstrate that the water storage systems meet the goals of the district water board and the expectations of Schiphol Airport. The water storage systems have been tested and have been operational for several months now. Both the tests and their performance in the first few months show that the systems are working efficiently.
What are the next steps?
In new projects involving a great deal of pavement, the Schiphol Group can now make agreements with the district water board on the proportion of pavement to be balanced out with open water. The construction of the water storage systems has reduced the surface area of open water to be created by Schiphol Group. Schiphol Group is also exploring other appropriate locations for the water storage systems, e.g., underneath car parks, bicycle paths, and green areas. The systems have already been used in three projects now.
Lessons to be learned
As yet, the Schiphol Group has learned the following from the pilot project:
- Support for other solutions: With this project, Schiphol intended to demonstrate that the district water board goals could also be achieved by other methods. Garnering support for such methods called for two things: properly substantiating the solutions and enthusing all the parties concerned.
- Collaboration with various parties: Joining forces with the district water board, contractors, and engineers has enabled the Schiphol Group to develop innovative solutions much faster.
- Working group commanding diverse expertise: The working group collectively commanded all the required expertise. This enabled the members to quickly share the pros and cons of various ideas among one another.
- Coordinating project with internal policy: The project ties in with the policy pursued by Schiphol Airport: Schiphol is looking for and investing in innovations that have less of an impact on the environment.