The Cromvliet park in The Hague is being renewed to serve its residents better. The current park suffers from dry periods and since the renovated park will contain even more green spaces, an urban animal farm and community gardens, more water needs to be available. A full-scale Bluebloqs pilot will provide a seasonal buffer by storing both pluvial water and surface water. Although the area does not suffer pluvial flooding currently, the ambition of the municipality to retain water locally is also met.
In the Cromvlietpark, the Bluebloqs technology is integrated in the so-called Urban Waterbuffer concept, similar to the application of the Bluebloqs technology at the Sparta Stadium in Rotterdam. In order to secure freshwater availability all year round, the disconnected surface area proofed to be insufficient to achieve the desired water balance between demand and supply. As such, the Bluebloqs system in the Cromvlietpark will not only buffer rainwater, but will also collect, treat and store surface water to provide sufficient fresh water to the park. As such, the specific research focus for the demo in the Cromvlietpark is to extensively research the innovative application of treating and buffering excess surface water in addition to rainwater. Additionally, the demo in The Hague allows for an assessment of the applicability of the Bluebloqs technology in situations were water demand is the key challenge, rather than the prevention of pluvial flood events.
Since the demo in the Cromvlietpark is a full-scale application in public space, in contrast to the private research facility at Aquafin it is important to understand the overarching project objectives for the implementation of the system in the Cromvlietpark:
Figure 1. Bluebloqs system in the Cromvlietpark.
The design of the Bluebloqs system in the Cromvlietpark comprises all five steps required for a decentralised circular water system: 1) Collect; 2) Retain; 3) Treat; 4) Store and 5) Use (see Figure 1). These five steps have been translated in a system configuration that allows for taking both types of influent water through one Bluebloqs system (see Figure 2).
Rainwater from 7.000 m2 of the surrounding streets is collected into 70 m3 buffer below an outdoor sports ground. The rainwater his pumped with priority to the Bluebloqs biofilter. The filter is dimensioned to process 10 m3/h. During peak rainfall, the buffer overflows to the Noordpolder, a nearby surface water body. In total around 7.000 m3 of rainwater is to be stored per year.
If the buffer is empty, surface water from the Noordpolder will flow to the pump sump. The surface water is drained by a pumping station nearby, so when the water level in the Noordpolder is relatively high, water is let into the system. This inlet is regulated with a level control. It is estimated that around 35.000 m3/year is to be stored.
The treated water flows under gravity into the subsoil, no pre-pressure tube is needed. At a distance of 10 m from the infiltration well, the water is pumped up again ready for use. Due to the soil passage (at least 10 m and more than 30 days travel time) the water is expected to be sufficiently safe (disinfected) for use in public spaces.
Figure 2. Cross section of the proposed Bluebloqs system.
The demonstrator at the Cromvlietpark is a unique opportunity to showcase the potential of Bluebloqs circular water systems to professionals, but also to increase the water awareness among citizens in the region. In addition to an exploration of various means to maximise the impact through communication and education activities around the project, various events have already been identified to interact with multiple stakeholders. For example, the plans for circular water management were presented by Field Factors at a resident’s panel, who were involved in the design of the Cromvleitpark. The feedback from the residents was very positive: they fully understood the concept and the benefits of the system and were able to ask critical questions about the subsoil storage. Additionally, the concept of the circular water system at the park will be communicated at a local parade and potentially various other community events. The official opening of the systems after implementation will be an important showcasing event. Workshops with professionals are planned for 2020, once construction of the demonstrator is finished.