Project EIA - Renovation Kluizen Reservoirs

De Watergroep supplies drinking water from the Kluizen water production centre to a large proportion of North East Flanders, from Meetjesland to Waasland. Using surface water that is captured and buffered in two large reservoirs, the production centre can produce up to 60 million litres of drinking water per day.

Both reservoirs are located entirely above ground. However the oldest reservoir’s waterproofing system has eroded, which means that renovation is required. In preparation for this renovation, Witteveen+Bos is handling the urban design component of the all-in-one permit application, preparing a project EIA and is supporting the communication and participation process. The main objective is to ensure that the reservoir is leak-proof again.

Reservoir renovation required following weathering of PE film

A thin PE film that runs along the reservoir bed and up the dykes safeguards the reservoirs’ water-proofing. As the dykes were built around 50 years ago and a lot of sand and silt has accumulated between the dyke quarry stones, the dyke’s structure is now partially overgrown and plants have taken root in it. The water level in the reservoirs also fluctuates throughout the year, which means that the film is subject to temperature and humidity fluctuations. All of this erodes the PE film and causes leaks.

Monitoring and surveys have shown that as a consequence of the reservoirs’ age and the weathering of the PE film, around 5,000 m3 of water per day is lost via leaks in the reservoir bed and dyke structures. As these leaks are spread across the entire surface it is currently difficult to pinpoint their exact location.

The following renovation works are, therefore, being carried out:

  • Removal and replacement of existing stones on the dykes and reservoirs;

  • Removal of sand and silt from the reservoir bed and from the dykes, as well as replacing the soil on the reservoir bed;

  • The re-construction of the asphalt road on top of the dykes and asphalt on the access roads, which are located on the dykes as well as on the reservoir bed;

  • Replacement of the PE film to ensure reservoir water-tightness;

  • Replacement and modifications to concrete structures for the reservoirs’ water supply;

  • The construction of collector and suction pipes as well as a leak detection system.

Prioritising drinking water continuity

The biggest challenge during this project is that WPC Kluizen needs to be able to guarantee drinking water production during the entire duration of the works, which is why we will be working in phases, spread over a 2-year period and Witteveen+Bos will produce two permit files:

  • An all-in-one permit for the production and implementation of a new solar panel field to supply the reservoirs with the energy they need.
  • An all-in-one permit for the effective renovation of the reservoirs.

Project EIA provides insight into renovation impact

Considering the size of the project, a project EIA is needed to estimate the impact of the works on the local environment. This will be added to the all-in-one permit application for the works.

In the project EIA, we studied various disciplines including mobility, soil, noise and vibrations, air, biodiversity and the associated disciplines of groundwater, landscape, human health and climate. The impact study showed that there will be a particularly significant impact on the following domains, for which we have also proposed mitigating measures in the EIA:

  • mobility: the construction site exits and two cycle paths cross, which impacts local environment quality and accessibility for cyclists;
  • biodiversity: the bird population will be disturbed;
  • air: We estimate an impact on air quality as a consequence of material transport and the use of certain machinery.

Only limited negative impact or negligible impact was determined for the other disciplines.

Supporting the communication process

As well as formulating the permit aspect and the project EIA, Witteveen+Bos is also advising the client on the communication process. For example, we have produced an infomercial to inform local residents about the works and we supported the client during the first physical information meeting.

The renovation works on the reservoirs are set to start in summer 2023. The project EIA is currently being further refined.


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