In 2020, Henk van Tongeren Water & Techniek placed 20 new FHVI wells in Apeldoorn. They are part of the agreement in the context of the AERFIT project that will place 150 of these wells over a period of 3 years. Fifty new wells are planned for 2021
Placing an FHVI well is quite a job: the wells are 15 to 20 metres deep. Therefore the construction of the wells is linked to work that would have to be carried out anyway, such as replacing a sewer.
Searching for the best layer
When the location of the wells is chosen, the soil is carefully examined: is it judged to be permeable enough? Even if it is, the functioning of the infiltration wells can differ quite a bit between locations due to differences in the amount of sand or clay in the soil. If the soil is less permeable, then this can slow down the infiltration. Experience has shown that the effectiveness of the infiltration can vary by 30 to 40%.
The depth chosen for the filter also plays a role. Accordingly, careful attention is paid to the composition of the soil during the drilling of a well by making a soil profile. In this overview, the composition of the soil at each depth can be seen: does it contain more clay or more sand, and how much gravel is present? The filter is subsequently placed at the level of a well-drained layer.
New filters keep the well clean
In the meantime, experience has also been gained with new filters, which have proved to be a success! In the past, problems regularly occurred due to smearing or clogging because of the accumulation of organic matter. The new filter consists of an outer and inner filter. The inner filter can simply be brought up to the surface and subsequently cleaned. In this way, the filter can continue to work well without considerable maintenance costs.
The first experiences with the FHVI wells are positive. The streets that regularly flooded before 2020, did not become waterlogged during the past year despite the heavy rainfall. A further analysis of the functioning of the wells during downpours is still in progress.