Have you ever seen the tubes along the Osylaan: this is what they serve

Have you ever seen those gray curved pipes that rise above the ground, for example along the Osylaan opposite the CKC? Of course they are there for a reason, but what are they for? You can read that here!

These are the vent pipes of a so-called ‘mountain settling basin’. A what?

A mountain settling basin

To prevent dirty sewage water from entering the surface water, these storage settling basins are used in various places. During heavy rain showers, the water level in the sewer rises. The excess water then runs into these basins. The pipes that rise above the ground allow the air to escape from the basin when it fills with water.

Clean water

The pollution in the sewage water sinks into the basin. The cleaner water that floats on the surface in the basin then flows through a flushing reservoir to the surface water of a river or other water.

The container in which the pollution from the sewage remains is sprayed clean after the heavy shower. The dirty water is pumped back into the sewer. This keeps the water in the rivers clean and the pollution is sent to the sewer where it belongs. The gray cap that protrudes above the ground is the filter that sits on the vent tube.

Underground

So those pipes above the ground serve for ventilation, but what does such a basin look like under the ground? This can be seen in the schematic drawing below. Sometimes a filter is placed on a vent tube. You can see that in the bottom photo.

Source: Rens Blommaert, technical coordinator and prevention officer at the Port Service of the Municipality of Haarlem