The ponds at the Renbaan district have had this problem for years: when it is raining a lot, water levels keep rising. A special pipe designed to transport excess water to a lower area, is getting clogged each year, which makes water levels rise slowly but surely, making fishing or jogging impossible.
The problem is not caused by mud or branches, but by mussels. The freshwater mussels adore the spot and the clean water. "We cleaned the pipe various times in the past", says the alderman for the Environment Karel De Ridder. "But what we see is that the pipe gets clogged faster and faster each time. This is because the mussels adore the place: there is running water instead of still water in the pipe, and that's exactly what they like to get their food."
Workers tried to clear the pipe using a kind of drill, but it didn't really work. It seems the only option will be to replace the whole pipe, but this is not easy because it's quite long, going under a major road and a railtrack to make the connection with a lower pond.