Rainwater retention basin overflows onto the property

Is this supposed to be some kind of natural inflow to the rainwater retention basin?

That's exactly what I suspect as well. Well, actually Steffen is not entirely wrong. Although it’s not about a financial reason/mistake. I guess they looked at the property on the development plan but didn’t thoroughly check it on site during the inspection. Just the white pipe alone would have made me suspicious and deterred me from buying, assuming its function. On the development plan, some properties look dreamy to us too. In reality, they turn out to be barrels without bottoms with obstructed views.

1) In the building plan excerpt. Where is the white pipe there.

I guess near the blue area and the number 6.79?

2) On the photos one can see staking marks. Are these the line with 40.73 or 17.73?

3) Exactly where on the photos does the lower boundary of your property start?

And regardless of that. Who did you speak with at the municipality? Is the stormwater retention basin operated by the city or possibly by a special-purpose association?

"This is your problem" / "we are not responsible for that" is not a decision verbally. And in writing it must also be correct, otherwise it becomes uncomfortable for the municipal employee. Incidentally, the municipality also has to drain its property on its own land.

The basin looks huge. What is supposed to go in there or how big is the new development area? Aren't the streets drained on the sides with small ditches? And what does it mean since the basin was filled? Was water artificially pumped in there? Maybe too much and it will settle again?

By the way, the attached photos show the basin and part of our property. It starts above or to the right of the pipe.

Our property is No. 38a. The blue one is the stormwater retention basin and the green one is a green strip on which a pumping station stands.

In front of your property, on the green strip, there is a pumping station to pump away the accumulated rainwater because there is no slope or it has to go to the sewage plant somewhere over a hill. The stormwater retention basin is used to reduce the peak load during heavy rain events by first absorbing the water, which is then continuously pumped away again. The white pipe will probably be the outlet from the retention basin. I can’t imagine that the terrain level along the footpath remains the same. There is a hollow where all the water naturally collects. And the pipes are usually laid in trenches and not level with the surrounding ground. Has the building readiness already been granted? Is construction already underway somewhere in the area? No matter what the municipality says, the path is unusable as it is – regardless of your property. Is the pumping station new? Is it already operational? If it is not yet finished, or the new basin is not yet connected, it is clear that everything there will be flooded. The response from the municipality is still outrageous. I would suggest inquiring at the city drainage / municipal utilities since they ultimately plan, build, and operate it and probably know best.

What kind of property is that? Retention basin, railway line, industry... did you really pay for that? oh dear

From the west terrace, a view of the "lake", a street only at one corner in the form of a roundabout/turning area, and after all over 600 sqm of land. The railway line can of course be annoying, but maybe at least a visual/noise protection fence will be installed there. There are definitely worse things.