[aloer]

I don’t think so. Bombs are usually found during construction so leaving them in place would not work if they block progress on a hole/tunnel etc

For reference the state of NRW (Germany) alone found 2811 bombs in 2018 so it’s much more common than you’d think.

Laws seem to differ by state but afaik new construction must include some kind of bomb assessment, often done via aerial photos to quickly filter out areas that were not bombed at all