Back in the village where I used to live in England we ran into this same problem when plans for extending the village school went before the Council. There were three underground wartime ammunition stores on the outskirts of the village which are now used to store black powder for a display fireworks company.
The Health & Safety Executive initially blocked the school extension on the grounds that it was within the blast radius of the ammo dumps, but when it was pointed out to them that they were working from 1950s inventory statistics they withdrew it. It did cause a bit of a broughaha at the time though, as the blast radius enclosed most of the village.
Cheers
Gary