toki! Since we don't know if the bridge lies over water, I'd suggest:

nasin pi sewi telo
-> nasin pi sewi anpa = way over depth

what do you think?

Probably it's a bridge over water in more than 90% of the cases, in which case "they made a road over the water" is much easier to understand, IMO. In most cases this is a useful translation, and when it isn't, most people should be able to figure out how to change "telo" to something else.

By the way, here it's not "nasin pi sewi telo" but "pali (...) lon sewi telo", so I meant more like "sie haben über dem Wasser eine Straße gemacht" than "they made a road that is located above the water".

I agree that your translation is about 90% correct. ;) (OK. Other translations have already been added.)

"lon" v. "pi": at the end of a sentence, both can be correct. There is no rule that I know of that dictates that "lon sewi telo" can only refer to the sentence as a whole, i.e. to the construction of the road. (Sonja says in Pu, that prepositions can be used at the end of a sentence, not what they refer to. Cf. "mi lukin e meli pimeja lon sinpin tomo" in Pu.)