PHASE 1 Issue

Just had a Phase 1 conducted on a potential purchase and they have identified an unnamed tributary running through the rear portion of the park. Owners do not have flood insurance and the property is not in a flood zone. Called town and they say they are aware of the tributaries on that and other properties, but thier are no violations…, They say thier are many unnamed tributaries in the township. Anyone ever deal with this? What else can be done? Sellers say they have never had any issues regarding the tributary (it runs through many properties in the area). Anyone??