Re: Neighbor is about to add 3' of vertical fill on entire lot
Does your town have stormwater or drainage ordinances for home construction and soil disturbance? If so, get a copy or call your town office and talk to them about what the codes/regs allow and your concerns. Maybe there's someone you need to talk to besides the Conservation Committee. If the builder's engineer is clueless, there should be an evaluation by someone with expertise in this area.
-Daryl, learning how to keep up with an 80 year old house in PA