Try 155.9550. It's on the same license as the fire and EMS frequencies and it states on the license "Government entity will use for official and essential communications with fire, ambulance, and public works".
I can't get a PL or DPL for you as I am too far away to pick it up.
I was gonna add - 155.955 (but the library was closing)
while the PD/FD are dispatch by the county - dont know how the town handles the DPW dispatch; The PD officers are not in the HQ taking calls they are on the road or doing other assignments; as most towns that have thier own dispatch they -local PD's take sometimes dpw calls and then dispatch the dpw - so...if you find out how its done in Ridgefiled let us know