One end seems to be filled in completely, the other end seems to be not so filled in. If there's anything UE has taught me it's that "filled in" isn't permanant as long as there's a shovel, pickaxe or sledgehammer around and neighborhood kids are great at finding ways into places.
The end that doesn't look filled in is in back of what I assume is state property on the waterfront, so it might be best to check it out on a weekend, unfortunately I've gotta work the next three weekends!
There's another tunnel in Clinton, MA which is wide open and a hangout spot for local kids.
