I stumbled back upon this topic while cleaning up my RR related internet bookmarks over the weekend. I studied the notes between this thread, and the one in the NE Forum (Arches in New England). It appears that we've clearly located the arches at Bog Brook in Whitefield, and at an inlet to the Connecticut River in Guildhall. I looked at Google Maps and could trace the old RR bed quite well, from Whitefield up to Lancaster, and north towards Guildhall . The only time the RoW crossed the entire Connecticut between Whitefield and Guildhall, was north of Coos Junction, so we can rule out a Conn. river arch crossing in South Lancaster. I noticed only two other brooks/rivers that seemed to pass under the line. The first was just north of French Road, right after the sandpit, over an inlet to the Johns River. I walked out, and that one is a concrete culvert. Definitely a more modern piece.
Paul, I took your geo coordinates from the Arches in New England thread, and they put you right on the RoW in a marshy area north of where the line crosses Route 142 at the Dalton Transfer Station.
https://www.google.com/maps/@44.4450266 ... a=!3m1!1e3
There is a structure there, but it looks more like a snowmobile bridge; the trail makes a noticeable S curve to get over the bridge, and it looks to me to be way too tight for a train to pass over. Street View from Route 135 shows us that the grass growing in the wetlands there is far too tall to see whatever is out there, but 600 yards sounds like a fair estimate. Definitely private land, I'll see if I can walk out there sometime soon to confirm what that structure is.
Avatar: NHV 669 at the south end of the "Pompy" in White River Jct., VT on 4/29/1993. Photo by Richard Roberg.
https://youtube.com/@NHVT_Productions