Jack -
The tunnel on the Chenango Branch was on the west side of Cazenovia Lake, passing under what is now NY Route 92 about 1.55 miles north of its intersection with US Route 20, and about 100 yards north of the intersection of NY 92 and West Lake Road.
The coordinates of that point are
N42̊ 56.749'
W075̊ 53.075'
About 400 feet northeast along West Lake Road from its intersection with Route 92 is Tunnel Lane which appears to follow the right of way from the east end of the tunnel curving south toward Cazenovia Station and Rippleton, where the Chenango Branch crossed the Lehigh Valley.
The track grade through the tunnel appears to have been at about 1,220 foot elevation, with about 50 feet of cover above the top of rail elevation at the deepest point of the tunnel. The tunnel was about 1600 feet long.
The Lehigh Valley ran through Cazenovia, and the Cazenovia station on the Chenango Branch was about one-half mile west of town, on what is now US 20 heading west toward Pompey Center.
The Chenango Branch was built as the Syracuse and Chenango Valley Railroad by a contractor named William B. Litchfield. Litchfield also took over the construction of the Rondout and Oswego Railroad in 1872, and extended it from Roxbury to Stamford as the New York, Kingston and Syracuse with the avowed intention of connecting it with the S&CV via Oneonta and Earlville.
That didn’t work. Thomas Cornell and the Coykendalls regained control of the NYK&S, reorganized it as the Ulster and Delaware, and spent the next 25 years going to Oneonta via Bloomville. I just couldn’t help getting in that plug for the U&D. Sorry.
You can find the tunnel on the 1899 15 minute topo map at
http://docs.unh.edu/NY/caze99nw.jpg
Gordon