In the early sixties the federal government determined that existing mines and caves might provide protection for significant numbers of the population. A national survey was undertaken and several locations in Southern New England were identified:
Connecticut
Location 1:
Litchfield County
Mine, 1 mi N of Roxbury Stn, 180 spaces.


Above, 2014 images of the Roxbury Station mine. Photos courtesy of Eddie Aldrich.
Location 2:
Mine, Sand Road, Canaan, 62 spaces.
Location 3:
Mine, Prospect Mtn, Bantam, occupancy not specified




Above, 2014 images of the Prospect Mountain mine. Photos courtesy of Eddie Aldrich.
Massachusetts
13L1 Hampden County
0002 Abandoned Emery Mines, Chester. 1180 spaces.
1965 Office of Civil Defense study on the use of mines and tunnels as shelters:http://www.dtic.mil/dtic/tr/fulltext/u2/617111.pdf
Source: http://www.ki4u.com/nuclear survival/states/ct.htm
Also,
The new Windam High School, built in March, 1965, reflected the international political climate. The High School's proposed gymnasium had fewer windows, and concrete was preferred to steel in its overall construction. It was designed to double as a Civil Defense fallout shelter for the town.