Board of Water Supply. City Water Tunnel No. 1. This concrete bulkhead and emergency door mark the entrance to a dynamite magazine, located in a "drift" off the main water tunnel. The Board of Water Supply had to apply for permission from the Municipal Explosives Commission to build the nineteen magazines needed for City Water Tunnel No. 1. Note the heavy construction of the door and attendant on guard while dynamite was stored. August 14, 1912.