“Boat Tunnel” for Harbor Crossing (Aug, 1932)
Well that certainly is an interesting way to cross a harbor. I can’t imagine why the Golden Gate beat out this design. Wouldn’t you feel completely safe driving through a “boat tunnel”?
“Boat Tunnel” for Harbor Crossing
PROPOSED as a substitute for the suggested Golden Gate suspension bridge at San Francisco is an ingenious boat tunnel of unique design which, it is claimed, can be built for one-third the estimated $35,000,000 cost of a suspension bridge. This and other advantages of the design have led authorities to consider seriously the erection of the boat tunnel bridge, which would be the only one of its kind in the world. It was conceived by Cleve F. Shaffer of San Francisco.
The plan comprises a combination of several short truss spans of ordinary construction, two seadrome type floating sections, the boat tunnel, anchorages and protective barriers. The two seadrome members are simply long platforms supported above the waterline by columns resting on buoyancy chambers below the surface.
Connected to and between the platform members is the boat tunnel section, consisting of a 1200-foot tubular tunnel floating 45 feet below water level, joining the two hulls. Inside the hulls are ramps at 4% grade on which automobiles travel up or down in high gear.
The advantage of this design to shipping is apparent, since a clear channel 1000 feet long and 45 feet deep is open at all times.
As a protection to the hulls and floating sections of the bridge, a resilient chain barrier would be hung from anchored buoys carrying lights and sound warnings. Because of strong tidal currents the floating units would have to be anchored in solid rock, and provision has been made for automatic motors to take up slack in the anchor lines. Underwater stresses are greatly reduced by streamline shape of the parts.