Primary Source

SEATTLE, Wash. (AP)–floating

on great, gray blocks of floating concrete, the world’s first and largest permanent floating bridge stretches eastward from Seattle.

It hugs the gently lapping water

of Lake Washington and points a blunt finger at the snow–tipped Cascade Mountains to the East.

Except for one just half its size

on the remote island of Tasmania the Lake Washington bridge is the only one of its kind in the world

But soon, Seattle will be up to its

ears in floating bridges.

Burgeoning population in Seattle

across the lake and across the turbulent salt waters of Puget Sound, has created a need for two and possibly three more bridges.

In the Seattle area, bridges mean

floating bridges because of the need for superhighways across long stretches of deep water and at a cost which the state can afford.

The present lake bridge cost

$8,850,000, probably the best bargain the State of Washington has ever made.

A second Lake Washington floating

bridge has been approved by the State Legislature. This 3.8 miles to the north of the present span, will be almost a companion piece. The floating – portion will cost something like 12 million dollars–A goodly sum but less expensive than, say, a truss bridge, or a suspension bridge. When completed, its 7,518 feet of pontoons will make it the longest. Tin–hatted construction workers have almost completed one phase of another bridge which floats — a $14,226,000, two–lane highway to span Hood Canal, on the Olympic Peninsula west of Seattle, a rambunctious, wind-swept arm of water which cuts down south and west from the stormy Strait of Juan de Fuca

Why this Seattle bent for floating

bridges.

Engineers planning the present

lake bridge were faced with the problem of spanning something like a mile and a half of water as deep as 210 feet in many places. Before 1940, bridge builders didn't believe a floating span could be built for more than 1,000 feet.  For long hauls, you took the ferry.

Lacey V. Murrow, then state

director of highways—he is a brother of television commentator Edward R. Murrow—and Charles E Andrew, a consulting engineer fresh from building the San Francisco–Oakland Bay Bridge, were handed the problem.

They finally selected concrete

for pontoons because of low cost and the ease with which they could be cast hollow and to exact dimensions.

Further tests showed that the

pontoons would not gallop out of place if steel cables were attached to concrete blocks sunk deep in the water.

Work began in January 1939.

Twenty–five pontoons, each weighing 4,500 tons, were poured in 350–foot concrete forms.

Each pontoon was divided into

12 watertight compartments and each compartment into eight cells. The honeycomb effect made the pontoons buoyant enough to easily support the 100,000–ton bridge linking Seattle with Mercer Island to the east.

Tolls paid off the bridge in 1949

—nine years to the minute of the bridge opening on July 2, 1940, and 19 years ahead of time. It has been toll free for nearly 10 years.