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Monday, November 26, 1990 - Page updated at 12:00 AM

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`The Biggest Thing Afloat'

In a front-page editorial June 30, 1940, Seattle Times publisher C.B. Blethen apologized for the doubts he had expressed about the first Lake Washington floating bridge, scheduled to open the following July 2.

``I felt that from an engineering standpoint it was too dangerous a toy on which to spend so much taxpayers' money,'' he wrote. Blethen previously had written that a pontoon highway bridge would lack buoyancy.

``What sinks me is, the durned thing really does float!'' he said.

Blethen wasn't around to see it, but his original prediction finally came true. It just took 50 years and 148 days.

After several days' buffeting by high winds and torrential rains, the Lacey V. Murrow Floating Bridge - named for a state highway director - broke up yesterday and sank into the mud on the bottom of Lake Washington. The span, popularly known as the Mercer Island floating bridge, had been closed for a $35 million renovation and was scheduled to reopen in 1992.

It's ironic that throughout its half-century of service, the world's first floating bridge never suffered significant storm damage.

When high winds and rough waves forced officials to shut the Evergreen Point Bridge to the north on Lake Washington and the Hood Canal Bridge, Mercer Island and Eastside commuters would smugly point out that their bridge was not so fragile.

When the bridge was opened, officials claimed it would be safe in a 90 mph wind and stay afloat even if 20-ton trucks were to line up bumper to bumper from shore to shore. Nobody thought about the hazards of renovation, 50 years in the future.

The old bridge did more than just carry traffic: It brought Eastern Washington and its agricultural produce closer to the Puget Sound market and ports, turned Mercer Island from a summer resort into a Seattle suburb and transformed the berry farms and fruit orchards of the Eastside into the state's fourth-largest city - Bellevue - with its own burgeoning suburbs extending almost to the Cascade Mountains.

The Times called the bridge, 1 1/4 miles long, ``the biggest thing afloat in the world,'' easily outdistancing the liner Queen Elizabeth, largest of that day.

The bridge was christened by Kate Stevens Bates of Olympia, daughter of the state's first governor, who smashed a huge urn containing water from 58 of the state's lakes, streams and bays against a pylon at the new bridge's west end.

In the morning the ferry Leschi made its final trip across the lake, and Mercer Island and Medina commuters gave ferry employees a loud and long horn serenade as they drove off the vessel. They knew they would be driving all the way home that evening.

In his dedication address at the Seattle terminus, Governor Clarence Martin described the bridge as ``original, distinctive, striking and graceful . . . a product of this great state's vision and constructive spirit.''

Then at 1 p.m., Martin's car led a parade across the bridge, meeting Eastside celebrants at the Mercer Island toll plaza where even the governor paid the 25-cent toll. Trucks, buses, trailers, motorcycles and carts drawn by one or two horses were required to pay a toll of 35 cents; for three-horse conveyances, the toll was 50 cents, and for pedestrians, a nickel.

A total of 12,000 vehicles crossed the bridge that first day.

Planners had expected about 5,000 vehicles, the number carried by the ferries in a whole month. They thought average weekday traffic would be about 2,800. But from the beginning, 5,266 cars were clocked on an average weekday, four vehicles a minute. Toll collectors reported people were even crossing the bridge at night.

Although Eastside development escalated in 1940 and 1941, it virtually halted during World War II, then exploded in 1946. By July 1949, 44 million vehicles had crossed the bridge, and the Toll Bridge Authority's $5.5 million construction bond issue was paid off - 21 years before its expiration date. The tolls were removed.

It was not until 1960 that a second bridge, at Evergreen Point, took some of the load off the Mercer Island bridge, but soon both were carrying 50,000 to 60,000 vehicles a day. By now, both record more than 100,000 on an average day.

Although temporary pontoon bridges had been used by the military since the days of Napoleon, the Mercer Island span was the world's first permanent floating highway bridge. The largest floating structure ever built anywhere up to that time, it was constructed of steel encased in concrete. It spanned 6,561 feet with 25 floating pontoon sections and weighed about 100,000 tons.

The bridge cost $8,854,400, paid for in part by the federal Public Works Administration, and took 18 months to build.

Engineers chose the pontoon design because an orthodox bridge would cost an estimated five times as much, and they questioned whether foundations could be laid at a reasonable depth on Lake Washington's unstable floor.

In experimenting with a pontoon bridge, engineers also experimented with a floating drawspan, and the result was a midlake bulge, an unexpected curve in the middle of the bridge. Prophetically, two hours before the official opening in 1940, an overeager motorist drove through the Seattle-side barricades, coasted onto the floating structure and plunged his car into an eight-foot opening in the middle of the bulge.

That was the first of many hundreds of accidents at the bulge, which included a number of unscheduled dives into Lake Washington, often late at night and occasionally unobserved. When divers inspected the anchor cables in the early 1980s they found a car that had been on the lake bottom for several years, containing the body of a missing teen-age girl.

In August 1981, the bulge was replaced by a straight, unmovable pontoon section as part of a series of safety improvements starting with completion of the new East Channel Bridge. At 65 feet, the East Channel span was high enough that marine traffic could be re-routed, and the drawspan was no longer needed.

Removal of the bulge, however, didn't noticeably improve the accident record on the four-lane bridge, for the undivided roadway was still prone to head-on collisions. Each year, before and after the bulge was removed, three or four people were killed and 70 to 80 more were injured.

For almost six miles of I-90, including the floating bridge, the Highway Department beginning in 1960 would reverse an inside lane during peak morning and evening hours.

Copyright (c) 1990 Seattle Times Company, All Rights Reserved.

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