Page 9 - COLLAGE

1. CHAPTER

INTRODUCTION

1.1. BACKGROUND

The original Evergreen Point Floating Bridge, also named for state governor Albert D.
Rosellini, opened on August 28, 1963, carrying the four-lane State Route 520 (at the time

designated temporarily as the Evergreen Point branch of Primary State Highway 1 until
the 1964 state highway renumbering). The 7,578-foot-long (2,310 m) floating span

consisted of 33 pontoons and cost $24.7 million to construct (equivalent to $206 million in
2020) the bridge carried four lanes of traffic, separated by a curb that was later replaced

with a simple Jersey barrier at the center was a drawspan that opened for large vessels

traversing the lake. The original bridge would also close to traffic during sustained wind
gusts of 50 miles per hour (80 km/h) or higher for more than 15 minutes.

Due to increased traffic generated by rapid growth of the Eastside area, bridge replacement
was explored as early as 1969, when building a parallel span was explored and rejected. The

Eastside is also served by the Interstate 90 floating bridges completed in 1940 and 1989,
carrying traffic across Mercer Island to and from Bellevue.

The original Evergreen Point Floating Bridge was designed before the implementation of
modern earthquake engineering standards, with vulnerabilities in its hollow support

structures that could have failed in a major earthquake. Additionally, near the end of its
lifetime, vibrations induced by storm surges and strong winds were able to compromise the

aging drawspan, anchor cables, and pontoons, leading to structural failure in a

major storm. Even if the storms were below the maximum threshold for failure to
occur, Washington State Department of Transportation (WSDOT) would still close the

floating bridge to traffic. Although the original bridge carried two lanes of traffic in each
direction, it did not include shoulders or pedestrian and bicycle infrastructure. The lack of

a shoulder led to traffic congestion in the event of an accident, which would block one or
two lanes in a given direction and block emergency services from accessing the bridge.

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