Lacey V Murrow Memorial Bridge

Floating bridge carrying I-90 across Lake Washington, Seattle.

At a glance

Source	Author	Role	In one line
The Hidden Engineering of Floating Bridges	Wesley Crump	subject	Homer Hadley’s 1921 idea of a bridge floating on hollow concrete pontoons became this span, which opened in 1940 as the first floating concrete highway across Lake Washington.

The Hidden Engineering of Floating Bridges — Wesley Crump (2025)

Source: Original · Readwise highlight

When it opened in 1940, it was the first floating concrete highway of its kind, a marvel of engineering and a symbol of ingenuity under constraint. But floating bridges, by their nature, carry some unique vulnerabilities. And fifty years later, this span would be swallowed by the very lake it crossed.

• Role: subject
• In the article: Homer Hadley’s 1921 idea of a bridge floating on hollow concrete pontoons became this span, which opened in 1940 as the first floating concrete highway across Lake Washington. In 1990, during rehabilitation, the watertight doors between pontoon chambers were removed to store hydrodemolition runoff; a Thanksgiving-weekend storm flooded the chambers and the bridge partly sank, severing cables on the adjacent Hadley Bridge. Its original retractable span also caused awkward curves and accidents and was later removed.
• Why it matters: Origin and cautionary tale of floating-bridge engineering: first of its kind, and its 1990 sinking illustrates how small operational oversights are catastrophic.