In 1990, the original Lacey V. Murrow Bridge sank because of a series of human errors and decisions. The process started because the bridge needed resurfacing and was to be widened by means of cantilevered additions in order to meet the necessary lane-width specifications of the Interstate Highway System. The Washington State Department of Transportation decided to use hydro-demolition to remove unwanted material. Water from this hydro-demolition was considered contaminated under environmental law and could not be allowed to flow into Lake Washington. Engineers then analyzed the pontoons of the bridge, and realized that they were over-engineered and the water could be stored temporarily in the pontoons. The watertight doors for the pontoons were therefore removed. A large storm on November 22-24, 1990, filled some of the pontoons with rain and lake water. On November 25, 2,790 ft (850 m) of the bridge sank, dumping the contaminated water into the lake along with tons of bridge material.

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