The first phase of the project, from 228th Street near Canyon Park to 208th Street at Thrashers Corner, was completed in 1991 at a cost of $5.6 million. Construction of the second phase, between Thrashers Corner and 164th Street in Mill Creek, was delayed by concerns that stormwater runoff would be inadequately handled by the new road. It began construction in 1993 and was completed four years later at a cost of $18.8 million. The City of Bothell also began its own widening project on a stretch of the highway south of Canyon Park in 1998, having decided against rerouting SR 527 onto a new bypass of the city center.