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Daylighting Bothell’s Horse Creek along an Urban Downtown Connector

The project included daylighting approximately 2,900 linear feet of the stream that had formerly been conveyed in an underground pipe.

In October 2016, the City of Bothell officially opened the Northeast 185th Street and 98th Avenue NE connector, including the newly daylighted Horse Creek. Along with relocating and improving the salmon-bearing creek in the City’s redeveloped downtown, this $19.7 million project created a future transit corridor linking State Route 522 (SR 522) to the city’s new multiway boulevard at SR 527.

At the fall 2017 American Public Works Association conference in Kennewick, Washington, Ross French from BergerABAM, Steve Morikawa from the City of Bothell, and Ken Nilsen from PACE Engineers, Inc. presented the challenges and unique design elements of this one-of-a-kind project.

As part of the City’s overall vision for the revitalized downtown area, 98th Avenue NE was significantly improved, Northeast 185th Street was extended, and a road to Pop Keeney Stadium was constructed to create infrastructure surrounding a new mixed-use urban neighborhood and to connect SR 522 to SR 527. Along with the corridor improvements, Horse Creek, which had been conveyed in an underground pipe, was daylighted next to 98th Avenue NE, creating a striking community attraction. A wide pedestrian pathway was constructed adjacent to the creek to provide viewing opportunities for pedestrians.

The project required close coordination with property owners and infrastructure projects west of Bothell’s redeveloped downtown core. As adjacent parcels were being developed, the roadway design had to be modified to meet the property owners’ needs. Unique challenges included mitigating hazardous underground materials with wall designs that prevent contaminated materials from entering the creek. The walls also had to be designed close to existing structures and accommodate future private development while maintaining access for adjacent property owners.

The project included travel lane reconstruction, utilities replacement, parking reconfiguration, sidewalk improvements, landscape improvements, and urban design element integration to provide a pedestrian-friendly atmosphere while maintaining the smoother flow of transportation.

BergerABAM provided innovative designs for the corridor widening, including three types of walls (soldier pile, structural earth, and cast-in-place reinforced concrete) with complex horizontal geometrics on each side of Horse Creek. Voided slab pedestrian bridges were designed to be precast on site. BergerABAM also designed decorative railings, wayfinding signage, and artistic elements in coordination with the team’s landscape architect.

In a rare, two-prime consultant arrangement, the team coordinated the interior creek channel elements that PACE Engineers designed with the various structural and hardscape elements that BergerABAM designed. The collaborative design approach resulted in an appealing urban connector that improves multimodal infrastructure while protecting the environmentally sensitive creek system.