Location: King County & Snohomish County, Washington
Owner: Washington State Department of Transportation
Construction Cost: $6,700,000
- As-built Plan Change Tracking
- Construction Support Services
- Design Management
- Design-Build Delivery
- Erosion/Sediment Mitigation
- Final Plans, Specifications, and Estimates (PS&E)
- Highway/Roadway Design
- Hydraulic Modeling
- Intelligent Transportation System Planning/Design
- Landscaping and Aesthetics Coordination
- Lighting Design
- Maintenance-of-Traffic (MOT) Plan Development
- Pedestrian Crossing Design (At-Grade)
- Retaining Wall Design
- Roundabout Intersection Design
- Signing Design
- Storm Sewer System Modeling
- Stormwater/Pavement Drainage Design
- Striping Design
- Structural Design
- Utility Coordination
The SR 92 and I-90 Improvements project consisted of four locations where sections of the highway and the interstate system needed improvement: SR 92/ 99th Avenue NE Roundabout (Location A); SR 92/113th Avenue NE Roundabout (Location B); Regionwide Redirectional Landforms Roadside Safety (Location C); and I-90/West Lake Sammamish Parkway Intersection Modification (Location D). Lochner was the lead designer for this Washington State Department of Transportation’s (WSDOT) design-build project.
The Lochner project team designed and constructed a single-lane, four-legged roundabout at Location A and a single-lane, three-legged roundabout at Location B—both of which were designed to improve traffic flow on SR 92, reduce the potential of collisions, and provide greater through-put for vehicles. At each intersection, the profiles were flattened to provide treatment of stormwater runoff, the illumination system and signing were replaced, and roundabout geometrics improved.
At Location C, beam guardrails were installed to protect the median bridge piers and reduce collision potential with fixed objects in the median. Location C involved nine mileposts along I-5 and one on SR 18. By implementing early design, staffing the work with a dedicated crew, and maintaining a consistent approach to staging and planning the work, the project team minimized impacts to the travelling public and local communities.
At Location D, the project team designed and constructed a two-lane teardrop roundabout (no travel-through south leg) almost entirely on existing pavement at the ramp terminal of I-90 westbound and West Lake Sammamish Parkway to reduce the risk of collisions at the intersection of West Lake Sammamish Parkway and the I-90 northbound ramp terminals. Improving the intersection at this location addressed the unprotected left-turn movements at this location. In addition, the project replaced the illumination system and signing.
Lochner completed the design for all four locations within four months of notice to proceed. In order to meet key milestones and ensure final design completion, Lochner collaborated directly with WSDOT through an “over-the-shoulder” review approach. This method expedited the review process and allowed design issues to be discussed and addressed early on.