November 16, 2017 | 9:00 – 10:30 am | Schematic Design
Meeting minutes – May 18, 2017
Background
Seattle Department of Transportation (SDOT) is proposing to design and construct a pedestrian and bicycle overpass across I-5 that will connect North Seattle College, the Licton Springs neighborhood, major medical facilities, and communities west of the freeway with Northgate Mall, the future Sound Transit light rail station, and the eastern portion of the Northgate Urban Center.
The new bridge will span roughly 1,600 ft over I-5, landing at North Seattle College on the west side and at 1st Ave NE and NE 100th St, near the future light rail station, on the east side. The bridge would include a spur linking directly to the mezzanine level of the light rail station.
The Design Commission approved a concept design of the bridge in September 2015. At that time the commission helped select a preferred alternative bridge type and alignment. Designers were LMN and Swift Company. After concept approval the project was on hold pending full funding of approximately $60 mil.. The project did not receive a TIGER Grant it was counting on. Since then the budget was reduced by half, to approximately $37.5 mil. and Via Architects have redesigned the project. We reviewed and approved the updated concept design on May 18th, 2017. We will review the schematic design during this meeting.
Previous review
On May 18th, 2017, you reviewed and approved, 6-2, the updated concept design for the Northgate Pedestrian Bridge with the following recommendations:
- Address pedestrian and bicycle safety at the mixing zones, specifically at the east landing near 1st Ave NE and NE 100 St
- Apply the principles of “universal accessibility” when designing bridge elements, especially when designing for the slope of the bridge. The lack of precedent is a concern for the proposed length and degree of slope
- Articulate goals for sustainability and outline strategies to meet identified goals
- Explore minimizing the length of the wall on the west side in order to improve stormwater flow, enhance views, and to minimize the bulkiness of the bridge design.
Two commissioners voted against the concept design. Both had concerns with the proposed 8.3 % slope and the lack of a sustainability plan. both of which will be addressed in the schematic design presentation.
This review
This is your second review of the Northgate Pedestrian Bridge since the updated design proposal. At this meeting you will review the schematic design for the project. The presentation will address how the design has changed in response to recommendations made during previous meetings. the presentation includes updates to the proposed alignment and slope, sustainability strategy , landscape, and art plan.
Revised alignment and slope
The proposed alignment, slope, and length of the pedestrian bridge have been revised . The previous bridge spanned 1681 ft. and included an alignment that provided a direct connection to North Seattle College. The previous alignment bisected a stormwater wetland and included a large MSE wall along the west approach. The previous bridge design also included 8.3% slope on the east and west approach.
The updated bridge design spans roughly 1,950 ft. The proposed alignment has been shifted northwest of the stormwater wetland, allowing for a better neighborhood connection and a slope of no great than 5% from the west approach to the light rail mezzanine entrance located on the east side I-5. The proposed slope from the light rail mezzanine entrance to 1st Ave NE has decreased from 8.3% to 8.1%. While this portion of the bridge still includes a steep slope, publicly accessible elevators will be available in the light rail station to move users between the street and mezzanine levels. It will be important to know if ST elevators between the street and mezzanine levels will be accessible at all hours.
Mixing zones
the updated design will include four types of paving patterns for different areas of the trail. the main trail will include light grey concrete, mixing zones will include grey concrete, and outlook areas will include finished light grey concrete with score joints. Transition zones between areas will include concrete embedded with thermoplastic band striping, which will help in slowing traffic prior to entering the mixing zones. It will be important to ask about the durability of the striping material.
Sustainability & equity
The project team will present a sustainability strategy for the project. The project team has included a combination of SDOT standard sustainability practices as well as sustainability decisions that are specific to the project. The project team does a good job in describing how the pedestrian bridge will promote mobility for cyclists and pedestrians while increasing access to commercial areas, open space, and light rail.
The project team also mentions capturing stormwater, using LED lighting, and providing educational wayfinding material along the bridge, but does not provide detailed examples of the proposed wayfinding. The draft presentation does not include in-depth material describing how building materials and landscape will be used to support the sustainability strategy. As the project progresses it will be important to have more information about specific plantings and bridge materials.
MSE Wall
The overall length of the proposed wall was reduced. With the realignment, the wall no longer bisects the stormwater wetland.
Art
Proposed art will be located at the hairpin turn along the east approach near the light rail mezzanine level. The project team will present two alternatives for artwork.
Things to think about
- Given the proposed slope of the bridge between the mezzanine and street level, will the ST elevators be accessible at all hours?
- How durable is the thermoplastic band striping?
- The proposal does not include planting or materials palettes
- Where are the proposed locations for the educational wayfinding signage?
May 18, 2017 | 1:00 – 3:30 pm | Final Concept Design
Information from previous meetings
This review
Seattle Department of Transportation (SDOT) is proposing to design and construct a pedestrian and bicycle overpass across I-5 that will connect North Seattle College, the Licton Springs neighborhood, major medical facilities, and communities west of the freeway with Northgate Mall, the future Sound Transit light rail station, and the eastern portion of the Northgate Urban Center.
The new bridge will span roughly 1,600 ft over I-5, landing at North Seattle College on the west side and at 1st Ave NE and NE 100th St, near the future light rail station, on the east side. The bridge would include a spur linking directly to the mezzanine level of the light rail station.
The Design Commission approved a concept design of the bridge in September 2015. At that time the commission helped select a preferred alternative bridge type and alignment. Designers were LMN and Swift Company. After concept approval the project was on hold pending full funding of approximately $60 mil.. The project did not receive a TIGER Grant it was counting on. Since then the budget was reduced by half, to approximately $37.5 mil. and Via Architects have redesigned the project.
At this meeting you will provide input on the revised concept design. At future meetings you will review the project at schematic and design development phases.
Background
This is how the project changed and where the budget was cut:
Location
Alignment
The alignment has remained the same except for at the east end and at the North Seattle College. At the east, instead of looping, the bridge is now a u where it drops down west of 1st Ave NE. This change removes the bridge from a WSDOT parking lot that was previously impacted by the design. The spur to the station has been moved slightly north and a more generous mixing zone is provided at that location. At the college, the bridge was shifted westward and now runs directly next to the college parking lot. The bridge hits grade sooner at this end than it did before, reducing the amount of elevated structure. It’s steeper though, and is on fill, as described in the section Architecture below.
Bridge Architecture
The most notable difference between the previously approved design and the new one is that the visually impactful tube truss structure has been reduced from being like a snake running from the light rail station to the community college to just a bump/mountain over the freeway. Expensive steel truss has been replaced by precast and cast in place concrete for the east and west approach spans. The steel mesh throw fence now serves as the transition from above deck bride structure to railings. The railing, which had previously been an extension of the truss geometry, is now wire mesh with a wooden railing.
Two belvedere overlooks have been added. In profile the bridge has gone from a thin steel deck to thicker concrete one.
Below the deck the open Y columns have been replaced with bulkier, solid ones.
Sadly, changes to the structure have resulted in a 30 ft wall and a large segment of bridge on fill and grade through the natural area at the college.
Circulation
Circulation has been improved in some ways, but has also been diminished in places. The anticipated pedestrian volumes are shown here:
The connection to North Seattle College has been greatly improved by dropping down the west approach to meet grade at the first point where it hits the campus. The commission had strong concerns about the previous design that had only a stairway at this point.
The cost of getting to grade sooner at the college was that the grade of the bridge went from 4.8% to 8.3 % (the ADA maximum) to achieve it.
The spur to the light rail station has been moved north and the mixing zone is more generously sized, making the connection more legible and prominent.
The bridge width has been reduced from 20 ft to 16 ft.
A stairway was eliminated at the east end of the bridge, making it necessary for people headed for buses, the Northgate TOD, mall and community facilities beyond travel considerably farther. As shown in the diagram above, at the beginning of the Circulation section, this stairway was anticipated to take almost as much travel volume as the spur to the light rail station. Officially, only people with a ticket may move through the station. If this is enforced, the path for people to get from the bridge to the mall, for example, becomes quite circuitous. Of course if a stairway is provided an elevator must also be provided incurring additional cost for construction and maintenance.
Landscape
The new design sits more heavily in the landscape with its thicker profile, larger columns and segment on fill that runs through the west storm water pond. Changes to the design have resulted in a 30 ft high wall through the storm water pond. At the same time, the bridge touches ground sooner and a significant segment at the west end is no longer above grade structure.
Old:
New:
Old:
New:
Items to Consider
- Cost benefit of narrowing the bridge, doing away with the tube truss, adding a segment on fill and eliminating the drop down at the east end.
- Overall architectural concept of the bridge, transitions, and relationship to various contexts it runs through.
- Realignment at east end simplifies the bridge but a stairway was eliminated and it is no longer possible to move directly east without using the long loop.
- Given the bridge is narrower, bike flow could be of concern at the sharp eastern elbow; railing in the overlook at the elbow also perhaps problematic.
- Visual and environmental impacts, cost savings, and design of the 30 ft high wall in west stormwater pond.
- Slope increase of the west approach from 4.8 to 8.3%.
- Gateway connection to neighborhood at College Way at far west end.
- Design of the mixing zones at the college and light rail station entrance given they are much larger now.
Seattle Design Commission 