Cost benefit analysis on repair/replace of West Seattle Bridge discussed in Task Force meeting
The sixth in the series of West Seattle Bridge Community Task Force (CTF) meetings took place Wednesday, Aug. 5 and as the short term repairs are continuing the focus is shifting more to the low bridge policies and traffic mitigation around the area.
SDOT offered a policy update for the low bridge noting that emergency vehicle response remains a top priority with enforcement on the new placards during peak periods. Those placards, a temporary measure until automated enforcement starts this fall, are being issued for display in the rear window. All vehicles are allowed on the bridge from 9 p.m. to 5 a.m., seven days a week. But from 5am to 9pm it is now limited to
• School buses
• 75 Maritime/industrial users proximate to Harbor Island
• 22 Employer shuttles
• 8 Vanpools of essential workers
• 113 ILWU
Out of the remaining “slots” available (up to 140 per hour) SDOT is recommending an additional two for essential vanpools and 13 for West Seattle businesses. Dan Austin noted that he believed the ILWU passes were for Friday use only and that the businesses in West Seattle were struggling needing access to SODO and points east. He said 13 were too few. He suggested a different color option for the placards. John Persak representing the Georgetown community explained the passes were for timely processing of freight and the operation of the port, not about commuting or personal use. He said without the passes, trucks would stack up on the roads nearby and that with new contracts coming on line next June the issue will come back. Heather Marx suggested that they carry on the discussion outside the CTF meeting and that the placards were a temporary measure until September when automated enforcement is scheduled to begin.
The traffic volume on the low bridge is currently peaking around the 8:30pm hour with 600 vehicles using it but otherwise hovering around 300 midday with another peak of near 300 near midnight.
Reconnect West Seattle Update
The Reconnect West Seattle program was successful in that SDOT got more than 15,000 surveys back before it closed on July 31. More are being collected and will be added.
The Neighborhood Prioritization Ballots total was 1,651
• Highland Park, Riverview, S. Delridge, Roxhill: 1,072
• Georgetown: 209
• South Park: 301
• SODO: 69
SDOT is planning on presenting an implementation plan to the Task Force on Aug. 19.
The outreach effort to get as many folks involved was extensive and the demographic breakdown was worth knowing about. The online ballots were 80% Caucasian and above age 40, the paper ballots were non-English speakers and people of color.
Most of the respondents said they were concerned about:
• Traffic & Congestion
• Pedestrian Safety & Accessibility
• Environmental Impacts & Pollution
They found that 29% of those responding would take the bus at least once a week. 19% would take the Water Taxi once a week.
SDOT went to some lengths to explain the Cost-Benefit Analysis (CBA) that produced some confusion in the community following the last meeting of the Task Force during which six primary options were presented.
Among them was a tunnel option that has found a lot of support from both the public and some members of the task force but the graphic used (Option 6) showed a tunnel essentially under the existing bridge pilings, leading many to believe it was a deep bore tunnel. SDOT wanted to be certain people understood that was not the case.
What it IS:
• The cost-benefit analysis weights the pros and cons of multiple options to inform
one specific decision – to repair or replace the West Seattle High-Rise Bridge
What it is NOT:
• A tool for evaluating the pros and cons of different types of replacement options,
including whether we should build a bridge or tunnel; such questions begin to be
explored in an Alternatives Analysis
• A precise cost estimate, though it does consider costs. Cost is so critical that it is a
given factor to be layered upon the attributes and factor in the final, quantitative
CBA Assumptions Clarified
• CBA will help us decide whether to repair or replace the bridge
• CBA focuses on an “in-kind” replacement or partial replacement
• An “in-kind” replacement: the same alignment as the current bridge and connects to the same roadways on either side
• An immersed tube tunnel, while not an in-kind replacement, will be part of the CBA
• A bored tunnel option will not be part of the CBA
The Cost Benefit Analysis Process
Phase 1: June - Early August
Narrow down the repair vs replace options and apply objective criteria to evaluate the feasibility of each.
• Identify key “attributes” or evaluation criteria
• Gain public input on the attributes
• Determine the most important criteria to begin the analysis
Phase 2: August – Early October
Apply the agreed-upon attributes to the different options in the cost benefit analysis.
• Score the attributes
• Introduce rough order of magnitude (ROM) $ costs
• Quantify the results
• Compare the options through the lens of the CBA
• Present the results to the Technical Advisory Panel for feedback
Phase 3: October
Analyze the quantified results and produce a report with the pros and cons of each option and a recommendation.
• Present report to the Community Task Force and Technical Advisory Panel for feedback
• Make a final determination on whether to repair or replace the bridge
Proposed Evaluation Criteria
• Constructability Will the contractor be able to build the chosen Duwamish crossing given site constraints and schedule?
• Environmental What kind of temporary and permanent impacts will the chosen Duwamish crossing have on the River and surrounding area? Can we build it within the mandated in-water work windows?
• Equity Will underrepresented communities be positively or negatively impacted by the preferred alternative?
• Forward compatibility It is compatible with Sound Transit light rail or other transit?
• Funding Is the preferred alternative eligible for federal, state, local, or emergency
• Maintenance, inspection & operation needs What will the preferred alternative need over its lifespan in terms of maintenance and inspection?
•Mobility Does the preferred alternative facilitate or hinder the movement of people and goods? How will it impact current local and regional traffic?
• Multimodality Will the preferred alternative accommodate multiple modes of transportation, including transit, pedestrian, and vehicle traffic?
• Regional business How will the preferred alternative impact regional and local businesses as pertains to the movement of people and goods and overall access? Will it impact the ship channel? Will construction affect business access?
• Safety/seismic What seismic standards will the preferred alternative have to meet?
In the process SDOT will use a “weighting” system to evaluate all the factors and arrive at a final recommendation by looking for the best fit and highest weighting.
In terms of feedback from the Community Task Force SDOT that the top three concerns were Seismic safety, Constructability, and Mobility, followed by funding, forward compatibility, environmental impact, regional business, equity, multi-modal impacts and maintenances and operations.
In the breakout session for Group B (Admiral group)
Heather Marx mentioned that SDOT was working on a revision for West Marginal Way, part of which would include a new sidewalk near the Duwamish Longhouse.
Peter Goldman was hoping for more clarity regarding forward compatibility and light rail. Heather Marx explained it meant the replacement would need to be forward compatible with light rail if the CTF gave it a high weighting. If it was heavily weighted it would direct the outcome of the CBA toward a replacement. Marx pointed out that if light rail was a primary choice the existing bridge even with repair since it could not hold it. Light rail trains of the type required weigh 284 tons (eight car trains) each, meaning two of them would total nearly 600 tons of live load to any bridge.
Scott Phelan said the stabilization plan was going to take a year since the bridge would have to cycle through all the temperature changes that occur over that time. The new Pier 18 bearing replacement would flex due to temperature flucuations.
David Bestock of DNDA brought up the idea of factoring in equity in the replacement process recommending diversifying the decision making panel. He acknowledged that constructability factor was primary.
Mayor Nickels reminded that the question of what does repair mean in terms of duration is still open. Heather Marx said that would be determined in the design phase.
In the breakout for Group A (South Park group)
Colleen Desmond said that they hoped the shift in modality would be more carefully considered and they had questions about biking going to 6%. There were questions about Sylvan Way SW, and 15th SW and Highland Park SW intersections.
Paulina said they just want to make sure various parts of the community are heard.
Bob Watters said Constructability and Seismic Safety were the same.. That Environmental and Equity piece were the same. Multimodal and Mobility were the same in his view. He believes the CBA criteria were over complicated.
Barbara Moffat said they had not seen anything to preclude adding light rail to the bridge repair as yet. Greg Nickels said the engineering of the current bridge could not support light rail. But he explained given the timing a repair and replace could match Sound Transit's timing.
Desmond said many people are questioning why a five or six year project is required, why does it take so long?
Technical Advisory Panel (TAP) Co-Chairs Barbara Moffat and Scott Phelan offered an update too.
Phelan explained that the TAP were not able to see much of the data needed to make a more thorough recommendation but that the feasibility of repair should be retained and "fully explored."
Moffat asked that people read the feasibility memo and get back to them with any questions.She explained that the non-destructive testing data provided good solid data but that the records are limited in access due to COVID.
Stressing records were among those records they could not see as yet, explained Phelan.
The "as-built" drawings provided to the TAP were not a reliable record according to SDOT's Heather Marx.
The seismic upgrade possibility will come in independent of the decision to repair or replace.
The Cost Benefit Analysis will be applied to make the final decision said Moffat.
Moffat explained that the replacement options would go through a Type, Size, and Location study. Such a study is required to obtain federal funding.
Phelan explained they are looking at the design for repair and Moffat further explained that they develop a risk register and then monetized as part of a comprehensive way to determine the best path forward.
Coming up in the Aug. 19 CTF meeting are Cost-Benefit Analysis Scenarios and the Reconnect West Seattle Draft Plan and the Sept. 9 meeting will cover part 2 of the CBA and present the final Reconnect West Seattle plan.