By Tracy Record
West Seattle Blog editor
Some new information today as the City Council got its first comprehensive West Seattle Bridge briefing since August.
The council’s independent consultant suggests a closer exploration of the repair option, it was revealed when City Councilmember Lisa Herbold asked council staffer Calvin Chow to talk about a memo the consultant sent councilmembers Friday. Here’s the memo (also embedded below):
More on that shortly.
Also, Transportation Committee chair Councilmember Alex Pedersen said Mayor Jenny Durkan has invited councilmembers to send her their individual repair-vs.-replace thoughts by week’s end.
And when Budget chair Councilmember Teresa Mosqueda pressed SDOT reps on the timeline for that key decision, director Sam Zimbabwe said that since they’re continuing to plan for both options, a final decision could theoretically wait as long as spring before they started losing time – though the need to seek federal/state funding would require action sooner.
Money is where the council will have the most say on whatever happens; asked about their role in the project, Chow noted, “(The) council always has control of the purse strings.”
Herbold continued to make her leaning clear: “The sooner we restore the bridge, the better, that is the premium value for me.”
She and Pedersen also have had some say as members of the West Seattle Bridge Community Task Force, though she explained to her colleagues that the CTF was not tasked with a consensus opinion, but members were providing individual feedback to the mayor.
SDOT has not taken a public position but Zimbabwe said of the bridge’s closure, “This should only be something that happens once”; the Cost-Benefit Analysis notes prominently that repairing the bridge would mean another closure at some time in the future – possibly even another emergency closure if repairs failed, and eventually a replacement closure no matter what.
Herbold stressed that the Technical Advisory Panel suggested there’s a strong likelihood that repairs would last another 40 years, taking the bridge to its full projected original life span.
Zimbabwe and project leader Heather Marx started the briefing with a recap of what’s happened since the bridge was suddenly shut down March 23rd after detection of rapid crack growth. “We’re coming to the end of the first stabilization efforts,” she said, showing on-bridge images – “these are really BIG things that are happening inside the bridge.” Zimbabwe says each bracket used in the stabilization work weighs a ton, and that each post-tensioning strand is 300 feet long and ratcheted up to 280,000 pounds of tension. This is being done in each of two box girders. Repair would be MORE of the same type of thing, he explained. Of the “post-tensioning,” Marx said, “There’s a huge amount of work that this steel rope is performing for us.”
She summarized what’s going into the decision, noting that “risk” is a huge factor from the department’s standpoint and again stressing that they’re continuing simultaneous planning for repairing or replacement. While repairs would restore cross-Duwamish traffic more quickly, there’s a “significant risk” of an unplanned future closure, she contended.
The SDOT presentation also touched briefly on funding – so far the project has spent $20 million on stabilization and traffic mitigation (the latter is under the Reconnect West Seattle umbrella), and they’ve secured $8.3 million in federal grants. Chow noted that the council has approved $70 million in funding so far and has another $30 million in next year’s budget.
The subsequent discussion is where Herbold brought up the council consultant’s memo (which was not included in meeting-related documents; we obtained it after the meeting). RHC Engineering writes in part:
In general, RHC Engineering believes that additional engineering analysis could be undertaken to better capture the existing bridge behavior and quantify the risks and benefits related to Alternative 2. The CBA attempts to compare all alternatives using a consistent approach to risk and contingencies, this approach may mischaracterize the costs and benefits of Alternative 2.
Unlike Alternative 4 that relies on a planning level concept, there is significant existing information, including original construction drawings, bridge inspection and health monitoring data, load rating and seismic evaluation, and the stabilization work, to support a refined engineering analysis for Alternative 2.
Further analysis has the potential to address risk factors associated with repair, which could affect the cost and performance assessment of Alternative 2, when compared to Alternative 4. As an example of this clarification of risk, SDOT has progressively found that the bridge is technically repairable, and the bridge foundation is solid under a design earthquake event.
We also note that the CBA comparison has some inconsistencies in the assessment of total lifecycle and what future project elements should be compared for the next 75 years of the corridor function. For instance, the replacement schedule for Alternative 2, after 40 years, will be a planned event instead of an emergency event, and managing traffic during the replacement is possible instead of closure.
Alternate 2 is repair; alternate 4 is partial replacement, potentially including the recently proposed “rapid span replacement.”
Zimbabwe said SDOT has seen the memo and stressed that the Cost-Benefit Analysis “doesn’t make the decision for us … it tries to take some level of information for all the alternatives and give us an apples-to-apples comparison.” He said that they have indeed been gathering more information on what repair would entail, via the advanced monitoring that’s been put into place. He also said that in the stabilization work so far, the bridge is responding the way their modeling suggested it would, though he cautioned that they have yet to go through a “full thermal cycle,” to see, for example, what happens in below-freezing temperatures. “If we repaired we’d still have to monitor performance and see how the bridge responds ‘off into the future'” – an ongoing, continuing monitoring effort “making sure we’re still providing a safe connection from a transportation perspective.”
That’s where Herbold noted that both the council’s consultant and the TAP have “high confidence” repairs would last 40 years, less than a 5 percent likelihood of failure. She also noted that repairs ranked highest on the “value index” in the CBA. She reiterated the effects on local businesses and other residents, plus the detour-traffic-choked communities, the longer the bridge stays closed.
Zimbabwe cautioned, “We still don’t know exactly what would be involved in full repair that restores traffic – also, the maintenance costs are not fully known.” The risks raised by repairs, he said, would have to be viewed through the lens of “where our tolerance for that risk is.”
ALSO DISCUSSED: Councilmember Tammy Morales asked if alternatives to repair/replace are being considered, and what the “climate impacts” are. Toward the latter, Zimbabwe said that right now the climate impacts of diverting traffic are having a disproportionate effect on air quality for communities that are “already stressed,” since the bridge is such a critical pathway for “thousands and thousands” of people who have to cross the river. Councilmember Mosqueda said she had spoken with walking/biking advocates whose concerns include safety in getting to the low bridge – possibly improving lighting on. pathways under the bridge and at the existing park/ride lot, for example. Councilmember Morales also asked about use of WMBE – women/minority businesses – and Marx said that was already built into the process. Mosqueda also asked what’s happening to see if the original bridge-builder can be held accountable for the bridge’s early failure; Chow said that should be taken up with the City Attorney. (added) Here’s video of the meeting:
WHAT’S NEXT: As mentioned above, the mayor has asked councilmembers for feedback by week’s end. Next public discussion of the bridge is at the scheduled Community Task Force meeting on November 18th. One other note: Marx said the work toward a Size/Type/Location Study – essential if a replacement is pursued – was getting under way with “the first workshop” today.