Urban Politics #154: Update On Alaskan Way Viaduct


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By City Councilmember Nick Licata.

Assisted by Legislative Assistant Newell Aldrich on this issue.

Urban Politics (UP) blends my insights and information on current public policy developments and personal experiences with the intent of helping citizens shape Seattle’s future.

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CONTENTS:

  • Update On Alaskan Way Viaduct
  • Rebuild/Retrofit Report
  • My Analysis
  • Leadership Group

Update On Retrofit Option For The Alaskan Way Viaduct

In the ongoing debate on what option to pursue with regards to fixing or replacing the Alaskan Way Viaduct, I had taken the position in prior Urban Politics #136, 137 and 144, that retrofitting of the viaduct had not been properly explored and that it could hold out a speedier and less expensive solution.

I had been approached by a several prominent structural engineers who asked that I encourage the State’s Department of Transportation to take a second look at retrofitting the structure. Given the frail condition of the Viaduct and the likelihood that it could sustain serious damage in a major earthquake I agreed that a quick, short term solution might be advisable. In addition the first estimates of under grounding the viaduct ranged up to $11 billion dollars.

To that end I organized a meeting with State Department of Transportation Secretary Doug McDonald and two engineers from Imbsen & Associates, a California firm specializing in bridge retrofitting. At the meeting, Dr. Roy Imbsen stated that a retrofit might provide a cost-effective interim solution.

As a follow-up to that meeting, I wrote MacDonald requesting that they analyze a retrofit option in order to save money and enhance public safety in the short run. In response, early this year the State DOT agreed to conduct an analysis and have now completed their report.

Rebuild/Retrofit Report

The State DOT, City DOT, and US Federal Highway Administration all participated in the report on the Rebuild/Retrofit option for the viaduct. I received the executive summary of this report, and met with Maureen Sullivan of the State DOT, as well as City of Seattle staff working on the viaduct project. I expect to receive the full report soon.

The report offers a comparison of rebuild options for single and double-level viaducts, a retrofit option, and the current viaduct. It examines how well each would withstand earthquakes; life expectancy; seismic performance; and relative cost. Most importantly, outside structural engineers, including Dr. Imbsen were involved in work on the report.

The Executive Summary contains charts which compare the options using terms such as excellent, very good, adequate, poor. No exact numbers or figures are listed.

For “overall earthquake resistance”, two rebuild options are listed as “excellent,” and “very good.” The retrofit option is listed as “adequate.” For an earthquake stronger than the Nisqually quake, the rebuild options are listed as “excellent” and “very good”, with the retrofit as “poor”. The current viaduct is listed as “very poor” in both categories.

Although each of the rebuild options, and the retrofit, would have a life expectancy of 75 years, if no earthquake occurred, the visual impact of the retrofit option is substantially greater. Sketches in the report clearly show that the retrofit design would be much more massive than the existing viaduct by requiring additional support columns (roughly double in number, according to the DOT), and they would be thicker than the current columns. A rebuild would allow columns to be spaced less frequently than the existing viaduct.

In addition, the report notes that the retrofit is only slightly less expensive than the least expensive rebuild option, although without exact figures, it’s hard to know the exact difference. December 2002 estimates for the more expensive rebuild option were $2.4 to $2.9 million.

The upshot of the Executive Summary is that, while it is possible to carry out a retrofit of the existing viaduct, it would save very little money compared to the “rebuild” option and provide less safety. The report concludes that the rebuild plan “is far superior to the retrofit…when seismic performance, aesthetics, cost and risk are balanced.”

However, investigation has revealed that part of the viaduct near the Battery Street tunnel can be retrofitted. In fact, the “rebuild” option now includes a section from the tunnel to Pike Street that can be retrofitted; this section is single-level. The report states that a retrofit performs well in this section.

My Analysis

I thank the State DOT for completing an analysis of retrofitting the viaduct. I believed the original decision to foreclose a retrofit option was made too quickly. My goal in pushing for a complete analysis was to see if it was possible to gain cost benefits and enhance near-term safety.

Given that outside experts were brought in and that additional analysis was undertaken, the evidence now clearly shows that an option to completely retrofit the viaduct is no longer viable.

However retrofitting could be incorporated into the rebuild alternative; it appears in this case it may bring cost savings while not harming safety.

I will review the full report when it is available to see how the other viaduct replacement options have been impacted by the new analysis. From discussions with those who have conducted the study, it appears that there may also be some less costly options available than the original tunnel plan.

Leadership Group

The Leadership Group for the Alaskan Way Viaduct will meet Wednesday, June 11, from 4:30 to 6:30 at Town Hall at 8th & Seneca. There will be a discussion of the five current options to be analyzed in the Environmental Impact Statement (EIS): rebuild, aerial, tunnel, surface, and surface with a bypass tunnel.

There may be an additional meeting in July. It looks like a new round of estimates from the Cost Estimate Validation Procedure will be available in July.

Keep in touch…

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