I’m no engineer. But I am a Seattleite who cares deeply about the city’s waterfront, long fenced off from the city by an aging two-story viaduct that’s due for replacement. And, as a city councilmember vitally interested in the welfare of the city, I am listening these days to engineers who can tell me what’s happening as contractors tunnel beneath our streets.
For those reasons and others, I was deeply grateful to the Washington Department of Transportation (WSDOT), the engineers and officials who came to a Seattle City Council Monday morning to brief the council on issues involving the Alaskan Way Viaduct replacement project.
In recent days, the Seattle Times and other local media have been reporting on a soil settlement of up to 1 ¼ inches discovered in the Pioneer Square neighborhood. The engineers suspect the soil settlement may have been caused by activities surrounding the tunnel boring machine. The 57-foot-diameter machine, known as Bertha, has been stuck, idle, underground for a year, while the contractor has been trying to effect repairs.
The plan to repair the stuck machine involves digging a 120-foot-deep rescue pit. The pit would enable the contractor – a consortium known as Seattle Tunnel Partners (STP) — to replace the damaged cutting surface of the machine. In order to dig the rescue pit, STP has had to “dewater” the soil. Dewatering is known by experts to be a cause of settlement, and the experts are looking into that.
Some key takeaways from the presentation Monday:
The project to replace the aging Alaskan Way Viaduct – also known as SR 99 — is a state, not a city, project. The state negotiated a design-build agreement with the Seattle Tunnel Partners (STP), its contractor, and continues to oversee the project’s progress. The city does not – let me repeat that – the city does not have any financial nor contractual obligation to STP.
The city does have a concern for municipal infrastructure that may have been affected by the tunnel project. At last report, soil settlement has caused Seattle Public Utilities to look at possible damage to water and drainage pipes in the Pioneer Square area. If there is damage to the pipes, the City will look to the state to fund any repairs under its agreements with the state.
The Alaskan Way Viaduct has settled more than 5 inches since the 2001 Nisqually Earthquake, but is monitored constantly by the state and its engineers for public safety. It has received bracing and retrofitting. On Monday, state engineers assured us that the Viaduct continues to be safe They also told us that the viaduct could and would be shut down if deemed a hazard by any of the engineers who regularly monitor its condition.
WSDOT, the state agency, will place more sensors to the East of Pioneer Square to better assess any settling that might be occurring in the area. The agency continues to check data on a regular basis and regularly monitors buildings in the area. Since the soil settlement was detected, some 30 buildings have undergone inspection. To date only so-called “cosmetic” damage has been recorded by WSDOT.
Both the Seattle Department of Transportation and the city’s Office of Emergency Management have developed contingency plans for Viaduct shutdown, if needed before the tunnel is ready. The Washington Department of Transportation has also developed plans for a shut-down in the event of public safety problems.
Public safety continues to be the prime concern of both state and city departments of transportation. There are plans to have regular reports to the Seattle City Council. The goal is to have as much public information available as possible via the Council’s meetings of the Committee on the Central Waterfront, Seawall, and Alaskan Way Viaduct Replacement Program.
Councilmembers spent more than two hours Monday reviewing in great detail the state’s work monitoring the Alaskan Way replacement project with public safety as the first concern. The project, has now, according to WSDOT, reached 70 percent completion. The road ahead – the 30 percent remaining — may have an uncertain timeline, but the City government supports WSDOT’s safe completion of this project, and as Chair of the city’s Waterfront Committee, I will prioritize public safety, mobility of people, transit, and freight, and transparency throughout this public project.