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Tuesday
Nov202012

Seattle Still Debating Design Plans For A Project To Rebuild Its Crumbling Downtown Seawall

In the recent aftermath of Hurricane Sandy’s devastating destruction on the East Coast of the United States, citizens in the City of Seattle on the West Coast have decided to take preventative measures to make sure the same thing doesn’t happen to them – they just haven’t hammered out all the details yet!

The Elliot Bay Seawall (also called the Alaskan Way Seawall) originally being built in 1934. Photo courtesy of the Seattle Department of Transportation.

Earlier this month, Seattle residents overwhelmingly approved city funding for a new seawall for the city’s downtown district.

On Election Night, 77 percent of Seattle residents voted in support of the seawall measure – also known as Proposition 1 – to approve “a $290 million, 30-year bond measure and excess property tax levy for the purpose of replacing the Alaskan Way Seawall and associated infrastructures, including city-owned waterfront piers,” says the project’s budget legislation fiscal notes.

For years, city officials had been trying to gain public support to finance the project, warning of the danger of the now heavily deteriorating seawall.

The day of the vote, Seattle Councilmember Tom Rasmussen, chair of the council’s transportation committee, urged citizens to pass the measure in a statement telling them that the “aging seawall” had been considered vulnerable to an earthquake collapse ever since the Nisqually earthquake hit Washington State in 2001.

The Nisqually earthquake was one of the state’s largest quakes on record, registered at a 6.8 and lasting about 45 seconds. The Nisqually earthquake violently shook the Puget Sound region from Olympia to Everett 10 years ago, caused roughly $2 billion in damage, injured 400 people and was blamed for one fatal heart attack, said The Olympian in 2011 on the 10-year anniversary of the quake.

Rasmussen warned voters that if the seawall collapses it will have “grave effects” on the businesses, utilities, and roads along the waterfront and into downtown Seattle.

An even more graphic picture was illustrated in the project’s legislative fiscal notes, saying:

The existing Alaskan Way Seawall was not designed to withstand earthquakes and has been structurally weakened due to tidal forces (of Elliot Bay), aging materials and marine borer damage. There is a one in ten chance of an earthquake leading to liquefaction and seawall failure, within the next ten years.

Failure of the seawall could disrupt public transportation and utilities, damage regional commerce and potentially lead to loss of life.

In addition, Pier 58 and 62/63, which are publicly owned, have reached dangerous levels of deterioration. Pier 58 is seismically vulnerable, and Pier 62/63 is structurally compromised to the degree that limited physical activity is now permitted.

“Approximately 50 percent of the existing wall (is) currently damaged,” says the project’s ordinance.

Last week, the Seattle Department of Transportation released a Draft Environmental Impact Statement (EIS), providing detailed information on the project’s purpose, seawall replacement alternatives, and their potential effects during and after construction.

There are three plans that are being discussed, known as Alternatives A, B, and C, with the city most favoring ‘C.’

 As described in the Draft EIS, Alternative A would provide the lowest structural cost option, constructing the seawall as close as possible to the current alignment, moving the new seawall face between three feet seaward and 15 feet landward of the existing seawall face. It would also use soil improvement to form the structural support for the seawall.

As part of Alternative A and all of the plans, habitat enhancement is one of the important features of the plans.

The Seattle Department of Transportation explained, saying that, “Tens of thousands of salmon migrate along the Elliot Bay Seawall and then up the Green/Duwamish River and its tributaries every year to spawn. After beginning their lives in freshwater rivers, juvenile salmon then swim down the Green/Duwamish River to enter Elliot Bay in the spring and summer,” adding that this is an important link in the salmon migratory route and “improving salmon habitat within Elliot Bay is pivotal to the success of the regional salmon recovery.”

Providing habitat enhancement, Alternative A would include the installation of a continuous intertidal migration corridor, light-penetrating surfaces in portions of the sidewalk adjacent to piers, and substrate improvements in several areas along the seawall.

Further in improving local infrastructure and public amenities, Alternative A would also include an additional northbound lane on the Alaskan Way from S. Washington Street to Madison Street, and would restore the existing view corridor between the piers.

In an overview of Alternative B, this plan would largely reshape the area by moving the seawall and downtown Seattle waterfront inward of the existing seawall face from 10 feet to a maximum of 75 feet near the Seattle Aquarium. This plan would also use braced soldier piles to form the new seawall structure.

In terms of habitat enhancement, Alternative B would include those of Alternative A, but the intertidal habitat would be larger. Also, habitat enhancements would include an intertidal habitat bench and backshore south of Colman Dock that would be bordered by riparian (waterside) plants, rocks, and drift logs. 

This plan would also include either expanded upland riparian plantings or an additional intertidal habitat near the Seattle Aquarium.

As far as improvements to local infrastructure and public amenities, Alternative B would provide the most improvements, with additional gathering areas and enhanced viewing areas along the length of the project. This would also include new decks featuring seating steps between Piers 54 and 55 and between 56 and 57.

Alternative B would also make possible a new plaza or water plaza (with tide pools) near the Seattle Aquarium, providing recreational and cultural features. This plan would also create connections to the water with a short-stay boat moorage at the restored Washington Street Boat Landing.

As said earlier though, the city most favors Alternative C, which combines the first two plans. This plan would move the face of the new seawall about 10 to 15 feet inward of the existing seawall face along its entire length. It would also use soil improvement to form the seawall’s structural support.

For habitat enhancement, this plan would include a continuous intertidal migration corridor and continuous light-penetrating surfaces. Also, substrate enhancements would be placed in key areas of the expanded habitat along the seawall.

In addition, the area south of Colman Dock would include an intertidal habitat bench and backshore habitat as featured in Alternative B.

As for improving local infrastructure and public amenities, Alternative C would include the additional northbound lane as described in Alternative A, and would also provide enhanced viewing spaces along the length of the seawall as well as new viewpoints between piers as described in Alternative B.

Seattle residents will have an opportunity to voice their opinions on these alternatives. The Seattle Department of Transportation is seeking comments from the public on the Draft EIS during a 30-day comment period.

Comments will be accepted online, via email to seawallDEIS@seattle.gov, or in writing to Elliott Bay Seawall Project Draft EIS Comments, c/o Mark Mazzola, Seattle Department of Transportation, PO Box 34996, Seattle, WA 98124-4996. Comments must be postmarked no later than Dec. 13, 2012.

It will also be possible to make comments in person at a public open house on Dec. 5, 2012, from 4:00 p.m. to 7:00 p.m. at the Bell Harbor Conference Center’s Maritime Events Center.

 

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