Wednesday, June 12, 2013

No worries: this is not a permanent installation

Parked bridge pontoon worries Madison Park residents

It's known as Pontoon W, and its arrival on the scene has spread consternation in the neighborhood as many Madison Parkers asked themselves, "Is this going to be what the new floating bridge looks like?"  Well, yes and no.

The pontoon is moored just north of the existing floating bridge at a point where the bridge begins its ascent to the Western high rise. In this position the pontoon's upright columns tower menacingly over the old bridge, imposingly taller and significantly wider. Several readers emailed us to get reassurance that this is not a portent of the future view of 520 from Madison Park.

We quizzed WSDOT on the subject and can reassuringly report that while the bridge will not be that high and wide at this particular Westside venue, Pontoon W is ultimately destined to be placed on the Eastside of the bridge--where it will be that wide and, actually, even higher (the roadbed, obviously, will go on top of the columns).

Pontoon W is only temporarily parked at its current position on the Lake, awaiting a move in mid-July to a Seattle drydock, where it will be repaired, according to WSDOT spokesperson, Debera Carlton Harrell. As has been extensively reported in the mainstream media, the pontoons are not precisely lakeworthy.  Repairs are on the agenda for many of them, since cracks have appeared in four of the first six pontoons deployed on the Lake, the result of a now-infamous design error. The repairs will take place for these imperfect pontoons during June and July.  For our readers who are not keeping up, the epic saga of the pontoons is detailed here.  WSDOT, meanwhile, has a handy graphic showing in detail how the pontoons will be repaired here.  For those who just want the overview:  the defective pontoons are going to be subjected to epoxy injections, "transverse post-tensioning" of their walls, and carbon-fiber wrapping of their "keel slabs."  The completed pontoons that have not already been moved to the Lake are being retrofitted to the new standard in Aberdeen, while the pontoons that have yet to be constructed for the new bridge will be built using a new, improved design.

Pontoon W

Pontoon W will ultimately be placed near the "Eastside Navigation Channel" of the new floating bridge.  Larger boats seeking to move between the North and South ends of Lake Washington, such as the bigger Argosy Cruise ships, will do so through this Eastside aperture (which is currently not open due to construction). The new bridge will have a 44-foot-high Westside navigation channel but no opening span in the middle, so it's the Eastside channel or nothing for the larger boats. Clearance there, according to Harrell, will be approximately 70 feet, equal to the I-90 floating bridge channel's height.

There will be plenty of time for Madison Park residents to get upset about future 520 floating bridge developments, should they choose to do so.  Right now, one of the Western piers of the bridge is under construction, not easily visible from Madison Park. Work is underway to the Northwest of Pontoon W, on the Laurelhurst side. Known as Pier 36, this into-the-lakebed structure will anchor the new bridge's Western high rise. As work continues on this and other parts of the now-funded West Approach to the new 520 bridge, the implications for Madison Park's views may become more obvious, at least to those on the Northside of the neighborhood.

This graphic shows the positioning of Pier 36 off the "coast" of Madison Park:

Meanwhile, just to round out our coverage, here's the latest on the progress of bridge construction on the Eastside:

Pier 1 under construction with Pier 2 in the background

Our Pontoon W is destined to be the very first pontoon drivers will encounter after passing over the Eastside piers on their route over the bridge Westbound.

[Upper photo by Madison Park Blogger.  All other photos courtesy of the Washington State Department of Transportation (WSDOT).]

1 comment:

  1. If you think the new 520 bridge will look anything like what is there now, you will be very disappointed. The new bridge will be more than twice as wide and the part on the water will be twice as high. It will be massive and a view blocker when you look north from Madison Park

    Jim Hagan


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