Seattle, Washington: Sound Transit

General discussion of passenger rail proposals and systems not otherwise covered in the specific forums in this category, including high speed rail.

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Re: Seattle, Washington: Sound Transit

Postby lpetrich » Sat Apr 01, 2017 2:44 am

Northgate Link Extension | Sound Transit -- construction continues. Its construction cams show the extension's three stations: U District, Roosevelt, and Northgate, along with the Maple Leaf tunnel portal a little south of Northgate. U district and Roosevelt are being built in cut-and-cover fashion, with their walls and floors now being in place, though not much more. The Northgate station, however, will be elevated.

Lynnwood Link Extension | Sound Transit north of Northgate -- still in planning. It will closely follow I-5, and it will alternate between surface and elevated trackage.

Downtown Redmond Link Extension | Sound Transit east of Bellevue and Federal Way Link Extension | Sound Transit south of Sea-Tac are still in planning. The latter will alternate between surface and elevated along I-5.

Seattle Streetcar: Center City They've selected a route for it:
First Hill streetcar line - S. Jackson St. - 1st Ave. near the waterfront - Stewart St. - South Lake Union line

Seattle Streetcar: First Hill Streetcar: Broadway Extension north of First Hill for two stations. "Design of the project is currently on hold. (12/12/16)"

ETA: The end is near for Bertha: After nearly 2 miles in 4 years, tunnel machine about to break through | The Seattle Times Seattle's other big tunneling project is about to be completed.
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Re: Seattle, Washington: Sound Transit

Postby mtuandrew » Sat Apr 01, 2017 12:24 pm

Pontoon railroad bridges have been built before, in particular by the Milwaukee Road on the Mississippi. Nothing quite on this scale though, and I can't seem to find a combination road/rail pontoon bridge in the historical record.
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Re: Seattle, Washington: Sound Transit

Postby lpetrich » Tue Apr 04, 2017 2:18 am

Project update: East Link Extension, I-90 | Sound Transit
Crossing Lake Washington | Sound Transit
They had to build and test special track bridges for between the fixed and the floating parts of the I-90 bridge.

Lake Washington Floating Bridge - Wikipedia lists three bridges.

The first of them is the Lacey V. Murrow Memorial Bridge - Wikipedia, opened in 1940. It now carries the eastbound lanes of I-90.

The second of them, to the north of the first one, is the Homer M. Hadley Memorial Bridge - Wikipedia, opened in 1989. It carries the westbound lanes of I-90, and it has two reversible High-Occupancy-Vehicle lanes to the south of the main lanes. Those HOV lanes are where the light-rail tracks will be going.

There is a third one over Lake Washington, for state route 520. It's the world's longest and widest floating bridge.
Evergreen Point Floating Bridge - Wikipedia, opened in 1963.
Evergreen Point Floating Bridge (2016) - Wikipedia

About that other tunneling project, Alaskan Way Viaduct - Follow Bertha -- it's to break through on Tuesday, April 4.
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Re: Seattle, Washington: Sound Transit

Postby lpetrich » Thu Apr 06, 2017 3:19 am

Project update: Northgate Link Extension, March 2017 | Sound Transit -- shows support columns going up for the Northgate station.

I notice that the north and east extensions have very little street-level trackage, unlike the original line, with a long stretch in MLK Way.

In other tunneling news, Bertha broke through the end on April 4:
Daylight for TBM Bertha at ‏end of epic journey
Alaskan Way Vaduct - Follow Bertha
Alaskan Way Viaduct replacement tunnel - Wikipedia
Bertha (tunnel boring machine) - Wikipedia
Bertha's diameter: 57 ft / 17.4 m, weight: 6700 tons / 6100 mt

Digging for San Jose BART begins in two years - Silicon Valley Business Journal mentions a proposal for using a TBM almost as big as Bertha: a 45-ft tunnel where two tracks would run. The article's illustration shows two stacked tracks, though they might also be side-by-side.

However, they may use smaller TBM's and excavate twin single-track tunnels, as has been done for Seattle light rail.
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