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Originally Posted by hat
Hey, yeah my concern is that the city will focus on the E/W corridor, and neglect the connection to the new SW Corridor, Orange line (and inevitable Powell line), which are equally important.
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Agreed. The one thing that gave me pause about the survey is that it only mentions the Red/Blue Lines. It's understandable, as this segment is the biggest bottleneck. However, Yellow/Green can only grow, not only for the reasons you mentioned but also if an extension to Vancouver becomes reality.
Quote:
Originally Posted by Nunya
Keep in mind if you are tunneling under existing buildings you have to consider the foundation depth and settlement implications. That route would push the stations very deep. For example it would run right under the Fox Tower which the bottom of the parking garage is 65' below grade. Then you have to go down even further for foundations and/or piles and whatever additional depth to mitigate any foundation settlement concerns. Unfortunately, PDX doesn't have bedrock near the surface like some other places (NYC) that makes tunneling beneath structures much more practical.
That would put any stations very deep and likely only accessible by elevators. Ideally they'd align the route beneath roads where possible and keep any corners below buildings with limited foundation depth to keep the stations closer to the surface so that they could also be served by escalators.
Also, any tunneling under private property presumably would need an easement (i.e. $$$) as well as potentially limit future development options for underground work and/or make future building over any subway more complex and expensive.
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Although the initial construction would be far more disruptive, it appears cut-and-cover might be the way to go (at least one exception I can think of: going under the I-405 trench). However, if the intention is to run the tunnel N/S under SW 5th/6th, that would require tearing up the Transit Mall (again!) and majorly impacting Yellow/Green Line service.