Green Line Extension to Medford & Union Sq

Bridge spans being installed over Washington st. today
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About time! Who thinks they are going to hit the may 20th underpass reopening goal? That's 11 days. A lot of work to do still
 
Viaduct progress along McGrath/O'Brien Highway.
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Union Square Branch viaduct. The fork is the lead to the maintenance facility. That's going to be one high bike path.

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ceo said:
Union Square Branch viaduct. The fork is the lead to the maintenance facility. That's going to be one high bike path.
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I've been wondering what the hell that was.. Thanks
 
Yeah...one of the reasons the Community Path design east of Washington wasn't locked down until very late in the game. It's STEEP walking on the viaduct, and until the Great Fiscal Reboot they thought that extra berth of steel & concrete was a frill they'd have to trim to save money. Ultimately the views are going to be way more spectacular than the climb is a workout when all is said and done, but this is the nerve center of the GLX universe right here so the limited insertion angles send the stacking way skyward.
 
I don't understand why they build these berms in order to install the retaining wall and sound barrier pilings. Can't they drill the holes and place the pilings from ground level?
 
ceo said:
I don't understand why they build these berms in order to install the retaining wall and sound barrier pilings. Can't they drill the holes and place the pilings from ground level?
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Umpteen different possible reasons, but two theories for that particular spot based on eyeballing the picture. . .

1) Ground isn't perma-packed yet, and that was a quick-and-dirty grading job around the wall for staging. Which sorta looks like is the case here in squinting between the fence chain links. Until the utility conduits are trenched and laid next to the completed wall pour they aren't ready to do final packing for the roadbed. So the metal berms keep the soil from shifting and risking the edge of the hard-packed Fitchburg roadbed shifting with it (esp. when waterlogged to 'Jell-O'-like consistency, like so much of the soil has been throughout this interminably wet not-a-Spring).

2) Keep the bucket loaders from swinging out into the Fitchburg Line clearance envelope by making them liable to physically hit something on the backswing. Which may explain why there's a tall supporting I-beam driven behind the metal berm at about 50 ft. intervals. Seems like a conspicuous spacing choice for avg. bucket loader 'wingspan'.


And they would be doing this on the Fitchburg ROW where they would not be doing this on the Lowell ROW because the defining difference between the two is big embankment cut vs. all at same ground-level.
 
This is on the Lowell Line (the previous set of photos). They build this temporary embankment up almost the level of the top of the retaining wall, then drill shafts and install the pilings through it, then clear it away. They did this behind the DPW and along the high school site as well. Only think I can think of is that it serves to brace the pilings in place while the concrete foundation cures.
 
The drill rigs are designed to drill below the operator cab, and they need a considerable area accommodate their swing.
 
ceo said:
This is on the Lowell Line (the previous set of photos). They build this temporary embankment up almost the level of the top of the retaining wall, then drill shafts and install the pilings through it, then clear it away. They did this behind the DPW and along the high school site as well. Only think I can think of is that it serves to brace the pilings in place while the concrete foundation cures.
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RandomWalk said:
The drill rigs are designed to drill below the operator cab, and they need a considerable area accommodate their swing.
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Also they need a level platform to sit on. Most of the drilled shafts on the southwest side of the corridor are getting installed through what is an existing slope. Imagine a right triangle - and trying to drill straight down while you're perched on its hypotenuse at a 45 degree angle.
 
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