Ballast has been laid about half-way across from the Cambridge end, on the new permanent Boston-bound track. Ballast has been laid on the shoo-fly from the Cambridge end to about the first tower. Today, they're installing Jersey barriers to protect traffic from the new shoo-fly on the upstream side of the bridge -- progress now is only about 100 yards from the start of the track (which as you can see from the picture is not connected).
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Longfellow Bridge Repairs: Red Line to be Disrupted
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This morning they're laying ties for the new inbound shoo-fly, close to the point where the cut-in will be on the Cambridge side. As seen from Tower One.
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As of June 17 (Friday) the concrete roadbed for the permanent track at the extreme Boston end has not been started. This is the complicated portion of the project where the active tracks leaving Charles Station are over rebuildable bridge structure.
Looks to me as if, in order to avoid a Red Line shutdown extending into the work week, a technique other than poured in place concrete roadbed will be needed for this section of the track.
Rebuilding the big bridge arches does not have to be held up since temporary steel girders supporting the active tracks can be reconfigured repeatedly as needed. It is the portion of the structure just beneath the tracks that is complicated to build.
The permanent track appears to be laid in the same fashion as the shoo fly track. Ties are laid directly on the concrete roadbed, and then the rails and ballast added.
Looks to me as if, in order to avoid a Red Line shutdown extending into the work week, a technique other than poured in place concrete roadbed will be needed for this section of the track.
Rebuilding the big bridge arches does not have to be held up since temporary steel girders supporting the active tracks can be reconfigured repeatedly as needed. It is the portion of the structure just beneath the tracks that is complicated to build.
The permanent track appears to be laid in the same fashion as the shoo fly track. Ties are laid directly on the concrete roadbed, and then the rails and ballast added.
Build something. Anything.
The Red Line reservation over spans 2 and 3 will be reconstructed after the new permanent outbound track is complete. This phase of construction will take place mostly during nights and weekend shutdowns. I never saw anything about the Red Line reservation over span 1 so I'm not sure if that section of the bridge will be rehabilitated.
Unfortunately that extremely tall construction fence on both sides of the current reservation blocks nearly all onboard views of what they're doing on the other side. I've been trying to track progress, but it's frustrating to squint through holes in the fence on an in-motion train and try to piece together a full picture of what's going on. No railfan seats for this one. 
The Red Line will be suspended over the bridge for the next two weekends, for the cut-over.
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Saturday afternoon -- Cambridge end showing Boston bound track from portal connected to new shoo fly track.
Not many places on the ground where all four tracks over the bridge can be seen but here the stub ends of the "inner" tracks can be made out in the background.
Shuttle buses between Kendall and Park St. were running "bidirectional" over the single traffic lane on the bridge with persons on the ground directing them at each end of the bridge. (Five days prior)
Temporary timbers laid neatly in place outside Charles Station to support temporary Cambridge bound track which will become permanent Boston bound track.
Shoo fly track (temporary Boston bound track) will pass through area marked off by red hose.
Not many places on the ground where all four tracks over the bridge can be seen but here the stub ends of the "inner" tracks can be made out in the background.
Shuttle buses between Kendall and Park St. were running "bidirectional" over the single traffic lane on the bridge with persons on the ground directing them at each end of the bridge. (Five days prior)
Temporary timbers laid neatly in place outside Charles Station to support temporary Cambridge bound track which will become permanent Boston bound track.
Shoo fly track (temporary Boston bound track) will pass through area marked off by red hose.
Build something. Anything.
Today's view from Tower One. The train seen is on the new shoo-fly, inbound to Boston. Outbound trains are still running on the "old" shoo-fly track. So this week's service is reminiscent of outer/local inner/express service. Except the "express" tracks aren't connected at either end!
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Diverging Route is back in Tower One after a week's absence. In today's picture, we see a tie-eating machine chewing up the old outbound / temporary inbound track, with the two recently-opened tracks just above.
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This is your last chance to walk on the downstream side of the bridge to get a view of the construction. Effective Monday, August 29, pedestrians will be diverted to the upstream side of the bridge, per MassDOT. Here's the August update.
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It's been a while since I posted some pictures from Tower One in Cambridge.
The future permanent Alewife-bound trackway is being used as a service lane for vehicles and workers to access the parts of the bridge under construction. Currently, all of the over-water spans on the north side of the bridge have the deck removed, revealing the steel arches. One span, mid-bridge, is having the new deck's rebar installed.
The future permanent Alewife-bound trackway is being used as a service lane for vehicles and workers to access the parts of the bridge under construction. Currently, all of the over-water spans on the north side of the bridge have the deck removed, revealing the steel arches. One span, mid-bridge, is having the new deck's rebar installed.
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FWIW...the views from a train have been particularly outstanding ever since the tarp-covered chain-link fence came down. A little diminished now because they've lined all the steel arch supports with wood construction platforms. During winter before those temp planks went up you could see all the way down to the water through the deckless skeleton. One-of-a-kind view we've never had before and never will again.
Concrete progress. As seen from Tower One.
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Today's update from Tower One! Ties being delivered and installed on the permanent Cambridge-bound trackway.
September 30 - December 17
MassDOT will implement MBTA Red Line Diversions that replace trains with shuttle buses between Park Street and Kendall/MIT Stations, with a stop at Charles/MGH Station, on weekends beginning on Saturday, September 30, through Sunday, December 17. Red Line trains are currently scheduled to be in use for the Head of the Charles weekend (October 21-22).
These diversions will allow the contractor, White-Skanska-Consigli JV (WSC), to perform work required to replace the bridge structure supporting the Red Line tracks over Longfellow Bridge Spans 2 and 3 near the Charles/MGH Station. Red Line trains will resume service on Monday mornings. The replacement of the track may also require some speed restrictions in this area of the Red Line for the days immediately following each weekend.
Please visit the MBTA's service updates webpage and see the September 2017 Red Line Diversions and Bridge Closures Advisory for additional information.
The project includes replacing the MBTA Red Line tracks, and other work in close proximity to them. The work will take place on 25 weekends over the project duration, and requires replacing Red Line trains with buses. During the MBTA weekend diversions, the Longfellow Bridge will be closed to all motor vehicle travel, except shuttle buses. The bus route will carry passengers between Kendall/MIT Station and Park Street Station, with a stop at Charles/MGH Station. All shuttle bus stops are accessible for people with disabilities. All other motor vehicles, including passenger vehicles, trucks, and all other buses, will need to use one of two detour routes to reach Boston.
Emergency response, bicycle, and pedestrian access will be maintained across the bridge during these weekend diversions. Bicyclists, both inbound and outbound, and pedestrians will share the upstream sidewalk.
The Cambridge-bound detour remains in place during diversion weekends. Details on the route can be found on the Traffic Information page.
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Pedestrians & bicycles in both directions sharing one sidewalk. Nice.
