Sunday, March 11, 2012
Contract One - Nearly Done
S3 Tunnel Constructors Nears Completion of Contract 1
By the end of this month, S3 Tunnel Constructors (a joint venture of Skanska USA Civil, Schiavone Construction, and J.F. Shea Construction) is expected to substantially complete its work on Contract 1 of the project.
This contract, which was awarded on 3/20/2007, included construction of two tunnels under Second Avenue using a Tunnel Boring Machine (TBM) and other mining methods.
The contract also included the preparation work for tunneling, such as utility relocation and construction of the so-called TBM Launch Box from 92nd to 95th Streets. It also included construction of access shafts at 69th and 72nd Streets for the 72nd Street station cavern.
The photos that follow were taken on Friday, March 9th, inside the TBM Launch Box and the west tunnel.
MTA Capital Construction approved my request to shoot this set of underground images for the blog. My guide on the tour was a field engineer from Skanska.
near 92nd Street
Looking south from the stairs towards the entrances to the new tunnels.
On the right is the entrance to Tunnel No. 1 (the west tunnel). On the left is the entrance to Tunnel No. 2 (the east tunnel).
From this vantage point, you are standing on the floor of the TBM Launch Box looking south towards the tunnels.
The arch form situated on the right was, until recently, being used for concrete operations inside the tunnels. It will soon be used by another contractor to complete the concrete lining in the east tunnel.
The entrances to the tunnels stand in the distance.
Now for a moment let's take a step back in time...
Metropolitan Transportation Authority
How time flies. Here's a shot from 2010 that shows the tunnels before the TBM started its work.
The workers in this image are mining the two 40-foot starter tunnels.
Two months later -- the TBM is positioned in front on the west tunnel.
Over the next nine months, the machine mined a distance of 7,162 linear feet of the west tunnel under Second Avenue.
Metropolitan Transportation Authority
This image, from about a year ago, shows the TBM soon after it had started to mine the east tunnel. The cutterhead of the TBM is, in this shot, just a few hundred feet inside the tunnel.
On 9/22/11, the Second Avenue Subway TBM arrived at its final destination -- the north side of the lower level of the 63rd Street/Lexington Avenue station -- after mining a distance of 7,789 linear feet.
Now let's take a walk in the west tunnel to see how it looks today.
Just inside the entrance to the west tunnel - looking south
Ahead of me, my guide pauses while I work to capture the light and depth of the tunnel.
Here you can see the tunnel's new concrete lining, which is approximately one foot thick.
Two sections of the west tunnel have been waterproofed and lined with concrete thus far:
Section 1: from a point just south of 92nd Street to a point just north of 86th Street (the north end of the future 86th Street station cavern).
Section 2: from a point just south of 84th Street (the south end of the future 86th Street station cavern) to a point just north of 72nd Street (the north end of the 72nd Street station cavern).
I then turned around to take a shot of the view in the other direction -- back into the TBM Launch Box.
Now we are about 200 feet inside the tunnel -- the entrance appears more distant.
Note the tubes protruding from the tunnel walls.
Tubes like these are used to inject grout into the wall to fill any gaps that exist between the rock and the concrete tunnel lining.
Just north of 86th Street - looking south
We are now coming to the end of the first section of concrete lined tunnel. The yellow sealing material ahead is used to waterproof the tunnel wall.
(The standing water in the tunnel is coming from the section of tunnel ahead of us, which has not yet been waterproofed.)
This is a view of sealing material, or membrane, that was applied to the rock before the concrete lining was applied.
Just south of 86th Street - looking north
We have now entered a section of the west tunnel that has not been waterproofed or lined with concrete.
Why not, you might ask...?
Because this section of tunnel is inside the perimeter of the future 86th Street station cavern. This section of tunnel will be exposed when the 86th Street station cavern is excavated over the next year or so.
The water here is about 5" deep. We walked at a slower pace so as to reduce the chances of tripping and falling into the water.
(Observant viewers will wonder why the water is so calm if we have just walked through it. In actuality, this shot was taken on our way out of the tunnel.)
Near 83rd Street - looking south
We stand clear of the oncoming vehicle, which I'm told is called a man carrier. This machine is used to transport workers from the TBM Launch Box to a job site deep inside the tunnel.
Approx. 73rd Street - looking south
This is the end of our tunnel tour for today. The workers ahead of us are blasting out a cavern between the east and west tunnels, just north of the 72nd Street station cavern.
Eventually, a crossover track will be installed in this new cavern, just north of the station.
Now back to the TBM Launch Box...
A view of the arch forms that were used for the concrete lining inside the west tunnel.
Near 94th Street - looking straight up
A view of the concrete road decking above.
Various utility lines (e.g. water, gas, electric, etc.) can be seen suspended underneath the road decking. Eventually these lines will be re-buried once the 96th Street station is finished.
about 93rd Street - looking north
The north end of the TBM Launch Box, near 95th Street, can be seen here in the distance.
93rd Street - looking north
On the way up the stairs to the exit, I take one last image.
The large steel struts that support the east and west walls will be removed when the station concourse is built out by the next contractor.
btw. 96th and 97th streets, on the east side of 2nd Avenue
About five years ago, this simple image was taken on Second Avenue, before the TBM launch box was excavated.
If all goes well, the first trains will be running underneath Second Avenue in a little more than about four years.
The MTA has announced the date of the next Public Workshop for the Second Avenue Subway project.
Second Avenue Subway Public Workship
Scheduled for 3/20/2012
If you wish to attend this workshop, click on the link above to register.
Here's a listing of the recent additions
to the right-hand column of The Launch Box
Photo Tour Of Humongous Cavern Under Second Avenue
By Jake Dobkin
Gothamist.com - 3/8/12
"Residents: Subway Work Causing Cracks in Building"
By Linda Schmidt
Fox 5 News
Video (3:26) - 3/5/12
Posted by Ben Heckscher on 3/11/2012 10:00:00 PM