Here’s what you can expect to see as construction progresses along the Central Subway alignment.
4th and Brannan Station
Construction for the 4th and Brannan Station is progressing, and activity along the surface portion of the alignment will continue on 4th Street from Bryant to King. Utility work is expected to continue through 2016. The crew is working on a high pressure auxiliary water supply system on 4th between Brannan and Townsend. Two sewer lines will be installed on the east side of 4th and another will be reconstructed between Townsend and King.
To power the trains, an Overhead Catenary System (OCS) needs to be installed between Harrison Street and King Street. Installation of the OCS has three components: foundations, poles and wires. The foundations currently being installed are the bases for the poles. Once these are constructed, the poles will be mounted later in the year. The last step is the connection of electrical wires. These wires provide power to Muni’s light rail vehicles. The OCS work is expected to be completed in early 2017.
In the fourth quarter, crews are expected to begin trackwork and infrastructure installation in the tunnel.
Yerba Buena|Moscone Station
At Yerba Buena|Moscone, crews will be focusing on building the interior levels of the station box. The contractor will continue to excavate downward inside the station box from the mezzanine level to the concourse level. In the headhouse, crews will complete excavation and construct internal walls upward through the concourse, mezzanine and surface levels.
Most of the construction activity for the station is conducted underground. The mezzanine is under construction and is expected to be completed by June. Installation of steel supports is underway in the station box and the headhouse. Construction of the station box walls and flooring is anticipated to begin in the fourth quarter.
By December, it is expected that all four travel lanes will be open on 4th Street between Howard Street and Folsom.
Union Square|Market Street Station
For the Union Square|Market Street site, excavation is ongoing. Beneath Stockton Street between Geary and O’Farrell, excavation of the station box progresses. Excavation is being performed on O’Farrell Street in order to install the final roof deck panels.
The demolition and restoration of the southeast corner of the Union Square Garage is underway. This area will become the north station entrance at Geary and Stockton. A portion of the garage wall will be demolished which will connect the entrance with the north concourse of the station.
Jet and compensation grouting are being performed on Stockton Street from Maiden Lane to Ellis Street. Jet grouting limits ground water from seeping into the station. Compensation grouting provides stability to the foundations of surrounding structures of the station.
Utility work continues at Geary Street and Maiden Lane.
In Chinatown, crews are excavating the north access shaft beneath Stockton Street between Washington and Jackson. This shaft will become an emergency exit stairwell for the station. Temporary steel supports have been installed in the headhouse to prepare for the next phase of excavation.
At the arched entrance way, crews are injecting grout to harden the soil where excavation will begin. This work reinforces the structure of the station. After the entrance way is excavated, “shotcrete,” a fibrous concrete material, will be sprayed onto the walls for stability. Excavation, waterproofing and rebar installation will continue through 2016.