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Central Subway Construction Update 3/9/18

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Thank you for your interest in the Central Subway Project, which is a significant project in the history of San Francisco's public transportation network. This project is the first underground line to link the north and south corridors of the city, and will provide a direct connection to major retail, sporting and cultural venues while efficiently transporting people to jobs, educational opportunities and other amenities throughout San Francisco.

This is an exciting time as the San Francisco Municipal Transportation Agency's | Central Subway team works to construct a vital transportation link that, when open in 2019, will improve connectivity for the city.
Escalators and corrugated steel for stairs are being installed at the south end of the Yerba Buena/Moscone Station box under 4th Street at Folsom. Central Subway | Project Advancement

March 9 through March 18, 2018

This notice provides a construction update and a look ahead for what to expect in the areas where we are building four new stations along the alignment. You’ll find information about work activities, traffic and transportation impacts taking place over the next two weeks at SoMa, Yerba Buena/Moscone, Union Square and Chinatown.

Construction schedules, bus routes, and stop locations are subject to change due to unforeseen conditions. Signs will be posted at affected stops to advise of service changes.

Our thanks go out to the businesses, residents, shoppers, commuters, and all those who are touched by the Project, for their continued engagement as we work to extend the city's public transportation system.

The Central Subway Team

Workers continue to build the rebar cage for the 4th and Brannan surface platform station. Surface Station, Trackwork and Systems Work along 4th Street between Bryant Street and King Street includes construction of a surface station between Bryant Street and Brannan Street. The construction team is upgrading utilities and trackwork on 4th Street between the tunnel portal at Bryant Street and the connection with the existing light rail system at King Street.

Construction of the 4th and Brannan surface station platform is ongoing.  Water line replacement work is underway on 4th Street at Brannan, and night work is ongoing between 8:00 PM and 5:00 AM.  Track installation work is ongoing between Brannan and King.  Some lane closures may also occur at night.  Regular day shift hours are from 7am to 4pm.  Sections of tunnel walkway continue to be constructed moving northward up both tunnels, as seen inside the southbound tunnel. Initial concrete formwork and continued rebar cage installation work continue at the 4th and Brannan Station site. Overview

  • Utility upgrade and relocation
  • Night work on 4th between King and Bryant
  • Street and sidewalk restoration


What: Night utility work on 4th between King and Bryant
Time: 8 p.m. - 5:00 a.m.
When: Monday to Saturday
Where: 4th Street between King and Bryant
What: Utility installation and street restoration work

What: Street and sidewalk restoration
Time: 7 a.m. - 5:30 p.m.
When: Monday to Saturday
Where: 4th Street between King and Bryant

What to expect

  • Work may involve saw-cutting, potholing and jack-hammering on the roadway and sidewalk
  • Sidewalk access may be limited
  • Access will remain open for pedestrians and businesses 
  • Parking and Traffic Impact
    • Partial lane closures on 4th Street between Townsend and King streets.
    • Parking will be unavailable in the work area on both sides of 4th Street.
    • Two lanes of traffic open on 4th Street, one on the east side and one on the west.
    • Traffic impacts are in effect 24 hours a day.
  • Muni Impact
    • Bus stops for the 47 bus inbound have been relocated to 4th and Bryant and 4th and Townsend.

A massive scaffolding structure is being built inside the Yerba Buena/Moscone Station headhouse to prepare for construction of the permanent roof deck. Yerba Buena | Moscone Station

4th Street from Howard to Folsom

Work along 4th Street between Howard Street and Folsom Street consists of construction of the underground Yerba Buena | Moscone Station. The cut and cover method involves construction of a box frame structure within a trench excavation that is subsequently backfilled.

Sewer replacement work continues at night at 4th and Howard streets until Thanksgiving. Work hours are 8 p.m. to 5 a.m.  The current traffic configuration from north of the station to Howard Street will remain, but may change in the coming weeks. Two through lanes are in place southbound 4th Street. Westbound traffic on Howard Street will be impacted.

Interior walls and other structural elements continue to be finished inside the headhouse and station box. Elements of the two station platform elevators have begun to be installed at the center of the station platform. Overview

  • Sewer replacement work at 4th and Howard
  • Installation of headhouse and station interior elements
  • Roadway and sidewalk restoration on 4th south of Howard


What: Sewer replacement work
Time: 7am - 3pm
When: Monday to Friday
Where: 4th and Howard Street intersection.

What: Installation of headhouse and station interior elements
Time:  7am - 7pm
When: Monday to Friday
Where: 4th Street between Howard Street and Folsom Street

What: Roadway restoration on the west side of 4th Street south of Howard
Time:  7am - 4pm
When: Monday to Friday
Where: 4th Street between Howard Street and Folsom Street

What: Curb installation work
Time: 7am - 7pm
When: Monday to Saturday
Where: Clementina between 4th and 5th What to expect

  • Clementina Street is closed for traffic and pedestrians through to 4th Street
  • The sidewalk on the west side of 4th Street is closed south of Howard
  • Parking and Traffic Impact
    • Two lanes of traffic open on the east side of 4th Street, may be reduced to one lane at night between 9 pm and 5 am Monday through Friday.
  • Muni Impact
    • No scheduled impacts at this time

    Huge concrete forms can be seen being built at the south headwall or end wall of the Union Square/Market Street Station. Union Square | Market Street Station

    The construction of an underground Union Square|Market Street Station uses the cut and cover method known as a "top-down" or "bottom-up" approach and involves construction of a box frame structure within a trench excavation that is subsequently backfilled. Some work continues at night along Stockton Street between Ellis Street and Post Street.

    Workers have begun to disassemble the 2017 Winter Walk.  One lane on the south side of Ellis Street is open at all times for eastbound traffic.  Parking garage access is open on north side of Ellis Street. Street restoration work is continuing north of the intersection of Stockton and Market streets.  The installation of waterproofing, structural steel, and concrete at the southeast corner of the Union Square Garage continues.  There will be a continued presence of vehicles and equipment as work at this location continues.  Installation of internal structural elements and utilities is ongoing under Stockton Street as well as the northeast corner of Stockton and O'Farrell.

    Trenches for utilities are being dug along Stockton between O'Farrell and Ellis.  This stretch of Stockton is slated to be reopened first. Finished reinforced concrete interior walls continue to be built in the upper floors of the station box. Overview

    • Utility work at the Ellis and Stockton intersection
    • Utility work at the Geary and Stockton intersection
    • Installation of internal structural elements and temporary bracing
    • Union Square Garage plaza level concrete and structural installation
    • Union Square Garage plaza temporary bracing installation


    For all activities, construction hours may be 24 hours a day, Monday to Saturday, Sunday work may be required What to expect

    • Sidewalk access may be limited at times
    • Parking and Traffic Impact
      • Stockton Street between Ellis Street and Geary Street is closed to vehicular traffic
    • Muni Impact
      • No scheduled impacts at this time.

    Excavation of the Chinatown Station platform cavern and track crossover cavern has been completed, and workers are now smoothing walls for waterproofing sheeting. Chinatown Station The construction of Chinatown Station uses the sequential excavation method (SEM) along Washington Street and Stockton Street. The SEM provides a high degree of flexibility during construction and makes it possible to control virtually all kinds of ground conditions, thereby greatly reducing the risks of construction. This method of tunnel construction is used worldwide for small to large openings in a variety of ground types ranging from rock to soil.

    Sprayed concrete (shotcrete) and other supporting elements are applied and installed promptly after exposing ground, which provides a safe and stable opening.

    Current activities include excavation of the north and south platform caverns.  A pedestrian walkway is open on the north side of Washington connecting Trenton and Stockton.

    Some waterproofing membrane has already begun to be installed, seen here inside the northern portion of the platform cavern. An initial foundation slab or "rat slab" has been poured at the south end of the station headhouse, ahead of rebar cage work there. Overview

    • Excavation of station headhouse
    • Excavation of the north and south platform caverns


    What: Station site excavation
    Time: 24 hours
    When: Monday to Saturday
    Where: Stockton Street and Washington Street What to expect

    • Sidewalk access may be limited at times
    • Parking and Traffic Impact
      • No parking on both sides of Stockton Street between Washington Street and Jackson Street
      • One lane of traffic on both sides of Stockton Street between Washington Street and Jackson Street
      • Washington Street:
        • remains closed between Stockton Street and Trenton Street, except to pedestrians
        • is converted into a two-way street between Powell Street and the construction zone
    • Muni Impact
      • No scheduled impacts at this time.

    Connecting People. Connecting Communities.

    Contact Us: If you have questions about construction or the Central Subway Project you can email us at or leave a message at (415) 701-4371.

    For More Information: The Central Subway team posts frequent project updates on a variety of social media outlets. To find out more about the project and construction progress, follow us on Facebook, Twitter, or Flickr.

    Construction schedules are subject to change.