Central Subway Construction Update 10/20/17

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. Workers smooth the surface of the western slurry wall of the Yerba Buena/Moscone station headhouse ahead of installing shotcrete and a vinyl waterproofing barrier. Central Subway | Project Advancement

October 20 through October 29, 2017 

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

A shallow trench is being excavated as part of station platform footing construction, exposing rebar from the tops of foundation piles between Freelon and Brannan on 4th. 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.

Water line and track work are underway on 4th between Bryant and King Streets, and night work is ongoing between 8:00 PM and 5:00 AM.  Some lane closures may also occur at night.  Regular day shift hours are from 7am to 4pm.  Workers are uncovering the tops of foundation piles as part of 4th and Brannan station platform work. Lengths of conduit for communication lines are being installed in trenches on the east side of 4th between Townsend and Brannan. Overview

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

Details

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 Welsh

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.

Workers prepare the outer slurry walls of the station headhouse near Clementina for installation of rebar, to construct smooth, finished walls. 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 and water supply infrastructure replacement work continues at 4th and Folsom streets, Monday through Friday, from 9 p.m. to 6 a.m. During these work hours southbound 4th Street will be reduced to one lane and eastbound Folsom Street will be reduced to two lanes.  The right hand turn lane will be affected.  Two through lanes are in place southbound 4th Street. Westbound traffic on Howard Street will be impacted.

Sewer replacement work continues at night at 4th and Howard streets until late October. 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.

Corrugated steel sheeting, concrete formwork, and rebar are installed as part of station platform construction inside the station box. A forklift operator works to maneuver a piece of temporary steel bracing being removed from inside the station headhouse. Overview

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

Details

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

What: Night work at Folsom and 4th
Time:  8pm - 5am
When: Monday to Friday
Where: Folsom Street west of the intersection at 4th, and at the 4th 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: Utility potholing at 4th and Howard
Time: 9pm - 5am
When: Monday to Friday
Where: 4th and Howard intersection

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

A welder cuts rebar to length inside the north concourse of the Union Square/Market Street Station, where formwork for a two-level interior structure is being built. 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.

Ellis may be closed between Powell and Stockton to vehicular traffic for utility and roadway restoration work from 9 pm to 5 am 7 days a week.  This work may impact sidewalk access on the north side of Market at Ellis.  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.  Station excavation and installation of structural steel bracing is ongoing under Stockton Street as well as on O'Farrell.

Carpenters build concrete formwork as part of terrace construction work at the north station entrance in Union Square. Teams of workers lift huge lengths of rebar from sorting areas to be installed as part of floor slab construction inside the north station concourse. Overview

• Utility work at the Ellis and Stockton intersection
• Utility work at the Geary and Stockton intersection
• Station excavation and installation of temporary bracing
• Union Square Garage plaza level concrete and structural installation
• Union Square Garage plaza temporary bracing installation
• Partial closure of Ellis between Powell and Stockton

Details

What: Partial closure of Ellis for roadway restoration work
Time: 7 am to 8 pm.
When: 7 days a week
Where: Ellis Street between Powell and Stockton

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
  • Ellis may be closed to vehicular traffic at night between 9 pm and 5 am 7 days a week for utility upgrade and roadway restoration work
  • Stockton Street between Ellis Street and Geary Street is closed to vehicular traffic
• Muni Impact
  • No scheduled impacts at this time.

Pieces of rebar are cut to length inside the top heading of the north platform cavern as part of wall and ceiling reinforcing, as a surveyor checks measurements for potential ground movement. Chinatown Station The construction of an underground 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.

As excavation has progressed toward the north egress shaft, sections of ventilation ducts no longer needed are removed. Crews have uncovered the reinforced shotcrete shell of the north egress shaft, which has already been excavated. Overview

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

Details

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 central.subway@sfmta.com 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.