15 June 2012 ~ 10 Comments

Construction Update: Launch box and headwall construction proceeding in SoMa, road restoration progressing in Union Square

Construction at the site of the tunnel launch box, shown here, ramped up this week. 

Construction to prepare for the Central Subway tunnel ramped up this week, and the new sidewalks on the west side of Stockton Street are almost completely restored. Here’s what to expect in the next three weeks as tunnel preparation continues and the Union Square utility relocation nears completion:

  • Tunnel Launch Box (4th Street between Bryant and Harrison streets): Next week, heavy construction equipment is planned to arrive at the site of the tunnel launch box, and the contractor expects to begin constructing below-ground walls around the perimeter of this major excavation site. At nearly 500 feet long, 50 feet wide and up to 40 feet deep, the launch box will take up most of the block. Next year two tunnel boring machines will start digging the Central Subway tunnels from the launch box, traveling north under 4th Street and then Stockton Street. Work hours at this site are 7 a.m. to 9 p.m., Monday through Friday. At least two lanes of traffic will remain open at all times.
  • Yerba Buena/Moscone Station Headwalls (4th Street between Folsom and Howard streets):  The tunneling contractor is installing below-ground walls, called headwalls, at the site of the future Yerba Buena/Moscone Station. The walls will cross 4th Street at two points on this block. To prepare to install the headwalls, utility relocation and guide wall construction will be underway. Work hours at this site are 7 a.m. to 9 p.m., Monday through Friday. At least two lanes of traffic will remain open at all times. For more information on traffic, pedestrian and Muni impacts at this site, check out this recent blog post.
  • Union Square Utility Relocation (on and around Stockton Street between Market and Post streets): With sidewalks being restored along Stockton Street and road restoration underway, utility relocation at the site of the future Union Square/Market Street Station is nearing completion. Work is scheduled seven days a week from 7 a.m. to 7 p.m., although night work may be necessary.

Complete, current three-week construction schedules are available online for Union Square utility relocation work and for the tunnel contract. We also post construction, auto detour and Muni impact information on our project Google Map.

Muni Service Impacts

Current Muni service impacts are described below. As construction begins at additional locations, additional Muni routes may be impacted.

  • The 30 Stockton and 45 Union/Stockton began re-routing in January around major construction sites in Union Square and SoMa. These reroutes will continue throughout the duration of Central Subway construction.
  • The 38/38L Geary and the 8X/8AX/8BX Bayshore Express may experience delays.

Traffic and Pedestrian Impacts


  • At both currently active construction sites, at least two lanes on 4th Street will be open to traffic at all times.
  • All I-80 on- and off-ramps will remain open during the day, but brief nighttime ramp closures may be required.
  • Traffic delays are anticipated. Motorists are encouraged to use the onramp at Harrison and 7th streets as an alternative to access westbound I-80 while launch box construction is in progress. Those traveling to the peninsula may prefer to access the I-280 via 6th Street or Highway 101 via 10th Street.
  • Access to Clementina Street between 4th and 5th streets may be restricted at times, but the contractor will facilitate access for deliveries.
  • Sidewalks may be impacted.
  • Electronic messaging boards will be in place and parking control officers and flaggers will monitor and facilitate the flow of traffic as appropriate.

Union Square:

  • Currently, traffic on Stockton Street between Market and Post streets is limited to Muni buses, taxis, tour buses, emergency vehicles and delivery trucks only.
  • Two traffic detour options are in place to allow for better access to the Union Square area and to aid the flow of traffic:


We appreciate your continued patience while construction is in progress.

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10 Responses to “Construction Update: Launch box and headwall construction proceeding in SoMa, road restoration progressing in Union Square”

  1. mikesonn 18 June 2012 at 8:51 am Permalink

    I don’t see any mention of the work in North Beach, is there still a possibility this work will begin within 3 weeks?

  2. Central Subway 19 June 2012 at 5:47 pm Permalink

    @mikesonn:disqus  – Thanks for your question. Ongoing communications and outreach are underway to determine a construction schedule to relocate utilities in North Beach.  We will provide additional information about North Beach construction soon.

  3. John Cwikla 23 June 2012 at 11:43 am Permalink

    Can you tell me what’s being built on 5th and Bryant by the onramp?

    • CentralSubway 25 June 2012 at 1:10 pm Permalink

      Hi John – The construction by the 5th and Harrison onramp is not Central Subway-related, although we do have a staging area for tunnel contract work nearby (beneath the I-80 overpass).

      You may want to check with the Department of Public Works about the construction by the onramp. Thanks for the question!

  4. Canfield 19 March 2013 at 3:58 pm Permalink

    I have a sound sensitive business on Bryant at 5th. We are completely out of business this week (3/18/13) due to the digging. Please provide your schedule for this site and let me know what to expect over the life of this project. We are a small business. We cannot afford this downtime. Thank you.

  5. Jacob Bernard 19 April 2013 at 11:32 am Permalink

    Such kind of situations are very tough for people specially for business owners, closing of major roads can be very troublesome.

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