[Update: Despite grim early assessments, Alameda announced Tuesday that work was complete and all lanes of the tube would reopen, and Tuesday’s commute passed without incident.
As a Curbed SF reader points out, the commute into Alameda was never affected, although the non-specificity of some notices made this unclear—not that it matters now.]
A Saturday sinkhole on the Oakland side of the Posey Tube (which carries traffic beneath the estuary and connects Oakland to Alameda) has created gridlock for commuters that could last all week, even as Oakland Public Works labors to fix the fault and get both lanes running again.
The city of Alameda reported the problem Saturday afternoon and warned drivers to “expect significant delays into next week” as the sinkhole keeps at least one lane in the tunnel closed at all times. Oakland blames the problem on a faulty storm drain.
Alameda’s emergency alerts page warned morning commuters Sunday night that the entire tube will be closed most of Monday:
The City of Oakland is in the process of fixing the sinkhole on the Oakland side of Posey Tube, which could be done early in the week if weather permits. On Monday, March 19th, one of the lanes in the tube will be closed exiting Alameda until 10am.
Then after 10am, BOTH LANES will be closed until midnight, which will have a significant impact on traffic. If you typically commute off island, please consider [...] alternatives for Monday, March 19, and until the sinkhole is fixed.
Earlier announcements via social media suggested that repairs could take all week.
Sinkholes form when water flowing underground carves a large pocket that the land above eventually falls into in a sudden, violent motion.
Posey Tube backed up on Webster Street all the way to Willie Stargell Avenue in Alameda. Sinkhole on exit side in Oakland caused 1 lane to be closed. Both lanes from Alameda to Oakland scheduled to close from 10am-midnight. pic.twitter.com/kqbcY5oAu6— Matt Keller (@MattKellerABC7) March 19, 2018
Natural streams can spend years or even decades slowly wearing away ground materials to create a sinkhole; however, in the case of urban sinkholes, it’s usually a case of burst pipes or other faulty infrastructure flooding an underground space in a relatively short period.
“A broken sewer line can create an hourglass effect, with soil slowly falling into it and being washed away,” Public Utilities Commission spokesperson Tyrone Jue said in 2015, commenting on a sinkhole that interrupted the J-Church Muni line. Jue added that “dirt has to stay really compacted to support the street’s weight.”
On Saturday city official warned that Posey Tube repairs could last all week, although as of late Sunday there seems to be optimism that the work could wrap up a few days sooner if the weather holds. The current forecast calls for rain beginning Tuesday.