A portion of southbound Interstate 280 in San Francisco will be closed through the end of Memorial Day as Caltrans replaces one of four freeway hinges needing an upgrade to meet modern seismic standards.
While the 50-year-old hinges have been previously strengthened to prevent collapse in the event of an earthquake, Caltrans determined upon inspection that they should be replaced, said agency spokesman Steven Williams.
All lanes of southbound I-280 from the downtown on-ramps at King and Sixth streets to the on-ramp at Pennsylvania Avenue will be closed through 5 a.m. Tuesday as crews demolish a fairly sizable portion of concrete to reach the hinge, replace it and refill the concrete.
Northbound I-280 will be closed July 4 and Labor Day weekends for the same work on three other hinge sections. Caltrans had considered the option of closing a lane of traffic to reduce capacity on the freeway while doing the work, but that would have caused a 7-mile backup, Williams said.
"In other words, if you're trying to get into San Francisco, you'd be backed up to Candlestick Park basically to get to AT&T Park," he said. "You'd have a backup of a little over an hour, so a lot went into this decision."
The hinges allow each section of the freeway deck to move independently in a seismic event. Traffic control officers with Caltrans will be out on the streets to patrol flow, and the San Francisco Municipal Transportation Agency will also provide officers from 8 a.m. to 8 p.m.
"We'll do everything we can to monitor traffic and to help keep it moving as much as possible," SFMTA spokesman Paul Rose said.
U.S. Highway 101 is expected to be busy as a result of the holiday weekend work on I-280.
"It will absorb the lion's share of traffic," Williams said. "But we're encouraging people to use public transportation."