police-light-bar1.jpg12:15 PM (BCN): A cable failure in an underground vault that blew off a 300-pound manhole cover in San Francisco this morning did not cause any injuries or power outages, PG&E spokesman Brian Swanson said.

San Francisco Fire Department Lt. Mindy Talmadge said the incident was reported as an explosion in a manhole at Post Street and Grant Avenue just before 9:30 a.m.

Swanson said an electrical cable failure in an underground vault generated pressure that pushed the 300- to 350-pound manhole cover off the manhole.

PG&E has redundancy built into the electrical system in that area and was able to avoid power outages from the incident, Swanson said.

No injuries or property damage was reported, Talmadge said.

Traffic was initially diverted around the area, but as of about 11:45 a.m. pedestrian and vehicle traffic had returned to normal on Post Street. Grant Avenue, however, was still blocked between Post Street and Campton Place while crews continued to work to repair the cable, Swanson said.

Swanson said PG&E is in the process of installing new manhole covers in San Francisco that are designed to prevent events like this from happening in the future.

The new covers have a spring-loaded locking system that allows the cover to raise up and safely vent pressure from inside the vault but prevents the cover from coming off, Swanson said.

Swanson said the utility started replacing the manhole covers in 2010 and has so far replaced about 100 of the 1,000 covers they intend to replace.

10:23 AM: Authorities have shut down several streets in San Francisco this morning while they respond to an incident involving PG&E equipment, a San Francisco Fire Department dispatcher said.

According to KRON4, “multiple explosions” were heard at around 9:30 a.m. at Post Street and Grant Avenue.

A spliced electrical line appears to have caused an explosion that blew the cover off a manhole, San Francisco Fire Department spokeswoman Lt. Mindy Talmadge said.

According to KRON broadcast the manhole cover opened in what one PG&E official described as a “burp.”

There were no reports of fire or injuries as a result of the incident, the dispatcher said.

Talmadge said PG&E crews have confirmed that they had done some work on the affected electrical line, which appears to have failed. The area around the intersection has been closed off while crews repair the line. While power to those in the area has not been wiped out, the area is reportedly a “traffic nightmare.”

Want more news, sent to your inbox every day? Then how about subscribing to our email newsletter? Here’s why we think you should. Come on, give it a try.

the author

Eve Batey is the editor and publisher of the San Francisco Appeal. She used to be the San Francisco Chronicle's Deputy Managing Editor for Online, and started at the Chronicle as their blogging and interactive editor. Before that, she was a co-founding writer and the lead editor of SFist. She's been in the city since 1997, presently living in the Outer Sunset with her husband, cat, and dog. You can reach Eve at eve@sfappeal.com.

Please make sure your comment adheres to our comment policy. If it doesn't, it may be deleted. Repeat violations may cause us to revoke your commenting privileges. No one wants that!