It's an odor residents who live near the worksite would rather live without. Two months after the spill, which happened on land that is part of the old Concord Naval Weapons Station, the awful smell returned.
"As soon as I walked outside, it was just like a wall of odor. It smells like rotten eggs," neighbor Julie Griffin said.
"I thought another leak, another problem, so of course you're worried, but if it's just a smell and it's going to be OK, then that's good news," neighbor David Fogel said.
The original spill happened November 8 from a pipeline owned by Conoco-Phillips. After the November leak, some work was done to patch the hole, but that was suspended during the holidays. Earlier this week, when work crews removed the tarps that covered the hole and the faulty pipe, the strong sulfur smell was back.
"They're still cleaning up the oil, the debris and the saturated soil there," Randy Sawyer with CoCo Environmental Health told ABC7. "But on the holidays, they tarped it and covered it, and then when they started working on it, they pulled it up and some of the odors could've accumulated underneath the tarps."
"They are at least letting us know something where initially, we never heard anything," said neighbor Brenda Grady.
A spokeswoman for Conoco-Phillips told ABC7, "The cleanup efforts associated with the leak in November are ongoing. Once in a while, we may hit a pocket of dirt that contains crude oil and produces an odor."
"It is unpleasant. It is causing discomfort in some of the residents apparently, and the Air District is certainly in contact with Conoco-Phillips, and they are aware of the nuisance that's ongoing," said Mark Ross with Bay Area Air Quality Management District, who is monitoring the odor.
At this point, there is no indication that the occasional sulfur smell will pose any health hazards. This work is expected to go on for several weeks.