Residents in Concord are likely to smell sulfurous odors again Tuesday evening as a result of the rupture of a ConocoPhillips pipeline carrying crude oil.

Pipeline personnel discovered the release of crude oil in the southern end of the U.S. Army Military Ocean Terminal, formerly known as the Concord Naval Weapons Station, Contra Costa Health Services spokeswoman Kate Fowlie said.

Contra Costa Hazardous Materials staff responded to the ConocoPhillips pipeline leak at the terminal, Fowlie said.

"There is a small hole in the pipeline and they will depressurize the pipeline in order to fix it," Fowlie said.

Air readings show the leak from the 16-inch pipeline does not pose a significant health threat but is releasing a sulfurous odor. However, when the repair process begins and contaminated soil is moved, the odor may intensify, according to an advisory posted on the Contra Costa Health Services' website.

Steve Morioka, assistant director at Contra Costa Health Services, explained that at around 4:30 p.m. Monday the contaminated soil with sour crude oil containing heavy amounts of sulfur was dug up.

The rupture is located about 50 meters from the end of Holly Drive in eastern Concord, Morioka said.

"We discovered that the odors were strong, and may cause nausea, but they are well below levels that would present a health risk," Morioka said.

Morioka explained that after discovering the leak, contractors hired by ConocoPhillips covered the excavated soil with tarps to minimize the smell and brought vacuum trucks to remove the spilled oil.

"Crude oil contains different levels of sulfur and it may be impacting ground water. It is unlikely that it will affect drinking water wells," Morioka said.

A pit has been dug and is being expanded to do repairs to the "finger-sized hole," and workers have recovered 30 gallons of crude oil, Morioka said.

ConocoPhillips has hired contractors to fix the pipeline and Contra Costa Health Services will continue to monitor the clean-up process and ensure that the soil is tested, Morioka said.

Mark Hughes, manager of public relations at ConocoPhillips, was onsite this morning with ConocoPhillips personnel and contractors to repair the rupture.

Air monitoring has taken place and the soil surrounding the spill will be treated or disposed of, Hughes said.

Much of the crude oil that is pumped through the pipeline originates from the San Joaquin Valley and Central Valley, running hundreds of miles to the ConocoPhillips refinery in Rodeo. The pipeline is one of the multiple sources feeding into the Rodeo facility, Hughes said.

ConocoPhillips has not released the amount of crude oil that has leaked into the ground as a result of the rupture.