The protesters are rallying against a plan by WesPac Energy Group to modernize and reactivate an old PG&E oil storage and transfer terminal at 696 West 10th Street near downtown Pittsburg.
The City Council is set to vote on the project's environmental impact report in the coming months.
As part of the project, trains, ships and pipeline would bring oil to the terminal, where it would be stored in tanks, according to WesPac.
Crude oil is a complex mixture including toxic chemicals that have been shown to cause cancer, according to the Centers for Disease Control and Prevention.
A statement on WesPac's website notes that the new storage facility and transfer process will use the most up-to-date technology as well as operators and automatic control systems and will be monitored for safety 24 hours a day.
But protesters say the project will expose residents to the potential danger of crude oil leak or explosion. In addition, opponents say emissions from increased rail and ship traffic will overburden a population that already suffers from high rates of asthma and cancer stemming from industrial pollution.
"This is a real David and Goliath fight," said Rev. Greg Osorio, an organizer of Saturday's march. "We need to be righteously angry."
Another organizer, Lyana Monterrey, said residents should be aware of the project's implications.
"Our air quality will go south, our property values will plummet. If there's an accident it could wipe out whole neighborhoods...We must stop WesPac now."
Protesters will march at 1 p.m. from Mariner Park at Herb White Way and Eighth Street to City Hall at 65 Civic Ave.