The operation is the first cleanup effort since Orange County's anti-encampment ordinance went into effect last month, which allows the county to arrest and fine people camping on county property.
According to Supervisor Katrina Foley, county teams previously conducted initial outreach to offer individuals living in the Santa Ana River Marsh access to shelter, housing, treatment, and supportive services.
"When conditions pose fire risks, threaten sensitive habitat, or endanger the community, we must act," she said in a statement.
The county said the U.S. Army Corps of Engineers posted notices, letting people know that they may be cited for a first offense, and arrested for multiple offenses, pursuant to federal regulations governing the property.
"We've given them prior notice that they need to vacate the area and any remains that are in the habitat area, we are currently cleaning up," said Nicolas Figueroa, a park ranger with the Army Corps.
Those warnings apparently worked.
No one was found living in the area Wednesday, but crews found plenty of trash - enough to fill multiple trucks.
"This is our nature preserve. We're trying to protect this area," said Foley. "We also know that last summer, this park, because people were camping in here, lighting fires, this park caught on fire."
"We have to make sure that people understand this is not appropriate to be out here," she added. "It's not safe."
The county's Office of Care Coordination was also there on Wednesday, ready to offer help.
"We care about people," said Foley. "Orange County cares. We want to help people, but we cannot just continue to turn away when we see an encampment forming."