Hydraulic oil spilled into the Ala Wai Canal on Thursday, according to Department of Health spokeswoman Janice Okubo.
Okubo says city crews were removing debris at Manoa Stream near the Palolo Junction when the hose in an excavator ruptured.
About 10 gallons of hydraulic oil leaked from the excavator. City crews recovered as much oil as they could, according to Okubo. But, some oil traveled down the stream to the Ala Wai Canal.
The health department says the remaining oil in the Ala Wai Canal appears to be dissipating.
The Department of Health hazard evaluation staff surveyed the scene after KITV called them, but they do not believe there are any health or hazard risks.
"The equipment is assigned to and operated by the Department of Facility Maintenance who is working with the State of Hawaii Department of Health and the City's Department of Environmental Services Storm Water Quality Branch to resolve any issues resulting from the inadvertent release," said Ross Sasamura, Director and Chief Engineer of the Department of Facility Maintenance.