A grease trap malfunction located outside of Heirloom, a restaurant in northeast Fresno, caused a spill that spread across the parking lot Tuesday evening, according to Fresno Fire officials.

The incident occurred at the restaurant on Friant Road between Audubon Drive and Fresno Street, leading to an overflow of grease bubbling from the street. Firefighters responded around 8 p.m., blocking off parking stalls and trapping some vehicles temporarily.

Patrons initially believed the foul odor was due to sewage, but tests conducted by hazardous materials teams and environmental health officials confirmed it was grease, not raw sewage, said Sean Johnson, Fresno Fire battalion chief. The restaurant remained open despite the situation outside.

“There is a malfunction in their grease retention system, which resulted in a venting out into the street,” Johnson said.

Johnson said the failure of the retention system clogged the vent, causing it to over pressurize and spew grease into the parking lot.

The spill, though non-flammable, posed a slip hazard. Firefighters used gravel to absorb the oily residue and worked with the restaurant to clean up the area. A plumbing company was called to repair the grease trap system.

How Can Restaurants Prevent This?

Johnson explained that large commercial kitchens can experience grease trap malfunctions from time to time and emphasized the importance of regular maintenance.

“If you’re a restaurant owner, definitely make sure those grease traps are cleaned out, and especially for fire protection — the hood systems, the vent systems — it’s all clean to prevent this kind of situation,” he said.

Johnson recommended that local businesses conduct annual inspections and preventative maintenance to avoid similar issues.

He noted that fire inspectors also check grease buildup as part of fire safety evaluations.