More than 500,000 gallons of partially treated wastewater were accidentally released late last month from a Gwinnett County water treatment facility into a creek that feeds the Chattahoochee River.

The spill occurred between 10 p.m. Oct. 24 and 1 a.m. Oct. 25 at the F. Wayne Hill Water Treatment Plant in Buford. The water was discharged into a tributary of Ivy Creek, which flows to Suwanee Creek then the Chattahoochee.

The spill was caused by a failed sensor in a tank of partially treated sewage, according to a report to the state’s Environmental Protection Division. The tank overflowed into a storm sewer that led to a detention basin that overflowed.

When the spill was discovered, the partially treated sewage was moved to a working storage tank. Some of what spilled was captured in a detention pond.

The Gwinnett County Department of Water Resources said no significant environmental issues were found, including fish kills.

The department estimated 592,000 gallons entered the creek. The faulty sensor was repaired and employees will visually check levels until an additional sensor can be added.