This post has been updated.

More than 100 million gallons of sewage have been diverted straight into the Ohio River, following an electrical fire and power outage Wednesday night at the Morris Forman treatment plant, in what an official said is one of the largest overflows the city has had in the past decade.

The mishap occurred Wednesday night when a fire at Morris Forman in Louisville’s Rubbertown neighborhood caused an eight-hour power outage. Power was restored by Thursday morning, but sewage continues to seep into the waterway.

MSD Collection System Director Dennis Thomasson said it could take three days to get the plant back to where it’s fully operational, and the sewage could keep on flowing for another day or more.

“I’m hoping in 24 to 36 hours that we should be looking at stopping the overflows,” he said. “It’s going to be a progressive process of bringing the plant online, and we can’t just bring it back at once. It’s a slow process.”

Meanwhile, he said combined sewer systems upstream are also overflowing, because Morris Forman can’t fully treat the sewage. The preliminary estimate is 100 million gallons, but he said the final number could definitely be greater than that.

“100 million gallons is a drop in the bucket in the Ohio River right now,” Thomasson said. “But we don’t look at it from that perspective. Our focus is we don’t want any overflow, obviously, and we’re working towards that.”

Thomasson said there are forensic investigators on site working to determine the cause of the electrical fire, but preliminary evidence suggests a lightning strike could be the cause. The Environmental Protection Agency could fine MSD for the event, but Thomasson said if a force outside MSD’s control–like a lightning strike–ends up being the cause, the agency could declare it a “force majeure” and ask for the fine to be waived.

This latest incident comes on the heels of a tough few weeks for Louisville-area waterways and sewage treatment plants.

Because stormwater and sewage goes into the same system inside the old city limits, all of the rain the region has caused regular sewer system overflows into the Ohio River and its tributaries. In addition, Louisville Metropolitan Sewer District has sustained several infrastructure failures, causing unauthorized discharges even when there wasn’t any rain.

The other recent incidents also resulted in thousands of gallons of sewage streaming into the river.

Just last week, the failure of a 10-inch sanitary sewer deposited more than 1,000 gallons of sewage into the South Fork of Beargrass Creek in Louisville.

On March 12, another structural failure sent more than 50,000 gallons into the Pope Lick Tributary of Floyds Fork in east Louisville.

MSD is under a federal consent decree to reduce the number of sewer overflows. The agency is spending more than $850 million on the project, which includes fixing aging infrastructure and adding green infrastructure (like rain gardens and green roofs) to absorb stormwater.

