Untreated sewage could be flowing into the Meramec River for days as officials wait for the water to recede from a flooded Fenton treatment plant.

Sewage has been flowing into the river since Monday night after floodwater disabled the Metropolitan St. Louis Sewer District’s Fenton plant, and the district spent much of Tuesday trying to save another plant in Valley Park.

MSD, which expects the Fenton plant to be completely inundated, has blocked off sewer mains to prevent the floodwater from backing up into area homes.

“We’re anticipating it is going to be a loss,” MSD Executive Director Brian Hoelscher told the Post-Dispatch in an interview. “Based on the current projections and our ability to react, we’re anticipating the entire plant is going to go underwater.”

Sean Hadley, an MSD spokesman, said water flooded the control room at the treatment plant around 8:20 p.m. Monday, causing a power outage. The plant’s lone operator was able to escape.

Ameren Missouri then cut off power to the plant for safety reasons. Sewage that would normally be treated at the plant is flowing untreated into the river.

The Fenton plant, which is located near South Old Highway 141 and Gravois Road, was designed to treat up to 6.75 million gallons per day. On Monday, it handled nearly 24 million gallons, or 1 million gallons an hour. Hoelscher said water appeared to be entering the system somewhere new, because flooding this summer didn’t lead to similar spikes.

Hoelscher said MSD has blocked off the mains leading to the Fenton plant and installed pumps to divert the untreated sewage. Those contingency measures appear to be working, he said.

“That allows us to maintain some level of service and more importantly prevents the river levels in the sewers from backing up into people’s basements,” Hoelscher said.

MSD isn’t instituting any service restrictions, but Hoelscher said if MSD customers around Fenton used less water, it would help.

“Obviously anything folks can do to reduce the amount of water they use will help the situation,” he said.

RESTART UNCERTAIN

It’s unclear whether the Fenton plant can be restarted anytime soon. The water levels will have to recede to allow MSD crews to re-enter the plant and assess the damage. Hadley, the MSD spokesman, said it could be several weeks before the plant is again fully operational, but the facility could again start to treat sewage on a limited basis before that.

“It’s going to be quite some time” before it’s fixed, he said.

The Meramec River is expected to crest upstream in Valley Park on Thursday at its highest level ever recorded: 43 feet. That would be more than 3 feet higher than its last record, set in 1982.

The Fenton plant, built in 1988, has never flooded before, Hoelscher said. The only other time an MSD treatment plant has flooded was during the Great Flood of 1993, when the Missouri River flooded its plant in Maryland Heights.

Missouri American Water produces about 10 percent of the water for its 1 million St. Louis County customers from a Meramec River facility downstream from the MSD plant. The plant serves South County customers.

Spokeswoman Ann Dettmer said the water company doesn’t expect flooding to affect its Meramec plant or the MSD release to impact water quality standards, even if the plant is down for an extended period.

“We’re watching this carefully, and we’re making adjustments as needed, but we don’t believe the MSD spill will pose any problems,” she said.

MSD’s Fenton plant is the smallest of the seven operated by the district, handling an average of 4.8 million gallons of sewage a day.

It’s not the first time in recent memory MSD has released a large volume of untreated sewage. Last year, the district released about 12.5 million gallons of untreated sewage into the Missouri River near Chesterfield after a main broke.

MSD has long talked about closing the Fenton plant. When it was planning to construct its Meramec treatment facility near the Mississippi River, it said it eventually planned to extend tunnels to take sewage from the Fenton plant.

That was almost 10 years ago. Hadley said MSD still plans to eventually close the Fenton plant and treat its wastewater elsewhere, though it could still be up to a decade before that happens. Tunnels would have to be extended to another plant.

ANOTHER PLANT IMPERILED

Meanwhile, MSD spent Tuesday working to save another treatment plant along the Meramec River. Crews piled several feet of sandbags to keep floodwater out of its Grand Glaize plant in Valley Park, and Hoelscher said MSD will continue to treat sewage at the plant even if it is accessible only by boat.

“We are going to do our best to keep it running,” Hoelscher said.

Workers continued adding sandbags outside the Grand Glaize plant on Wednesday morning, and the plant was still operating.

The good news is MSD doesn’t expect the floodwater to affect its other treatment plants, including its Meramec treatment plant located near that river’s confluence with the Mississippi River.

“The rest of the plants seem to be weathering the storm,” Hoelscher said.

If anyone comes into contact with floodwater or sewage in the Fenton area, they should thoroughly wash with soap and water.

Floodwater is generally contaminated, Hadley said, but people should avoid the floodwater around Fenton “now more than ever.”

Heather Navarro, director of the Missouri Coalition for the Environment, said the incident highlights the need to better plan for stormwater management. More pavement and impervious surfaces make urban areas prone to flooding.

The coalition was part of a lawsuit over MSD discharges into area waterways that led to a federal settlement and a $4.7 billion spending campaign to fix the problem over the coming decade.

While the flooding at the Fenton plant is unprecedented, it’s one of many sewage discharges that have been ongoing for years.

“The immediate concern with any incident like this is the bacteria that’s in the water and seeping into people’s basements,” Navarro said. “One incident by itself isn’t going to wipe out our ecosystems, but this happening over and over again just makes our waterways inaccessible.”

Kim Bell of the Post-Dispatch contributed to this report.