Wastewater infrastructure along the Mississippi River took a beating during a 100-year flood event in December 2015. Learn about the recovery process and what the Metropolitan St. Louis Sewer District learned from the event.
The Metropolitan St. Louis Sewer District plans to have its flood-damaged Fenton Wastewater Treatment Plant restored to full treatment capability by April after it was damaged by floods in late December. For several weeks, the plant discharged 5 million gallons of raw sewage every day into the Meramec River.
MSD suffered about $25 million in damages to two wastewater treatment plants and the collections system during record rains from Dec. 28-30. Across the region, anywhere from 6 to 12 inches of rain fell, causing a 500-year flood event that swelled the Mississippi River to historic levels and pushed the Meramec River 4 feet above the previous record.
The Fenton plant is situated along the Meramec in southwestern St. Louis, surrounded by a 6-foot levy designed for a 500-year flood. The Grand Glaize Wastewater Treatment Plant, located several miles upstream, is outside the 100-year floodplain but was also damaged and put out of service for several days.
The weather system eventually caused flooding across 13 states, killing at least 25 people. It spawned 28 confirmed tornadoes that killed 23 more. It also brought winter storms from Texas to Wisconsin and then eastward into New England, causing or contributing to about 20 more deaths.
The Fenton plant experienced two events. “The flows coming into Fenton the evening of the 28th spilled out of the wet wells and blew out a transformer and the switch gear,” says Jon Sprague, MSD director of operations.
The power outage forced the plant offline, but more was to come.
The cause of such high internal flows is not yet known. I&I contributed, but other factors could include flooded manholes, a break in a line, or it could have come from the 12 pump stations near the Meramec that were flooded, many in areas that had never experienced flooding before.
As rain continued across the region, the Meramec River rose 25 feet in three days. “It went from a level of 20 feet up to 45 feet deep. The forecast just kept getting higher,” says Sprague.
And that put another plant at risk. Since the 5 mgd Fenton plant was already offline due to internal flooding and was surrounded by the 500-year levy, crews began work on the larger 15 mgd Grand Glaize plant a few miles upstream in case the river reached that high.
“We were doing all we could, scrambling to build sandbag walls,” says Sprague.
“When you’re sandbagging, you ask how high you need to build it,” says Division Manager Todd Heller. “We arbitrarily picked 45 feet. At the time, it was almost 3 feet over where we thought we needed to be and everyone was saying it was a little extravagant. But as we’re sandbagging, the forecast was changing hour by hour. And it wasn’t by inches, it was by almost a foot per hour.”
The river crests
The Meramec reached its peak on Dec. 31. At Fenton, a bad situation became worse when waters overtopped the plant’s levy.
“We lost everything,” says Sprague. “Every piece of switchgear, all the control systems, every motor, every system. All of the buildings were flooded with over 6 feet of water and the whole plant was wiped out.”
The mood was much brighter at Grand Glaize. The sandbag levy was just high enough. “We were high-fiving each other; we thought we had it knocked,” says Heller.
But as MSD spokesman Lance LeComb adds, “Mother Nature can always trump you.” As the Meramec receded, part of the sandbag wall gave way.
“Holding as long as it did — and sandbagging all the doors — mitigated the flooding enough that we didn’t have major damage,” says Sprague. “It took out the plant, but we were able to get it up within days.”
Although full treatment was restored at Grand Glaize by the third week of January, it will be June before all redundant equipment is restored and building damages such as drywall and flooring are repaired.
It’s a different story at Fenton, where primary treatment wasn’t restored until Feb. 12. Full treatment won’t be back online until April, and it will probably be July before all the damaged equipment is replaced and building repairs are complete.
Drinking water hasn’t been affected, but warning signs have been posted all along the Meramec River advising people to avoid contact with the water. Once full treatment is restored, the river is expected to return to normal within a few weeks.
Not the first time
It was just 2008 when St. Louis experienced another 100-year rain event with almost 10 inches of rain over three days from the remnants of Hurricane Ike. That happened just as the district began improving its Capacity Management, Operations and Maintenance Program.
“In 2008, we had 6,700 water backup calls with nearly 4,000 being our responsibility,” says Sprague. By ordinance, MSD pays up to $3,000 per case for sewage backups that are deemed to be its responsibility. This time, there were only 3,000 water backup calls with the district being responsible for 1,400.
“Less than half of the call volume and less than half being our responsibility — as bad as it was, it just shows the improvement we’ve made to our system through proactive cleaning and better maintenance and rehab on our system, and we have a program to install check valves in homes that have repeated backups,” says Sprague.
“Our stormwater maintenance group was out 24/7 responding to calls and worked 10 days straight,” he continues. But they got help from other workers who had been trained to help. “We do a great job day to day taking care of our plants and our system. When it comes to emergency response like this, our folks have really shown their dedication.”
Funding during emergencies
Normally, procurement rules require governmental agencies to develop specs and issue bid requests for large projects. MSD has an emergency procurement process to bypass those usual steps along with a list of emergency contractors. Within hours of incurring flood damage, contracts were issued, workers were mobilized and recovery work was underway.
KCI Construction was hired to handle repairs at Fenton with Goodwin Brothers Construction selected for work at Grand Glaize. In addition, KAI Design & Build was hired to provide construction management for both projects.
Total damages won’t be known until recovery is complete, but the estimate is about $25 million. Damage to the Fenton plant is expected to be $10 million and damage at Grand Glaize is $5 million; insurance should cover all but $500,000 in plant damages. The sewer district also faces around $4.6 million in basement backup claims. Because it was declared a federal disaster, funds may be available from the Federal Emergency Management Agency, but that can take many months, if not years, to determine.
Lessons learned from this and the previous event are now being documented. “We’re putting together a manual on lessons learned and what precautions to take based on river levels,” says Sprague. “We’re also looking at mitigation efforts. Should we raise the levy at Fenton, what are the odds versus the costs? Even though Grand Glaize is above the 100-year floodplain, do we build a levy or take other provisions to protect the plant?”
And there’s the unanswerable question about weather patterns, according to LeComb. “It seems a new bar is being set the past 10 or 20 years. Does that necessitate a whole new set of design standards? That’s something the industry and regulators will have to struggle with over the next couple of years.”