At least 14 wastewater treatment plants in Vermont reported sewage overflows due to wet weather on Dec. 18 and 19, sending millions of gallons of overflow into local streams and rivers, the state Department of Environmental Conservation reported on its website.
Officials said the overflows should cause little concern for public health or the environment because the discharges were so diluted with rain and floodwater.
But wastewater plant operators said the event still revealed the limitations of wastewater infrastructure’s ability to respond to extreme weather.
“You look at things that you normally wouldn’t … have thought would have happened, and they did,” said Middlebury Wastewater Superintendent Bob Wells. “So if it happened once, it can potentially happen again.”
Among the sites that reported wet weather-related overflows on Dec. 18 or 19 were Middlebury, Montpelier, Rutland, St. Albans, Bethel and Vergennes. In total, the state has reported 17 weather-related incidents in the past month, compared with an average of six for the same time period over the previous nine years.
Michelle Kolb, a watershed supervisor for the department, confirmed the number of incidents was unusual for this time of year.
Many plants were overwhelmed by the amount of water coming into their systems from drains, maintenance holes and groundwater seeping in, she said.
“Some places saw 8 times more flow coming into their facility on Monday (Dec. 18) than the day before,” she wrote in an email.
Under those conditions, some facilities experienced overflows from flooded pump stations or maintenance holes, she said. In others, “facilities that had to go into ‘storm mode’ where they have to reduce treatment time because there is so much water coming into the plant.”
“In extreme weather conditions, facilities do the best they can to keep running but often just have to wait for waters to recede,” she said in the email.
In Rutland, storm drains are connected to the same system as wastewater lines, so the total amount of water exceeded the plant’s capacity, said Tyson Barlow, the plant’s assistant chief operator. On top of that problem, the Otter Creek River got so high that it began backing up and coming into the collection system.
The city is undergoing an engineering study to look into how to update the collection system and prevent overflows through careful management of wastewater lines and retention ponds for excess water, Barlow said.
He said recent years have been a struggle for the plant because of the rising cost of everything from electricity to the chemicals they use for disinfection.
“If things keep getting more and more expensive, it’s going to be a real struggle down the road,” Barlow said.
Wells said the wet weather in the weeks and months prior to the storm contributed to the overflows that occurred in Middlebury during it. When the ground gets saturated, water can find areas that it doesn’t normally come into.
Wells has been working in wastewater systems since 1986, and he said the weather patterns now are completely different from when he started. “The storms are isolated, (and) they’re intense,” he said.
Weather events like this year’s flooding are beyond what anyone has prepared for, he said. Rutland had a flooding event in August that knocked out its main pump station for months.
“If you look at the topography, and you look at the roadway down to that pump station — I’ve been here for 28 years — and I’m like, ‘you know that ain’t gonna flood,’ and next thing you know it comes in and inundates everything and fills up my drywall and shuts my pumps off,” he said. “It was a train wreck at that point.”
He’s now reviewing the damage in more detail and thinking of how the city needs to change its plans for system upgrades and maintenance with the assumption that this is the “new normal.” Mitigation efforts could include everything from widening culverts to putting holes in fences so water can drain out of them.
“You lick your wounds. You try to make better decisions next time, and you try to address any areas that you can get ahead of,” he said.
