Last month, a main sewer pipe on Falls Road in Shelburne broke, and between 100 and 1,000 gallons of raw sewage spilled into the nearby LaPlatte River.
It was the latest of four spills this year, according to the Vermont Agency of Natural Resources. The others included overflows into McCabe’s Brook and Munroe Brook, in addition to the LaPlatte.
The spills posed no real health threats to people in Shelburne — the real risk is to Lake Champlain.
Sewage spills into the lake can result in anything from pesticides and pathogens to pharmaceuticals in the water, according to Lake Champlain International. Bacteria and viruses in the water can force beach closures, and phosphorus from overflows can feed cyanobacteria outbreaks, many of which occurred this summer and into September.
The Falls Road main that leaked is located at a pumping station, which moves water from a low-lying area near the river up toward the town sewage-treatment plant on Turtle Lane, near Shelburne Community School, said Shelburne Water Quality Superintendent Chris Robinson.
Robinson said sewage overflows in March and April were caused by plugged lines, including one caused by grease that a user dumped into the sewer system — against town regulations.
An August discharge of about 10,000 gallons of sewage effluent that hadn’t been disinfected resulted from a power failure in the treatment plant’s UV disinfection system, he said.
Other Vermont towns, too, have had spills in recent months — and lots more than Shelburne.
For instance, Rutland has had 73 wastewater releases or spills this year, Burlington has had 11, and Essex Junction three, according to Lake Champlain International.
“Wastewater spills potentially pose a hazard to human health, as well as to the environment, but it largely depends on the type, size and location of the spill,” said Jared Carpenter, a water protection advocate with the Lake Champlain Committee. He said pathogens can threaten swimmers in untreated wastewater, and wastewater nutrients can also worsen the pollution of both rivers and Lake Champlain.
Robinson says last month’s leak in Shelburne may have been a result of the underground pipe simply failing. This is the third break in a little over a year in “generally the same location.”
The town-owned main is due to be replaced next spring as part of a $1.8 million project, Robinson said. The upgrade will also eliminate the line that broke in March, he said.
The sewer main and the pumping station are two pieces of a very large puzzle, with many parts cooperating to treat Shelburne’s wastewater from homes and businesses, Robinson said during a tour of the Turtle Lane facility last week.
Toilets, sinks, washing machines, showers — all feed into Shelburne’s two treatment facilities.
The Turtle Lane plant, the larger of the two, just received an “excellent” grade from the Department of Environmental Conservation. It handles the eastern part of town; a smaller treatment plant on Bay Road handles the western portion of Shelburne.
After wastewater leaves homes and businesses, it travels through pipes, helped along by pumping stations, until it reaches one of the treatment plants.
In Shelburne, treatment starts with a screening process that removes grit and other solid materials, Robinson said. The secondary treatment isn’t physical, but biological – a sequencing batch reactor, technically, which Robinson calls a “bug farm.” This teeming colony of microorganisms comes from the guts of the humans who send their waste into the sewer system, and the microbes digest waste, Robinson said.
Lake Champlain International notes that personal care products, including pharmaceuticals, can enter the lake even after treatment, because not all of them may be removed during treatment.
Aluminum sulfate is added to the wastewater during treatment; it binds to phosphorus, removing it from the wastewater, and the microbes help with phosphorus removal, too, Robinson said. Once the organisms settle to the bottom as solids, the fluid is run through cloth filters, treated for pathogens under UV lights, and released to Lake Champlain.
And what about those solids? They’re full of phosphorus and high in organics. They get mixed into fertilizer.
All these moving parts require constant monitoring, and computers throughout the treatment plants track the various components. Oxygen sensors on the roof help to ensure the microbe colony stays healthy; a lab in the building is the site of daily testing for such factors as phosphorus levels, pH and temperature of the wastewater.
Carpenter said spills are being reported more frequently, but that doesn’t necessarily mean there are more actual spills. Rather, the reporting of spills has improved.
Heavy rains, too, can cause overflows.
But don’t think that spills and breaks are inevitable in a sewer system, Carpenter said.
“These breaks and spills should not be seen as a common occurrence, but something that can be prevented and planned to address before they occur,” he said.
One challenge for Robinson and his staff of five is that they have little control over what actually goes into the sewer system.
Most of the time, what’s inside the sewer pipes is just what you’d expect someone to flush down a toilet. But sometimes it’s not. Grease plugs lines, and if toxins like gasoline, chlorine from a swimming pool, or industrial cleaners enter the system, they can kill off the crucial colony of microbes, Robinson said.
That actually happened within the past couple of years. The solution: a shipment of microbes from another sewer plant to reseed the “bug farm” on Turtle Lane.
Robinson added that, although people tend to be critical when a spill or accident happens, no system is foolproof. What matters, he said, is how people respond to challenges.
“The problem with being a water treatment facility is we can’t control what people dump down their drains,” Robinson said.