[B]URLINGTON — A combination of heavy rain and problems with sewage-digesting microbes at Burlington’s main sewage treatment plant was the cause of two almost back-to-back releases that spilled nearly 2 million gallons of partially-treated wastewater into Lake Champlain.
The first release, early Saturday morning, spilled 700,000 gallons of partially-treated wastewater into the lake from an outlet pipe a half mile offshore from Burlington. There was a second discharge from the same outlet on Monday morning, sending an additional 1.1 million gallons of wastewater into the lake.
City officials said the risk to public health from the events was minimal because the outlet is far from swimming areas, and the E. coli concentration was less than it would have been had the spills been raw sewage. Tests of lake water near the outlet on Saturday indicated an E. coli count more than twice what is allowed under the city’s “wet weather permit.” Tests on Monday showed the count to be much lower, and well within the permit requirements.
The city ordered the closure of beaches within a one-mile radius of the release, including Blanchard Beach, Perkins Pier, the Coast Guard boat launch and the beach by the bike path between the Blodgett Property and Barge Street Canal. Although the bacterial count was lower on Monday, beaches were kept closed as a precautionary measure, according to a city memo. All beaches reopened at 5 p.m. Wednesday.
Burlington has a combined sewage system that treats stormwater and industrial wastewater as well as sewage — in addition there are stormwater drains discharging directly into the lake. Wastewater entering the combined system first passes through screens that filter out most solids before passing into tanks containing microbes that digest the sewage, forming a sludge that settles out of the water.
But Burlington’s industrial customers, who pay a surcharge to send their waste into the municipal system, have been sending wastewater to the plant that is overwhelming the microbes, Burlington Water Resources head Megan Moir said.
“We’re seeing bacteria still there, but because of the nutrient imbalance, they’re not able to form or function properly,” she said.
Last April, the city blamed a similar release of partially-treated wastewater on an influx of chemical cleaning compounds, which led to a mass bacterial die-off.
“This event was certainly seen as undesirable and we are doing everything we can to prevent it happening in the future,” Chapin Spencer, director of Burlington’s Department of Public Works, wrote in a memo following the release.
Burlington’s Water Resources department has hired a consultant to work on improving the health of its biological partners in wastewater treatment system. The city is also considering requiring its industrial customers to make a new plan for the disposal of their more noxious wastes. Moir said the city has called a meeting of its “known high strength” customers.
“It’s not an increase in volume of domestic wastewater that’s the problem. Right now our problem is the high strength wastewater,” said Moir.
Among the nutrients present in the high strength wastewater is phosphorus, the overabundance of which has been a longstanding problem in Lake Champlain and elsewhere, and is connected to a recurring problem of cyanobacterial blooms. Moir said that despite the city’s problems with its wastewater treatment systems, total phosphorus that the city sends into the lake is being reduced.
Nursing the treatment plant’s beleaguered bacteria back to health is one part of a stormwater and wastewater plan the city has been developing to comply with the Lake Champlain TMDL, the federal order calling for a reduction in the lake’s phosphorus loads, as well as prevent sewage backups caused by its aging infrastructure. One component of that plan will be to require new developments like Cambrian Rise and BTV CityPlace to install stormwater management systems, according to Moir.
“A lot of the growth that we’re seeing is upward — they’re not making stormwater any worse,” Moir said.
The state is reviewing the outflows, to determine whether Burlington should be fined. Jessica Bulova, manager of the DEC’s Wastewater Management Division, said that the state assesses wastewater permit violations on a “case by case basis.”
“We’re dealing with living systems, so you have to take all those factors into consideration,” Bulova said.
As the city works to ameliorate conditions for its microbes, Moir said there is a possibility of additional beach closures this summer. She said the department is taking short-term precautionary measures, such as having additional disinfectant on hand.
“We are on high alert,” she said. “We are diligently watching every rain storm to try to assess the risk.”
