When 30,000 gallons of raw sewage overflowed into Wolverine Lake in late November 2010, village officials opted to collect water samples to see if there were any negative effects and have recently analyzed the results which indicate some short-term residual effects but minimal long-term impact.
Water testing was conducted a month after the incident and then again a few months later. The first sampling was conducted while there was ice covering the lake, 20 and 40 feet from the shoreline where the spill occurred.
“We bored holes and took samples under the ice and those results showed negligible E-coli (bacteria) results,” said Wolverine Lake Water Management Board Chairman Cliff Yantz.
Water samplings were also collected in August from deeper levels in the lake, ranging from 20 to 30 feet in depth.
“Lakes stratify so we decided to look deeper and thought maybe the surface wasn’t totally representative,” Yantz said.
The results identified 173 colonies of E-coli bacteria per 100 milliliters of water. Officials use a baseline of over 130 bacteria colonies per 100 milliliters of water for closing a beach, according to Yantz.
“There’s a five sample minimum for a 30-day geometric average, but we apply it per sample to be conservative,” Yantz said. “That said, no one swims 20 feet down.”
The sewage spill occurred when a pump station failed along South Commerce Road and directly across from the lake. Of the pair of pumps operating, only one had developed a blockage in the 10-inch force main that carries sewage from the pump station to the Novi-Walled Lake Treatment Plant.
Due to the obstruction, waste water couldn’t be pumped. Eventually sewage flowed out of a manhole cover, into the street and into storm sewers.
The event took place at 3:30 p.m. on Nov. 28, 2010 and was corrected by 5:25 p.m. the same day.
Yantz stated that while the lake was slightly impacted by the sewage in the short term, in the long run there will be negligible effects.
“The lake may have been affected by the sewage in the short term and there may be some long-term effects in deep water, but overall there’s a modest effect,” he said.
Village Council President John Magee said he is pleased with the overall trend compared to the problems experienced in previous years.
“We used to see spikes of E-coli in the summer in the Penny Lake and Nantucket Beach areas and had beach closures, but we’ve had better results since we put sewers in along Wolverine Drive and had the Greenaway Drain study that identified erosion problems that were repaired and had road drains properly cleaned,” Magee said. “Right now the trend is good — one sample doesn’t alarm me. I’m confident its clean and safe down there.”
Magee added there is an ongoing testing regimen in place to ensure the lake’s health and user safety.