After conducting a thorough internal investigation into how and why 30,000 gallons of raw sewage overflowed into Wolverine Lake in November, the Oakland County Water Resources Commissioner’s (WRC) Office detailed their findings to the Wolverine Lake Village Council at its Wednesday, Feb. 9 meeting.
It is the WRC’s task to maintain the sanitary sewer system.
At 3:30 p.m. on Nov. 28, a pump station situated along South Commerce Road in Walled Lake, directly across from Wolverine Lake, failed. It has been determined that of the pair of pumps operating there, only one developed a blockage in a 10-inch force main that carries sewage from the pump station to the Novi-Walled Lake Wastewater Treatment Plant. The spillage was under control by 5:25 p.m.
“One of the pumps was taken out of service to replace it, but it wasn’t completely wired, while the second one still running became plugged up and stopped producing flow,” said WRC Manager Sue Coffey.
Sewage flowed out of the manhole cover, and into the street and storm sewers because there was no place else for it to go, according to Mike Powell, the village’s engineering consultant.
When crews arrived on the scene to hook up the replacement pump, the first pump had already malfunctioned.
“We shouldn’t have the pump waiting for electricity because it puts the station in trouble,” said Village Council President John Magee.
An alarm failure was a compounding problem.
“The emergency float (alarm) failed before replacing the fully-wired pump,” said Coffey.
The WRC found that the alarm was in operating condition, but failed to trip at the time of the overflow resulting in a lag to notify the village.
“The WRC explained that they’re working on an alarm verification process to alert staff,” Magee said. “They also plan on notifying the Spinal Column Newsweekly as part of the notification process.”
The Oakland County Health Department collected water samplings at the site, but deemed there was no immediate problem. The WRC has also collected various water samples and reported findings to the state Department of Natural Resources and Environment (DNRE).
“While initially there was a high e-coli count, follow-up testing at the site and the lake indicates it’s been completely diluted and is clean, but we will continue to extra testing at the end of the lake this summer,” Magee said.
Coffey said the WRC has put safety nets in place to mitigate future problems and is committed to conducting better site specification procedures for the more than 250 stations they maintain.
“We will be retraining staff of how to check equipment because we take sanitary sewer overflows very seriously,” Coffey said. “We will also be increasing the frequency of site checks when equipment is down until equipment is fully in service again.”
The WRC also intends to pre-purchase replacement pumps for aging stations and plans on wiring pumps immediately after they are installed.
“By working on a pump replacement schedule to replace pumps before they fail, it is a more proactive approach and poses a lot less risk,” Coffey said.