When thinking about infrastructure, what comes to mind may be roads, sidewalks and bridges, but probably not the lowly manhole.
But manholes, noted Glenn Schneider, Manitoba Hydro public affairs division manager, are a critical part of a city’s electrical system.
“Manholes are built to provide access to underground electric cables and transformers,” Schneider pointed out. “A catastrophic failure of a manhole would cause extended power outages to customers.
“While no one notices them, they are often quite large – usually two metres deep and three metres long by two metres wide.”
Schneider reported that Manitoba Hydro has about 2,400 manholes throughout the province with about 1,800 of them in central Winnipeg.
Many of them date from the immediate postwar period and some are much older.
He noted that while Manitoba Hydro typically budgets about $300 million a year for upkeep, including manhole rehabilitation and new transformers and poles, the age of the province’s electrical structures is such that the utility is going to have to up the ante.
The Crown corporation will invest $500 million a year over the next 20 years to accommodate the rehabilitation or replacement of facilities.
For example, Manitoba Hydro is setting aside $52 million over the next 20 years to repair or replace about 350 manholes in Winnipeg.
The focus this summer is seven manholes under Portage Avenue right in the heart of Winnipeg’s busiest downtown artery, including three at Portage Avenue East near Westbrook Street.
“In the early years, the manhole walls were made of brick with clay ducts to run the wires through,” he said.
“Some of the metal supports are rusting away, while the brick walls are crumbling.”
To perform the work, Manitoba Hydro has its own specialized, eight-person underground construction crews that include journeymen powerline technicians.
“It’s hazardous work,” said Schneider.
“We have live cables down there that have to continue to carry electricity, while the old manhole is being removed and a new concrete manhole put in place.
“It is also challenging because our crews are working in a very confined space.”
There is also the matter of impeding traffic for up to five weeks, while the work is being done.
The work, Schneider said, consists of digging around the outside of the manhole and putting support timbers around it while the old walls are being taken out.
“Our guys have to be methodical,” he said.
While Manitoba Hydro has its own crews doing most of the work, Schneider said that the utility company does bring in subcontractors to remove the earth from around the old manhole and to pour water into the opening to create a slurry.
The costs of repairing or replacing each manhole costs anywhere from $45,000 for roof repairs to $150,000 for a complete rebuild.
Other manholes that will be rebuilt by the end of this year include three more farther west on Portage Avenue towards Polo Park.
“Our primary focus is manholes that are located on public roadways because they present the highest risk to the public,” Schneider said.
“They are subjected to the most severe conditions, including weight and vibration associated with vehicle traffic.”