There's a 68-tonne 'Celtic Tiger' under Toronto. But don't worry, it's boring a tunnel for Hydro One

There's a "Celtic Tiger" that weighs 68 tonnes that'll be chewing up the earth underneath Toronto for about a year.

But don't worry. This isn't a horror movie we're talking about. 

Hydro One lowered the massive Celtic Tiger Tunnel Boring Machine into the ground on Monday to build a tunnel that will house new transmission cables under the city core. The provincial utility used a large crane to hoist the machine into the air and down a shaft at its Esplanade Transformer Station.

The infrastructure renewal project will cost Hydro One about $120 million.

"The existing infrastructure has served us well, but it's 70 years old and it's time to renew and invest," Andrew Spencer, vice president, transmission and stations, for Hydro One, told reporters at the station. 

The 2-km tunnel will run about 26 metres under the surface from the Esplanade up Sherbourne Street, along Dundas Street East to Bay Street and Dundas Street West, where Hydro One has its Terauley Transmission Station.

"Originally built in the 1950s, the underground cables located between our Esplanade Transformer Station (TS) and Terauley TS are reaching their end of life and will be replaced to ensure that we continue to energize the city's most crucial institutions," Hydro One's website.reads.

Those "crucial institutions" include hospital row, city hall and the financial district, according to Hydro One. 

The tunnel boring is expected to be finished by early 2024 and the installation of the new cables is expected to be completed by 2026.

Hydro One said it is working closely with the city and Toronto Hydro to minimize disruptions to residents and local businesses. It said most of the required construction will take place underground.