Archdeacon Roger Whalen is waiting for the city to give the go-ahead to build an extension on the Anglican Cathedral of St. John the Baptist in St. John's. (Carolyn Stokes/CBC)

There's a lot of history in the Anglican Cathedral of St. John the Baptist — but it's the history under the building that could be a challenge to the church's expansion plans.

The diocese wants to build a new two-storey annex and ministry centre attached to the historic building off Duckworth Street in St. John's.

But a local historian is concerned that expansion will disturb the burial ground of as many as 20,000 migrant fishermen from more than 300 years ago.

"I'm going to say something politically incorrect, but if this were a burial ground of Indigenous people, there would be no question they wouldn't go ahead with this," Robert Sweeny told CBC's On the Go.

Robert Sweeny is a retired historian and an honorary research professor at Memorial University. (CBC)

Archdeacon Roger Whalen, however, says they dug five exploratory holes around the construction site and found no evidence of any bodies.

"What we found when we did our test digging was rubble from the fire mostly — the fire of 1892," he said.

The area was a cemetery, but Whalen said the bodies seemed to have been moved sometime around 1885, and possibly re-interred at the cemetery on Forest Road.

Construction began on the Anglican Cathedral in the 1840s. (Bruce Tilley/CBC)

A provincial archeologist will be on site for the construction — if it gets the approval from the City of St. John's — and will flag any issues as they come up.

Many of the graves would be unmarked and dating back to the late 1600s. Sweeny said people would have been wrapped in cloth and placed on top of each other.

"There's no real way of knowing how many bodies are there," he said.

Whalen says he's heard some criticism of the expansion's modern design, but says it's not unusual to attach a modern building to an older structure. (Submitted)

Sweeny said well over a million men came through the province during the days when the cemetery was operating, and with the short life expectancies of the 17th, 18th and early 19th centuries in the fishing and trading industries, plus rampant spread of disease, it's difficult to pinpoint how many people could be buried there.

"This operated for 170 years, with a much larger mobile population moving through it. So, we're probably dealing with the largest pre-Confederation cemetery for working people in Canada," he said.

"People would have been stacked. In Quebec City they're 10 deep, so probably 14 to 15 deep here."

Building will replace other properties

The new building will also include the bishop's office and staff, a new resource centre, and a small café. It will replace the current functions of the parish hall on King's Bridge Road, but the church will keep that property as well.

"That's going to be very important for functions that we have with the parish and for our outreach to the community," Whalen told CBC News.

The design of the new proposed building is in stark contrast from the mid-1850s church it will be attached to, and while Whalen has heard criticism of the modern design, he said an old church with a modern extension is not uncommon, citing examples of old cathedrals in Toronto and Chicago with modern additions.

This is another rendering of the proposed extension. (Submitted)

Whalen says the church hopes to begin construction by August.

The building proposal is making its rounds through approvals from the City of St. John's, and Whalen said it has passed by the city's heritage panel with some small changes.

The plan though, has yet to be signed off on by city council itself, something Whalen hopes will happen soon.

Funding will come from the diocese itself, and not from the congregation, he said.

Read more from CBC Newfoundland and Labrador