Construction of Ivor Dent School could be up in the air because of what lies beneath: an old coal mine.

At one time coal kept this city going. Now it might be an obstacle to new development.

Prior to the introduction of natural gas, coal was used to heat homes in Edmonton.

With the fuel conveniently buried underneath the city, it resulted in more than 150 mines of varying sizes being dug between 1880 and 1970.

When the use of coal faded out, some old mines were simply boarded up and forgotten, only to be discovered years later.

That could be the case at the site of a future replacement school in Rundle Heights, according to Brian Fedor, assistant deputy minister with the Learning Facilities Division of Alberta Infrastructure.

"They (environmental consultants) were able to find an actual registration of the mine that was registered in 1905 and then closed in 1925," he said.

There is a map of the old mine but Fedor isn't sure how reliable it is.

"The map accuracy in those days was general, no GPS for sure," said Fedor, adding that they will be conducting tests to figure out what exactly is under the ground on the proposed school site.

"One is to determine or confirm if there are any methane issues associated with the mine, and number two is to determine if there are geotechnical or structural issues related to the mine. In other words, do any of the mine tunnels come underneath the site?"

If coal-mine tunnels do encroach on the site there are solutions.

"One of the things we could do is just extend our structural footings and/or pilings," Fedor said. Another option could be to fill it with concrete, "that could be a possibility depending on how big the mine is."

That decision will likely come after officials get the results of seismic tests at the end of March. That could delay the start of construction set for April, but Fedor is optimistic that even if that does happen, Ivor Dent School will still open as scheduled in September 2017. The school would host 650 students from kindergarten to Grade 9.

"I'm actually very confident of that at this point in time because the technical solution does not look like it would be very complicated. Nowadays the technology and the ability to mitigate these types of things is very comprehensive."