Construction was paused at the Harbour House site at 31 Huron St. last week when excavation crews noticed bubbling water in a dig site and realized there was gas coming up from the ground.
Collingwood Fire Department was called to the scene around 8 a.m. on Oct. 26 to ensure public safety and respond to the report. They shut down the construction on site and worked with the foreman to report the incident to the provincial environment and natural resources and forestry ministries.
No gas lines were involved. It has since been determined the gas was bubbling up from the shale deep underground.
Les Mallins, president of the Harbour House developer, Streetcar, said the gas was coming from a hole that was drilled when they were exploring the idea of geothermal heating and cooling options for the building as part of their environmental initiatives.
About six months ago, said Mallins, they were set to drill two test holes on the site to find out what the rock was like in the area and whether geothermal options were feasible.
"We drilled the first one and it was supposed to go down 200 metres, but we got to about 50 metres and there was gas coming out that usually would dissipate, but it persisted," said Mallins. "They had to abandon the drilling and concluded that we couldn't do geothermal on site because, if at 50 metres there was persistent gas, at 200 metres it would be worse."
The drilling crew followed protocol and capped the hole by filling it with concrete. However, Mallins said the concrete didn't go deep enough and the cap was removed by the site excavation work. Without the cap, the gas started coming up and out of the hole again and a new cap had to be added that went further down.
"All shale would have certain amounts of gas at certain depths," said Mallins. "It's pretty standard, but we would never have known about any of this if we hadn't tried to drill down 200 metres. Our excavation [for the building] is six metres. We were only going down 50 and 200 metres because we were trying to do something as part of an environmental program."
Collingwood Fire Department confirmed the site was monitored for gas readings while work was underway to add a new cap to the test hole.
Construction has since resumed.
