Here's why you heard a big boom last night

A number of people reported hearing and feeling a very loud noise last night around 1 a.m.

Algoma Steel Inc. confirms that around that time liquid slag contacted "some residual water on the ground" leading to an explosive reaction.

Algoma's Brenda Stenta tells SooToday that the plant dumps liquid slag at its Material Processing facilty on a daily basis and it is a necessary step in the steelmaking process. She said the plant makes every effort to keep the surface onto which the slage is poured dry and the pit contained. 

"Sincere apologies to our neighbours for the late-night boom," Stenta wrote.

She said everyone is safe and there were no injuries or impact to operations.

The slag in question is recycled after it cools. Stenta said it is reused in concrete and road construction.