Megalith Found in Edmonton, Alberta?

In this video I highlight an interesting discovery during a construction project in Edmonton in 2018. As crews were preparing for the construction of the new Tawatina bridge to service the Valley line of the LRT system, they were working in a cofferdam and they found a large object about 30 feet below the surface of the river, way down under the riverbed. They said the object was made of concrete and was the size of a car. Crews attempted to drill into the object to break it up but they were unable to do this. It was announced that due to safety and environmental concerns the object would not be moved, and it was not directly interfering with the actual bridge structure.
There is not much information on this object, but the location where it was found was shocking to the engineers and planners who were leading this project. They had done extensive research on the area and were aware of past construction in the area and possible related complications, but they were very surprised to find an object of this size that far down into the riverbed. Could a piece of concrete from an old structure near the river have fallen into the water and ended up buried 20 feet below the riverbed?
I also mention another YouTube video by Alexander Farley called "Megalithic Mysteries around Alberta" in which he mentions the discovery of this object in Edmonton as well as a few other interesting rock structures and formations throughout the Canadian prairies. The locations highlighted include the Majorville Cairn and Medicine Wheel Site and the mystery rocks of Saskatchewan near Cypress Hills. These locations are not necessarily connected, they just highlight some other interesting old rock structures throughout the prairies.
And yes, I know that the title of this video is a bit of a clickbait, but it seems like there is enough of a legitimate mystery here to warrant some curiosity. There has been a lot of local interest in this object in Edmonton, and there has been much speculation on Reddit including a pretty entertaining piece of "fan fiction" surrounding this object in the r/nosleep group.

There are definitely a few potential explanations for the discovery of this object, and I am interested to hear your comments and thoughts.

Thanks for watching!