This is why huge rocks are being placed in Lake Ontario on Toronto's waterfront

Ashbridges Bay is seeing some big changes — and by big, I'm talking about piles of hefty rocks along the shore. 

Work is underway on the Ashbridges Bay Treatment Plant Landform Project, a $96 million undertaking by the Toronto and Region Conservation Authority (TRCA). 

The Ashbridges Bay Treatment Plant Landform Project will cost the city $96 million.

The point of the project is to prevent erosion, manage sediment deposits in the harbour entrance of Coatsworth Cut (which sits just south of Coxwell Avenue) and to enhance the shoreline's fish habitat. 

Partnering with the city, the TRCA's work in Toronto's eastern bay includes building land for a future sewer overflow plant. 

The landform construction project will result a loss of about 20 hectares of aquatic habitat along Lake Ontario's coast, according to city documents.

The project will run down from Coatsworth Cut down to part of Tommy Thompson Park. Photo via Toronto and Region Conservation Authority.

To offset the fish habitat loss, piles of rubble are being placed in the water, along with four submerged rock shoals, log tangles, tree wads, gravel fill in the central breakwater, a "vertical sunken tree field"and submerged rock berms. 

The TRCA and the city say the project is slated to be complete sometime in 2025.