Mysterious structure in Lake Ontario not an alien city after all

If, like me, you have been puzzling for MONTHS over the mysterious structure taking shape on Lake Ontario, off the coast of eastern Toronto (Woodbine Beach and the Leslie Street Spit), prepare to be enlightened. What can it be? Oil platform? Theme park? Border wall? Lost city resurfacing?

We have watched the structure(s) come and go, change shape and position, generate and engender mini-structures, some of which remain and some of which disappear again, over many months now, at least since early spring. Bizarrely, the structures - which seem to consist of cranes, towers, platforms, and various other elements - change and come and go on a DAILY basis, so we're never quite sure what to expect from ome day to the next.
Anyway, it turns out that someone else has already done the legwork, and Ports Toronto has confirmed that the platform is actually a "jack-up barge" for the Ashbridges Bay Treatment Plant Outfall (ABTPO). That will mean very little to most people, but ABTPO is part of Toronto's wastewater treatment and purification system, and the barge is constructing risers for a 3.5km underwater tunnel or pipeline that will transport (clean, treated and disinfected) wastewater from the Ashbridges Bay plant out into the middle of the lake, where it will be safely discharged.
The project is expected to continue until mid-2023, so we will be seeing its ever-changing profile for some time to come. It's a shame really: I still prefer my own theory of a beneficent alien civilization much better.