How Deep Should I Go?

I’m in the Chicago suburbs and getting ready to build a new deck on the back of my house this spring. Before the deck goes in, I’d like to bury a 2" PVC conduit from the house to my detached garage (about 35 feet). Roughly half of the run will end up under the new deck.

The goal is to future-proof so an electrician can eventually pull feeders for a subpanel in the garage, most likely for an EV charger (240V) and possibly a mini split if I decide to heat/cool that space later.

I’m getting conflicting information on burial depth. My village website appears to say residential conduit needs only needs to be 18 inches below finished grade, but I’ve also seen references suggesting 240V lines need to be below the 42" frost line in this area.

Can someone clarify what depth is actually required for PVC conduit in this situation? Does voltage change the required burial depth, or is 18" sufficient?

Thanks in advance!