@sbarnhard - I’ve found a chart from Hunter that shows these distances:
From: https://www.hunterindustries.com/support/valves-maximum-wire-distance-between-controller-and-valves
So 18 AWG/1.0 MM is fine for those purposes. I’d use purpose built sprinkler field wire like this ->
as this wire is designed to be directly buried and comes various configurations for the number of wires (zones, plus common) in the cable. This cable is 18 gauge, too. This would be my recommendation - purpose built, can cover the distance, not too flimsy when inserting, etc. (FYI, I’m not associated with Rachio).
Not sure why the angst from the electrician.