Strathcona Science Park is a provincial park just outside Edmonton. It’s rutted and full of gopher holes and apparently has toxic seepage in places. There’s no sandy area but it does have a big downhill with long stairs for a runup.
This is my “home course” because I used to live just across the river, so it’s a convenient place to practice my cx race techniques, do laps to build my stamina and just generally rip around.