Crystal will shit all over you if you go digging up inside their ski area. It better be well hidden or somewhere more privately owned.
Also, I think that those ramps that downhill bikers use could make great ski takeoffs for drops and all... that would be kinda cool.
As for the jump, you're going to be working for days if you want to get soil in the PNW. Just pile some logs or branches to get a basic shape. Its not going to be much in all honesty, it would be better to just scout a already well defined spot and just keep it maintained all year.