The Buffalo Grove park district runs the doubles event there. They have been for many years now. It's an annual thing. The guys running it know almost nothing about PDGA, they just want to promote disc golf in Buffalo Grove and give the local kids something to play in.
They don't do alternate tees, they probably don't even know what that is. It used to be 36 from the concretes at Willow Stream, but two years ago they changed it up to doing 18 from the concretes at Willow Stream then 18 from the concretes at Twin Creeks.
The only reason any of the good people come out is because for the pro division the first prize is a basket. Usually it's a Discatcher Sport, so you'll see some good players out there for a chance to win that basket. They usually offer two AM divisions (think of it as upper and lower). If you know anything about disc, you should be playing the upper division. The lower division is filled with 8 year olds and their parents and people that throw 50ft air shots in the wrong direction. If they happen to do just two divisions this year (they did it one year) then just sign up for Pro... You'll feel like a major bagger playing with the kids. The prizes for other divisions are just discs and I believe a bag for the winner. You don't get a choice of what plastic you get.