http://img253.imageshack.us/img253/4821/columbusgpwy5.jpg
Would be one of the fastest tracks in the world. Seatine could be ample, as there would be many flat parking lots along the track in which to erect grandstands. The island int he middle would serve as race control and offer seating as well. Floatillas may also be an option, allowing boats to put-in at a premium cost.
Logistics:
Below is an area of map of the minimum amount of highway needing to be closed for the event. One could add to that the closure of east-bound lanes as well, and use it for behind-pit seating. Anyone who's stood on 4-5 lanes of highways knows that there is allot of room on it, the spaces in yellow would serve as parking and paddock, as well as offering behind-wall emergency vehicle access to much of the track.
http://img512.imageshack.us/img512/3301/closuresti2.jpg
670 traffic can be detoured to I70. Local traffic shouldn't be much of an issue, as it is primarily a buisness district. The apartment comlex could be "vented" by providing a temporary dirt/gravel exit to Grandview Ave south of the track crossing.
So, who do I submit this to?