Damn,now that I'm passed edit time I see I spelled agenda wrong. It's been a long day here.
Anyway, I'd also be interested in the "study" that was done and who asked/paid for it. If it was a zoning issue, noise/decible, or if it was a EPA/DNR violation notice.
If the city paid for it, the issue should have been on the agenda before to authorize the funds. If it's a private study, it's probably paid for by the party who's complaining.
Davenport had this issue with their circle track. They reduced the noise(somewhat) with mufflers. They also went to a curfew as in no races starting after a given time.
Most of the time these issues are addressed by a board of adjustment who can grant variences to existing ordinances if just cause is shown. Obviously laws vary from state to state. I'm just trying to point out that there may be a middle ground compromise if the opposition has a "justifiable" complaint.(Yes I know,..they don't)