Organic Certification

I just moved to my mother-in-law's farm and we want to get certified organic. Here's the problem: Last year, they sprayed the horse paddocks (which we planned to use for steer) and their home garden with Sevin. Clearly an organic no-no. So, I've got a few questions:

How long does it take for Sevin to dissipate out of soil?
Is there anything we can do to speed up that process?
If we grow our farm market gardens where Sevin was not sprayed, is it still likely to be contaminated?
When testing a farm for certification, do they sample where you're growing, or everywhere?

My mother-in-law realizes that Sevin was a really bad idea, particularly since we now want to focus on organic certification.

(I know certification isn't the be-all-end-all, but our cousin just landed a huge contract with her school district to provide organic produce to the schools). Thanks!