I am in the process of installing a radon 'chimney' in my basement. I
have measured ~35 pCi/L in the basement. The EPA website recommends a
3" PVC 'Tee' below the floor in a basement, connected to pipe that
passes up through the house, and out the roof. This would be a passive
system.
How close can I place the 'Tee' to any of the footers (below the
basement floor) and still expect the system to function?

I should mention that my house is odd. While the poured basement walls
approximately form a rectangle, there is a rectangular room (also
poured walls) in the middle of the basement that is filled with dirt.
The room takes up about 400 sq ft, and the basement would be about 2000
sq ft if it were not for that room.
I want to put the 'Tee' as close to one of the interior poured walls
(one of the walls of that room) as possible. However, those walls are
load bearing, thus they have footers. I am concerned that the Tee's
proximity to the footer will hamper gas flow to the Tee.

Any advice?
Thanks!

"Any advice? "

If I were faced with radon abatement, I would call in professionals. I
think this is a situation where experience in coming up with a correct
solution is well worth paying for.