Are you sure? What year did they switch from clay to hard? I think Coral Springs was the old venue which was clay.
Delray Beach TC has both green clay and hardcourts, i've played at that site.
Go to Hewitt's profile in ATPtennis site, check his activity in 1999 for singles and you'll see it's clay for Delray Beach that year.
So it's green clay, not red clay?
Green clay is quite a different surface than red clay, right?