Hmmm, I've never quite been in that situation, so I'm not sure what to tell you.
You could always ask an "innocent" question such as "How often do you typically work the ground in the arena?" to at least try to get the conversation started.
Or are there any other barrel racers at your barn? If so, a few of you could do together to the BO and explain that it is safest to have some real "ground" for your horses to dig into. And offer to work the ground for the BO, if they show you how.
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.