I did do a search on it, but apparently my searches were not well-phrased. I found a number of threads about using your tractor to build a septic system, but nothing about whether you can drive your BX over one.
Thanks for all the replies so far. I am a city boy who's never lived somewhere with a septic system, so I am not even sure which kind I have. Mine is about 8 years old, it covers an area that is about 20 feet wide by 30-40 feet long, with about 10 white vents sticking up out of the ground. That sounds like a drain field to me, which also makes sense because the ground is sandy there. On the other hand, the previous owner said we need to have someone come and pump it out every 2 to 3 years, so it also sounds like it has a tank (and there's a heavy-duty concrete manhole-style cover over what I assume is the tank. I don't know how deep the tank is. I was also told that the system is much larger than it really needs to be for our household size. Our inspector told us that the septic system is designed for a family with 6 to 8 people living in the home, but its just me and my wife now. What I might do is call the previous owner and see what he thinks. He owned a big old JD tractor, so maybe he drove over it. If he did, there shouldn't be a problem. I have to believe his tractor weight 2 to 3 times what mine does. He's a really good guy and might appreciate the call anyway just to say hi.