Stopping business rule processing on background script

We are attempting to retroactively update a batch of change records (about 2000) to populate a field that was developed as mandatory.   No problem there, developed a background script.

Only problem is that the script appears to be triggering business rules left, right, and center upon the update() call.   Which we don't want (one of the business rules is resetting all the approvals, a definite no-no).

Anybody have an idea on how to stop further business rule processing?   Or trigger an update without business rule processing?

Thanks