13-4/30 Grounding Club on Bridge in Water Hazard
Q: A player's ball lies on a bridge over a water hazard within the margins of the hazard when extended upward. May the player ground his club?
A: Yes. A bridge is an obstruction. In a hazard, the club may touch an obstruction at address or in the backward movement for the stroke -- see Note under Rule 13-4. Touching the bridge prior to address is also permissible, since an obstruction in a water hazard is not "ground in the hazard."
This applies even if the bridge has been declared an integral part of the course.