Encountering an unexpected site condition is one of the more common risks on a construction project. A “differing site condition”, or it is sometimes called a “changed condition”, is generally understood to be a physical condition that is discovered while performing work and that was not visible or otherwise expected at the time of bidding. Often, the condition could not have been discovered by a reasonable site investigation. Examples of common differing site conditions include: soil with inadequate bearing capacity to support the building being constructed, soil that cannot be reused as structural fill, unanticipated groundwater, quicksand, mud, rock formations, or other artificial subsurface obstructions. Differing site conditions may also occur within the walls or ceilings of a renovation project such as the renovation of a hospital or historic building.