A water storage tank is welded in accordance with AWWA Standard D100, the base metal temperature is at 25 degrees F and require preheating before welding. The 1 1/8″ plate steel must be preheated to within what minimum distance of the weld area?

A water storage tank is welded in accordance with AWWA Standard D100, the base metal temperature is at 25 degrees F and require preheating before welding. The 1 1/8″ plate steel must be preheated to within what minimum distance of the weld area?