Squeezed inside an enclosed box , a welder works in scorching conditions to join two steel legs that support the new eastern span of the Bay Bridge. A supervisor working for the contractor checks the crucial first weld, followed by an independent inspector required to test the weld within 30 minutes. Another inspector hired by Caltrans reviews the initial inspector's paperwork to make sure everything is OK. The Caltrans-hired inspector also randomly checks about 10 percent of the welds. If substandard welds exist on the new eastern span of the Bay Bridge, the work would have slipped by a chain...