12. The bolts exceded CalTrans specifications - and that may be the problem
Retired Bechtel metallurgist Yun Chung offered up a 32-page report last week stating that Caltrans engineers "were ignorant to the threat of hydrogen embrittlement — a process in which high strength metals, such as steel, become brittle and fracture due to hydrogen exposure." The type of steel used in manufacturing the bolts, he said, was more hard on the outside than is required in Caltrans own specifications, and that the state's engineers were only focused on hydrogen exposure during the manufacturing, and not on exposure to the elements, which he believes caused them to become brittle and snap. Chung's findings have been vetted by other experts, who agree.