The entire bridge was fabricated using hot steel rivets, which are impossible to heat treat and so remain relatively soft. Analysis showed that these could fail by shearing under extreme stress. Therefore, at most locations each given rivet was removed by breaking off the head with a jack-hammer buster and punching out the old rivet, the hole precision reamed and the old rivets replaced with heat-treated high-strength tension-control bolts and nuts. Most bolts had domed heads placed facing traffic so they looked similar to the rivets that were removed.[Caltrans contract 04-0435U4, 1999–2004. This work had to be performed with great care as the steel of the structure had for many years been painted with lead based paint, which had to be carefully removed and contained by workers with extensive protective gear.