The two-lane Canyon Road bridge over Moraga Creek, which dated from the 1930s, was rendered unstable last April, when heavy rains caused the ground along the creek to move. That, in turn, jarred a bridge support out of position, making the bridge unsafe to cross. A new temporary one-lane bridge, protected by stoplights at either end, is expected to be in use for about two years while a permanent structure is built. The combined cost of the temporary and permanent bridges is about $8 million, with the town of Moraga expecting to be reimbursed almost 90 percent of those costs through federal emergency dollars.