Much of the upper portion of the old San Francisco Bay Bridge will be gone by 2018.

California Engineering Contractors won a $69 million contract that will remove portions of five 504-foot, double-deck steel truss spans, 14 288-foot, double-deck steel truss spans and 13 steel towers.

The company's bid came in well below the state transportation agency's $93 million estimate. Some of the expected cost savings would come from lowering deck pieces onto barges so they can be dismantled elsewhere, rather than on the bridge.

The work is expected to begin this summer. It will be done to avoid the nesting seasons of birds that have made homes in the old structure.

It is the second phase of the demolition. The first involved cutting the cantilever section at its center and starting to dismantle both sides.

Contracts for the third phase - demolition of the foundations, including the possibility of using explosives - will be considered later.