The San Franciso Bay area is in the midst of its biggest building boom in 20 years. Almost $30 billion worth of major transportation projects have already started about to begin. The boom is being driven by the combination of federal stimulus funds, bond financing and low bids, according to the San Jose Mercury News.

Among the many big-ticket items are the replacement of Doyle Drive in San Francisco, extension of the BART mass transit system toward the South Bay, building high-speed rail and adding to the Caldecott Tunnel — among others.

Andrew Chesley, executive director of the San Joaquin Council of Governments, says the area has never had this many projects going at any one time. He adds that low bid prices — construction companies are entering bids up to 40 percent under projected costs — are enabling officials to tackle more projects than expected with the available funding. That has saved state and local agencies about $4 billion since 2006.

And money is available. Federal stimulus money must be allocated by the end of September, local voters have approved bonds totaling $30 billion for road and transit upgrades that must be under way by 2012, bridge tolls have increased raised four times in the last decade, and most counties in the region are collecting millions coming from local sales tax hikes approved by voters.

The area has not seen as much construction work since the mid-1990s, when the state focused on repairing or rebuilding 2,000 overpasses and bridges in the wake of the Northridge earthquake. Many of the current large-scale projects have been on hold for 10 years or more due to funding concerns.