The collapse of a span in Minneapolis yesterday is raising questions about the overall safety of Bay Area bridges. Though the cause of the collapse - which sent as many as fifty cars into the Mississippi River below - is still unknown, the forty-year-old bridge was deemed "structurally deficient" in 2005, and was in the midst of repairs. According to the American Society of Civil Engineers, 26.3 percent of the nation's 595,363 bridges (or 156,335) were "structurally deficient" or "functionally obsolete" as of 2005. This was a slight improvement from 34.6 percent in 1992. The Federal Highway Administration shows just how old the country's bridges are. Most of California's bridges were built during the period from 1947 to 1981. And of the total 23,625, 6,708 were considered "structurally deficient" or "functionally obsolete" as of 2006. The American Society of Civil Engineers estimate eliminating all bridge deficiencies will cost $9.4 billion (in 2000 dollars) annually for a period of 20 years. A spokeswoman for the Golden Gate Bridge District reassured that bridges in the Bay Area are constantly being re-engineered because of the potential for earthquakes.