Surveyors work below the Interstate 495 bridge over the Christina River near Wilmington, Del., on Tuesday. The bridge was closed at the beginning of the week after officials discovered that eight support columns were tilting. Patrick Semansky/AP hide caption

itoggle caption Patrick Semansky/AP

Divers found a 2-inch-wide crack at the bottom of the fourth spillway pier from the left in this photo of the Wanapum Dam. Grant County Public Utility District hide caption

itoggle caption Grant County Public Utility District

Saudi women get into a taxi outside a shopping mall in Riyadh in 2012. Plans for a subway system in the Saudi capital are likely to provide the biggest benefits to women and the poor. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

An analyst works at a federal cybersecurity center in Idaho in 2011. Experts say Internet-connected infrastructure is a possible target of cyberwarfare. Mark J. Terrill/AP hide caption

itoggle caption Mark J. Terrill/AP