sentences:  A renewed focus was placed on maintenance and monitoring of radial gates, many of which were retrofitted to strengthen struts and bracing and ensure sufficient lubrication.After the 2001 terrorist attacks, the Bureau of Reclamation analyzed potential targets for vulnerability and measures that could be taken to eliminate or reduce possible threats.With 500,000 residents in the vicinity of the Folsom Dam, the possibility of an attack on the dam was great enough concern for Bureau officials to close Folsom Dam Road.