on and off briefly while the vessel passes under the bridge. During the 2011 Mississippi River floods, the bridge became dark for about 2 months because the transformers that supply the electricity for the lights were removed to prevent damage to them by flood waters. The bridge was re-lit in a ceremony which occurred on June 21, 2011. It was announced after the opening of the Big River Crossing along the Harahan Bridge to the south that the existing sodium vapor lights along the Hernando Desoto Bridge would be replaced with a new LED lighting display, thus making the Hernando de Soto Bridge the second bridge over the Mississippi River to be lit as such after the Harahan. The new display can be lit in sync with the Harahan Bridge and display various color patterns dependent upon special occasions or requests. Both displays have been created under an initiative called "Mighty Lights." The $14 million privately funded project was completed in 2018. Seismic retrofit project Between 2000 and 2015, the bridge underwent a seismic retrofitting project, allowing it to withstand a 7.7 magnitude earthquake, the similar magnitude of earthquakes during the 1811–12 New Madrid earthquakes. The retrofit project is also a means to protect the bridge as it is located within of the New Madrid Seismic Zone and serves as a major cargo route and traffic thoroughfare across the river. As part of this project, the main span, approaches, and ramps for the downtown exit were retrofitted. A bridge about west of the main span was rebuilt with earthquake considerations in mind. The federal government covered 80% of the cost, with Tennessee contributing 12% and Arkansas 8%. Incidents On August 23, 2007, an inspector discovered that a bridge pier on the approach bridge west of the river had settled overnight, and the bridge was subsequently closed to perform a precautionary inspection. The bridge was reopened later that day. On May 11, 2021, an inspection discovered a partially fractured tie girder on the Span A North truss. Two of the four plates comprising the box-shaped tension tie member were completely fractured and the bottom plate was partially fractured, leaving only the inside-facing plate intact. Since the severely compromised girder was one of a pair of load-bearing tension members that were critical to the structural integrity of the bridge's tied-arch design, the bridge was structurally unsound and at risk of collapse. The