Infrastructure is something that we use every day, like roads, bridges, and tunnels, but probably never think too much about. However, in the United States, many parts of the country's infrastructure are old, falling apart, and desperately need repair and upgrading. Tunnels especially are vital to transportation, and extremely dangerous when they collapse. This book explores eight tunnels of different types that are lifelines for transportation in the US, but are now at risk. Whether its Boston's Big Dig, the twin railroad tunnels under the Hudson River, California's Hetch Hetchey water system, or a rail tunnel in Baltimore that's more than 100 years old, these tunnels are very important to the entire country. Without emergency repairs and expansion, these tunnels could fail, with catastrophic results.