Witness a high-stakes repair job as Sean Riley and a crew of 100 highly trained men and women shut down the Trans-Alaska oil pipeline—the only conduit to market for almost 15 percent of the US domestic oil production. This major fix calls for swapping out a 32-ton valve system, but the size of the job is the least of their problems. Crude oil is not just highly toxic—its explosive. Follow the crew as it races to complete the fix in just 36 hours.