Pipelines provide a safe and economic means of transporting fluids such as natural gas, crude oil, refined products, and natural gas liquids products across great distances and over all manner of terrain. As man-made systems, however, they can and do fail from time to time, sometimes with catastrophic effect. Figure 11.1 illustrates the aftermath of a recent gas pipeline rupture followed by a fire which resulted in the death of 12 people [1]. Such fatal events, however, are rare, accounting for less than 0.02% of the 45,000 transport-related deaths that occur annually in the United States [2]. The consequences of failures, when they do occur, are more commonly measured in terms of lost product and its effect if any, on the environment, as well as a disruption to business while a repair is made [3]. Repairs and environmental remediation, especially in sensitive areas, can however be very expensive. For example, the clean up cost of a recent relatively modest crude oil pipeline break in Canada amounted to $24 million, in addition to a $1.4 million fine levied on the company for causing environmental pollution. In recent years several high profile pipeline leaks and ruptures particularly on liquid hydrocarbon lines have created a poor public image of pipelines. On July 26, 2010 a 30 inch diameter pipeline conveying diluted bitumen ruptured near Marshall in Michigan spilling almost 20,000 barrels into Talmadge Creek, which flows into the Kalamazoo River. Fortunately the response effort to this, the largest onshore spill in US history prevented bitumen reaching Lake Michigan. The cleanup effort has been estimated to have cost almost one billion dollars. In June and December 2010, two pipeline breaks resulted in 1,200 barrels of crude oil being leaked into Red Butte Gardens in Salt Lake City. In June of the following year 42,000 gallons/1,000 barrels of oil leaked into the Yellowstone River from a pipeline break associated with seasonal heavy flooding. Even more recently the same pipeline operator suffered a break on its 65 year old line in Arkansas releasing 500,000 gallons (11,900 barrels) of crude oil causing significant environmental damage in the process and posing a threat to the local water supply. While environmental damage can eventually be remediated or mitigated such is not the case when fatalities result from natural gas pipeline ignitions. In September 2010, eight people died when a natural gas pipeline located in the neighbourhood of San Bruno, California, ruptured and ignited. The root cause of this incident was attributed to a faulty long seam weld.