Nearly half a million miles of high-volume pipeline transport natural gas, oil, and other hazardous liquids across the United States. These transmission pipelines are integral to U.S. energy supply and have vital links to other critical infrastructure, such as power plants, airports, and military bases. While an efficient and fundamentally safe means of transport, many pipelines carry volatile, flammable, or toxic materials with the potential to cause public injury and environmental damage. The nation's pipeline networks are also widespread, running alternately through remote and densely populated regions, some above ground and some below. These systems are vulnerable to accidents and terrorist attack. Recent pipeline accidents in Marshall, MI, San Bruno, CA, Allentown, PA, and Laurel, MT, have demonstrated this vulnerability and have heightened congressional concern about pipeline risks. The federal program for pipeline safety resides primarily within the Department of Transportation (DOT), although its inspection and enforcement activities rely heavily upon partnerships with state pipeline safety agencies. The federal pipeline security program began with the DOT as well, immediately after the terror attacks of September 11, 2001, but pipeline security authority was subsequently transferred to the Department of Homeland Security (DHS) when the latter department was created. The DOT and DHS have distinct missions, but they cooperate to protect the nation's pipelines. The Federal Energy Regulatory Commission is not operationally involved in pipeline safety or security, but it can examine safety issues under its siting authority for interstate natural gas pipelines, and can allow pipeline companies under its rate jurisdiction to recover pipeline security costs. Collectively, these agencies administer a comprehensive and complex set of regulatory authorities which has been changing significantly over the last decade and continues to do so. The federal pipeline safety program is authorized through the fiscal year ending September 30, 2015, under the Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 ( P.L. 112-90 ), which was signed by President Obama on January 3, 2012. This report reviews the history of federal programs for pipeline safety and security, key policy issues, and recent developments leading up to P.L. 112-90 . Although the act contains over 30 substantive sections, this report focuses only on a subset of provisions of key interest in recent congressional debate. Of the nation's approximately half million miles of transmission pipeline, roughly 180,000 miles carry hazardous liquids—over 75% of the nation's crude oil and around 60% of its refined petroleum products, along with other products. Within this network, there are nearly 200 inter state crude oil and liquid fuel pipelines, which account for roughly 80% of total pipeline mileage and transported volume. The U.S. natural gas pipeline network consists of around 300,000 miles of inter state and intra state transmission. It also contains some 14,000 miles of onshore field and gathering pipeline, which connect gas extraction wells to processing facilities. Around 120 systems make up the inter state gas transmission network; another 90 or so systems operate strictly within individual states. These inter state and intra state gas transmission pipelines feed around 900,000 miles of regional pipelines in some 1,400 local distribution networks serving over 66 million customers. Natural gas pipelines also connect to 127 active liquefied natural gas (LNG) storage sites, which can augment pipeline gas supplies during peak demand periods. Taken as a whole, releases from pipelines cause few annual fatalities compared to other product transportation modes. According to the DOT, there were 14 deaths per year on average from all U.S. pipeline systems from 2007 through 2011. Accidental pipeline releases result from a variety of causes, including third-party excavation, corrosion, mechanical failure, control system failure, and operator error. Natural forces, such as floods and earthquakes, can also damage pipelines. There were 140 hazardous liquid pipeline accidents, 84 natural gas transmission (including gathering) pipeline accidents, and 58 natural gas distribution accidents in 2011. Although pipeline releases have caused relatively few fatalities in absolute numbers, a single pipeline accident can be catastrophic in terms of deaths and environmental damage. Notable pipeline accidents in recent years include: 1999― A gasoline pipeline explosion in Bellingham, WA, killed three people and caused $45 million in damage to a city water plant and other property. 2000― A natural gas pipeline explosion near Carlsbad, NM, killed 12 campers. 2006― Corroded pipelines on the North Slope of Alaska leaked over 200,000 gallons of crude oil in an environmentally sensitive area and temporarily shut down Prudhoe Bay oil production. 2007― An accidental release from a propane pipeline and subsequent fire near Carmichael, MS, killed two people, injured several others, destroyed four homes, and burned over 70 acres of grassland and woodland. 2010 ―A pipeline spill in Marshall, MI, released 819,000 gallons of crude oil into a tributary of the Kalamazoo River. 2010 —A natural gas pipeline explosion in San Bruno, CA, killed 8 people, injured 60 others, and destroyed 37 homes. 2011― A natural gas pipeline explosion in Allentown, PA, killed 5 people, damaged 50 buildings, and caused 500 people to be evacuated. 2011 ―A pipeline spill near Laurel, MT, released an estimated 42,000 gallons of crude oil into the Yellowstone River. 2012 —A natural gas pipeline explosion in Springfield, MA injured 21 people and heavily damaged over a dozen buildings. Such accidents have generated persistent scrutiny of pipeline regulation and have increased state and community activity related to pipeline safety. In addition to their vulnerability to accidents, pipelines may also be intentionally damaged by vandals and terrorists. Pipelines may also be vulnerable to "cyber-attacks" on supervisory control and data acquisition (SCADA) systems or attacks on electricity grids and communications networks. Oil and gas pipelines, globally, have been a favored target of terrorists, militant groups, and organized crime. In Colombia, for example, rebels have bombed the Caño Limón oil pipeline and other pipelines over 950 times since 1993. In 1996, London police foiled a plot by the Irish Republican Army to bomb gas pipelines and other utilities across the city. Militants in Nigeria have repeatedly attacked pipelines and related facilities, including the simultaneous bombing of three oil pipelines in May 2007. A Mexican rebel group similarly detonated bombs along Mexican oil and natural gas pipelines in July and September 2007. In June 2007, the U.S. Department of Justice arrested members of a terrorist group planning to attack jet fuel pipelines and storage tanks at the John F. Kennedy (JFK) International Airport in New York. Natural gas pipelines in British Columbia, Canada, were bombed six times between October 2008 and July 2009 by unknown perpetrators. In 2009, the Washington Post reported that over $1 billion of crude oil had been stolen directly from Mexican pipelines by organized criminals and drug cartels. Since September 11, 2001, federal warnings about Al Qaeda have mentioned pipelines specifically as potential terror targets in the United States. One U.S. pipeline of particular concern, and with a history of terrorist and vandal activity, is the Trans Alaska Pipeline System (TAPS), which transports crude oil from Alaska's North Slope oil fields to the marine terminal in Valdez. TAPS runs some 800 miles and delivered approximately 600,000 barrels of oil per day in 2011 (over 10% of U.S. domestic oil production). In 1999, Vancouver police arrested a man planning to blow up TAPS for personal profit in oil futures. In 2001, a vandal's attack on TAPS with a high-powered rifle forced a two-day shutdown and caused extensive economic and ecological damage. In January 2006, federal authorities acknowledged the discovery of a detailed posting on a website purportedly linked to Al Qaeda that reportedly encouraged attacks on U.S. pipelines, especially TAPS, using weapons or hidden explosives. In November 2007 a U.S. citizen was convicted of trying to conspire with Al Qaeda to attack TAPS and a major natural gas pipeline in the eastern United States. Notwithstanding the incidents cited above, to date, there have been no known Al Qaeda attacks on TAPS or other U.S. pipelines. The most recent U.S. federal threat assessment concludes "with high confidence that the terrorist threat to the U.S. pipeline industry is low ... [with] no specific or credible threat information indicating that violent transnational extremist groups or domestic extremists are actively plotting to conduct attacks on the U.S. pipeline industry." Terrorist activities are in constant flux, however, and difficult to predict, so terrorist attacks remain a possibility in the future. Although Al Qaeda attacks on U.S. pipelines may be perceived as unlikely, attacks by individuals not associated with organized or terrorist groups may be a growing concern. For example, in August 2011, federal agents arrested a U.S. citizen—acting alone—who confessed to planting an improvised explosive device (which failed to detonate) under a natural gas pipeline in Oklahoma. In June 2012, a man was critically injured attempting to plant an improvised explosive device along a natural gas pipeline in Plano, TX. One specific area of pipeline security risk that has recently come to the fore is SCADA system cybersecurity. In March 2012, the Industrial Control Systems Cyber Emergency Response Team within DHS identified an ongoing series of cyber intrusions among U.S. natural gas pipeline operators dating back to December 2011. According to the agency, various pipeline companies described targeted spear-phishing attempts and intrusions into multiple natural gas pipeline sector organizations "positively identified … as related to a single campaign. " In 2011, computer security company McAfee reported similar "coordinated covert and targeted" cyberattacks originating primarily in China against global energy companies. The attacks began in 2009 and involved spear-phishing, exploitation of Microsoft software vulnerabilities, and the use of remote administration tools to collect sensitive competitive information about oil and gas fields. In 2010, the Stuxnet computer worm was first identified as a threat to industrial control systems.