Trans-Alaska Pipeline System

The Trans-Alaska Pipeline System (TAPS) is an oil transportation system spanning Alaska, including the trans-Alaska crude-oil pipeline, 12 pump stations, several hundred miles of feeder pipelines, and the Valdez Marine Terminal. TAPS is one of the world's largest pipeline systems. The core pipeline itself, which is commonly called the Alaska pipeline, trans-Alaska pipeline, or Alyeska pipeline, (or The pipeline as referred to by Alaskan residents), is an 800-mile (1,287 km) long, 48-inch (1.22 m) diameter pipeline that conveys oil from Prudhoe Bay, on Alaska's North Slope, south to Valdez, on the shores of Prince William Sound in southcentral Alaska. The crude oil pipeline is privately owned by the Alyeska Pipeline Service Company.

Quick Facts Location, Country ...

Trans-Alaska Pipeline System
The trans-Alaska oil pipeline, as it zig-zags across the landscape
Location of trans-Alaska pipeline
Location
Country	Alaska, United States
Coordinates	70°15′26″N 148°37′8″W
General direction	North–South
From	Prudhoe Bay, Alaska
Passes through	Deadhorse Delta Junction Fairbanks Fox Glennallen North Pole
To	Valdez, Alaska
Runs alongside	Dalton Highway Richardson Highway Elliott Highway
General information
Type	Pump stations
Owner	Alyeska Pipeline Service Company
Partners	BP (1970–2020) ConocoPhillips (1970–present) ExxonMobil (1970–present) Hilcorp (2020–present) Koch Industries (2003–2012) Unocal (1970–2019) Williams Companies (2000–2003)
Commissioned	1977; 47 years ago (1977)[1][2][3]
Technical information
Length	800.3 mi (1,288.0 km)
Maximum discharge	2.136 million bbl/d (339,600 m3/d)
Diameter	48 in (1,219 mm)
No. of pumping stations	12

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Oil was first discovered in Prudhoe Bay in 1968 and the 800 miles of 48" steel pipe was ordered from Japan in 1969 (U.S. steel manufacturers did not have the capacity at that time). However, construction was delayed for nearly 5 years due to legal and environmental issues. The eight oil companies that owned the rights to the oil hired Bechtel for the pipeline design and construction and Fluor for the 12 pump stations and the Valdez Terminal. Preconstruction work during 1973 and 1974 was critical and included the building of camps to house workers, construction of roads and bridges where none existed, and carefully laying out the pipeline right of way to avoid difficult river crossings and animal habitats. Construction of the pipeline system took place between 1975 and 1977. It was important for the United States to have a domestic source of oil to offset the high rise in foreign oil and the Alaska Pipeline fulfilled that obligation.

Building oil pipelines in the 1950s and 60s was not difficult in the contiguous United States. However, in building the Alaska Pipeline, engineers faced a wide range of difficulties, stemming mainly from the extreme cold and the difficult, isolated terrain. The construction of the pipeline was one of the first large-scale projects to deal with problems caused by permafrost, and special construction techniques had to be developed to cope with the frozen ground. The project attracted tens of thousands of workers to Alaska due to high wages, long work hours, and paid-for housing, causing a boomtown atmosphere in Valdez, Fairbanks, and Anchorage.

The first barrel of oil traveled through the pipeline in the summer of 1977,^[1][2][3][4] with full-scale production by the end of the year. Several notable incidents of oil leakage have occurred since, including those caused by sabotage, maintenance failures, and bullet holes.^[5] As of 2015, it had shipped over 17 billion barrels (2.7×10⁹ m³) of oil.^[6] The pipeline has been shown capable of delivering over two million barrels of oil per day but nowadays usually operates at a fraction of maximum capacity. If flow were to stop or throughput were too little, the line could freeze. The pipeline could be extended and used to transport oil produced from controversial proposed drilling projects in the nearby Arctic National Wildlife Refuge (ANWR).

Iñupiat people on the North Slope of Alaska had mined oil-saturated peat for possibly thousands of years, using it as fuel for heat and light. Whalers who stayed at Point Barrow saw the substance the Iñupiat called pitch and recognized it as petroleum. Charles Brower, a whaler who settled at Barrow and operated trading posts along the Arctic coast, directed geologist Alfred Hulse Brooks to oil seepages at Cape Simpson and Fish Creek in the far north of Alaska, east of the village of Barrow.^[7] Brooks' report confirmed the observations of Thomas Simpson, an officer of the Hudson's Bay Company who first observed the seepages in 1836.^[8] Similar seepages were found at the Canning River in 1919 by Ernest de Koven Leffingwell.^[9] Following the First World War, as the United States Navy converted its ships from coal to fuel oil, a stable supply of oil became important to the U.S. government. Accordingly, President Warren G. Harding established by executive order a series of Naval Petroleum Reserves (NPR-1 through -4) across the United States. These reserves were areas thought to be rich in oil and set aside for future drilling by the U.S. Navy. Naval Petroleum Reserve No. 4 was sited in Alaska's far north, just south of Barrow, and encompassed 23,000,000 acres (93,078 km²).^[10]

The first explorations of NPR-4 were undertaken by the U.S. Geological Survey from 1923 to 1925 and focused on mapping, identifying and characterizing coal resources in the western portion of the reserve and petroleum exploration in the eastern and northern portions of the reserve. These surveys were primarily pedestrian in nature; no drilling or remote sensing techniques were available at the time. These surveys named many of the geographic features of the areas explored, including the Philip Smith Mountains and quadrangle.^[11][12]

The petroleum reserve lay dormant until World War II provided an impetus to explore new oil prospects. The first renewed efforts to identify strategic oil assets were a two pronged survey using bush aircraft, local Inupiat guides, and personnel from multiple agencies to locate reported seeps. Ebbley and Joesting reported on these initial forays in 1943. Starting in 1944, the U.S. Navy funded oil exploration near Umiat Mountain, on the Colville River in the foothills of the Brooks Range.^[13] Surveyors from the U.S. Geological Survey spread across the petroleum reserve and worked to determine its extent until 1953, when the Navy suspended funding for the project. The USGS found several oil fields, most notably the Alpine and Umiat Oil Field, but none were cost-effective to develop.^[14]

Four years after the Navy suspended its survey, Richfield Oil Corporation (later Atlantic Richfield and ARCO) drilled an enormously successful oil well near the Swanson River in southern Alaska, near Kenai.^[15] The resulting Swanson River Oil Field was Alaska's first major commercially producing oil field, and it spurred the exploration and development of many others.^[16] By 1965, five oil and 11 natural gas fields had been developed. This success and the previous Navy exploration of its petroleum reserve led petroleum engineers to the conclusion that the area of Alaska north of the Brooks Range surely held large amounts of oil and gas.^[17] The problems came from the area's remoteness and harsh climate. It was estimated that between 200,000,000 barrels (32,000,000 m³) and 500,000,000 barrels (79,000,000 m³) of oil would have to be recovered to make a North Slope oil field commercially viable.^[15]

In 1967, Atlantic Richfield (ARCO) began detailed survey work in the Prudhoe Bay area. By January 1968, reports began circulating that natural gas had been discovered by a discovery well.^[18] On March 12, 1968, an Atlantic Richfield drilling crew hit paydirt.^[19] A discovery well began flowing at the rate of 1,152 barrels (183.2 m³) of oil per day.^[18] On June 25, ARCO announced that a second discovery well likewise was producing oil at a similar rate. Together, the two wells confirmed the existence of the Prudhoe Bay Oil Field. The new field contained more than 25 billion barrels (4.0×10^⁹ m³) of oil, making it the largest in North America and the 18th largest in the world.^[19]

The problem soon became how to develop the oil field and ship product to U.S. markets. Pipeline systems represent a high initial cost but lower operating costs, but no pipeline of the necessary length had yet been constructed. Several other solutions were offered. Boeing proposed a series of gigantic 12-engine tanker aircraft to transport oil from the field, the Boeing RC-1.^[20] General Dynamics proposed a line of tanker submarines for travel beneath the Arctic ice cap, and another group proposed extending the Alaska Railroad to Prudhoe Bay.^[21]

To test this, in 1969 Humble Oil and Refining Company sent a specially fitted oil tanker, the SS Manhattan, to test the feasibility of transporting oil via ice-breaking tankers to market.^[22] The Manhattan was fitted with an ice-breaking bow, powerful engines, and hardened propellers before successfully traveling the Northwest Passage from the Atlantic Ocean to the Beaufort Sea. During the voyage, the ship suffered damage to several of its cargo holds, which flooded with seawater. Wind-blown ice forced the Manhattan to change its intended route from the M'Clure Strait to the smaller Prince of Wales Strait. It was escorted back through the Northwest Passage by a Canadian Coast Guard icebreaker, the CCGS John A. Macdonald. Although the Manhattan transited the Northwest Passage again in the summer of 1970, the concept was considered too risky.^[23]

In February 1969, before the SS Manhattan had even sailed from its East Coast starting point, the Trans-Alaska Pipeline System (TAPS), an unincorporated joint group created by ARCO, British Petroleum, and Humble Oil in October 1968,^[24] asked for permission from the United States Department of the Interior to begin geological and engineering studies of a proposed oil pipeline route from Prudhoe Bay to Valdez, across Alaska. Even before the first feasibility studies began, the oil companies had chosen the approximate route of the pipeline.^[25]

Because TAPS hoped to begin laying pipe by September 1969, substantial orders were placed for steel pipeline 48 inches (122 cm) in diameter.^[26] No American company manufactured pipe of that specification, so three Japanese companies—Sumitomo Metal Industries, Nippon Steel Corporation and Nippon Kokan Kabushiki Kaisha—received a $100 million contract for more than 800 miles (1280 km) of pipeline. At the same time, TAPS placed a $30 million order for the first of the enormous pumps that would be needed to push the oil through the pipeline.^[27]

In June 1969, as the SS Manhattan traveled through the Northwest Passage, TAPS formally applied to the Interior Department for a permit to build an oil pipeline across 800 miles (1,300 km) of public land—from Prudhoe Bay to Valdez.^[28] The application was for a 100-foot (30.5 m) wide right of way to build a subterranean 48-inch (122-centimeter) pipeline including 11 pumping stations. Another right of way was requested to build a construction and maintenance highway paralleling the pipeline. A document of just 20 pages contained all of the information TAPS had collected about the route up to that stage in its surveying.^[29]

The Interior Department responded by sending personnel to analyze the proposed route and plan. Max Brewer, an arctic expert in charge of the Naval Arctic Research Laboratory at Barrow, concluded that the plan to bury most of the pipeline was completely unfeasible because of the abundance of permafrost along the route. In a report, Brewer said the hot oil conveyed by the pipeline would melt the underlying permafrost, causing the pipeline to fail as its support turned to mud. This report was passed along to the appropriate committees of the U.S. House and Senate, which had to approve the right-of-way proposal because it asked for more land than authorized in the Mineral Leasing Act of 1920 and because it would break a development freeze imposed in 1966 by former Secretary of the Interior Stewart Udall.^[30]

Udall imposed the freeze on any projects involving land claimed by Alaska Natives in hopes that an overarching Native claims settlement would result.^[31] In the fall of 1969, the Department of the Interior and TAPS set about bypassing the land freeze by obtaining waivers from the various native villages that had claims to a portion of the proposed right of way. By the end of September, all the relevant villages had waived their right-of-way claims, and Secretary of the Interior Wally Hickel asked Congress to lift the land freeze for the entire TAPS project. After several months of questioning by the House and Senate committees with oversight of the project, Hickel was given the authority to lift the land freeze and give the go-ahead to TAPS.^{[citation needed]}

TAPS began issuing letters of intent to contractors for construction of the "haul road", a highway running the length of the pipeline route to be used for construction. Heavy equipment was prepared, and crews prepared to go to work after Hickel gave permission and the snow melted.^[32] Before Hickel could act, however, several Alaska Native and conservation groups asked a judge in Washington, D.C., to issue an injunction against the project. Several of the native villages that had waived claims on the right of way reneged because TAPS had not chosen any Native contractors for the project and the contractors chosen were not likely to hire Native workers.^[33]

On April 1, 1970, Judge George Luzerne Hart, Jr., of the United States District Court for the District of Columbia, ordered the Interior Department to not issue a construction permit for a section of the project that crossed one of the claims.^[34] Less than two weeks later, Hart heard arguments from conservation groups that the TAPS project violated the Mineral Leasing Act and the National Environmental Policy Act, which had gone into effect at the start of the year. Hart issued an injunction against the project, preventing the Interior Department from issuing a construction permit and halting the project in its tracks.^[35]

After the Department of the Interior was stopped from issuing a construction permit, the unincorporated TAPS consortium was reorganized into the new incorporated Alyeska Pipeline Service Company.^[36] Former Humble Oil manager Edward L. Patton was put in charge of the new company and began to lobby strongly in favor of an Alaska Native claims settlement to resolve the disputes over the pipeline right of way.^[37]

Opposition to construction of the pipeline primarily came from two sources: Alaska Native groups and conservationists. Alaska Natives were upset that the pipeline would cross the land traditionally claimed by a variety of native groups, but no economic benefits would accrue to them directly. Conservationists were angry at what they saw as an incursion into America's last wilderness.^[38]

Conservation objections

Although conservation groups and environmental organizations had voiced opposition to the pipeline project before 1970, the introduction of the National Environmental Policy Act allowed them legal grounds to halt the project. Arctic engineers had raised concerns about the way plans for a subterranean pipeline showed ignorance of Arctic engineering and permafrost in particular.^[39] A clause in NEPA requiring a study of alternatives and another clause requiring an environmental impact statement turned those concerns into tools used by the Wilderness Society, Friends of the Earth, and the Environmental Defense Fund in their Spring 1970 lawsuit to stop the project.^[40]

The injunction against the project forced Alyeska to do further research throughout the summer of 1970. The collected material was turned over to the Interior Department in October 1970,^[41] and a draft environmental impact statement was published in January 1971.^[42] The 294-page statement drew massive criticism, generating more than 12,000 pages of testimony and evidence in Congressional debates by the end of March.^[43] Criticisms of the project included its effect on the Alaska tundra, possible pollution, harm to animals, geographic features, and the lack of much engineering information from Alyeska. One element of opposition the report quelled was the discussion of alternatives. All the proposed alternatives—extension of the Alaska Railroad, an alternative route through Canada, establishing a port at Prudhoe Bay, and more—were deemed to pose more environmental risks than construction of a pipeline directly across Alaska.^[42]

Opposition also was directed at the building of the construction and maintenance highway parallel to the pipeline. Although a clause in Alyeska's pipeline proposal called for removal of the pipeline at a certain point, no such provision was made for removal of the road. Sydney Howe, president of the Conservation Foundation, warned: "The oil might last for fifty years. A road would remain forever."^[44] This argument relied upon the slow growth of plants and animals in far northern Alaska due to the harsh conditions and short growing season. In testimony, an environmentalist argued that arctic trees, though only a few feet tall, had been seedlings "when George Washington was inaugurated".^[45]

The portion of the environmental debate with the biggest symbolic impact took place when discussing the pipeline's impact on caribou herds.^[46] Environmentalists proposed that the pipeline would have an effect on caribou similar to the effect of the U.S. transcontinental railroad on the American bison population of North America.^[46] Pipeline critics said the pipeline would block traditional migration routes, making caribou populations smaller and making them easier to hunt. This idea was exploited in anti-pipeline advertising, most notably when a picture of a forklift carrying several legally shot caribou was emblazoned with the slogan, "There is more than one way to get caribou across the Alaska Pipeline".^[47] The use of caribou as an example of the pipeline's environmental effects reached a peak in the spring of 1971, when the draft environmental statement was being debated.^[47]

Native objections

Main article: Alaska Native Claims Settlement Act

In 1902, the United States Department of Agriculture set aside 16,000,000 acres (64,750 km²) of Southeast Alaska as the Tongass National Forest.^[48] Tlingit natives who lived in the area protested that the land was theirs and had been unfairly taken. In 1935, Congress passed a law allowing the Tlingits to sue for recompense, and the resulting case dragged on until 1968, when a $7.5 million settlement was reached.^[49] Following the Native lawsuit to halt work on the Trans-Alaska Pipeline, this precedent was frequently mentioned in debate, causing pressure to resolve the situation more quickly than the 33 years it had taken for the Tlingits to be satisfied.^[50] Between 1968 and 1971, a succession of bills were introduced into the U.S. Congress to compensate statewide Native claims.^[51] The earliest bill offered $7 million, but this was flatly rejected.^[52]

The Alaska Federation of Natives, which had been created in 1966, hired former United States Supreme Court justice Arthur Goldberg, who suggested that a settlement should include 40 million acres (160,000 km²) of land and a payment of $500 million.^[52] The issue remained at a standstill until Alyeska began lobbying in favor of a Native claims act in Congress in order to lift the legal injunction against pipeline construction.^[52] In October 1971, President Richard Nixon signed the Alaska Native Claims Settlement Act (ANCSA). Under the act, Native groups would renounce their land claims in exchange for $962.5 million and 148.5 million acres (601,000 km²) in federal land.^[53] The money and land were split up among village and regional corporations, which then distributed shares of stock to Natives in the region or village. The shares paid dividends based on both the settlement and corporation profits.^[54] To pipeline developers, the most important aspect of ANCSA was the clause dictating that no Native allotments could be selected in the path of the pipeline.^[55]

Another objection of the natives was the potential for the pipeline to disrupt a traditional way of life. Many natives were worried that the disruption caused by the pipeline would scare away the whales and caribou that are relied upon for food.^[56]

In both the courts and Congress, Alyeska and the oil companies fought for the pipeline's construction amidst opposition concerning the pipeline's EIS (environmental impact statement). The arguments continued through 1971. Objections about the caribou herds were countered by observations of Davidson Ditch, a water pipeline with the same diameter of the Trans-Alaska Pipeline, which caribou were able to jump over.^[57] To those who argued that the pipeline would irrevocably alter Alaska wilderness, proponents pointed to the overgrown remnants of the Fairbanks Gold Rush, most of which had been erased 70 years later.^[58] Some pipeline opponents were satisfied by Alyeska's preliminary design, which incorporated underground and raised crossings for caribou and other big game, gravel and styrofoam insulation to prevent permafrost melting, automatic leak detection and shutoff, and other techniques.^[59] Other opponents, including fishermen who feared tanker leaks south of Valdez, maintained their disagreement with the plan.^[60]

All the arguments both for and against the pipeline were incorporated into the 3,500-page, 9-volume final environmental impact statement, which was released on March 20, 1972.^[55] Although Alaska Sen. Ted Stevens felt the statement "was not written by a proponent," it maintained the general approval for pipeline construction that was demonstrated in the draft statement.^[61] U.S. Secretary of the Interior Rogers Morton allowed 45 days of comment after the release, and conservationists created a 1,300-page document opposing the impact statement.^[62] This document failed to sway Judge Hart, who lifted the injunction on the project on August 15, 1972.^[63]

The environmental groups that had filed the injunction appealed the decision, and on October 6, 1972, the U.S. District Court of Appeals in Washington, D.C., partially reversed Hart's decision. The appeals court said that although the impact statement followed the guidelines set by the National Environmental Policy Act, it did not follow the Minerals Leasing Act, which allowed for a smaller pipeline right of way than was required for the Trans-Alaska Pipeline.^[63] The oil companies and Alyeska appealed this decision to the U.S. Supreme Court, but in April 1973, the court declined to hear the case.^[64]

Although the legal right-of-way was cleared by January 1974, cold weather, the need to hire workers, and construction of the Dalton Highway meant work on the pipeline itself did not begin until March.^[79] Between 1974 and July 28, 1977, when the first barrel of oil reached Valdez,^[3][80] tens of thousands of people worked on the pipeline.^[81] Thousands of workers came to Alaska, attracted by the prospect of high-paying jobs at a time when most of the rest of the United States was undergoing a recession.^[82]

Construction workers endured long hours, cold temperatures, and brutal conditions. Difficult terrain, particularly in Atigun Pass, Keystone Canyon, and near the Sagavanirktok River forced workers to come up with solutions for unforeseen problems.^[83] Faulty welds and accusations of poor quality control caused a Congressional investigation that ultimately revealed little.^[84][85] More than $8 billion was spent to build the 800 miles (1,300 km) of pipeline, the Valdez Marine Terminal, and 12 pump stations.^[86] The construction effort also had a human toll. Thirty-two Alyeska and contract employees died from causes directly related to construction. That figure does not include common carrier casualties.^[87]

Oil going into the Trans-Alaska Pipeline comes from one of several oil fields on Alaska's North Slope. The Prudhoe Bay Oil Field, the one most commonly associated with the pipeline, contributes oil,^[19] as do the Kuparuk,^[137] Alpine,^[138] Endicott, and Liberty oil fields, among others.^[139] Oil emerges from the ground at approximately 120 °F (49 °C) and cools to 111 °F (44 °C) by the time it reaches Pump Station 1 through feeder pipelines that stretch across the North Slope.^[140] North Slope crude oil has a specific gravity of 29.9 API at 60 °F (16 °C).^[141] Pipeline flow rate has been steady from 2013 to 2018, hovering just over half a million barrels per day. The minimum flow year was 2015 which averaged 508,446 barrels per day (80,836.5 m³/d),^[142] which is less than its theoretical maximum capacity of 2.14 million barrels per day (340,000 m³/d)^[143] or its actual maximum of 2.03 million barrels per day (323,000 m³/d) in 1988.^[144] From Pump Station 1, the average time taken by the oil to travel the entire length of the pipeline to Valdez has increased from 4.5 days to 18 days from 1988 to 2018.^[145]

The minimum flow through the pipeline is not as clearly defined as its maximum. Operating at lower flows will extend the life of the pipeline as well as increasing profit for its owners.^[146] The 2012 flow of 600,000 bbl/d is significantly less than what the pipeline was designed for. Low flowrates require that the oil move slower through the line, meaning that its temperature drops more than in high-flow situations. A freeze in the line would block a pig in the line, which would force a shutdown and repairs.^[146] A 2011 engineering report by Alyeska stated that, to avoid freezing, heaters would need to be installed at several pump stations. This report noted that these improvements could bring flow as low as 350,000 bbl/d, but it did not attempt to determine the absolute minimum. Other studies have suggested that the minimum is 70,000 to 100,000 bbl/d with the current pipeline. Alyeska could also replace the 48" pipeline from Prudhoe Bay to Fairbanks with a 20" pipeline and use rail the rest of the way, which would allow as little as 45,000 bbl/d.^[146]

Pumping stations maintain the momentum of the oil as it goes through the pipeline.^[147] Pump Station 1 is the northernmost of 11 pump stations spread across the length of the pipeline. The original design called for 12 pump stations with 4 pumps each, but Pump Station 11 was never built. Nevertheless, the pump stations retained their intended naming system. Eight stations were operating at startup, and this number increased to 11 by 1980 as throughput rose.^[148] As of December 2006, only five stations were operating, with Pump Station 5 held in reserve.^[149] Pump Stations 2 and 7 have a capacity of moving 60,000 gallons/minute (227,125 L/min), while all other stations have a capacity of 20,000 gal/min (75,708 L/min).^[150] The pumps are natural-gas or liquid-fueled turbines.^[143]

Because of meanders and thermal and seismic accommodations, the amount of 48-inch-diameter (1,200 mm) welded steel pipeline between the pipe stations and the end of the line is 800.3 miles (1,288.0 km), while the linear distance between the Prudhoe Bay and Valdez station endpoints is 639.34 miles (1,028.92 km).^[151] The pipeline crosses 34 major streams or rivers and nearly 500 minor ones. Its highest point is at Atigun Pass, where the pipeline is 4,739 feet (1,444 m) above sea level. The maximum grade of the pipeline is 145%, at Thompson Pass in the Chugach Mountains.^[151] The pipeline was created in 40 and 60-foot (12.2 and 18.3-meter) sections. Forty-two thousand of these sections were welded together to make a double joint, which was laid in place on the line. Sixty-six thousand "field girth welds" were needed to join the double joints into a continuous pipeline.^[152] The pipe is of two different thicknesses: 466 miles (750 km) of it is 0.462 inches (1.17 cm) thick, while the remaining 334 miles (538 km) is 0.562 inches (1.43 cm) thick.^[26] More than 78,000 vertical support members hold up the aboveground sections of pipeline,^[153] and the pipeline contains 178 valves.^[154]

At the end of the pipeline is the Valdez Marine Terminal, which can store 9.18 million barrels (1,460,000 m³) of oil across eighteen storage tanks.^[155] They are 63.3 feet (19.3 m) tall and 250 feet (76 m) in diameter. They average 85% full at any given time—7.8 million barrels (1,240,000 m³).^[156] Three power plants at the terminal generate 12.5 megawatts each.^[157] Four tanker berths are available for mooring ships in addition to two loading berths, where oil pumping takes place. More than 19,000 tankers have been filled by the marine terminal since 1977.^[158]

The pipeline is surveyed several times per day, mostly by air. Foot and road patrols also take place to check for problems such as leaks or pipe settling or shifting. The pipeline can be surveyed in as little as twenty one days, but most surveys take longer to ensure thoroughness.^[159] These external inspections are only part of standard maintenance, however. The majority of pipeline maintenance is done by pipeline pigs—mechanical devices sent through the pipeline to perform a variety of functions.^[160]

The most common pig is the scraper pig,^[161] which removes wax that precipitates out of the oil and collects on the walls of the pipeline. The colder the oil, the more wax buildup. This buildup can cause a variety of problems, so regular "piggings" are needed to keep the pipe clear.^[162] A second type of pig travels through the pipe and looks for corrosion. Corrosion-detecting pigs use either magnetic or ultrasonic sensors. Magnetic sensors detect corrosion by analyzing variations in the magnetic field of the pipeline's metal. Ultrasonic testing pigs detect corrosion by examining vibrations in the walls of the pipeline. Other types of pigs look for irregularities in the shape of the pipeline, such as if it is bending or buckling.^[163] "Smart" pigs, which contain a variety of sensors, can perform multiple tasks.^[164] Typically, these pigs are inserted at Prudhoe Bay and travel the length of the pipeline. In July 2009, a pig launcher was installed at Pump Station 8, near the midpoint of the pipeline.^[164]

A third type of common maintenance is the installation and replacement of sacrificial anodes along the subterranean portions of pipeline. These anodes reduce the corrosion caused by electrochemical action that affect these interred sections of pipeline. Excavation and replacement of the anodes is required as they corrode.^[165]

The pipeline has at times been damaged due to sabotage, human error, maintenance failures, and natural disasters. By law, Alyeska is required to report significant oil spills to regulatory authorities.^[167] The Exxon Valdez oil spill is the best-known accident involving Alaska oil, but it did not involve the pipeline itself.^[168] Following the spill, Alyeska created a rapid response force that is paid for by the oil companies,^[169] including ExxonMobil, which was found liable for the spill.^[170]

An explosion on July 8, 1977, Pump Station No. 8, killed one worker, injured five others, and destroyed a pump station.^[171][172] A Congressional committee later announced the cause was workers not following the proper procedures, causing crude oil to flow into a pump under repair at the time.^[173] In its first two months of operation, from June 20 to August 15, 1977, seven incidents and accidents caused the pipeline to be shut down periodically. The NTSB investigated the system, and made recommendations.^[174][175]

The largest oil spill involving the main pipeline took place on February 15, 1978, when an unknown individual blew a 1-inch (2.54-centimeter) hole in it at Steele Creek, just east of Fairbanks.^[176] Approximately 16,000 barrels (2,500 m³) of oil leaked out of the hole before the pipeline was shut down.^[166] After more than 21 hours, it was restarted.^[177]

The steel pipe is resistant to gunshots and has resisted them on several occasions, but on October 4, 2001, a drunken gunman named Daniel Carson Lewis shot a hole into a weld near Livengood, causing the second-largest mainline oil spill in pipeline history.^[178] Approximately 6,144 barrels (976.8 m³) leaked from the pipeline; 4,238 barrels (673.8 m³) were recovered and reinjected into the pipeline.^[179] Nearly 2 acres (8,100 m²) of tundra were soiled and were removed in the cleanup.^[180] The pipeline was repaired and was restarted more than 60 hours later.^[181] Lewis was found guilty in December 2002 of criminal mischief, assault, drunken driving, oil pollution, and misconduct.^[182]

The pipeline was built to withstand earthquakes, forest fires, and other natural disasters. The 2002 Denali earthquake occurred along a fault line that passed directly underneath the pipeline.^[183] The slider supports in that particular 1,900-foot section of the pipeline, right over the fault line, were designed to accommodate the ground slipping 20 feet horizontally and 5 vertically. In this 7.9 magnitude earthquake, the ground shifted 14 feet horizontally and 2.5 vertically. The pipeline did not break, but some slider supports were damaged, and the pipeline shut down for more than 66 hours as a precaution.^[181][184] In 2004, wildfires overran portions of the pipeline, but it was not damaged and did not shut down.^[185][186]

In May 2010, as much as several thousands of barrels were spilled from a pump station near Fort Greely during a scheduled shutdown. A relief valve control circuit failed during a test of the fire control system, and oil poured into a tank and overflowed onto a secondary containment area.^[187]

A leak was discovered on January 8, 2011, in the basement of the booster pump at Pump Station 1. For more than 80 hours, pipeline flow was reduced to 5 percent of normal. An oil collection system was put in place, and full flow resumed until the pipeline was again shut down while a bypass was installed to avoid the leaking section.^{[188][189][190]}

Heavy rains in Alaska resulting from climate change^{[citation needed]} have brought flooding uncomfortably close to the pipeline in recent years. In May 2019, the Dietrich River flooded north of Coldfoot, eroding 25–50 feet of riverbank, necessitating emergency work that left only an 80-foot buffer between the river and the pipeline. A few months later, in August, the Sagavanirktok River flooded, eroding 100 feet of river bank, and leaving only a 30-foot buffer between the river and the pipeline. The Lowe River also flooded near the pipeline in March 2019, and again in June 2020. Although Alyeska appears to be responding by stockpiling construction and emergency response materials, and has installed ground chillers beneath a stretch of pipeline 57 miles northwest of Fairbanks, comprehensive information on plans for addressing pipeline breaks in "high consequence areas" is not readily available.^[191]

In 2021, the pipeline was damaged due to thawing permafrost for the first time. Permafrost, which is ground that has been frozen for more than two years, is essential to the integrity of the pipeline. About 57 miles northwest of Fairbanks, thawing permafrost caused slope creep, which in turn caused the supports of the pipeline to twist and bend. Alyeska Corporation had to petition the Alaska Department of Natural Resources to conduct emergency defensive work to keep the permafrost stable.^[192]

The original design for the pipeline in the early 1970s called for a 25-year useful life with an expected 10 billion barrels of Prudhoe Bay oil production. By most economic, engineering and construction measures, the Alaska Pipeline has been a huge success. However, since the early 2000s, declines in oil production have posed a serious problem for the pipeline.^[193] As the flow rate slows, oil spends longer in the pipeline, which allows it to cool much further while travelling to Valdez. It cannot be allowed to fall below freezing (32 °F), otherwise the pipeline could seize up, crack, and rupture, as the water content would separate from the oil and freeze in place.^[145] A "Low Flow Impact Study" conducted by the pipeline operators, Alyeska, concluded in June 2011 that the minimum flow for the pipeline as it currently existed was 300,000 to 350,000 barrels per day in the winter.^[194]

This minimum flow rate is a legally contentious figure, since the taxable value of the pipeline is largely dependent on how long it can be operated.^[194] In late 2011, the Alaska Superior Court ruled that Alyeska's low flow study was invalid, and it ruled in favor of an internal BP study.^[146] The BP study concluded that with the installation of heaters along the pipeline route, the minimum flow could be lowered to 70,000 barrels per day (11,000 m³/d).^[194] This court ruling increased ninefold the taxed property value of the pipeline.^[195] A study by the National Resources Defense Council that was also cited in this court case put specific numbers to this suggestion, and concluded that an investment of $0.8 billion in shoring up the pipeline could extend its lifespan long enough to extract an additional $28 billion of oil from existing wells alone.^{[194][146][196]} This NRDC study additionally explained: "This is a lower minimum throughput level than what is implied in Alyeska’s Low Flow Impact Study (LoFIS). We did not use the minimum throughput level implied by LoFIS because we have serious reservations about the assumptions used in the study and the LoFIS does not provide adequate data to support its claims."^[196]

The Trans-Alaska Pipeline System Renewal Environmental Impact Statement estimated in 2010 that flow levels would be workable through at least 2032^[197] due to ongoing exploration outside ANWR. Improvements that allow low flow-rates could extend its lifespan as far as 2075.^[146]

As the pipeline's flow has diminished, its ownership has fluctuated. In 2000, as Exxon and Mobil merged, Mobil sold its 3.1% stake in the pipeline to Williams Companies as a condition of the merger.^[198] Three years later, Williams sold that share to Koch Alaska Pipeline Company, a subsidiary of Koch Industries.^[199] Nine years later, Koch announced it would sell its share to the other pipeline owners, as did Unocal, which had held a small ownership share since 1970.^[200] In 2019, BP announced plans to sell its Alaska operations to Hilcorp Energy Company.^[201] The deal, which closed in 2020, included BP's 49.1% ownership share of the Trans-Alaska Pipeline System.^[202] Opponents of the deal expressed concerns that Hillcorp, which did not fully disclose its finances, will lack the resources and expertise needed to address flooding and thawing-related safety concerns resulting from climate change.^[203]

By the terms of its land grants and leases, the owners of the Alaska Pipeline will be required to remove the pipeline and supporting equipment at the end of its life, except for cleaned and capped underground pipes.^[204] This multi-billion-dollar project is required to be paid for out of funds specifically charged to oil transport customers for this purpose, though as of 2004 these funds were co-mingled with other money and the amount needed was in dispute.^[204]

• Alaska gas pipeline, proposed
• Boeing RC-1, a proposed cargo aircraft to transport the oil from Alaska
• Canol pipeline
• Dalton Highway, which parallels the northern section of the pipeline
• Prudhoe Bay oil spill
• Athabasca, the novel by Alistair MacLean where the pipeline is prominently featured