The Trans-Alaska Pipeline System (TAPS) is an oil transportation system in Alaska. It includes the trans-Alaska crude-oil pipeline, 12 pump stations, hundreds of miles of feeder pipelines, and the Valdez Marine Terminal. TAPS is one of the largest pipeline systems in the world. The main pipeline, often called the Alaska pipeline, trans-Alaska pipeline, or Alyeska pipeline, is 800 miles long and 48 inches wide. It carries oil from Prudhoe Bay on Alaska’s North Slope to Valdez on the shores of Prince William Sound in southcentral Alaska. The crude oil pipeline is owned by the Alyeska Pipeline Service Company.

Oil was first found in Prudhoe Bay in 1968. In 1969, the 800 miles of 48-inch steel pipe were ordered from Japan because U.S. steel companies could not make enough at that time. However, construction was delayed for about five years due to legal and environmental problems. Eight oil companies that owned the oil rights hired Bechtel to design and build the pipeline and Fluor to build the 12 pump stations and the Valdez Terminal. From 1973 to 1974, workers built camps, roads, and bridges where none existed. They also planned the pipeline route carefully to avoid rivers and animal habitats. Construction of the pipeline system happened between 1975 and 1977. It was important for the United States to have a domestic source of oil to reduce reliance on foreign oil, and the Alaska Pipeline helped achieve this goal.

Building oil pipelines in the 1950s and 1960s was easier in the lower 48 states of the U.S. However, engineers faced many challenges when building the Alaska Pipeline. These included extreme cold and difficult, remote terrain. The pipeline project was one of the first large-scale efforts to address problems caused by permafrost, which is frozen ground that stays frozen for long periods. Special construction methods were needed to handle the frozen ground. The project brought tens of thousands of workers to Alaska because of high pay, long hours, and free housing, which led to rapid population growth in Valdez, Fairbanks, and Anchorage.

The first barrel of oil moved through the pipeline in the summer of 1977, and full production began by the end of the year. Since then, several oil leaks have occurred due to sabotage, equipment failures, and damage from bullets. By 2025, the pipeline had transported over 19 billion barrels of oil. It is capable of moving more than 2 million barrels of oil per day but currently operates at about 470,000 barrels per day. If the flow stops or slows too much, the pipeline could freeze. The pipeline could be extended in the future to transport oil from proposed drilling projects in the nearby Arctic National Wildlife Refuge (ANWR).

Origins

The Iñupiat people of the North Slope in Alaska used oil-filled peat as fuel for heat and light for many years. Whalers who stayed at Point Barrow noticed the substance the Iñupiat called "pitch" and recognized it as petroleum. Charles Brower, a whaler who lived in Barrow and ran trading posts along the Arctic coast, showed geologist Alfred Hulse Brooks where oil seeped from the ground at Cape Simpson and Fish Creek, which are far north of Barrow. Brooks’ report supported earlier observations by Thomas Simpson, an officer of the Hudson’s Bay Company who first saw the seepages in 1836. Similar oil seepages were found at the Canning River in 1919 by Ernest de Koven Leffingwell.

After World War I, the U.S. Navy began switching its ships from coal to fuel oil, making a steady oil supply important for the government. President Warren G. Harding created four Naval Petroleum Reserves (NPR-1 through -4) across the United States by executive order. These reserves were areas believed to contain oil and set aside for future drilling by the Navy. Naval Petroleum Reserve No. 4 was located in northern Alaska, just south of Barrow, and covered 23,000,000 acres (93,078 km²).

The first studies of NPR-4 were done by the U.S. Geological Survey from 1923 to 1925. These studies focused on mapping coal resources in the western part of the reserve and looking for petroleum in the eastern and northern areas. At that time, no drilling or advanced technology was used, so the work was done by walking and observing. These surveys named many geographic features, including the Philip Smith Mountains and quadrangle.

The petroleum reserve remained unused until World War II created a need to find new oil sources. In 1943, Ebbley and Joesting reported on early efforts to locate oil using bush aircraft, Inupiat guides, and teams from multiple agencies. Starting in 1944, the U.S. Navy funded oil exploration near Umiat Mountain on the Colville River in the Brooks Range foothills. The U.S. Geological Survey studied the area until 1953, when the Navy stopped funding the project. Surveys found several oil fields, including the Alpine and Umiat Oil Fields, but none were cost-effective to develop.

Four years after the Navy stopped its work, Richfield Oil Corporation (later known as Atlantic Richfield and ARCO) drilled a successful oil well near the Swanson River in southern Alaska, near Kenai. This discovery, called the Swanson River Oil Field, was Alaska’s first major oil field that produced oil for sale. By 1965, five oil fields and 11 natural gas fields had been developed. Engineers later concluded that the area north of the Brooks Range likely held large oil and gas reserves. However, the region’s remoteness and harsh weather made it difficult to develop. Experts estimated that between 200,000,000 and 500,000,000 barrels of oil would need to be extracted to make a North Slope oil field profitable.

In 1967, Atlantic Richfield (ARCO) began detailed surveys in the Prudhoe Bay area. By January 1968, reports suggested natural gas had been found. On March 12, 1968, an ARCO drilling team discovered oil, with a well producing 1,152 barrels (183.2 m³) of oil daily. A second well, drilled in June 1968, also produced oil at a similar rate. These findings confirmed the existence of the Prudhoe Bay Oil Field, which contained over 25 billion barrels (4.0 × 10⁹ m³) of oil, making it the largest in North America and the 18th largest in the world.

The challenge then became how to develop the field and transport oil to U.S. markets. Pipelines are expensive to build but cheaper to operate, but no pipeline of the needed length had been built. Other ideas included Boeing’s proposal for large 12-engine tanker aircraft, General Dynamics’ plan for submarines to travel under Arctic ice, and extending the Alaska Railroad to Prudhoe Bay.

To test the idea of using ships, Humble Oil and Refining Company sent the oil tanker SS Manhattan in 1969. The ship had an ice-breaking bow, strong engines, and reinforced propellers. It successfully traveled the Northwest Passage from the Atlantic Ocean to the Beaufort Sea. However, the ship suffered damage to its cargo holds, which flooded with seawater. Strong winds forced the Manhattan to change its route from the M’Clure Strait to the Prince of Wales Strait. The ship was escorted back by a Canadian Coast Guard icebreaker, the CCGS John A. Macdonald. Although the Manhattan completed the journey again in 1970, the plan was considered too risky.

Forming Alyeska

In February 1969, before the SS Manhattan left its starting point on the East Coast, the Trans-Alaska Pipeline System (TAPS), a group formed by ARCO, British Petroleum, and Humble Oil in October 1968, asked the United States Department of the Interior for permission to begin studying a proposed oil pipeline route from Prudhoe Bay to Valdez, across Alaska. Before any studies started, the companies had already chosen the general path for the pipeline.

Because TAPS wanted to begin laying the pipeline by September 1969, it ordered large amounts of steel pipe that was 48 inches (122 cm) in diameter. No American company made pipe of that size, so three Japanese companies—Sumitomo Metal Industries, Nippon Steel Corporation, and Nippon Kokan Kabushiki Kaisha—received a $100 million contract to supply more than 800 miles (1,280 km) of pipeline. At the same time, TAPS ordered $30 million worth of large pumps needed to move oil through the pipeline.

In June 1969, as the SS Manhattan traveled through the Northwest Passage, TAPS formally requested a permit from the Interior Department to build an oil pipeline across 800 miles (1,300 km) of public land from Prudhoe Bay to Valdez. The request included a 100-foot (30.5 m) wide area for a buried 48-inch (122 cm) pipeline with 11 pumping stations. Another area was requested for a highway to support construction and maintenance. A 20-page document provided all the information TAPS had collected about the route up to that point.

The Interior Department sent experts to analyze the proposed route and plan. Max Brewer, an Arctic expert from the Naval Arctic Research Laboratory in Barrow, concluded that burying most of the pipeline was not possible due to the large amount of permafrost along the route. In a report, Brewer explained that the heat from the oil could melt the permafrost, causing the pipeline to collapse as its support turned to mud. This report was shared with U.S. House and Senate committees, which had to approve the project because it required more land than allowed by the Mineral Leasing Act of 1920 and would break a development freeze imposed in 1966 by former Interior Secretary Stewart Udall.

Udall had frozen projects involving land claimed by Alaska Natives to encourage a settlement for Native claims. In the fall of 1969, the Interior Department and TAPS worked to bypass the freeze by getting waivers from Native villages that claimed parts of the pipeline route. By late September, all relevant villages had waived their claims, and Interior Secretary Wally Hickel asked Congress to lift the freeze for the entire TAPS project. After months of review by House and Senate committees, Hickel was given authority to lift the freeze and approve the project.

TAPS began sending letters to contractors to build the "haul road," a highway along the pipeline route for construction. Heavy equipment was prepared, and crews were ready to start work after Hickel gave permission and the snow melted. Before Hickel could act, however, Alaska Native and conservation groups asked a judge in Washington, D.C., to stop the project. Some Native villages that had waived their claims later changed their decision because TAPS had not hired Native contractors, and the chosen contractors were unlikely to hire Native workers.

On April 1, 1970, Judge George Luzerne Hart, Jr., of the U.S. District Court for the District of Columbia, ordered the Interior Department not to issue a construction permit for a section of the project that crossed a Native claim. 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 taken effect at the start of the year. Hart issued an injunction that blocked the Interior Department from giving a construction permit and stopped the project.

After the Interior Department was prevented from issuing a permit, the unincorporated TAPS group was reorganized into the new company Alyeska Pipeline Service Company. Edward L. Patton, a former Humble Oil manager, became the company’s leader and strongly supported an Alaska Native claims settlement to resolve disputes over the pipeline route.

Opposition

Opposition to building the pipeline mainly came from two groups: Alaska Native communities and conservationists. Alaska Natives were upset because the pipeline would cross land that these groups had traditionally claimed, but they would not receive any direct economic benefits from the project. Conservationists were concerned that the pipeline would harm America’s last wild areas.

Before 1970, conservation and environmental groups had already spoken out against the pipeline. However, the National Environmental Policy Act (NEPA) gave them legal tools to stop the project. Engineers working in the Arctic had warned that the plans for an underground pipeline ignored important details about building in cold regions, especially permafrost. NEPA required a study of other possible options and an environmental impact statement. These requirements became tools used by groups like the Wilderness Society, Friends of the Earth, and the Environmental Defense Fund in a lawsuit in 1970 to block the pipeline.

A court order forced Alyeska, the company building the pipeline, to do more research during the summer of 1970. The findings were sent to the Interior Department in October 1970, and a draft environmental impact statement was released in January 1971. This 294-page report faced strong criticism, leading to more than 12,000 pages of testimony and evidence in Congress by March. People criticized the project for its effects on the Alaska tundra, possible pollution, harm to animals and natural features, and the lack of detailed engineering information from Alyeska. However, the report addressed concerns about alternatives to the pipeline, such as using the Alaska Railroad, building a route through Canada, or creating a port at Prudhoe Bay. These options were said to cause more environmental harm than the pipeline itself.

Opposition also focused on the construction and maintenance highway built alongside the pipeline. Although Alyeska’s proposal included a plan to remove the pipeline at a future date, no similar plan was made for the highway. Sydney Howe, president of the Conservation Foundation, warned that the highway could last much longer than the oil it helped transport. He pointed out that plants and animals in northern Alaska grow very slowly because of harsh conditions and short growing seasons. In testimony, an environmentalist noted that small Arctic trees, though only a few feet tall, had been growing since the time of George Washington’s presidency.

A major symbolic debate centered on the pipeline’s effect on caribou herds. Environmentalists compared the pipeline’s impact on caribou to the harm caused by the U.S. transcontinental railroad to American bison. Critics argued the pipeline would block caribou migration routes, leading to smaller populations and easier hunting. This idea was used in anti-pipeline ads, including a picture of a forklift carrying legally shot caribou with the slogan, “There is more than one way to get caribou across the Alaska Pipeline.” This issue became especially important in 1971 when the draft environmental statement was being debated.

In 1902, the U.S. Department of Agriculture set aside 16 million acres of Southeast Alaska as the Tongass National Forest. Tlingit Native people who lived there protested that the land belonged to them and had been unfairly taken. In 1935, Congress passed a law allowing the Tlingits to sue for compensation. The case lasted until 1968, when a $7.5 million settlement was reached. After the Native groups opposed the Trans-Alaska Pipeline, this precedent was often mentioned in debates, pushing for a quicker resolution than the 33 years it took for the Tlingits to be compensated. Between 1968 and 1971, several bills were introduced in Congress to address Native land claims. The earliest bill offered $7 million, but it was rejected.

The Alaska Federation of Natives, formed in 1966, hired former Supreme Court justice Arthur Goldberg. He suggested a settlement that included 40 million acres of land and $500 million in payments. The issue remained unresolved until Alyeska lobbied Congress to support a Native claims act, which would lift the legal block on pipeline construction. In October 1971, President Richard Nixon signed the Alaska Native Claims Settlement Act (ANCSA). Under this law, Native groups gave up their land claims in exchange for $962.5 million and 148.5 million acres of federal land. The money and land were divided among village and regional corporations, which then gave shares of stock to Native people in the area. These shares paid dividends based on the settlement and the corporations’ profits. For pipeline developers, the most important part of ANCSA was the rule that no Native land could be chosen for the pipeline’s path.

Another concern from Native groups was the pipeline’s potential to disrupt their traditional way of life. Many worried that the pipeline’s construction would scare away whales and caribou, which are important food sources for their communities.

Legal issues and politics

In both the courts and Congress, Alyeska and the oil companies worked to build the pipeline despite concerns about the environmental impact statement (EIS). These arguments continued until 1971. People who worried about caribou herds were told that caribou could jump over Davidson Ditch, a water pipeline with the same size as the Trans-Alaska Pipeline. Others who believed the pipeline would permanently change Alaska’s wilderness were shown the overgrown remains of the Fairbanks Gold Rush, which had mostly disappeared after 70 years. Some opponents were satisfied with Alyeska’s early design, which included underground crossings for caribou, insulation to protect permafrost, leak detection systems, and other safety features. However, fishermen worried about oil spills near Valdez and still opposed the plan.

The final EIS, which included all arguments for and against the pipeline, was released on March 20, 1972. It was a 3,500-page, 9-volume document. Senator Ted Stevens said the EIS was not written by someone supporting the pipeline, but it still showed general support for building it. The U.S. Secretary of the Interior allowed 45 days for public comments, and conservationists created a 1,300-page report opposing the EIS. However, Judge Hart lifted the legal stop on the project on August 15, 1972.

Environmental groups appealed this decision, and in October 1972, a court in Washington, D.C., partially reversed Judge Hart’s ruling. The court said the EIS met the rules of the National Environmental Policy Act (NEPA) but did not follow the Minerals Leasing Act, which allowed for a smaller pipeline right-of-way. The oil companies and Alyeska appealed to the U.S. Supreme Court, but the court decided not to hear the case in April 1973.

Because the court said the Minerals Leasing Act did not cover the pipeline’s needs, Alyeska and the oil companies asked Congress to change the law or create a new one. The Senate Interior Committee started hearings on new laws in March 1973. Environmental groups shifted their focus from fighting the pipeline to opposing changes to the law or new bills. By 1973, these groups tried to push for alternatives like a Trans-Canada pipeline or a railroad, believing these options would be easier to stop. However, these alternatives would cover more land and cause more environmental harm than the Trans-Alaska Pipeline.

Hearings in the Senate and House continued through 1973. On July 13, an amendment asking for more study of the project was rejected. Later, an amendment by Senator Mike Gravel, which said the pipeline met all NEPA requirements and allowed a larger right-of-way, passed in the Senate. The vote was tied, and Vice President Spiro Agnew cast the deciding vote. A similar amendment was approved in the House on August 2.

On October 17, 1973, the Organization of Arab Petroleum Exporting Countries announced an oil embargo against the United States. This caused gasoline prices to rise, shortages, and rationing. President Richard Nixon, who had supported the pipeline before the crisis, pushed for it as a solution. He emphasized the pipeline as a priority in September and November 1973. Under pressure from voters, Congress passed the Trans-Alaska Pipeline Authorization Act, which removed legal barriers, offered financial support, and granted a right-of-way for construction. The House approved the act on November 12, and the Senate passed it the next day. Nixon signed it into law on November 16. A federal right-of-way was granted on January 3, 1974, and the oil companies began work on January 23.

Construction

Although the legal path for the pipeline was cleared by January 1974, work on the pipeline itself did not start until March 1974. This delay was caused by cold weather, the need to hire workers, and the construction of the Dalton Highway. From 1974 until July 28, 1977, when the first barrel of oil reached Valdez, tens of thousands of people worked on the pipeline. Many workers came to Alaska because they were looking for high-paying jobs during a time when much of the rest of the United States was experiencing a recession.

Construction workers faced long hours, cold temperatures, and very tough conditions. Difficult terrain, especially in areas like Atigun Pass, Keystone Canyon, and near the Sagavanirktok River, required workers to solve unexpected problems. Issues with faulty welds and claims of poor quality control led to a government investigation, but the investigation found little evidence of serious problems. Over $8 billion was spent to build the 800-mile (1,300 km) pipeline, the Valdez Marine Terminal, and 12 pump stations. The construction also had a human cost: 32 Alyeska and contract employees died from causes directly related to the work. This number does not include deaths of workers from other transportation companies.

Impact

The construction of the pipeline brought a large increase in economic activity to towns along its route. Before the pipeline was built, many people in towns like Fairbanks, which was still recovering from a serious flood in 1967, supported the project. However, by 1976, after the town faced higher crime rates, overused public services, and a large number of newcomers unfamiliar with local traditions, 56% of residents said the pipeline had made life in Fairbanks worse. In Valdez, the population grew rapidly: it was 1,350 in 1974, 6,512 by summer 1975, and 8,253 by 1976.

This population increase caused many problems. Home prices rose sharply. A house that sold for $40,000 in 1974 cost $80,000 in 1975. In Valdez, land that sold for $400 in the late 1960s was priced at $4,000 in 1973, $8,000 in 1974, and $10,000 in 1975. High demand for housing and rising prices caused rents to increase. Small log cabins with no plumbing rented for $500 a month. In Fairbanks, one two-bedroom home housed 45 pipeline workers who shared beds on a rotating schedule for $40 per week. In Valdez, an apartment that cost $286 per month in December 1974 rose to $520 per month in March 1975 and reached $1,600 per month—plus two required roommates—in April 1975. Hotels in nearby areas, such as Glenallen, 115 miles north of Valdez, were fully booked.

High wages paid to pipeline workers led to increased spending, which caused demand for higher wages among other workers in Alaska. Many businesses struggled to meet this demand, and job turnover became very high. In Fairbanks, yellow cabs had a turnover rate of 800%, and a nearby restaurant had a turnover rate of over 1,000%. Many jobs were filled by high school students, even if they had little experience. To help students who worked full-time, a Fairbanks high school operated in two shifts: one in the morning and one in the afternoon. More people and higher wages increased the demand for goods and services. Long lines became common in Fairbanks, and the local McDonald’s became the second-highest-selling store in the world, after a new store in Stockholm. Companies like Alyeska and its contractors bought large amounts of supplies from local stores, causing shortages of items like cars, tractor parts, water softener salt, batteries, and ladders.

The large amounts of money being earned and spent led to an increase in crime and illegal activities in towns along the pipeline route. This was worsened by the fact that many police officers and state troopers left their jobs to become pipeline security guards, which paid much higher wages. Second Avenue in Fairbanks became a place where prostitution was common, and many bars operated in the area. In 1975, the Fairbanks Police Department estimated that between 40 and 175 prostitutes worked in the city of 15,000 people. Some conflicts occurred between pimps, who fought over territory. In 1976, police responded to a shootout between rival pimps who used automatic weapons. Most police work focused on stopping drunken fights. On the pipeline itself, theft was a major problem. Poor record-keeping allowed tools and equipment to be stolen. In 1975, the Los Angeles Times reported that as many as 200 of Alyeska’s 1,200 yellow-painted trucks were missing from Alaska and found in places like Miami and Mexico City. Alyeska denied the claim, saying only 20–30 trucks were missing. Theft was common, as workers sent empty boxes to pipeline camps, which were later filled with stolen items and shipped out. After Alyeska required all packages to be sealed in front of a security guard, the number of packages sent from camps dropped by 75%.

The wealth from oil production in Prudhoe Bay and other North Slope fields since 1977 is worth more than all the fish ever caught, all the furs ever trapped, all the trees ever cut down, and all other resources ever extracted from Alaska. The economic impact of the pipeline is clear: the value of oil production from Prudhoe Bay alone exceeds the total value of all other resources taken from Alaska in its history.

After the Trans-Alaska Pipeline System was completed in 1977, the state of Alaska became dependent on taxes from oil producers and shippers. Before 1976, Alaska had the highest personal income tax rate in the United States at 14.5%. The state’s gross product was $8 billion, and Alaskans earned $5 billion in personal income. Thirty years later, Alaska had no personal income tax, its gross product was $39 billion, and Alaskans earned $25 billion in personal income. The state moved from being the most taxed in the U.S. to one of the least taxed.

The pipeline and the taxes it generated changed Alaska’s economy. Alyeska and oil companies invested billions of dollars into the state during construction and in the years that followed. These taxes also changed the state’s tax system. By 1982, 86.5% of Alaska’s revenue came directly from the petroleum industry.

Alaska’s oil taxes have changed several times since 1977, but the basic structure remains similar. The state receives royalties from oil produced on state land. It also collects property taxes on oil production structures and pipeline facilities, which is the only state property tax in Alaska. A special corporate income tax applies to petroleum companies, and the state taxes the amount of oil produced. This production tax is calculated by taking the market value of oil, subtracting transportation and production costs, and then applying a percentage to the remaining amount.

Under a tax system introduced by former governor Sarah Palin in 2007, the maximum tax rate on oil profits is 50%, but this rate changes based on oil prices. The state also claims 12.5% of all oil produced in Alaska, called “royalty oil,” which is sold back to oil companies for additional revenue. At the local level, pipeline owners pay property taxes on pipeline sections within districts that impose such taxes. These taxes depend on the pipeline’s assessed value and local tax rates. For example, in the Fairbanks North Star Borough, pipeline owners paid $9.2 million in property taxes—about 10% of all property taxes in the area.

The large amount of money generated by the pipeline led to debates about how to use the funds. A $900 million oil lease sale in 1976 occurred when the state’s entire budget was less than $118 million, and the money was spent by 1975. Taxes from the pipeline and oil transportation promised to bring even more revenue. To avoid spending oil money quickly, the Alaska Legislature and governor Jay Hammond created a plan to manage the funds responsibly.

Technical details

Oil entering the Trans-Alaska Pipeline comes from several oil fields on Alaska's North Slope. The Prudhoe Bay Oil Field is most often linked to the pipeline, but other fields such as Kuparuk, Alpine, Endicott, and Liberty also contribute oil. Oil is extracted from the ground at about 120 °F (49 °C) and cools to 111 °F (44 °C) by the time it reaches Pump Station 1 through feeder pipelines across the North Slope. North Slope crude oil has a specific gravity of 29.9 API at 60 °F (16 °C). From 2013 to 2018, the pipeline’s flow rate remained steady, averaging just over half a million barrels per day. The lowest flow occurred in 2015, with an average of 508,446 barrels per day (80,836.5 m³/d), which is much less than the pipeline’s theoretical maximum capacity of 2.14 million barrels per day (340,000 m³/d) or its actual maximum of 2.03 million barrels per day (323,000 m³/d) in 1988. From Pump Station 1, the time it takes for oil to travel the entire pipeline length to Valdez increased from 4.5 days to 18 days between 1988 and 2018.

The minimum flow through the pipeline is not clearly defined. Operating at lower flows can extend the pipeline’s lifespan and increase profits for its owners. In 2012, the flow was 600,000 barrels per day, which is much less than the pipeline’s original design. At lower flow rates, oil moves more slowly through the pipeline, causing its temperature to drop more than at higher flow rates. A freeze in the pipeline could block a cleaning device called a "pig," leading to a shutdown and repairs. A 2011 engineering report by Alyeska stated that heaters would need to be added at several pump stations to prevent freezing. This report suggested that the pipeline could operate as low as 350,000 barrels per day, but it did not determine an absolute minimum. Other studies estimate the minimum flow with the current pipeline could be as low as 70,000 to 100,000 barrels per day. Alyeska could also replace the 48-inch pipeline from Prudhoe Bay to Fairbanks with a 20-inch pipeline and use rail for the rest of the journey, allowing as little as 45,000 barrels per day.

Pump stations help keep the oil moving through the pipeline. Pump Station 1 is the northernmost of 11 pump stations located along the pipeline’s route. The original design included 12 pump stations with 4 pumps each, but Pump Station 11 was never built. Despite this, the stations kept their original numbering system. Eight stations were operating when the pipeline started, and this number grew to 11 by 1980 as oil production increased. As of December 2024, only four stations—Pump Stations 1, 4, 5, and 9—are moving oil. The pumps use natural gas or liquid fuel to power turbines.

Because of curves and adjustments for temperature and earthquake activity, the 48-inch-diameter (1,200 mm) welded steel pipeline stretches 800.3 miles (1,288.0 km) between pump stations and the pipeline’s end, even though the straight-line distance between Prudhoe Bay and Valdez is 639.34 miles (1,028.92 km). The pipeline crosses 34 major streams or rivers and nearly 500 smaller ones. Its highest point is at Atigun Pass, where the pipeline reaches 4,739 feet (1,444 m) above sea level. The pipeline’s steepest slope is 145% at Thompson Pass in the Chugach Mountains. The pipeline was constructed in 40- and 60-foot (12.2- and 18.3-meter) sections. Forty-two thousand of these sections were welded together to form double joints, which were then placed along the pipeline. Sixty-six thousand "field girth welds" were used to connect the double joints into a continuous pipeline. The pipeline has two thicknesses: 466 miles (750 km) of it is 0.462 inches (1.17 cm) thick, and the remaining 334 miles (538 km) is 0.562 inches (1.43 cm) thick. More than 78,000 vertical supports hold up the aboveground sections of the pipeline, and the pipeline includes 178 valves.

At the pipeline’s end is the Valdez Marine Terminal, which can store 9.18 million barrels (1,460,000 m³) of oil in eighteen storage tanks. The tanks are 63.3 feet (19.3 m) tall and 250 feet (76 m) in diameter. They are typically 85% full, holding about 7.8 million barrels (1,240,000 m³) of oil at any time. Three power plants at the terminal each generate 12.5 megawatts of electricity. Four tanker berths are available for mooring ships, in addition to two loading berths where oil is pumped into ships. More than 19,000 tankers have been filled by the marine terminal since 1977.

Maintenance

The pipeline is checked several times each day, mostly by air. Foot and road patrols also happen to look for issues like leaks or when the pipe moves or shifts. Surveys can take as little as 21 days, but most take longer to be thorough. These outside checks are only part of regular maintenance. Most maintenance is done using pipeline pigs—mechanical tools sent through the pipeline to complete tasks.

The most common pig is the scraper pig, which removes wax that forms from oil and builds up on the pipeline’s walls. Colder oil causes more wax buildup, which can cause problems. Regular "piggings" are needed to keep the pipe clear. Another type of pig, called a smart pig, moves through the pipe to find corrosion. Corrosion-detecting pigs use either magnetic or ultrasonic sensors. Magnetic sensors find corrosion by checking changes in the pipeline’s metal magnetic field. Ultrasonic testing pigs find corrosion by studying vibrations in the pipeline’s walls. Other pigs look for problems like bends or buckles in the pipeline. Smart pigs, which have many sensors, can do multiple tasks. These pigs are usually sent from Prudhoe Bay and travel the full length of the pipeline. In July 2009, a pig launcher was added at Pump Station 8, near the pipeline’s middle.

A third type of maintenance involves installing and replacing sacrificial anodes on the buried parts of the pipeline. These anodes help reduce corrosion caused by chemical reactions that affect these buried sections. People must dig up and replace the anodes when they corrode.

Incidents

The pipeline has sometimes been damaged because of sabotage, human mistakes, poor maintenance, and natural events like earthquakes or fires. By law, Alyeska must report major oil spills to government agencies. The Exxon Valdez oil spill is the most famous oil accident in Alaska, but it did not involve the pipeline. After the spill, Alyeska formed a team to respond quickly to future spills, funded by oil companies like ExxonMobil, which was held responsible for the spill.

On July 8, 1977, an explosion at Pump Station No. 8 killed one worker and injured five others, destroying the pump station. A government committee later found that workers did not follow proper safety steps, causing oil to flow into a pump that was being repaired. In its first two months of operation, from June 20 to August 15, 1977, seven incidents caused the pipeline to shut down several times. The National Transportation Safety Board (NTSB) studied the system and suggested improvements.

The largest oil spill involving the main pipeline happened on February 15, 1978, when someone drilled a 1-inch hole in the pipeline at Steele Creek, near Fairbanks. About 16,000 barrels of oil leaked before the pipeline was closed. It took over 21 hours to restart the pipeline.

The steel pipe is strong enough to resist gunshots, but on October 4, 2001, a man named Daniel Carson Lewis, who was drunk, shot a hole in the pipeline near Livengood. This caused the second-largest oil spill in the pipeline’s history, with about 6,144 barrels of oil leaking. About 4,238 barrels were recovered and returned to the pipeline. Nearly 2 acres of tundra were damaged and removed during cleanup. The pipeline was repaired and restarted after more than 60 hours. Lewis was found guilty of crimes like damaging property, drunk driving, and polluting the environment in December 2002.

The pipeline was built to survive earthquakes, wildfires, and other natural disasters. In 2002, the Denali earthquake occurred along a fault line directly under the pipeline. The pipeline’s supports in that area were designed to handle up to 20 feet of horizontal movement and 5 feet of vertical movement. During the 7.9 magnitude earthquake, the ground moved 14 feet horizontally and 2.5 feet vertically. The pipeline did not break, but some supports were damaged, and the pipeline shut down for over 66 hours as a safety measure. In 2004, wildfires came close to the pipeline but did not damage it.

In May 2010, several thousand barrels of oil spilled from a pump station near Fort Greely during a planned shutdown. A part of the system called the relief valve control circuit failed during a test, causing oil to overflow into a secondary containment area.

On January 8, 2011, a leak was found in the basement of the booster pump at Pump Station 1. For more than 80 hours, the pipeline’s flow was reduced to 5% of normal. An oil collection system was used to manage the leak, and full flow resumed until the pipeline was shut down again to install a bypass around the damaged section.

Heavy rains in Alaska have caused flooding near the pipeline in recent years. In May 2019, the Dietrich River flooded north of Coldfoot, eroding 25–50 feet of riverbank and leaving only an 80-foot buffer between the river and the pipeline. In August 2019, the Sagavanirktok River flooded, eroding 100 feet of riverbank and leaving only a 30-foot buffer. The Lowe River also flooded near the pipeline in March 2019 and again in June 2020. Alyeska has stockpiled emergency supplies and installed cooling systems under a 57-mile section of pipeline near Fairbanks, but details about plans to handle pipeline breaks in high-risk areas are not widely available.

In 2021, the pipeline was damaged for the first time by thawing permafrost. Permafrost is ground that has been frozen for more than two years and is important for the pipeline’s stability. Thawing permafrost caused slope movement, which bent and twisted the pipeline’s supports. Alyeska had to ask the Alaska Department of Natural Resources to do emergency work to stabilize the permafrost.

21st century

The original plan for the Alaska Pipeline in the early 1970s included a 25-year lifespan and expected production of 10 billion barrels of oil from Prudhoe Bay. By most economic, engineering, and construction standards, the pipeline has been very successful. However, since the early 2000s, declining oil production has created serious challenges. As oil flows more slowly through the pipeline, it stays in the pipeline longer, cooling more during its journey to Valdez. If the temperature drops below freezing (32 °F), the pipeline could stop working, crack, or break because water in the oil might freeze and block the flow. A study called the "Low Flow Impact Study" by Alyeska, the pipeline operators, found that the pipeline could safely handle 300,000 to 350,000 barrels of oil per day during winter.

This minimum flow rate is a legal issue because the pipeline’s value for taxes depends on how long it can operate. In late 2011, the Alaska Superior Court ruled that Alyeska’s study was not valid and supported a study by BP instead. The BP study suggested that installing heaters along the pipeline could allow the minimum flow to be reduced to 70,000 barrels per day (11,000 m³/d). This court decision increased the pipeline’s taxed value by nine times. A study by the National Resources Defense Council (NRDC), used in the court case, estimated that spending $0.8 billion to improve the pipeline could extend its life enough to extract an additional $28 billion in oil from existing wells. The NRDC study also stated: "This is a lower minimum throughput level than what Alyeska’s Low Flow Impact Study (LoFIS) suggested. We did not use the minimum throughput level from LoFIS because we had concerns about the study’s assumptions and it did not provide enough data to support its claims."

The Trans-Alaska Pipeline System Renewal Environmental Impact Statement estimated in 2010 that flow levels could remain workable until at least 2032 due to new oil exploration outside ANWR. If improvements are made to allow lower flow rates, the pipeline’s life could last until 2075.

As oil production has decreased, ownership of the pipeline has changed. In 2000, when Exxon and Mobil merged, Mobil sold its 3.1% share to Williams Companies as part of the merger. Three years later, Williams sold that share to Koch Alaska Pipeline Company, a subsidiary of Koch Industries. Nine years later, Koch announced it would sell its share to other pipeline owners, as did Unocal, which had owned a small share since 1970. In 2019, BP announced plans to sell its Alaska operations to Hilcorp Energy Company. The deal, completed in 2020, included BP’s 49.1% ownership of the Trans-Alaska Pipeline System. Some people worried that Hilcorp, which did not fully share its financial details, might lack the resources or expertise to handle safety issues caused by flooding and thawing from climate change.

According to the pipeline’s land grants and leases, owners must remove the pipeline and its equipment at the end of its life, except for cleaned and capped underground pipes. This multi-billion-dollar project must be funded by money specifically charged to oil transport customers for this purpose. However, as of 2004, these funds were mixed with other money, and the required amount was disputed.

Additional sources

• Allen, Lawrence J. The Trans-Alaska Pipeline. Volume 1: The Beginning. Volume 2: South to Valdez. Seattle: Scribe Publishing Co., 1975 and 1976.
• Alyeska Pipeline Service Co. Alyeska: A 30-Year Journey. Alyeska Pipeline Service Co., 2007.
• Baring-Gould, Michael and Bennett, Marsha. Social Impact of the Trans-Alaska Oil Pipeline Construction in Valdez, Alaska 1974–1975. Anchorage: University of Alaska Anchorage, 1976.
• Brown, Tom. Oil on Ice: Alaskan Wilderness at the Crossroads. Edited by Richard Pollack. San Francisco: Sierra Club Battlebook, 1980.
• Dixon, Mim. What Happened to Fairbanks? The Effects of the Trans-Alaska Oil Pipeline on the Community of Fairbanks, Alaska. Social Impact Assessment Series. Boulder, Colorado: Westview Press, 1978.
• Dobler, Bruce. The Last Rush North. Boston: Little, Brown & Company, 1976.
• Fineberg, Richard A. A Pipeline in Peril: A Status Report on the Trans-Alaska Pipeline. Ester, Alaska: Alaska Forum for Environmental Responsibility, 1996.
• Hanrahan, John and Gruenstein, Peter. Lost Frontier: The Marketing of Alaska. New York: W.W. Norton, 1977.
• Kruse, John A. Fairbanks Community Survey. Fairbanks: Institute of Social and Economic Research, 1976.
• LaRocca, Joe. Alaska Agonistes: The Age of Petroleum: How Big Oil Bought Alaska. Rare Books, Inc., 2003.
• Lenzner, Terry F. The Management, Planning and Construction of the Trans-Alaska Pipeline System. Washington, D.C.: Report to the Alaska Pipeline Commission.
• Manning, Harvey. Cry Crisis! Rehearsal in Alaska (A Case Study of What Government By Oil Did to Alaska and Does to the Earth). San Francisco: Friends of the Earth, 1974.
• McGinniss, Joe. Going to Extremes. New York: Alfred A. Knopf, 1980.
• McPhee, John. Coming Into the Country. New York: Farrar, Straus & Giroux, 1976.
• Miller, John R. Little Did We Know: Financing the Trans Alaska Pipeline. Cleveland: Arbordale Publishing, 2012.
• Romer, John and Elizabeth. The Seven Wonders of the World: A History of the Modern Imagination. New York: Henry Holt & Company, 1995.
• Simmons, Diane. Let the Bastards Freeze in the Dark. New York: Wyndham Books, 1980.
• Strohmeyer, John. Extreme Conditions: Big Oil and the Transformation of Alaska. New York: Simon & Schuster, 1993.
• Wolf, Donald E. Big Dams and Other Dreams: The Six Companies Story. Norman, Oklahoma: University of Oklahoma Press, 1996.
• Yergin, Daniel. The Prize: The Epic Quest for Oil, Money and Power. New York: Simon & Schuster, 1991.

• Armstrong, John. Pipeline Alaska. Pelican Films, 1977.
• Davis, Mark. The American Experience: The Alaska Pipeline. PBS, Season 18, Episode 11. April 24, 2006.
• World's Toughest Fixes: Alaska Oil Pipeline. National Geographic Channel, Season 2, Episode 10. August 20, 2009.