Construction of the Trans-Alaska Pipeline System facts for kids

The construction of the Trans-Alaska Pipeline System was a huge project that built over 800 miles (1,287 km) of oil pipeline, 12 pump stations, and a new port for oil tankers. This massive effort happened between 1975 and 1977, mostly on frozen ground called permafrost, connecting Prudhoe Bay in the north to Valdez, Alaska in the south. It cost about $8 billion and needed tens of thousands of workers. They often worked in very cold and tough conditions. Special building methods had to be invented, and a new road, the Dalton Highway, was built just for this project.

The first part of the pipe was laid in 1975, after more than five years of legal and political discussions. There were concerns about welds not being strong enough, which led to close checks. A unique work culture grew around building the pipeline. Different worker unions had their own jobs and reputations. Sadly, 32 workers died during the project. The main construction finished in 1977, and the first oil arrived on July 28 of that year. More pump stations were added until 1980 as more oil started flowing.

Planning the Pipeline Route

Intense geological surveys and planning for the pipeline route began in the spring of 1970. Teams took aerial photos and mapped out a first route. Small survey groups then visited the route on the ground, placing markers. This work was very hard. Crews had to carry weapons because of animal dangers, and they were in remote areas with few facilities. In some places, the trees were so thick that they had to be cut down, slowing progress.

The planned route went through several mountain passes, including Atigun Pass, Isabel Pass, Thompson Pass, and Keystone Canyon. In Keystone Canyon, surveyors even had to climb down cliffs to do their job.

Surveyors and planners also had to deal with the Denali Fault, a major earthquake zone, and large amounts of permafrost (permanently frozen ground). In 1969, a group called Trans-Alaska Pipeline System drilled samples that showed how much permafrost was along the route. This meant the pipeline had to be built above ground in many places. This elevated design was tested with a 1,000-foot (305 m) loop near Barrow. Building the pipeline above ground also meant it needed to be insulated. This was because extreme cold could make the metal brittle, even with hot oil flowing through it.

To allow animals like caribou to cross, some parts of the pipeline had to be buried underground. For these sections, engineers created a system to keep the ground around the pipe frozen using chilled liquid. These buried parts were also placed in Styrofoam-lined trenches and covered with gravel for insulation. About 3.5 miles (5.6 km) of the pipeline were built this way. In other areas without permafrost, the pipeline could simply be buried without special cooling.

A lot of gravel was needed for all sections of the pipeline. It helped insulate above-ground structures from melting the permafrost. Gravel was also used to build the construction and maintenance road. Surveyors found 470 places across Alaska where the needed 65 million cubic yards (50 million cubic meters) of gravel could be found.

The law that allowed the pipeline to be built required it to withstand the strongest earthquake ever recorded in the area. Where the pipeline crossed the Denali Fault, special Teflon-coated sliders were designed. These allowed the pipeline to move side-to-side during an earthquake. To protect against forward and backward shocks and to allow for the pipe to expand and shrink with temperature changes, the pipeline was not built in a straight line. Instead, it was laid in an S-shape, so the bends could absorb movement without breaking.

Because most of the pipeline was built above permafrost, each support leg holding up the raised sections contained a sealed tube of ammonia. As the permafrost below warms, the ammonia absorbs the heat and rises to a radiator on top of the support. The cold outside air cools the ammonia, making it condense and fall back down. This process repeats, keeping the ground frozen.

The pipeline route crossed hundreds of streams and rivers. To cross these, engineers designed concrete "jackets" to surround the pipe and make it heavy enough to sink to the bottom. Without these, the pipeline would float because oil is lighter than water. Digging up rivers and burying the pipeline directly in the streambed was not allowed due to environmental concerns. In some places, to avoid disturbing the river or because of the river's features, bridges were built for the pipeline. The most famous ones are over the Yukon River and the Tanana River. To protect the pipeline from rust in wet areas, it was designed with a special electrical protection system.

For spill prevention, the pipeline had one-way valves. This meant oil moving forward could not leak out of a hole behind a certain point. It also had computer systems to detect leaks. The pipeline was designed to be pressurized, so any leak would immediately cause a drop in pressure at a pump station. This would trigger an alarm and stop the oil flow quickly.

The first plan for the pipeline aimed for a smaller amount of oil flow at the start. But after the 1973 oil crisis, these plans changed. The initial oil flow capacity was increased. This meant that eight pumping stations, instead of the original five, had to be ready when the pipeline started. This greatly increased the number of workers needed for construction.

Valdez Marine Terminal

The Valdez Marine Terminal, where the pipeline ends in the south, was planned across the Port Valdez fjord from the town of Valdez. Early studies thought solid rock was only six feet (1.8 m) deep. But when digging started, they found the rock was actually sixty feet (18 m) down! This meant they had to remove 15 million cubic yards (11.5 million cubic meters) of extra dirt and rock.

The terminal was designed with four berths for oil tankers, with space for a fifth. It also had holding tanks that could store as much oil as the entire pipeline. This meant the whole pipeline could be emptied if needed. A system to filter oil from the ballast water of tankers also had to be designed, as required by law. This system removes oil from the water tankers use for balance, so it isn't released into Prince William Sound. Fishermen were worried about this when the pipeline was first proposed.

Getting Ready for Construction

Soon after the permit was approved, convoys of equipment on snow tractors started moving north. They used special snow roads and an ice bridge over the Yukon River. Their goal was to reach seven construction camps that had been empty since 1970. In just 83 days, from mid-January to mid-April when the snow and ice melted, 680 workers moved 34,000 short tons (30,844,000 kg) of supplies to these camps. They also built five more camps and five temporary airstrips.

In February, while the ice bridge and snow road were still being used, Alyeska hired a company to design the construction and maintenance road. This road would become the Dalton Highway. The state of Alaska designed the E. L. Patton Yukon River Bridge for the road and pipeline to cross the Yukon River, paying two-thirds of its cost. Alyeska paid the rest. Construction of the Dalton Highway began on April 29. At its busiest, Alyeska and its contractors had over 3,400 workers building the road from the Yukon River to Prudhoe Bay.

A huge airlift operation was set up to supply the road builders. More than 700 flights per day, totaling 170,000 flights, were needed before the road was finished on September 29. In just 154 days, a 360-mile (579 km) gravel road was built. Final touches and more than 20 small permanent bridges were still needed, but by November, the road was open to traffic, crossing the Yukon River on another ice bridge.

Managing the Project

To manage the pipeline construction, Alyeska hired two main companies to oversee all the other contractors. Bechtel Corporation was in charge of building the pipeline itself. Fluor Alaska Inc. managed the pumping stations and the Valdez Marine Terminal. The terminal was the most complex part because it involved transferring oil from the pipeline to large oil tankers.

These two main companies didn't do the actual building. That work was given to many other contractors. Each contractor was responsible for one or two of the six sections of the pipeline (or seven if you include the marine terminal). The bidding for these jobs started in late March, and the contracts were announced on June 12, 1974.

Pipeline Camps

When the contracts were announced, Alyeska already had 12 construction camps built or being built. However, these were all north of the Yukon River. Camps were needed along the entire pipeline route. Alyeska planned for 29 camps, but 31 were actually created. Seven were built south of the Yukon, and one was built at each of the 12 pump stations.

The camps were built on thick layers of gravel. This gravel insulated the ground to protect the permafrost and prevent pollution. After construction, the gravel was removed, which was supposed to take any oil leaks or other pollution with it. On top of the gravel were prefabricated buildings. These were either flown in or trucked along the Dalton Highway. The standard buildings could house 28 people, and two were often joined together to create two "wings." Most were one-story, except at Valdez and the pump station camps, where buildings were stacked due to limited space. Like the gravel, the buildings and utility pipes were raised above the ground to avoid heating the permafrost.

The camps housed from 250 people (at each pump station) to 3,500 people (at Valdez). A typical pump station camp cost $6 million to build, while the main camps cost about $10 million. The camps had beds for 16,500 workers and were nicknamed "Skinny City" by the workers. This name came from the fact that the "city" was 800 miles (1,287 km) long but only a few hundred feet wide.

The main construction headquarters was at Fort Wainwright near Fairbanks. Alyeska rented land and buildings from the U.S. Army there. Empty barracks were turned into housing, and empty offices were used by oil workers. As air traffic increased, Alyeska arranged to use Fort Wainwright's airfield to ease the pressure on Fairbanks International Airport. The camp at Wainwright was the only one that didn't use prefabricated buildings.

Pipeline Workers

The Trans-Alaska Pipeline System was built entirely by union workers. Because construction was slow in the rest of the United States, the pipeline attracted workers from all over the country. These workers had to follow a strict hiring process based on union experience and the specific jobs needed. Priority was given to people living in Alaska and Alaska Natives. A labor agreement between Alyeska and the unions meant no strikes were allowed. In return, workers were paid very well and received good benefits.

The labor contract guaranteed every worker 40 hours of pay per week, even if bad weather stopped work. Also, contractors were paid based on their costs plus a fee, so there was no reason to keep staffing levels low. These factors often led to more people being assigned to a job than needed, in an attempt to make up for time lost to weather delays. At the busiest time in fall 1975, over 28,000 people were working on the pipeline. About 14 to 19 percent of the workers were minorities, and 5 to 10 percent were women. Because many workers came and went, more than 70,000 people worked on at least part of the pipeline project.

Welders

The welders who worked on the main pipeline came from a special union called Pipeliners Local 798, based in Tulsa, Oklahoma. They specialize in large pipeline projects. Other welders, from a different union, did all the welding not directly on the main pipeline, like at pump stations and the Valdez Marine Terminal. Welders were the highest paid workers, earning $18.25 per hour normally. To get hired, welders had to pass tough tests. If they failed a test weld, they couldn't try again for several weeks.

These welders were known for their unique style, including cowboy boots and special hats. They were the only ones allowed to weld the 48-inch (122 cm) main pipeline. They sometimes had a reputation for being confident in their skills. For example, when hot lunches were stopped, these welders started cooking their own steaks using their welding torches, even though it was against camp rules. This sometimes caused arguments with other workers.

Teamsters

The Teamsters Union was the largest group of workers on the pipeline project. Teamsters handled all transportation and supply. They drove all the trucks, managed supply warehouses, and drove the buses that took workers to job sites. Teamsters Local 959 had over 23,000 members at its peak, making it the biggest labor group on the project.

Teamsters controlled tools and equipment in their warehouses, which sometimes led to disagreements with other workers. Although they were not allowed to strike, they could stop work for "safety meetings." They used this a few times to get what they wanted from Alyeska and the contractors. The most famous example was in February 1975. After many serious truck accidents on the Elliott Highway, which connected to the new Dalton Highway, the Teamster leader stopped all truck traffic in the state for four days of safety meetings. Alyeska and the state then promised to improve the road, and traffic resumed.

Operators

The International Union of Operating Engineers, called Operators, were the men and women who controlled the heavy machinery used to build the pipeline. This included bulldozers, cranes, drilling rigs, and sidebooms (a mix of a bulldozer and a crane that could lay pipe). Since most of the heavy equipment was unheated, six operators were usually assigned to each machine, allowing for frequent breaks. A common joke was that an Operator's only qualification was being able to sit on a sideboom at 40 degrees below zero and not freeze.

Laborers

The Laborers International Union represented most of the less-skilled workers on the project. Laborers did many different jobs: digging trenches where heavy equipment couldn't reach, drilling holes for the pipeline's support members, spreading gravel, crushing rock, and moving supplies by hand. Laborers Local 942 from Fairbanks was the main Laborers group. Because their jobs didn't require special skills, this union attracted most of the people who came to Alaska just for the pipeline project.

Since there were more applicants than jobs for Laborers, getting a job through Local 942 was a multi-step process based on how much experience a person had with the union. People with the most experience got first pick. Many people tried to get jobs. On January 1, 1974, over 100 people spent the night outside the Fairbanks Laborers Union office, waiting for it to open to get a chance at a job.

Life at the Pipeline Camps

Life during the pipeline construction meant long hours, tough conditions, and limited entertainment. However, workers received excellent pay and benefits. Each worker got a small booklet with 23 camp rules, but these rules were often bent or broken.

Inside the living quarters, the atmosphere was like a college dormitory. Housekeeping and laundry services were provided, but the rooms were small, and there wasn't much entertainment. TV broadcasts were delayed by two days because tapes had to be flown in from California. Most workers had to find their own ways to have fun. In winter, some went skiing or sightseeing; in summer, some went hiking. But generally, there wasn't much time for recreation due to the long work hours.

In the early years, workers often enjoyed fancy meals like prime rib and steak dinners. This was because of the way the food service contracts were set up. Later, the food became more like standard cafeteria meals, but many workers still appreciated it. When the haul road (Dalton Highway) was built, some things changed, including food and overtime pay for some unions.

In 1976, workers' pay averaged between $11 and $18 per hour. With workweeks often 70 to 84 hours long, many workers earned a lot of money. One worker wrote to Money magazine, asking for advice. He earned $57,000 per year, which was more than members of Congress or professional football players at the time. The large amounts of money in the camps and the lack of entertainment led to frequent gambling games, sometimes involving thousands of dollars. Instead of gambling, some workers saved their money for month-long vacations to warm places like Hawaii, only to return to work with no money left.

Laying the Pipe

The first section of the Trans-Alaska pipeline was laid on March 27, 1975, in the Tonsina River. Several 40-foot (12 m) sections of pipe were welded together and covered in concrete before the ceremony. Twelve sidebooms (bulldozers with side-mounted cranes) lifted 1,900 feet (579 m) of pipe, which was placed in a trench dug across the riverbed. Bulldozers then filled the trench with gravel, returning the river to its original shape. This process was repeated a few miles south at the Little Tonsina River. By the end of April, the first 1,800 feet (549 m) of elevated pipeline was also built in the same area.

In 1975, the first year of pipe laying, Alyeska aimed to complete 45 percent of the 800-mile (1,287 km) route. This wouldn't be a straight line, as river crossings were expected to take longer than land sections. Work on the pumping stations and the Valdez Marine Terminal, which started in late 1974, was also expected to take longer. However, work on these two projects could continue during winter, when pipe laying on the frozen ground was difficult.

Laying pipe involved several steps. First, the path had to be cleared using chainsaws, bulldozers, and scrapers, following the route mapped by surveyors. Then, another group of surveyors and engineers checked if the pipeline could be laid in the planned spot. Sometimes, it had to be moved due to permafrost, soft ground, or other issues. State and federal officers, working with engineers, could approve moving the pipeline's path up to 200 feet (61 m) left or right to avoid obstacles.

After the path was set, machines drilled holes for the Vertical Support Members (VSMs) that held up the pipe. These holes were filled with a mix of water, gravel, and dirt before a VSM was placed in each. Because the ground was frozen, the gravel and dirt froze as hard as concrete, holding the VSMs firmly. The VSMs were placed in parallel pairs, each with a curved rest for the pipeline segments. These segments, 40 or 80 feet (12 or 24 m) long, were carried by cranes or sidebooms, lowered into place, and then welded together. Quality control engineers then inspected the welds using X-rays.

The construction was managed by Frank Moolin Jr., an engineer known for his strong work ethic. He was said to be the first person in the office and the last to leave. To encourage progress, he started the "Alyeska Sweepstakes," where the five contractors were compared based on how much of their work they completed on time. In a major decision, he ended Bechtel's contract as the management contractor, feeling they added too much bureaucracy.

In October, snow and cold weather stopped most pipe laying for the year. Employment went from 12,000 workers in spring to over 21,000 in summer, then down to 7,000 by Christmas. Alyeska estimated that about 50 percent of the pipe laying was done, with 390 miles (628 km) of pipeline welded and in place. But work on the pump stations and in Valdez was slower. The project as a whole was only 35 percent complete when the pumps were included.

Speeding Up Construction

During the winter of 1975–1976, Frank Moolin Jr. was not happy with the progress but promised improvements. He set an ambitious goal for 1976: to have all the pipeline installed, insulated, and tested by November 1. This was a big goal because most of the work done so far was on flat ground. Difficult sections in Atigun Pass and Keystone Canyon were still ahead.

Even though winter stopped pipe laying on the main route, work on the pump stations and in Valdez continued without stopping. At Pump Station 1 in Prudhoe Bay, temperatures dropped below -70 degrees Fahrenheit (-57 degrees Celsius), but work went on. This pump station was where the main pipeline started, and it also had to process oil from the wells.

Challenges at Atigun, Keystone, and Sag River

Many of the suspected faulty welds were in Section Five of the pipeline, the northernmost 200 miles (322 km). This area also had two major problems in 1976: Atigun Pass and the Sagavanirktok River (Sag River). The pipeline had been laid in a trench under the Sag River in late 1975. Because it was laid so late in the season, the trench material froze, making it impossible to fill the submerged trench. Spring snowmelt flooded the river, and the submerged pipe was damaged. In June, a 1,700-foot (518 m) section of concrete-coated pipe broke free and floated to the surface. To avoid disturbing migrating fish, the state allowed only 24 hours for repairs. After preparing the site, it took just four hours to dig a new trench, weld and lay a replacement pipe, and fill the trench.

At Atigun Pass, south of the Sag River, workers faced different challenges. In 1975, surveyors found the pass was full of permafrost and glacial soils. But because the pass has frequent avalanches, an elevated pipeline wasn't possible. The solution was to design a strong, insulated ditch for the pipeline. This resulted in a 6,000-foot (1.83 km) long concrete box lined with 21 inches (53 cm) of Styrofoam. The challenge was to build it before the first snow in October.

At the other end of the pipeline, just north of Valdez, engineers dealt with difficulties in Keystone Canyon. This canyon was the only route to Valdez, but it was already occupied by the Richardson Highway and the Lowe River, leaving no room for the pipeline. The only solution was to build the pipeline through the Chugach Mountains and along the canyon rim. Winter work was impossible due to over 300 inches (762 cm) of snow. When the snow melted, workers had to figure out how to climb a 60 percent slope and then lay the pipeline on it. A rock-crushing plant was built at the canyon's rim to avoid carrying gravel up the steep slope. Even bulldozers needed help from two others to climb the grade. A bulldozer had to be changed to carry 80-foot (24 m) pipe sections up the slope. Still, most sections and equipment had to be lifted by helicopter to the canyon rim. Similar methods were used at nearby Thomson Pass, and both sections took the entire 1976 construction season to complete.

Pump Stations and Marine Terminal

Work at the pump stations and marine terminal continued through the 1976 construction season. Pump Station 6, just south of the Yukon River, had to be redesigned when digging revealed permafrost below the site. The five pump stations needed for startup received their pumps, turbines, and pipes. As they were finished, the pump stations were tested by filling parts of the pipe with water and putting them under very high pressure. After this, the first five pump stations were disconnected from the main pipeline and had oil run through them in a continuous loop. This was like "breaking in" a new car. Work on additional pump stations, not needed until the pipeline reached full capacity, was not rushed.

At Valdez, construction was two-thirds complete by September, with 4,200 workers rushing to finish the marine terminal. Because of loose soil at the site, huge retaining walls had to be built to secure the ground under some of the 58 structures completed by year-end. In early November, the first ship docked at the new Valdez quays. It was not a tanker, but a ship bringing more construction material. In December, the first signal was sent from the Valdez operations center, where two new control computers were installed, to Pump Station 2 on the North Slope.

Although the project made great progress in 1976, it didn't meet Moolin's goal of having all pipe installed, insulated, and tested by winter. The final section of the main pipeline was welded on December 6, but not all of it was tested before winter. By the end of 1976, the project was 92 percent complete. The pipeline itself was 97.5 percent done, the pump stations were 92 percent done, and the marine terminal was 83 percent complete. Since the terminal was the slowest part, its full work crew continued operations through the winter and into 1977.

Finishing the Line

Few tasks remained when the 1977 construction season began. Most pump stations had been handed over to the operating staff. Environmental cleanup was in full swing as Alyeska repaired damage to the tundra caused by construction. The company that had done well with its construction tasks was given the job of finishing the last touches on the main pipeline. The final 160 miles (257 km) of water pressure testing were done, 33 repair welds were completed, and 45 miles (72 km) of pipe were insulated, among other jobs. Because construction was much slower than in 1976, fewer workers were needed. Fewer than 11,000 people were employed at the busiest time in 1977, about half of the 1976 total. On May 31, the final pipeline weld took place.

Some additional tasks still needed to be completed, but the pipeline could start operating without them. The 2,290-foot (698 m) E. L. Patton Yukon River Bridge was not finished until October 1979. Until then, traffic used ferries to cross the river. More pump stations were also built between 1977 and 1980 as the flow of oil increased.

Cleaning Up the Camps

As part of the law that allowed the pipeline, Alyeska had to remove most signs of the 31 construction camps. Seven camps closed in November 1976, and six more closed before the 1977 construction season. In total, 20 camps were put up for sale. One was sold to the University of Alaska to be used as an Arctic research center, while another became a truck stop and motel.

Besides removing the camps, Alyeska also had to get rid of the heavy equipment used to build the pipeline. In January 1977, Alyeska listed over 20,000 pieces of equipment for sale. The New York Times called the auction of this extra equipment "one of the biggest going-out-of-business sales in history."

Turning On TAPS

In April 1977, Alyeska announced it planned to start filling the pipeline between June 20 and July 1. Engineers faced several challenges when filling the pipeline. First, they needed to balance temperatures. The steel pipeline was about 20 degrees Fahrenheit (-7 degrees Celsius) when filled with air. The oil from Prudhoe Bay wells was over 120 degrees Fahrenheit (49 degrees Celsius). There was a risk that if hot oil was introduced too quickly, the pipeline could crack due to thermal expansion.

The second problem was that the pipeline needed to be cleared of air to reduce the risk of fire or explosion. Usually, a pipeline is filled with water first, and the oil pushes the water out. But in Alaska, there was a fear that the water would freeze in the pipeline and damage it. This problem was solved by using pressurized nitrogen instead of water.

On June 20, 1977, the first section of the pipeline was filled with nitrogen, and oil was introduced behind it. Because the pipeline was cold and the oil was introduced slowly, it took 31 days for the first oil to travel from Prudhoe Bay to Valdez. As oil cools, it becomes thicker. Another challenge came when the oil traveled downhill from Atigun Pass. To prevent the oil from gaining too much speed and crashing into a pipeline section or pump, special valves were used to slow down the nitrogen ahead of the oil. This method was used at other downhill slopes during startup.

As the oil moved through the pipeline, it was followed by inspectors. They traveled along the route to make sure the weight of the oil didn't cause the pipeline to sink or create problems on bridges as the oil front passed over them. The first oil arrived in Valdez on July 28, 1977, at 11:02 p.m. The oil was only 45 degrees Fahrenheit (7 degrees Celsius) at first, but it slowly warmed up as the system reached a stable temperature. After the initial startup, the pipeline was meant to run continuously. An engineer said, "We start up this pipeline once... It will stay onstream then forever... 'forever' being the life of the oil field."

The startup did have some issues. On July 4, a nitrogen leak was found. The oil flow stopped for three days while workers fixed a pipe elbow that cracked due to the temperature difference. On July 8, oil flowed through a shut-off pump at Pump Station 8 while workers were replacing a filter. The oil spray mixed with air and was ignited by a spark. One worker was killed and five others were injured in the explosion, which also shut down the station until March 1978. On July 19, a heavy equipment accident caused a pipeline break that leaked 1,800 barrels (286 cubic meters) of oil.

The startup process and construction ended on August 1, 1977, when the tanker ARCO Juneau sailed out of Valdez with the first load of oil from the Trans-Alaska Pipeline System.

Project Cost and Impact

When the TAPS group first suggested the pipeline in 1969, they estimated it would cost $900 million and be finished by 1972. By January 1970, the estimated cost had risen to $2 billion. In October 1973, Alyeska updated its figures, expecting a cost between $3.1 billion and $3.5 billion, with a chance of another billion. A year later, Alyeska released its most detailed estimate: $5.982 billion. By June 1975, that figure had risen again to $6.4 billion. At that time, it was thought that $3 billion of the cost increase was due to inflation, and another $2 billion was due to environmental requirements. In July 1976, during the second year of construction, the project's cost was raised to $7.7 billion. Alyeska said the increase was due to material and shipping costs, repairs needed for poorly built sections, and unexpected expenses.

The final construction cost was $8 billion. This figure does not include interest on loans or the cost of improvements and repairs after 1977. The Valdez Marine Terminal alone cost $1.4 billion. The ownership of the pipeline has changed over time. As of 2009, the main owner was BP, controlling 46.93 percent. Second was ConocoPhillips Transportation Alaska Inc. with 28.29 percent, followed by ExxonMobil (20.34 percent), Koch Alaska Pipeline Company (3.08 percent), and Unocal Pipeline Company (1.36 percent).

The pipeline project also had a human cost. Thirty-two Alyeska or contract workers died during the construction. This number does not include other fatalities. Since the pipeline started operating in 1977, 10 more people have died while working for Alyeska or its contractors.

Images for kids

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  Pipeline on slider supports where it crosses the Denali Fault.

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  Radiators atop heat pipes keep permafrost below the pipeline frozen.

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  Before construction of the Dalton Highway, special vehicles like the Sno-Freighter were needed to take supplies north of the Yukon River.

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  A map of the Trans-Alaska Pipeline with pump stations and construction camps identified.

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  The pipeline crosses the Tanana River on a bridge north of Delta Junction.

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  The pipeline runs under this riverbed, emerging to cross a ridge on the opposite bank. Pipeline inspection access road is visible as well

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  The portion of the pipeline beneath the Sagavanirktok River, seen here, caused problems for construction workers.

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  Pump Station 9 as seen in 1994.

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  The E. L. Patton Yukon River Bridge was not completed until October 1979.