Trans-Alaska Pipeline

The trans-Alaska pipeline carries oil 800 miles from Prudhoe Bay on the Arctic Ocean to the pipeline terminus at Port Valdez. Begun in March 1975 and completed in 1977, pipeline construction employed some 30,000 workers at its peak and was the largest and most expensive privately funded construction project ever undertaken. The first tanker load of oil shipped out of Valdez on Aug. 1, 1977. Today, the pipeline is owned and operated by Alyeska Pipeline Service Company, a consortium of oil companies that includes BP, ConocoPhillips, ExxonMobil and Unocal.

The 48-inch-diameter pipeline winds through 3 major mountain ranges, with its highest point (4,739 feet) at Atigun Pass in the Brooks Range, 170 miles south of Prudhoe Bay. Along the Richardson Highway, the pipeline crests the Alaska Range at 3,420 foot at Isabel Pass, before descending into the Copper River basin. It crosses the Chugach Mountains at Thompson Pass and descends through the Keystone Canyon to Valdez, where it is fed by gravity into tanks or directly into waiting oil tankers at the marine terminal.

Built at a cost of $1.4 billion, the marine terminal complex holds about 9.18 million barrels of crude oil in its tank farms. Turnaround time for tankers, including berthing at Valdez, offloading ballast, loading crude oil and deberthing, averages 18 hours. Tankers are escorted by tugboats and other vessels, with safeguards in place to avoid accidents. The oil tanker Exxon Valdez ran aground on Bligh Reef (approximately 30 miles from Valdez) in March 1989, causing an 11-million-gallon oil spill in Prince William Sound.

Because of varying soil conditions along its route, the pipeline is both above and below ground. Where the warm oil would cause icy soil to thaw and erode, the pipeline goes above ground. Where the frozen ground is mostly well-drained gravel or solid rock, and thawing is not a problem, the line is underground. The zigzag pattern often seen in the above-ground sections allows for pipe expansion or contraction due to temperature changes or movement caused by other forces, such as earthquakes.

Travel time for crude oil from Prudhoe Bay Pump Station No. 1 to the Valdez terminal is 8.6 days, with more than 9 million barrels of oil in the pipeline at any given time.

The line was designed with 12 pump stations (although Pump Station 11 was never built). Pump Station No. 4, about 145 miles south of Prudhoe Bay, is a launching and receiving station for devices known as pigs. These “dumb” and “smart” monitors, matching the shape of the interior pipe wall, are pushed through the pipeline by the oil, cleaning accumulated deposits and enhancing pipeline flow as they travel (dumb pigs), and measuring pipeline curvature and inspecting for corrosion, changes in pipe diameter and other problems requiring maintenance or repair (smart pigs).

Examples of “pigs” are found at the Delta Junction Visitor Center, Milepost V 265.8, junction of the Richardson and Alaska highways, and at the Trans-Alaska Pipeline Viewpoint, located at Milepost F 8.4 on the Steese Highway just outside Fairbanks. The Steese Highway viewpoint, which has an information cabin, also allows visitors to walk up to the pipeline.

Opportunities abound for visitors to view and photograph the pipeline as it winds its way from Prudhoe Bay to Valdez, but visitor access to the pipeline is restricted to formal viewpoints along the Richardson, Steese and Dalton highways. These viewpoints may also be subject to closure due to security concerns.

Although the Dalton Highway most closely parallels the pipeline, the only formal public viewpoint is at the BLM Yukon River Crossing Visitor Contact Station at Milepost J 56, 140 miles from Fairbanks.