The pipeline was completed in 1977, and covers 800 miles of mountain and river valleys in its trip from Prudhoe Bay to Valdez. If you stretched the pipeline over the Lower 48 and it would reach from Los Angeles to Denver.

The pipeline is a tunnel of 1/2-inch thick steel with a diameter of 48 inches. It looks thicker from the highway because the steel pipe is wrapped with four inches of fiberglass insulation. The shiny wrapping we see is a coat of aluminum sheet metal.

The closer oil is to the molten core of the earth, the hotter it is when oil companies pull it to the surface. Prudhoe Bay is10,000-to-20,000 feet deep and is about 145 to 180 degrees Fahrenheit. Using heat exchangers cool the oil to120 degrees before it enters the pipeline.

Engineers would have buried the entire pipeline had it not been for permafrost lying in sheets and wedges beneath the ground surface. The pipeline couldn't be buried in permafrost because the heat of the oil would cause the soil to melt. The pipeline would then sink and possibly leak. Because much of Alaska is underlain with permafrost Alyeska routed just over half the pipeline above ground.

Where it is over land, the pipeline is held up by posts designed to keep permafrost frozen. Topped with fan looking aluminum radiators the posts absorb cold from the winter air and blow it onto the soil. When the air temperature is 40 degrees below zero.

The pipeline was built in a zigzag pattern to allow the pipe to expand and contract. Because workers welded allot of the pipeline at temperatures below zero, engineers expected that the metal would expand when hot oil began flowing through.

The temperature within the pipeline is pretty constant. Temperatures along the pipe line can range from nearly 100 degrees above zero to 80 below zero. The four inches of fiberglass insulation that covers the above-ground pipeline keeps oil warm enough to flow even on the coldest winter days. If the pipeline had to be shut down in the winter, the oil within could sit for several months before hardening.

The line is powered by ten pump stations and oil flows through the pipeline at about the speed the Yukon River. At that speed it takes about five and a half days for oil to complete the trip from Prudhoe Bay to Valdez.