The Trans-Alaska pipeline, the biggest construction project in history, is nearing completion and is almost on schedule.
The Trans-Alaska pipeline, the biggest construction project in history, is nearing completion and is almost on schedule. The pipeline, which stretches 798 miles (1277 kms) from Prudhoe Bay in the north to the ice-free port of Valdez, has taken 4 years so far to build and could cost up to 8.4 billion US dollars (4.9 billion sterling) when oil starts flowing, probably in June. It is being built by a consortium of oil companies, including British Petroleum which is the largest shareholder.
SYNOPSIS: Before the onset of the harsh Alaskan winter, there was a desperate rush to finish critical sections of the pipeline. One of the most difficult was in the Adigan Pass, where the pipeline reaches its highest point. Special techniques were necessary to overcome the problems of unstable soils and the danger of avalanches. The ditch is lined with concrete and the pipe insulated to ensure the surrounding soil remains stable when hot oil flows through.
Last spring, at the start of the 1976 construction season, the route through Keystone Canyon and Thompson pass was "bombed" with coal dust. Blackened snow absorbs more heat and melts faster, allowing an earlier start on work.
The Keystone Canyon section was particularly difficult because the pipeline had to be embedded in steep rocky slopes, high on the canyon wall to avoid disruption to traffic on the Murchison Highway on the canyon floor. Nearly two construction seasons went into preparing the four-mile stretch through the canyon, where up to 60 per cent gradients and sheer rock outcrops were encountered. Less than half the pipeline is buried. The pipe itself is covered in tape to protect it from corrosion.
The rest of the line is set above ground, to prevent hot oil in the pipe melting the permanently frozen ground, making it unstable. The pipe is supported at intervals of about 60 feet (20 metres). At each support, the pipe is clamped into a metal shoe which is set on a cross beam which in turn rests between a pair of vertical supports, driven deep into the ground.
To help repair bad welds, the pipeliners use this machine, which they call Snoopy. It is propelled by a 40 horse power diesel engine, with an exhaust elimination system. The ten foot (three metres) vehicle carries the welder and his assistant through the pipe. It has its own two-way radio and power system for welding the lighting, so there is no need for cables.
The pipe is zig-zagged to accommodate thermal expansion and retraction as a result of temperature changes throughout the year.
There are 12 major pipeline bridges, including two cable suspension bridges. This is the longest twelve hundred feet (380 metres) across the Tanana River, about 75 miles (125 kms) south of the capital, Fairbanks. To propel the oil along the length of the pipe, there are 12 pump stations, powered by natural gas from Prudhoe Bay. Eight stations will be needed for the initial capacity of 1.2 million barrels of oil a day.
The huge oil storage tanks with a diameter of 250 feet (80m) dominate the nearby completed terminal at Valdez. The first tanker to take crude oil to California, for which the Alaskan oil is intended, is expected at Valdez in the summer.