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Construction crews today began welding the first length of track for the Portland-Milwaukie light rail line.

Each 80-foot length of rail weighs just over 3,000 pounds. Those segments will be connected via a thermite welding process that superheats aluminum, iron oxide and alloy elements to produce molten steel and permanently join the rails, according to a press release from TriMet.

Mary Fetch, spokesperson for TriMet, said each weld takes about 1.5 hours to complete; another 2.5 hours is then required to grind and finish the weld. Just under 1,000 welds will be made today on the west segment of the line.

Stacy and Witbeck/Mowat Construction is the construction manager/general contractor for the job and has hired union laborers for the task. Evraz Rocky Mountain Steel in Pueblo, Colo., manufactured the rail.

Witbeck/Mowat will fuse more than 29 miles of rail together to complete the 7.3-mile line, which will stretch from Portland State University in downtown Portland to North Clackamas County.

That works out to approximately 1,914 segments of light rail, weighing a total of 2,871 tons. The Portland-Milwaukie light rail line is slated to open in September 2015 and is approximately 30 percent complete.