By Steve Gorman
LOS ANGELES (Reuters) - Construction workers in downtown Los Angeles finished laying the foundation on Sunday for a planned 73-story skyscraper expected to be the tallest west of the Mississippi River as they completed the world's largest continuous pour of concrete.
The 21,200 cubic yards of concrete weighing some 84 million pounds (38,200 metric tons) was hauled to the site by a fleet of over 200 trucks making a total of 2,120 trips in a continuous 19-hour operation ending at 11:30 a.m. on Sunday, said project spokesman Sean Rossall.
The foundation is expected to take two weeks to completely harden, during which cool water will be pumped through a network of tubes embedded in the massive slab to absorb heat as the concrete cures.
The New Wilshire Grand tower, designed to include 900 luxury hotel rooms, 400,000 square feet (37,200 square meters) of offices, plus retail space, is slated to be completed in late 2016 and open in early 2017, Rossall said.
The $1 billion project is being developed by Korean Airlines, which also owned the old Wilshire Grand building that was demolished to make room for the new tower.
The marathon effort to lay its foundation was certified by the Guinness World Records as the largest continuous pour of concrete ever by volume, surpassing by just 200 cubic yards the previous record set at the Venetian hotel and casino in Las Vegas, according to Michael Empric, the Guinness adjudicator for Sunday's event.
The Venetian, he said, was completed in 1999.
Rising 73 stories into the Los Angeles skyline, the New Grand Wilshire tower will measure 1,100 feet (335 meters) high, including a spire affixed to the top of the building, in a design that developers boast will make it the tallest building west of the Mississippi.
That distinction currently belongs to the U.S. Bank Tower, located a few blocks away in downtown Los Angeles.
Michael Marchesano, general superintendent for Turner Construction, the general contractor for the Grand Wilshire project, said he was most proud that no one was injured during the complex, round-the-clock concrete pour.
"With that many workers and that many trucks, it can be very dangerous if you don't have a plan in place, but we really had a team effort and a plan," he said.
The continuous pour for the building's foundation was a construction design characteristic called for by the project's structural engineers, he said.
(Reporting by Steve Gorman; Editing by Eric Walsh)