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Nearly 4.2 million-wheelbarrows of dirt had to be removed in order to renovate the Arch Grounds

ST. LOUIS - Technology, earth moving, and engineering. Those are three elements involved in the remake of the Arch Grounds.

To give you an idea, take a wheel barrel full of dirt, or actually about 4.2 million-wheelbarrows full of dirt and then you'll have a better idea of the scale of this incredible upgrade.

The 50-year-old national monument has gotten a little bit of a face lift over the last four years.

“There was 100,000 square feet of museum space underground,” says Ryan Freeman, Vice President Operations McCarthy.  “We excavated down to that and punched through and created a new opening that looks out to the West and did a 50,000 square foot extension extending out to the city with a new entry point.”

With the new 50,000 square-foot addition the renovation of both the North and South grounds included the new museum addition re-grading, new landscaping, irrigation, and installation of soil and sod.

“One of the biggest challenges with doing work at the Arch is that there are 4-million visitors that come to see the landmark,” says Freeman.  “So, we have to be able to construct the new museum and renovate the old museum while carefully interacting with them and 100`s of dump trucks coming into and out of the site every day.”

Because it is a national historic landmark there were a lot of requirements oh, and all the work had to be done while the Arch remained open.

“To reduce the overall weight, instead of using natural fill material there`s a huge volume of geo foam blocks that are placed on the lid of the addition and then encapsulated with the dirt on top so you don`t overload the structure,” says Freeman.

An estimated 400,000 radishes planted to help aerate the soil on the ground under Eero Saarinen's Gateway Arch.

“We excavated 300,000 cubic yards of material to dig down to the foundation wall of the existing museum,” says Freeman.  “That`s the equivalent of 19 football fields filled with dirt, ten feet deep.”