Bechtel joined its partners and the U.S. Department of Defense to mark the construction of a plant designed to destroy the last U.S. stockpile of chemical weapons.

The new plant, known as the Blue Grass Chemical Agent-Destruction Pilot Plant, is located in Richmond, Ky. Following the end of the construction, the plant will now enter a multi-year testing phase using simulated chemical weapons. The plant is designed to use an alternative method to destroy the weapons. Instead of incineration, the plant will use different chemicals to neutralize the agents, and then use supercritical water oxidation to break down hazardous chemicals.

"This is such an important facility from a global safety and security perspective," said Craig Albert, president of Bechtel's Nuclear, Security & Environmental business unit, in a statement. "This is an important achievement but there's more work to do, and we look forward to the day when the plant starts actual operations."

The plant will be tasked with safely disposing of the remaining 10 percent of the stockpile of chemical weapons in the United States as part of the Chemical Weapons Convention, a treaty signed by 190 countries in 1997. Some 523 tons of mustard and nerve agent rockets and artillery shells will be neutralized.