A major step toward building Plant Vogtle’s Unit 3 nuclear reactor was completed this week after workers spent 41 consecutive hours pouring concrete to form the unit’s 6-foot-thick foundation.

The pouring of specially designed “nuclear concrete” was scheduled to occur last fall but was postponed to allow the U.S. Nuclear Regulatory Commission to rule on license amendments for the project’s design.

The concrete, known as basemat, will serve as the foundation for all of the nuclear island structures, including the containment vessel and the shield building. It covered an area about 250 feet long and 160 feet wide at its widest point.

A similar pour was completed Monday at South Carolina Electric & Gas Company’s V.C. Summer Plant, which – like Vogtle – is undergoing an expansion involving two Westinghouse AP1000 reactors.

The pours at both projects included efforts by an Augusta company – Ashmore Concrete Pumping Inc. – which was also helping pour the final roof sections this week at the mixed oxide fuel facility at Savannah River Site.

“It has been a great week for the nuclear construction field, and it has all happened in our area,” said the company’s president, Jerry Ashmore Jr.

Vogtle’s units 3 and 4 are expected to begin commercial operation during the fourth quarter of 2017 and 2018, respectively.