Construction is ramping up on a major mixed-use development in Downtown designed by Frank Gehry.

Over the weekend, the one of two concrete pours was completed at The Grand, laying down the foundation for the project’s 39-story residential tower. When finished, the Bunker Hill tower will hold 436 housing units, 20 percent of them affordable units.

“The mat foundation pour is an incredibly important construction milestone as it marks the beginning of the vertical construction,” said Rick Vogel, project lead and senior vice president at Related Urban, the mixed-use division of Related Companies.

The pour wrapped up on Saturday. It took 15 hours, and required about 140 workers and 1,348 trucks.

The Grand takes up a full block just east of the Walt Disney Concert Hall, also designed by Gehry. The block-sized development will also hold 176,000 square feet of shops and restaurant space, a movie theater complex, an Equinox Hotel, and a public plaza with landscaped terraces.

The project is developed by Related Companies and Core USA, a joint venture of China Harbour Engineering Company and CCCG Overseas Real Estate.

Vogel said The Grand will serve the “important purpose” of furthering connect Grand Avenue, which is already home to a number of institutions including The Broad, the Music Center, and the Museum of Contemporary Art.

The Grand is part of a larger development known as the Grand Avenue project. It includes Grand Park and the Arquitectonica-designed apartment tower, The Emerson, which debuted in 2014.

Projected to open in 2021, The Grand is will be across the street from a future stop on the Regional Connector at Second Street and Hope, just west of the Broad.