The construction company building a 330,000-square-foot county office building in downtown Redwood City took to Twitter to celebrate a milestone — the near completion of the concrete pouring.

The city says the five-story building is due to be completed by late 2023 and will provide a more sustainable and efficient environment for employees and the public.

Built with environmentally friendly cross-laminated timber to meet the county’s green building standards, it is designed to be a net zero energy structure and will qualify for LEED Gold certification. A building is net zero when it offsets 100 percent of its emissions, usually through a combination of clean energy sources and green building materials.

County Office Building 3 will be located on the lot across from the Hall of Justice. It will have enough space to accommodate 500 County employees, according to the County Manager’s office.

As part of the project, the portions of Hamilton and Bradford streets running through County Center will become pedestrian plazas dedicated to foot traffic.