Image courtesy of Sasaki Assoc.

Boston Mayor Marty Walsh announced the start of construction for the renovation of City Hall Plaza Saturday. The renovation, it is hoped, will transform the plaza into a civic space for all residents, with universal accessibility, new civic spaces, increased environmental sustainability and infrastructure improvements.

“This renovation is designed to turn our seven-acre space into a welcoming, accessible space for all,” Walsh said in a statement. “City Hall Plaza is one of Boston’s most-used public spaces, and we are working hard to create safe areas for residents to gather as we strengthen our commitment to civic services in our city.”

The plaza design and implementation is led by global design firm Sasaki Assoc., based in Watertown. Shawmut Design and Construction is the construction manager for the project. The project is managed by the city, assisted by owners project manager Skanska USA.

The $70 million first phase of the renovation will connect Congress and Cambridge streets with an accessible, sloped Hanover Promenade activated by with new amenities like shady seating and gathering areas, a destination play space, public art space and an “iconic” water feature. The main plaza will accommodate events of up to 12,000 people in a wide variety of potential configurations. The project also includes stormwater improvements, 100 new trees and a performing arts space.

The new design will also include three smaller event and gathering places, and a new civic building on Congress Street, equipped with a bathroom and other facilities to support public gatherings.