Hartford Hospital will break ground Thursday on a $70-million expansion of its sprawling South Green neighborhood campus.

The project centers around construction of a 49,550-square-foot addition to the north façade of its existing Bliss Building at 80 Seymour St., which will provide four floors of additional space to support clinical areas including MRI, interventional radiology, electrophysiology, a cath lab, critical care and surgical care, the hospital said.

“The Bliss building expansion supports a culmination of unprecedented growth at Hartford Hospital and a look to the future by giving us the necessary physical infrastructure to better support our hospital, Institutes and community,” said Bimal Patel, president of Hartford HealthCare’s Hartford region.

The new building will be located on the grassy area outside the hospital’s cafeteria, adjacent to the Cheney and Crane buildings. Its layout will make for an easier and more seamless patient experience, the hospital said, with separate areas for inpatient and outpatient care. It will also connect to the Emergency Department Observation Unit so patients can easily get an MRI rather than going to the Jefferson building.

There will also be additional covered seating outside the cafeteria and a covered walkway.

The building is scheduled to be open by Aug. 2021.

Hartford Hospital has gradually expanded its campus over the years, including the late 2016 opening of its $150 million Bone & Joint Institute.

Hartford HealthCare CEO Jeff Flaks told Hartford Business Journal in August the hospital system will also announce a 15,000-square-foot lease somewhere in downtown Hartford later this year to house its supply-chain division.

That will add to the system’s growing presence downtown. HHC moved its corporate offices to One State Street in 2011. Earlier this year, it announced a healthcare technology accelerator program that will launch in November at Constitution Plaza.