MARIETTA — WellStar Kennestone Hospital will break ground on a state-of-the-art emergency department next month.

The health system’s executives say the upgrades to the state’s busiest emergency room are long overdue as the community the hospital serves continues to grow. Construction of the $126 million, four-story facility will take 24 months and the new emergency room will open the first quarter of 2020.

The existing department was designed to treat 60,000 patients a year. It has grown to become the nation’s fifth busiest and in 2017, Kennestone’s emergency room received about 145,000 visits.

The new ER, planned for the triangle between Church, Cherokee and Cherry streets, has the capacity to treat 185,000 people annually. A two-level bridge crossing Church will connect the new department with the rest of the hospital.

The number of rooms available to treat patients will increase from 84 to 130 and include 16 pediatric rooms.

The new emergency room features additional entrances for the 400 cars and ambulances delivering patients to the ER each day, allowing those in dire need of medical attention to be seen sooner.

Executives say the $126 million addition will be funded through a combination of bonds, capital funds and donations from the community.