PORTLAND — The third and final phase of the $525 million expansion of Maine Medical Center was approved Monday by the Planning Board.

The board approved the construction of a six-story office building that will replace the 360,000-square-foot staff parking garage at the corner of Congress and Gilman streets.

In a press release Tuesday, MMC spokesman Matt Wickenheiser said work on the new 265,000-square-foot building will not begin for nearly two years.

“First, a new staff garage at 222 St. John St. must be complete,” Wickenheiser said. The new garage, adjacent to Union Station Plaza, was approved by the Planning Board Sept. 11; site work began six days later. It is expected to open in 2020.

Following that, Wickenheiser said, the staff garage will be torn down, and the new office building is expected to be completed in 2022.

The third phase will also re-orient the hospital to a “major point of entry on Congress Street,” according to a city Planning Department memo, instead of the Western Promenade where its oldest buildings are located.

Within the new building, the hospital will reorganize its cardiovascular care services. That includes 19 new procedure rooms, 64 private patient rooms and “means timely, efficient access for patients and care teams and reduction of time and effort spent traveling through the hospital corridors,” Wickenheiser said.

City Senior Planner Nell Donaldson said the new office is expected to add 200 employees to the campus by 2023.

Hospital expansion is occurring throughout its campus area, which is part of an institutional overlay zone approved by city councilors in 2017. There are four such city zones, also containing Mercy Hospital, the University of New England and the University of Southern Maine.

The first phase of MMC’s expansion has been underway since May, and includes the expansion of its patient visitors parking garage, uphill on Congress Street from the staff garage. Wickenheiser said work to add 225 parking spaces on three new floors was completed Sept. 10, “months ahead of schedule.”

Garage work also required closing Congress Street to vehicle traffic between Forest and Weymouth streets in May, but the street was reopened two weeks earlier than anticipated.

The expansion of the hospital’s East Tower continues, with two floors and two new helipads under construction.

Within the new floors are 64 new rooms for oncology services and patients, and work is expected to be completed later next year, Wickenheiser said.

The entire expansion is also intended to increase the number of private rooms at the hospital, which has faced a bed shortage at times because some patients cannot be placed in semi-private rooms, according to the 2017 application for a certificate of need submitted to the Maine Department of Health & Human Services.

David Harry can be reached at 780-9092 or dharry@theforecaster.net. Follow him on Twitter: @DavidHarry8.

The third phase of expansion at Maine Medical Center in Portland will come after parking is moved from the garage at Congress and Gilman streets to a new garage off St. John Street.

The new six-story Maine Medical Center office building approved by the Portland Planning Board on Dec. 17 will replace a parking garage now at the corner of Congress and Gilman streets.