Nationwide Children's Hospital officials announced a massive expansion today that will cost $730 million and transform the patch of campus west of Parsons Avenue. The plans detailed today include some previously announced projects that already are under construction. But perhaps the most lauded - and most surprising - piece of the plan is the Behavioral Health Pavilion, a comprehensive center devoted to mental-health care for children and adolescents. Few cities have centers that compare, especially located on the main campus of a children's hospital.

Nationwide Children's Hospital officials announced a massive expansion today that will cost $730 million and transform the patch of campus west of Parsons Avenue.

They made a similar announcement a decade ago: a more than $700 million explosive growth of the campus southeast of Downtown that included a new, 12-story main hospital east of Parsons. That helped vault Children's into a spot among the nation's top pediatric hospitals, officials said.

"Back in the day, it was the largest pediatric expansion in U.S. history," said hospital board chairman Alex Fischer.

But it turned out to be just a start.

"As much as I think we're good at projections, the institution experienced such phenomenal success" that it couldn't have predicted, said Dr. Steve Allen, CEO of Nationwide Children's.

>> See map of expanded campus

The plans detailed today include some previously announced projects that already are under construction, including a five-story, $115 million outpatient care center at the corner of Grant and Livingston avenues (opening next summer) as well as a six-story, $45 million office building at Livingston and Parsons avenues (slated to open this month).

But perhaps the most lauded � and most surprising � piece of the plan is the Behavioral Health Pavilion, a comprehensive center devoted to mental-health care for children and adolescents. Few cities have centers that compare, especially located on the main campus of a children's hospital.

"To do it adjacent to our main campus as a centerpiece of everything that we do � as opposed to everything out in the hinterlands, if you will � is a major statement," Fischer said.

The building, which will cost nearly $160 million, is scheduled to open in 2020 with 48 in-patient beds. The center will serve patients in crisis, but also will aim to train care providers and to connect with community resources that serve children with mental illnesses.

"It's unique for a children's hospital to commit to a comprehensive behavioral health facility with all of these components," said Dr. David Axelson, chief of behavioral health at Nationwide Children's. "I think that the community at large has recognized that mental and behavioral health is an incredibly important problem."

Other pieces of the plan include:

-- A proposed 220,000-square-foot, $110 million research building, to open late 2021.

-- A $50 million Near East office building and garage with 800 parking spots along 18th Street just north of Interstate 70, to open winter 2018.

-- A $47 million project to complete unfinished spaces in the main hospital, adding 51 in-patient beds and five operating rooms by 2017.

-- $1.5 million in enhancements to Livingston Park, including new basketball courts and playground equipment.

-- A $74 million energy plant and a $75 million data center, both west of Parsons Avenue.

Children's has been positioning itself for this expansion for some time, accumulating the 20 acres of land north of Livingston between Grant and Parsons avenues. In 2013, the hospital paid Columbus City Schools $19.2 million for 10 acres that housed the Columbus Africentric Early College football field.

A year later, the hospital announced that it would build the Livingston Ambulatory Center, which will offer primary and dental care and other services, on a patch of that land.

The full expansion, recognized as the second phase of the master facilities plan that began a decade ago, is expected to wrap up in 2022. Hospital officials estimate that it will create 2,000 additional jobs by 2024, adding to the current 10,000.

In return for those jobs, Columbus City Council in December approved a $15 million break for Children's on income taxes over 15 years.

The phase two project will be funded through three evenly split sources, said Patty McClimon, senior vice president for strategic and facilities planning at Children's � bond debt, hospital income and donations.

That's similar to the funding for the first phase, during which the Nationwide Foundation gave $50 million and the hospital changed its name to honor its benefactor.

@lorikurtzman