Inova Health System has big plans for the 117-acre former Exxon Mobil Corp. campus in Merrifield it acquired in 2015.

Over the long term, the health system plans to build up to 15M SF of medical care, research, office, residential and retail space on the Fairfax County campus, the Washington Business Journal reports.

The campus sits just outside the Beltway on Gallows Road, across the street from Inova Fairfax Hospital. The health system is using the existing 1.2M SF on the site as its Inova Center for Personalized Health and a conference center.

For the first phase of the project, it plans to turn the site into a 5M SF mixed-use development with 2.85M SF of office, 1.2M SF of residential, 850K SF of institutional space and 100K SF of retail. Most of the buildings would be between six and 14 stories, plus one 22-story tower. That phase could be built out over the next 10 to 15 years.

In later phases, it envisions another 10M SF of development, though that could be decades down the road and tied to future transit options and infrastructure upgrades. The health system requested Fairfax County update its plan to allow for 3.25M SF of development for the first phase.