Amazon Web Services is continuing to grow its data center footprint in Loudoun County under a new partnership with Corporate Office Properties Trust.

A COPT entity is under contract to buy 78 acres of the Waterside development in Sterling, where it plans to build data centers for AWS, the Washington Business Journal reports.

The deal follows AWS' proposal in February to build a 600K SF data center campus on a 44-acre Loudoun County site just south of Dulles International Airport. AWS has a large existing footprint in the area, which is the largest data center market in the country.

The two data center properties both sit within 10 miles of the 26-acre Center for Innovative Technology campus, one of the sites in the running for Amazon HQ2. Northern Virginia has been pegged as a front-runner for the 8M SF headquarters project, in part because of the large AWS presence in the area.

The 335-acre Waterside development site, near the intersection of Route 606 and Route 28, is owned by Chantilly Crushed Stone, an affiliate of the Gudelsky Group. It is approved for 1.9M SF of office space, 645K SF of flex-office space, 2,200 multifamily units, 350K SF of hotel, 782K SF of retail and 272K SF of civic space. The project has been slow to move forward as the developer struggles to land an office tenant.