An Iron Mountain data center. Photo by Iron Mountain

MANASSAS, VA–Boston-based Iron Mountain, a document storage and data center REIT, has begun construction on its third data center complex in Prince William County, a previously-announced project that was recently revised upward to be worth $441 million.

Kessinger/Hunter & Co. is developing the first 150,000 square-foot data center on the 83-acre data center campus. Other companies working on the project include JE Dunn Construction Group and Burns & McDonnell Engineering Co.

Iron Mountain's Northern Virginia data center campus will have 60 megawatts of capacity spread across at least four individual colocation facilities. The first building, expected to open in summer 2017, will offer 10.5 megawatts of power and a flexible design that can house cloud services providers, federal government agencies, systems integrators, financial services firms and healthcare companies.

Top Data Center Market in US

It is little surprise Iron Mountain has selected Northern Virginia for its data center development activity. Besides the robust list of possible customers, Northern Virginia's data center capacity has reached an eye-popping 105 megawatts, according to JLL. That is almost double the demand capacity for Silicon Valley, which has a net absorption rate of 57.6 megawatts. Other active markets include Chicago at 32 megawatts, the Northwest at 22 megawatts, Dallas (which used to be the No. 2 market last year) at 18 megawatts in net absorption and Phoenix at 14.1 megawatts.

In the space of a year the market has grown at an astounding rate Allen Tucker, managing director of the Mid-Atlantic Data Center Solutions practice at JLL told GlobeSt.com in an earlier interview.

At the end of last year Northern Virginia represented 20% of entire US market, Tucker said.“Now it has 30% of the entire US market.