The National Security Agency's (NSA's) newest -- and largest -- data center in Utah has been experiencing "meltdowns" that have destroyed hundreds of thousands of dollars worth of machinery, The Wall Street Journal has reported.

There have been 10 "chronic electrical surges" in the past 13 months at the data storage facility, which is essential to the agency's spying operation. As a result, the NSA hasn't been able to use computers at the data center. The "arc fault failures" were described by officials as "a flash of lightning inside a two-foot box," according to the Journal.

While the cause remains under investigation, NSA spokeswoman Vanee Vines told the Journal that the failures, which occurred during testing, have diminished. "A project of this magnitude requires stringent management, oversight and testing before the government accepts any building," Vines said.

The facility in Utah -- located in Bluffdale, about 20 miles south of Salt Lake City -- is one of the Pentagon's biggest U.S. construction projects, said to cost $1.4 billion, excluding the Cray supercomputers housed there. Engineers on the project estimate its capacity to be bigger than Google's largest data center. The Journal said experts believe NSA's data center will keep exabytes or zettabytes of data.

[ Are Tor communications safe from NSA surveillance? See NSA Battles Tor: 9 Facts. ]

Because of an unreliable electrical system, however, NSA's global surveillance data systems cannot function properly. According to project documents obtained by the Journal, the center's backup generators have failed several tests and the cooling systems haven't been tested. It appears that government officials and contractors also disagree over the capability of the electrical control systems.

The data center's construction is managed by the Army Corps of Engineers. The electrical system was designed by architectural firm KlingStubbins. Contractors working in the facility issued a joint statement describing the complicated situation: "Problems were discovered with certain parts of the unique and highly complex electrical system. The causes of those problems have been determined and a permanent fix is being implemented."

The initial failure at the data center took place on Aug. 9, 2012, project documents show. There were nine more failures since then, most recently on Sept. 25. Each incident caused $100,000 in damage, the Journal said.

The NSA has been facing a lot of criticism as of late. Earlier this year, former NSA contractor Edward Snowden leaked several of the agency's surveillance programs, including: Prism, which is meant to intercept foreigners' communication from sites like Facebook, Gmail and Skype; Boundless Informant, a data-mining tool that tracks where intelligence originates; and another program that analyzes millions of U.S. phone records.

Other documents leaked by Snowden revealed an NSA decryption program, codenamed Bullrun. The program is able to hack protocols such as HTTPS, VoIP and SSL; the latter is used to protect sensitive Web transactions including online banking and e-commerce