It looks like the National Security Agency's $1.5 billion data center in Utah just got even more expensive.

Chronic electrical surges have destroyed hundreds of thousands of dollars worth of equipment, according to documents cited by the Wall Street Journal, setting back the opening of the facility by one year.

"The failures that occurred during testing have been mitigated. A project of this magnitude requires stringent management, oversight and testing before the government accepts any building," an NSA spokeswoman told WIRED by email.

But the Wall Street Journal reports that there is disagreement about whether the proposed solutions will work. The Army Corps of Engineers is overseeing construction of the data center, and the electrical system itself was built by architecture firm KlingStubbins, which is a joint venture of three companies: Balfour Beatty Construction, DPR Construction and Big-D Construction Corp. Although the contractors have a fix in place, the cause of the surges – known as "arc fault failures" – is unknown.

"We did not find any indication that the proposed equipment modification measures will be effective in preventing future incidents," says a Army Corps of Engineers report cited by the Wall Street Journal.

The 1 million square foot data center, which WIRED reported on last year, is expected to intercept, analyze and store data passing through emails, phone calls and other communications networks. Part of the reason that the NSA built the center in Utah was because of its cheap electricity – the agency expects to spend around $40 million a year on energy bills.

The construction problems come as the NSA is under increasing scrutiny for its widespread domestic surveillance programs.

The electrical issues aren't the first surprise the NSA has faced while building the facility. Last May a state agency called the Utah Military Installation Development Authority proposed a new energy tax, which would be applied to the PacifiCorp-owned utility company Rocky Mountain Power, that could raise prices by about 6 percent.

The Army Corps of Engineers could not immediately be reached for comment.