By Erich Wagner (File photo)

One thing is certain about the planned relocation of the National Science Foundation from Arlington to Alexandria in 2015: It will have a big impact on the city’s coffers as well as the local economy.

But just how much money will flow the city’s way was briefly up for debate.

Last week, the Times erroneously reported that the foundation’s move would produce $83 million for Alexandria’s economy over the course of its 15-year lease. In June, the city announced that the relocation would produce $83 million annually.

But in researching the deal because of the error, it was revealed that city staff and Alexandria Economic Development Partnership officials were touting different stats about the economic impact of the foundation’s move.

Val Hawkins, president and CEO of the partnership, said his agency had been operating under the understanding that the original $83 million in direct and indirect benefits to the city economy each year was accurate. But Deputy City Manager Mark Jinks said in an email that that figure refers to gross tax revenue — the economic impact will be much higher.

After accounting for the various tax breaks that the foundation receives in its relocation deal, Jinks said the increase in tax revenues will be about $55 million over 15 years.

“The Delta Associates study that the city and [Alexandria Economic Development Partnership] commissioned projects a $99 million annual impact starting in 2015,” Jinks wrote. “[The] $83 million cited in your story is the 15-year gross tax impact to the city’s general fund.”

Hawkins said he was surprised by the figure announced by the city and, upon further review, realized that they were actually citing different numbers from the same report.

“So, technically, we’re both right,” he joked. “Obviously, we’d just as well prefer to use the $99 million figure.”

The Alexandria organization conferred with Delta Associates and confirmed that $99 million annually is the most up-to-date statistic for the economic impact of the foundation’s relocation.

Stephanie Landrum, executive vice president and COO of the partnership, said the study was performed over the course of several months. As such, the projected economic impact changed — with a final conclusion of $99 million annually — though the report’s summary was never updated.

But Hawkins said that no matter how you slice it, the foundation’s move already is producing results in future economic growth.

“This thing has already jump-started so much activity and return to the city,” Hawkins said. “People may complain about some small things, but this is just an overwhelming opportunity.”