Tests of the air quality inside Blacksburg's new town hall annex have determined it safe for municipal employees, who will begin moving in today.

Town officials placed monitors in the building Aug. 3 as a precaution after several incidents in which contaminated soil and groundwater complicated renovation of the former Blacksburg Motor Co. site.

Although he had not seen the official laboratory results Monday, Town Manager Marc Verniel said he was told the air quality was "within the limits" of acceptable workplace levels.

The new building, which will house about 25 employees from the town's planning, engineering and geographic information systems departments, sits on the site of a former gas station, where underground storage tanks leaked an unknown amount of gas into the surrounding soil over the years.

In June, gas vapors emerged from the soil as construction workers were digging trenches in the basement to correct a recurring flooding problem, reaching a potentially hazardous level.

"The only time we had a problem with the fumes was when we cut into the [basement] floor," Verniel said.

But workers have also encountered gas-tainted water at least twice while digging at the site -- once when installing an elevator pit and again when drilling a well for a geothermal heat pump system.

Details of the testing, such as how many monitors were installed and what chemical compounds were measured, were not available Monday.

David Griffiths, an environmental scientist who has raised concerns about the project as a Blacksburg resident, said the tests represent just one "snapshot in time," and that gas vapors could possibly find a way inside as the building settles over time.

"I don't mean to come across as a naysayer, but just because they got clean results one time doesn't necessarily mean it's a clean building forever," Griffiths said.

Verniel said it's likely the town will conduct additional tests in the future.

The $5.3 million project has been touted by Blacksburg officials as an example of how government can take over a troubled site and convert it into an energy-efficient and environmentally friendly building.

A private developer might have simply bulldozed the historic Blacksburg Motor Co. building, leveled the site and started over, supporters of the project have said.

But by preserving a building built in 1924 -- and claiming up to $1.2 million in state and federal historic tax credits to offset construction costs -- the town was limited in how much contamination it could remove from the site.

Two of five underground storage tanks remain under the building, and town officials have acknowledged that they don't know exactly how much gas-tainted soil and groundwater surrounds them.

"The fundamental fact is that there is heavy contamination surrounding the building, probably on all four sides and beneath it," Griffiths said.