Tesoro Hawaii yesterday said it hoped to complete a $1 million project to quadruple its asphalt storage facility by the end the month in a move that could help prevent potential shortages of the road-paving material in the future.

Crews are on track to complete the expanded storage facility one month ahead of schedule, said Tesoro spokesman Nathan Hokama.

At the same time, the company announced that it had stopped distributing asphalt and begun an investigation into an incident earlier this month in which a liquid asphalt storage tank at the refinery smoldered. Asphalt production should resume in early July, Hokama said.

Some asphalt is being set aside for emergencies, and the rest is directed to government priority projects such as a taxiway at Honolulu International Airport. For now, roadwork is continuing at a near-normal pace, said Department of Transportation spokesman Scott Ishikawa.

However, there still is a chance the local supply of asphalt could run out before more becomes available.

"It's going to be close," said Bob Wilkinson, president and chief executive for asphalt contractor Grace Pacific Corp.

"We could use up all our supply in about four days," Wilkinson said. "The way we're operating on a limited basis, we have about 10 days' supply."

About 45 Grace Pacific workers on the Neighbor Islands are out of work because of a lack of asphalt, Wilkinson said.

Tesoro is looking to increase liquid-asphalt storage capacity in response to a shortage of the petroleum byproduct in the Islands. By the end of this month the company expects to have reconfigured refinery tank capacity to 100,000 barrels, or enough to store a 50-day supply of asphalt.

Asphalt is produced from heavy crude oil. When heated and mixed with crushed rock, called aggregate, it can be used to build roads, driveways and parking lots and to fill potholes.

Chevron Hawaii used to produce about half the state's asphalt but, the company decided last year to switch to a lighter crude oil with less sulfur. The new crude isn't appropriate for making asphalt.

Reach Sean Hao at shao@honoluluadvertiser.com.