Port of Seattle commissioners would not guarantee there won't be a fourth runway at Sea-Tac International Airport when they approved final funding for the third runway last week.

At a recent Highline Forum meeting, Burien Deputy Mayor Jack Block Jr. asked Port officials about rumors of a fourth runway at the airport.

Block said later that he asked them to sign a no-fourth-runway agreement but they refused.

"Of course, we can't tie the hands of future commissioners," said Port Commissioner Bob Edwards.

"But we have no plans for a fourth runway," Edwards insisted. "The airfield is as big as it can be."

Edwards noted the Legislature has authorized a transportation study to find additional air travel capacity in about 20 years.

"But they are not going to get it at Sea-Tac," he said.

The Port commissioner said he is upset that the fourth runway rumor was started.

"I am concerned people are getting upset and alarmed about something that is not real," Edwards said.

Officials of surrounding airport communities meet monthly with Port staffers to discuss common issues.

Meanwhile, construction on the third runway embankment is finishing up.

Night truck hauls were suspended in midsummer as contractors focused on positioning dirt already delivered.

This year, trucks delivered nearly three million cubic yards of dirt. Workers moved around 1.5 million cubic yards at the runway.

Daytime truck traffic will resume in mid-spring as paving material for the third runway and for expansion of the safety area around the second runway is hauled in.

Port workers are also building a 1.7 million gallon underground stormwater vault at the airport's south end.

On the north end, the Federal Aviation Administration is building a light system for the third runway. The lights will be supported on five towers with an additional bridge over state Route 518.

According to Port officials, the environmental mitigation work is substantially complete.

Port commissioners have approved the final $220 million appropriation on the $1.1 billion runway project.

The original estimated runway cost in 1997 was $587 million.