The Port of Seattle is moving ahead with construction of a $413 million rental car facility at South 160th Street and International Boulevard, near State Route 518.

For Highline residents, the biggest impact for the next few years may be increased traffic congestion around the site.

Port commissioners had placed a moratorium on new capital projects following a sharply critical state audit in December. Auditors accused port staffers of being too cooperative with contractors and withholding information from the elected commissioners.

The board is charged with overseeing operations at Sea-Tac International Airport. The port operates the airport.

But earlier this month, the commissioners withdrew the moratorium after being convinced that port management has instituted reforms.

On March 11, the five-member board approved an additional $850,000 for design work on the facility. Commissioners also increased the total for the construction contract from $3 million to $7.1 million.

Construction is set to begin in June with an expected opening in spring 2011.

The SeaTac City Council has agreed to allow up to 46-truck haul per hour on the boulevard. Half of the trips will be entering the construction site and half leaving.

During major site evacuation work, the trucks will enter the site by leaving westbound from SR-518 onto southbound International Boulevard.

Exiting the site, trucks will cross the boulevard on a specially built roadway onto the eastbound SR-518 onramp.

Concrete brought from a Duwamish River site will be hauled over two routes.

A maximum of eight trips per hour will use State Route 509, SR-518, South 154th Street and International Boulevard.

Another maximum of four trips per hour will go through Tukwila utilizing State Route 599, Tukwila International Boulevard and International Boulevard.

Riverton Heights resident Roger Kadeg told SeaTac lawmakers the truck trips on South 154th Street "will create a traffic nightmare.

"It will bring an unacceptable level of congestions and safety hazards," Kadeg declared.

But City Engineer Tom Gut said surveys showed the truck trips would only increase congestion at the 154th/boulevard intersection by 5 to 8 percent.

Port officials emphasize not all phases of the truck hauls will be going on at the same time.

The facility will have space for 5,400 vehicles with all rental agencies serving the airport consolidated at the site.

There will also be areas to wash, fuel and maintain the vehicles.

A customer service area will feature Wi-Fi, express check-in areas and flight-information displays.

Customers will be shuttled to and from the airport in buses fueled by compressed natural gas.

Moving rental-car companies out of the airport garage will free up space for more parking. The five largest companies now occupy two of the eight floors.

Consolidating the companies together in one building will decrease traffic and pollution around the airport while leveling competition among companies and be easier for customers, according to airport staffers.