The designated noise contours around Sea-Tac International Airport will "absolutely" shrink as a result of the Port of Seattle's new noise study, the airport's program manager told SeaTac lawmakers March 8.
The existing noise contours were updated in 2002. So, it seems unusual that the noise contours would become significantly smaller following the opening of the third runway.

But the Part 150 noise studies in 1998 and 2002 took into account the expected added noise from the new runway in drawing up the contours, noise program manager Stan Shepherd said in a Times/News interview.
Chief reason for the shrinking contours is that modern aircraft are quieter, according to Shepherd. Alaska Air Lines and its partner, Horizon, have replaced their older planes with newer quieter models. Alaska and Horizon account for almost half of the flights at Sea-Tac.

Another reason is that fewer planes are using Sea-Tac. The airport counted 318,000 flights last year. Staffers had projected 475,000 flights. Shepherd noted airlines are using larger aircraft and making fewer flights. The larger planes are getting much quieter, he added.

The smaller contour area means no single family residences outside the current lines will probably qualify for noise mitigation, Shepherd acknowledged. However, Port staffers are conducting outreach within the current contours to provide mitigation to any eligible property that might have been missed, according to Shepherd. The Port operates the airport.

Shepard also explained how the Port conducted noise testing in 2009 when the second runway was closed six months for renovation. He said workers took the actual readings for the year and then extrapolated what noise levels would be if air traffic were distributed onto all three runways.

"We tested what it really was like and what it would have been," Shepherd said.

The Port will hold a public workshop Saturday, April 9, at the airport's Arrivals Hall from 10 a.m.- 4 p.m. Participants will be able to talk to Port staff and tour the airport.

The Port will validate for free parking in the airport garage.

Another alternative for those wishing to attend is taking light rail to the station at South 176th Street and International Boulevard.

Shepherd noted that staff must complete the Part 150 study and send recommendations to the Port Commission for approval. The study then goes to the Federal Aviation Administration (FAA), which makes the final determination.

Shepherd also briefed SeaTac lawmakers on the Port's evaluation of a potential hush house. Jets would back into the three-sided building to test engines. The building would be 35-40 feet tall with an opening facing southwest.

The house would cost $3-$6 million with the FAA providing 80 percent of the financing.

"It would be a large facility on a small airport," Shepherd noted.

The Port is considering six locations, all near the terminal, for the single facility. It would not be located away from the terminal to avoid having to tow aircraft across runways, according to Shepherd.

The hush house evaluation is part of the Part 150 study. The FAA would have to approve installation of the facility.

Shepherd also noted that the third runway is being used for about 28 percent of Sea-Tac flights. That is in line with previous Port estimates.