Around 800 aircraft take off and land at Sea-Tac International Airport everyday and with that traffic comes a lot of noise.

The Port of Seattle held an open house for the public at Sea-Tac on April 9 to display the latest possible remedies to reduce noise emanating from the airport that negatively effects surrounding communities, called the Part 150 study.

Part 150 Study

The impetus for this latest study (it’s the fourth they have done, with the last one in 2002) was the completion of Sea-Tac’s third runway in 2008. The third runway sits on the western edge of the airport and its use brought new communities within the affected area of airport noise pollution.

“We look all of the noise environment and it’s an opportunity for us to look and see if we can do things better,” said Stan Shepherd, manager of airport noise programs for the Port of Seattle.

The Port of Seattle uses a metric called DNL (a day-night average of noise over a year-long period) to determine a boundary around the airport where anyone living within the boundary can be negatively affected by airport noise. Shepherd said they look primarily at sleep loss and trouble speaking with others over the noise.

The boundary is determined by any area within 65 DNL of the airport, and Shepherd explained, “That’s the area the FAA terms as impacted to the community to where they would actually allow mitigation programs to take place and they fund those programs.”

Shepherd said mitigation proposals that are accepted by the FAA (and those proposals were on display at the open house) are 80 percent funded by the FAA with the Port of Seattle covering the other 20 percent. As an aside, the airport division of the Port of Seattle is not funded by tax dollars, but rather by fees they charge to landing airplanes and customers primarily, according to Patrick Clancy with the Port of Seattle.

The sound mitigation proposals on display at the open house were brought up by the communities surrounding the airport, Shepherd said, and they are all in the feasibility study phase at this time. He said the Port will decide on the best solutions and present them to the FAA at the end of 2011. The FAA will then do a 180 day review and decide which measures they will help fund.

Shepherd said a few factors have actually shrunk the 65 DNL sound contour since they last measured it in 1985 including quieter aircrafts and a dampened economy that has resulted in fewer flights coming into the airport. Based on those changes, a map on display (which can be seen in the slideshow at the top of the story) showed the old sound contour versus the latest countour (which has shrunk) and it shows the Port’s goal of reducing their sound to the smaller boundary by 2016.

Sound mitigation proposals

Here is a list of proposals to reduce sound around the airport presented at the open house:

-Building a Hush House, which reduces noise from checking airplane engines and engine run-ups. ““We think that’s going to have a fairly substantial reduction in noise in the community (15 to 20 decibels),” Shepherd said. “We still have to go through the evaluation to make sure that its going to fit on the airport, the biggest thing is that we have such a small airport (geographically confined) it’s hard to get that large of a facility (placed).” Shepherd said a Hush House would be at least two years out.

-Purchase residential properties experiencing noise levels of 65 dnl or greater in proximity of the third runway

-Install air conditioning for single-family homes within the updated noise remedy boundary that have not already been insulated

-Assist local jurisdictions with long-term land use planning

-Update noise remedy boundary

-Single family sound insulation

-Multi-family owner-occupied/tenant occupied sound insulation

-Purchase avigation easements for mobile/manufactured homes on private land withing the updates noise remedy (approximately 75 mobile homes on private land within the upadate noise remedy boundary

For more information on these proposals, visit the Port of Seattle here or their Part 150 Study site here.

Community concerns

Arlene Brown lives in Normandy Park and came to the open house to see the latest proposals. She said she generally wakes up at least twice a night from loud planes landing and had much more to say about the FAA and Port of Seattle’s 65 DNL metric.

“The noise boundaries and the DNL approach doesn’t reflect reality,” she said, “and noise can wake people up multiple times every night and studies show very clearly it increases cardiovascular illness and blood pressure in particular and that it doesn’t take much airport noise to make those increases and that’s completely ignored in this process.”

“It’s an average of noise over a huge period (one year) and so you could have an airplane over your head - you could put a lawnmower in your bedroom and have it turn it once an hour and it would be considered no noise with the way DNL noise calculations are done,” Brown said.

“There are other airports in the US that go out beyond the 65 in terms of contours, but the Port of Seattle doesn’t because the FAA only has certain levels that you have to do,” she continued. “There are other measures other than DNL, there are ways to look at single events instead of this averaging and we need single event mitigation not averages that can have you literally waking up every hour and calling it zero noise.”

Stan Shepherd said, “This is the best cumulative noise metric that can show the impact to a community over the given portion of a year so the FAA has … evaluated that metric many times and still haven’t come up with anything better to show what an impact would be to a community.”

Shepherd said they have a Sound Exposure Level (SEL) metric that measures individual instances, such as that one airplane coming in that wakes you up in the middle of the night, and described it’s relation to DNL in the following way: “If you take a bucketful of these … every aircraft that flew into this airport, if you take the bucket of these SELs and you put them into the big bucket then we can say it’s now a DNL so that’s how we do that cumulative impact with it.”

“It is a little confusing but it is a great way to assess that impact on the community … and until someone comes up with something better, which no one has been able to do, this is the best,” Shepherd said.