FAA Duwamish Flight Track Study Disappoints

The FAA has now published its long awaited study on increased use of the Duwamish River and Elliot Bay noise abatement corridor.  The study, dated December 19th, 2000 was requested by the Port Commissioners as a result of the Sea-Tac Part 150 Study.   Increased use of the established Duwamish noise abatement corridor was essentially the only approved Part 150 recommendation that might offer some relief during north flow to central and east Seattle neighborhoods as well as Mercer Island and Eastside residents.
The FAA excluded any solutions

that involved changing air traffic flows outside the Seattle TRACON airspace, claiming that "changes to national traffic flows... are being addressed by the National Airspace Redesign effort".  Limiting the study in this way resulted in less than ideal options being considered.
The FAA studied a total of six alternatives for rerouting various portions of the traffic destined for Los Angeles and other southern destinations, and that now makes a U-turn to the east.  They dismissed two of the six as being non-viable and another for presenting unacceptable safety concerns.  They found the remaining three alternatives to be "operationally feasible", meaning they could be safely accomplished.
Unfortunately, they also found

the three options would all "result in a significant increase in departure flow restrictions to maintain the current level of safety".  They also pointed out the alternatives would impose additional mileage (fuel consumption) increases.  They concluded: "This study determined that any of these alternatives would produce a very significant increase in the number and duration of departure delays at Seattle-Tacoma International Airport."
Although Sea-Tac currently experiences minimal delays due to local airspace capacity problems, a study suggesting more delay seems to give the Port Commissioners and staff the evidence they need to keep the status quo.  The study exposed some other interesting facts.  It reveals the need for diverting some of the east turn traffic is even greater than most realize.
The study identified a typical north flow summer day at Sea-Tac--August 30th, 2000.  On that day there were a whopping 1510 operations (take-offs and landings) at the airport.  Sea-Tac is traffic is clearly on the rise--especially in the summer months when traffic is predominantly in north flow.  For comparison, an average day in 1998 had about 1095 operations (see also chart on p. 3)
On August 30th, there were 503 jet departures and a staggering 327 of those were on the east turn.  This number is far in excess of the 200 - 230 range that was quoted during the recent Part 150 study.  During the 16 hours the east turn is in operation (6 a.m. - 10 p.m.), this averages out to more than one noisy jet every three minutes over dozens of densely populated east Seattle neighborhoods.
There were only 155, or less than half as many, jets using the mostly industrial and water route

Cont. on Pg. 5  -  FAA Study