Watchdog Group: MAC Fudges Noise Projections in Eagan Meetings

Over 100 citizens turned out at the Blackhawk Middle School in Eagan to hear a Metropolitan Airports Commission (MAC) noise presentation. The meeting was one of several planned by the City of Eagan, the area perhaps to be most-impacted by opening new Runway 17-35 at Minneapolis-St. Paul International Airport (MSP). The citizens were not amused by the prospects.

One citizens found the MAC presentation “Condescending as well as misleading.” SMAAC noted several errors in the twenty-minute presentation by a MAC spokesperson. One graphic reminded the audience that the Legislature “mandated” a 25% increase in MSP “capacity, requiring a new runway.”

Sure, blame the Legislature for the increased overflights. Not mentioned: Use of MSP increased 34% 1995 to 2004, although new runway construction must have limited use somewhat and the terrorist attacks in September 2001 reduced demand for awhile. This reflects more hub use as Northwest gained gates.

MAC said that aircraft noise over the school will be comparable to noise at recording stations “equidistant” from the airport as shown by concentric circles drawn on a map of MSP and the surrounding neighborhoods. Not mentioned: 2002 traffic, or current traffic, over any of the 30-some stations is not representative of traffic patterns or noise after Runway 17-35 opens next year. SMAAC notes that in the possibly intended sense that event noise – a single overflight – is representative for similar aircraft on projected tracks directly overhead, an steady increase in over-95 dbA events has occurred since 1996 at most stations.

MAC said that Runway 17 departures would be routed to the West over the Minnesota River as much as possible, especially at night, to reduce noise in Eagan. One citizen asked for clarification, noting that school was not ordinarily conducted in the building after 10 PM. It turned out that about 1% of Runway 17-35 use was planned for the River valley departure (2% of take-offs). The MAC spokesman denied any knowledge of studies of how airport noise affects traditional classroom education. SMAAC notes that numerous studies show an adverse effect, notably the multi-year (longitudinal) studies in Munich, Germany. At projected 2007 levels, there would be 950 flights per day over Eagan.

MAC said that a “normal conversation, about 65 db intensity, was comparable to aircraft noise at the 65 DNL (average noise) contour.” One citizen objected, remarking that most Eagan residents had a college education and understood hearing was on a log scale. SMAAC notes that sound intensity during multiple conversations in a room may vary between 63 db and 67 db, just over 65 db average intensity; overflight noise varies from 3 db to 95 db to 3 db as the aircraft passes over a station, yielding a 65 db “average” only when the event time base is a certain value (or the threshold levels are set accordingly).

MAC also fumbled the answer to how flight tracks were projected. The spokesman said that operations were based on air traffic management plans and runway use systems adopted by FAA. SMAAC notes that FAA plans are still pending. The noise contours were developed using a computer model and based on simplified and assumptive inputs developed by HNTB, a consulting firm contracted by the MAC. HNTB was limited by the scope of its contract and was directed to use projections furnished to MAC by the airlines. The safety and feasibility of these plans are yet to be reviewed by FAA. Besides, MAC begins next month to change operations, again increasing hub use of MSP.


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