The FAA chose to ignore the impact of overflight pollution according to internal USDOT/IG documents originated by FAA. The troubled Next Gen air traffic control program elevated "industry (airline) expectations" over public health and safety.
CAUTION: While we believe that the premise is correct --FAA usually designs PBN/RNAV route procedures only to increase hourly use of runways and other airport facilities --the IG study was of Metroplex implementations, multiple airports in urban areas.
When Next Gen could not resolve air traffic congestion in "more complex" airport and large metropolises without increasing air pollution and safety risks, they doubled down on "efficiency policy." During the last years of the George W. Bush administration, with the Next Gen program under development --and nothing else funded --FAA anticipated an expansion of routes, along the East Coast especially, and an "airline demand" for greater runway availability at many airports. Outside of the R&D departments, air traffic control management planned to "optimize runway use at minimum separations."
This is not news at MSP. FAA tried PBN routes at MSP soon after the September 2010 near-mid-air-collision, and the MAC maintained the illusion that environmental reviews and noise mitigation would be continued. FAA publicity featured "optimized efficient use of airport facilities and airspace," and airlines characterized noise complainers as being against the efficient and optimized flight routes needed for economic growth.
"Politicians (cynically or stupidly?) adopted the above views and did not question the MAC seriously when investigations of public health and safety or environmental impacts (GHG for example) were denied." Jim Spensley, SMAAC President
FAA ADMITS PUBLIC HEALTH AND SAFETY WERE NOT CONSIDERED IN IMPLEMENTING OVERFLIGHT ROUTES NEAR AIRPORTS: "......THE FOCUS WAS UPON OPTIMIZING ROUTES AND AIRSPACE DESIGN" RUNWAY-USE EFFICIENCY WAS "THE ONLY CONSIDERATION."
U.S. DEPARTMENT OF TRANSPORTATION OFFICE OF INSPECTOR GENERAL FINDINGS ON THE FAA'S METROPLEX AND NEXTGEN IMPLEMENTATIONS OF GPS-PLANNED AND FLOWN ROUTES (PBN/RNAV ROUTES).
In a bombshell and likely accidental admission, the FAA revealed the truth about how the MetroPlex and NextGen flight paths were designed
without noise, ground safety and public impact issues being considered. The FAA was responding in writing to an audit conducted
by the Transportation Departments Inspector General. The audit report stated that community noise issues were problems that were causing
delays with the FAA's implementation of the MetroPlex program across the Country. The FAA's response to the audits findings stated that
after noise issues became problematic, it later changed it's processes to include those concerns in future design procedures. But in doing
so, it admitted that the original design processes (which were used for the Sky Harbor NextGen flight paths) only considered optimization
of paths to benefit the industry. Here is the text of the FAA response regarding noise concerns from page 37 of the audit report:
"In order to address extensive community concerns about new noise exposure, procedures are designed and implemented that do not maximize
efficiency benefits, but do result in less noise exposure. When the Metroplex program began in 2010, the focus was upon optimizing routes
and airspace design. When community concerns were included in the design equation, optimization was no longer the only consideration. It
is an extraordinarily complex balancing act to provide both efficiency benefits to industry and to minimize new noise exposure in
communities. These are usually competing priorities."
The FAA also went on to admit that the programs only intent was to make use of all available airspace which created new noise impacts
over areas that previously had not experienced flight path intrusions:
"The intent of the Metroplex program was to make efficient use of all available airspace, which created new noise impacts. In many
communities, some neighborhoods experience less noise, and some more-relieved communities generally have not recognized the beneficial
noise reductions, while impacted communities strongly oppose the new or increased exposure."
The title of the audit report, issued on August 27th is "FAA Has Made Progress in Implementing Its Metroplex Program, But Benefits for
Airspace Users Have Fallen Short of Expectations". The report goes on to say the the FAA is behind schedule in implementing the programs and
that benefits as promised are questionable. Other statements from the report include:
"Delays have occurred largely due to increased community concerns about aircraft noise."
"Since 2014, further delays have occurred as FAA has implemented new PBN (Performance Based Navigation) procedures at more sites, largely
due to increased community concerns. For example, in fiscal year 2018, FAA cancelled the Phoenix Metroplex project due to litigation related to a previous PBN project."
SOURCE NOTE: We received the above information indirectly from the Scottsdale AZ citizens' group SCANA and condensed it a bit for the Twin Cities situation (messing around with routes to deal with the converging runways instead of to deal with nearby airports). In many ways, the safety issues and available technology at MSP is more difficult with respect to rates and routes than the Metroplexs being addressed by the DOT Inspector-General. Note that jets use some of the reliever airports, Holman and Lakeville are oveflown by airaft using MSP, and St. Cloud and Rochester are close enough to require consideration.