The debate is in large part over the unpredictability of wind in a high rise environment. Credentialed experts on both sides just don't agree.
Now, two new wind studies are being completed, and the state is proposing an April reopening to a public hearing on the heliport proposal.
Roughly 80 times a year, critically ill or injured children are airlifted for emergency care.
The heliport sits atop the new 23-story Lurie Children's Hospital. Its Streeterville neighbors welcome the hospital, but they don't want the heliport.
"This is all about public safety. From day one this has been about whether it's safe to nestle a heliport in a forest of skyscrapers," said Patty Frost, Streeterville Organization of Active Residents
The heliport, now largely done, sits 424 feet above street level. Arriving patients, all with time critical needs, would be elevatored down to emergency care. The hospital says safe operation is paramount. Its team of consultants has analyzed wind behavior and has concluded that "wind conditions will be favorable for helicopter operations."
The city has approved it. The Federal Aviation Administration has approved it. The State Department of Transportation two years ago gave its preliminary approval. But there are wind behavior experts who've raised red flags.
"The wind characteristics on the roof of a building including this hospital are incredibly complex. They are three dimensional," said Dr. Thomas Corke, director of the Hessert Laboratory for Aerospace Research, Notre Dame.
Dr. Corke was hired by Streeterville residents, and insists the wind analysis methodology used by the hospital's experts is flawed. Airflow around buildings, he says, creates wind micro-climates that can confound basic wind tunnel research. Wind bounces. It's unpredictable particularly in a high rise environment.
"There's no instrument on the roof. That you could place on that roof that would tell you precisely in every detail what you would need to know how the wind conditions are, and without knowing wind conditions, you wouldn't be able to determine if it's safe to land," said Dr. Corke.
Hospital-based life flight operations use AWOS - automated weather observing system - for information on wind speed, temp, visibility. And Children's says it would have the latest generation of AWOS.
Information it generates becomes part of a rigid protocol that pilots follow when deciding "whether to fly or scrub the mission."
But in a high rise setting, AWOS has limitations in revealing the likelihood of wind shear.
"Everyone has come back and said no good emergency landings here," said Dr. Corke.
Streeterville residents say a better alternative is to have Children's helicopter transports land a few miles away on this city owned lakefront helipad.
Children's says the additional travel time and extra movement of fragile young bodies would cause serious harm.
But the disagreement among experts over safety concerns with this heliport has led to two additional wind studies due to be completed soon and a reopened public hearing.
"Clearly we want to make sure we've looked at everything. We don't want to make a bad decision because we haven't looked at all the facts. We want to look at all the facts and get it right," said Gary Hannig, secretary, Illinois Department of Transportation.
"We want to make sure in advance of that public hearing that everybody has all the data, everybody has all the opinion and that this is a transparent process with a lot of light shone on it," Frost said.
The last public hearing on the heliport was in July of 2009, and in large part because of the objections of heliport opponents, the state commissioned the new wind studies.
IDOT promises to share the findings and methodology in advance of the new public hearings which are tentatively targeted for April. What IDOT could not tell ABC7 is whether the studies are built on data from wind testing on the new heliport itself.