Engineers Making Sure Interstate 485 Won't Interfere with Charlotte/Douglas Flight Paths

Sep. 14--Engineers are working with airport officials to make sure bridges and ramps planned for a future Interstate 485 interchange won't interfere with aircraft flight paths.

The future West Boulevard interchange must be low enough to accommodate Charlotte/Douglas International Airport and big enough to handle the thousands of vehicles that will travel between two major highways -- I-485 and the proposed Garden Parkway.

The bridges must be positioned so they won't be a safety issue for the airport's diagonal runway or the new north/south runway that's planned parallel to the freeway.

"It will work," aviation director Jerry Orr said. He says the state probably can add two levels of bridges.

In the next decade, that interchange will likely undergo a major transformation. It's now a simple overpass, carrying Garrison Road over I-485 southwest of the airport. Two pairs of dirt ramps are built but not yet paved.

Ramps and bridges would be added if the state follows through on a proposal to build the 20-mile Garden Parkway through Gaston County. The parkway would start at I-85 west of Gastonia and join I-485 at the West Boulevard interchange, to be called Exit 6.

The parkway is proposed as a toll road and could carry 36,000 to 50,000 vehicles a day, said Mike Holder, the state engineer assigned to Gaston and five nearby counties.

That heavy volume would require an interstate-type design with a major interchange at I-485.

That structure would not be as massive as the interchange between I-77 and I-485 near the state line, Holder said. But it must have several ramps and bridges so traffic can move smoothly between the two highways.

The tallest bridge must be at least 23 feet below the lowest area in which planes fly, Orr said. But in practice, the actual flight path will take planes far higher than that.

"If a plane was flying 23 feet above the highway, people would be holding their head," Orr said.

The airport has suggested solving the height issue by building a high-capacity interchange like the one at I-77 and Tyvola Road, an urban diamond. Holder argues that design, which requires traffic signals, would not move enough traffic.

The interchange's future design will only become an issue if the Garden Parkway is built. And it will only be built if its estimated traffic is high enough to make the toll road financially feasible.

If the N.C. Turnpike Authority decides to build the parkway, work would start late this decade.

The highway department has adjusted its plans in the past to make way for airplanes, said Benton Payne, the state engineer for Mecklenburg and four nearby counties. A few years ago, the state scrapped plans for building a communication tower in the Lowe's Motor Speedway area because it would interfere with Concord Regional Airport's flight path.

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