Interstate 485, turbine interchange near completion

Relief is in sight as two vital interstate highway projects approach completion in western Cabarrus and northeast Mecklenburg counties.

The N.C. Department of Transportation expects to complete the Interstate 485 outer loop around Charlotte, and the state’s first turbine interchange, in December.

The projects are being completed in conjunction with the widening of Interstate 85 from four to eight lanes near Concord’s Exit 49, one of the state’s busiest.

These projects were accelerated a couple of years ago with the help of then-Gov. Bev Perdue. She helped get funding through a process called Design, Build, Finance.

That process brought in lower bids and was expected to save the state roughly $130 million in construction costs for all three projects. And it added about 400 area jobs to local and regional economy.

Without that action, these projects wouldn’t even have started until 2015 at the earliest, said NCDOT spokeswoman Jen Thompson.

Thanks to those efforts, more than 1.7 million people living in surrounding counties – according to 2010 U.S. Census data – are expected to benefit from the new roadways.

The roads were built to accommodate projected traffic volumes between 142,000 and 190,000 vehicles per day by 2035, said Thompson. When the contract was awarded in 2010, traffic counts averaged 113,000-115,000 vehicles per day on I-85.

Project details

NCDOT is building the final 5.7 miles of I-485, which will run from west of N.C. 115 in northern Mecklenburg to west of I-85 near the Cabarrus County line, linking I-77 with I-85, according to its website.

The state is converting the existing I-485/I-85 interchange – which itself was a modification of the old flyover that connected I-85 to U.S. 29 – to the new turbine design. It is the first of its kind in the state. Although, unlike cloverleaf interchanges, if you take the incorrect exit, drivers will have to travel to the next exit to get back on track.

The final section of I-485 runs through the northeast part of Charlotte/Mecklenburg from east of N.C. 115 (Old Statesville Road) to east of Interstate 85 near the Cabarrus line.

The turbine design is estimated to save more than $50 million in project costs, Thompson said, compared to the four-level stacked interchange that would have cost roughly $140 million to construct.

“Think of the volume of traffic at I-77 and 485 (in south Mecklenburg near Carowinds),” Thompson said. “We’ve got to try and move that kind of traffic up on the north end, so we needed something that was going to be high-speed.

“It’s an improvement to safety. It’s going to move large volumes of traffic through more efficiently, and we’re saving money without expanding the footprint.”

A first for N.C.

The NCDOT had acquired rights-of-way in the early 1990s. The $92.2 million turbine interchange project, started in the summer 2011, set out to replace the existing interchange connecting I-85 to I-485, helping to complete Charlotte’s outer loop.

The contract to complete I-485 in northeast Charlotte was awarded to Blythe Construction in 2010 for $139.5 million, Thompson said. Construction started in July 2010 and should be complete by mid-December.

Completion of that 5.7-mile segment will complete the 67-mile interstate highway loop around Charlotte.

The turbine interchange moves all left-turning traffic around a central bridge in a counterclockwise direction, according to the NCDOT.

The design also touts high-speed, high-capacity ramps and the construction of 19 bridges, Thompson said. The four-level stacked interchange previously envisioned by the NCDOT – like the one at Interstates 77 and 485 near Carowinds – would have needed fewer bridges but would have been more costly and required maintenance in inclement weather.

“Drivers will notice significant improvements traveling, say, from I-85 to I-77 in northeast Charlotte, avoiding a lot of surface streets like Harris Boulevard, Statesville Road and Old Statesville Road,” Thompson said. “Having the outer loop completed will improve movement of people and goods more efficiently and in a safer manner.”

Economic effects

Patrick Coughlin, the president and CEO of the Cabarrus Regional Chamber of Commerce and Cabarrus Economic Development Corp, estimated the state’s investment in Cabarrus County during the past few years is more than $400 million.

“The completion of the I-485 loop and I-85 interchange gives Cabarrus County a competitive advantage we’ve never had before,” Coughlin said. “More importantly, it puts the entire Charlotte metro region in an extremely competitive position nationwide.

“The completion of the loop will generate more interest in our region and more jobs. We’re seeing a significant uptick in recent months in inquiries and economic development activity, compared to earlier this year and last year at this time.”

Design benefits

John Johnson is vice president of Charlotte-based STV Inc., the civil engineering group that helped create the turbine design in Charlotte, based on similar one in the United Kingdom.

The turbine design made construction work easier and safer and minimized congestion during construction, Johnson said. It also made fewer environmental impacts. For example, it avoided disrupting more than 300 feet of a nearby stream and preserved habitat for the endangered Schweinitz’s sunflower.

The project had been in the planning stages since the late 1980s, Johnson said. But as traffic volumes increased, previous design upgrades were ruled out because they couldn’t handle the projected volume.

“Road and Bridges Magazine ranked it the No. 1 award-winnng project happening in the nation last year,” Johnson said. “We won’t know what the full impacts will be for many years, as areas around the interchange develop and growth occurs. …

“That area is very highly populated, and it’s one of the last quadrants to get an outer loop, so it’s going to really improve mobility for the region.”