MARIETTA — The “diverging diamond” interchange planned for Windy Hill Road and Interstate 75 is moving forward.
The Cumberland Community Improvement District’s board of directors approved spending $85,000 with Montreal-based DE Design and Environment Consultancy for the architectural design and bridgescape plans on Thursday.
The firm designed the Jimmy Carter Boulevard diverging-diamond bridge in Gwinnett County.
Set to break ground in late 2015, it’s expected to be completed in 2017, which is the same year the new Atlanta Braves stadium is scheduled to open nearby.
The interchange would switch lanes to opposite sides of the road without stopping, alleviating the need for a left-turn signal for motorists entering the interstate. After the interchange, lanes return to their original sides of the road.
“The groundbreaking for that project will be a significant project,” said Tad Leithead, chairman of the Cumberland CID.
Overall, it’s expected to cost about $19 million. The CID hopes to fund it with $5 million combined with $7.5 million from the county’s transportation department, and $12.5 million from state and other sources.
The congested interchange has been in line for a revamp for 25 years. More than $3 million has been spent by the CID on studies and concepts.
Two of Cobb’s intersections with the highest accident rates are included in the Windy Hill project. The rate is also 13 times higher than the state’s accident rate, and it’seight times higher than Georgia’s injury rate, said Jim Wilgus, deputy director of the Cobb Department of Transportation.
“A lot of it is going to greatly improve efficiency, but it’s also going to be a heck of a lot safer,” Wilgus said.
In 2011, 43,600 vehicles traveled on Windy Hill Road at I-75. That number is expected to be 51,310 by 2037.
The $19 million interchange design will be done in conjunction with a separate road project widening Windy Hill Road between Cobb Parkway and Powers Ferry Road, using $25 million in special purpose local option sales tax. It also coincides with Gov. Nathan Deal’s optional toll lanes along Interstates 75 and 575 through Cobb and Cherokee. counties.