The Chicago Plan Commission recently voted to approve a $700 million development that's planned to include the city’s sixth-tallest building when it's completed.

Planned to replace a parking lot across from Holy Name Cathedral at the corner of State Street and Chicago Avenue, the mixed-use project from JDL Development calls for a pair of towers rising a respective 49 and 76 stories over shared podium. After some post-unveiling changes, the now-thinner, taller tower is planned to top out at 1,011 ft to become the eighth Chicago skyscraper to exceed the 984-foot “supertall” classification.

Chicago's Goettsch Partners along with Hartshorne Plunkard Architecture created the design which has changed since its debut at a public meeting in October to also include a height increase for the shorter tower and minor tweaks to the building’s podium and upper setbacks. Ron Klemencic, CEO and Chairman of structural engineer Magnusson Klemencic Associates noted that the taller tower will have two mass dampers and the whole development will utilize a secant pile shoring system in its basement to shore up a site that's near the underground Chicago Transit Authority red line subway. Klemencic said the concrete in the taller tower will likely have the highest modulus of elasticity of any Chicago tower.

"The most unusual part of that design is that we’re using very high-strength concrete," Klemencic says. "Not so much for its strength, but for its modulus of elasticity. We need the stiffness. We’re specifying what is, in my experience the highest modulus of elasticity in Chicago, it’s 7,000 KSI modulus."

Chicago-based JDL development is planning to break ground by the end of the year on what will be its biggest project in company history.

"We're happy with the approval," Jim Letchinger, president and founder of JDL, says. "There were some changes the city made to lanes on Chicago Avenue to ease traffic concerns but nothing in the actual project changed from what we brought to the planning commission."

Alderman Brian Hopkins, whose ward the One Chicago Square site is in, said the transit improvement program will eliminate some on-street parking to free-up lanes for better traffic flow and finance a long-discussed plan to widen the Chicago Avenue bridge.