Chicago has at least 10 billion-dollar-plus towers either under construction or at the planning stage. That's great news for Keller company Case Foundation, which recently delivered another very successful project - this time for a 60-storey tower being developed by America's most famous family.
Wolf Point is a historically important part of Chicago. Situated at a fork in the Chicago River, it was here that the city’s first church, hotel, taverns and bridges were built. Today, the north side of Wolf Point, which juts into the river, is owned by the Kennedy family, who are developing three luxury residential towers here: Wolf Point East, West and South.
Having successfully completed foundation works on the 48-storey West tower in March 2014, Case was chosen by general contractor Walsh to prepare the foundations for the East tower, scheduled for occupancy in 2019.
An aggressive schedule
Starting on site in early July, Case was contracted to construct 50 belled caissons with shafts ranging from 30 inches to 8ft in diameter and bells up to 16ft in diameter, drilled to a depth of 75ft. The work also included 14 rock caissons to support the tower itself, ranging from 8-10ft and drilled to a depth of 116ft.
“It was a pretty aggressive schedule and we could only work between 8am and 8pm due to local ordinance, but we guaranteed 25 days and we were right on target,” says the project’s Chief Estimator Bill Lederer. “Constructing such big piles so accurately through a range of conditions, in such a tight timeframe, was very challenging. The project required excellent planning, large-scale equipment and some very highly skilled operators.
“We also had to coordinate a lot of activity on what was a small site footprint of 32,000ft2, with only one way in and out.
“There are only a few local competitors that can do the size of shafts designed for this project – in fact I would say we probably have done a majority of the deep foundations when it comes to towers over 40 stories.”
Tunnel vision
Adding to the complexity was an abandoned underground freight tunnel running right through the site. Built at the turn of the last century, the tunnel is part of a network under the city that brought coal to buildings until the late 1950s. In 1992, Hayward Baker carried out a grouting programme to stabilise one of the tunnels pierced by a pile during construction work on the Kinzie Street Bridge. The incident caused widespread flooding in the basements of buildings in the downtown area, with damage estimated at more than $2 billion.
Since then, the city has mandated that any tunnels beneath developments must be secured by infilling. For Wolf Point East, this involved the Case team drilling through the top of the tunnel to enter and seal it at either end with concrete bulkheads, then grouting the whole space solid. This allowed the crew to drill large diameter holes through the solid tunnel and beneath to the design bottom elevation.
Top of the list
“This was a very successful project for us and for a client who we’ve developed a good relationship with. They were very happy,” adds Bill. “High-rise projects are very challenging and developers can’t afford for delays or things to go wrong. We’ve shown again that we can be trusted to deliver on time and in a safe manner. I’d say we’re right at the top of the list of people in Chicago who can do this type of work.”
With the third, even taller Wolf Point South tower in the pipeline, Case hopes to bring its expertise to that and many more of the ambitious high-rise projects transforming Chicago’s incredible skyline.