On the north side of Wolf Point, which juts into the Chicago river, the Kennedy family is developing three luxury residential towers: 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.
Starting on site in early July, Case was contracted to construct 50 belled caissons with shafts ranging from 30in (762mm) to 8ft (2.4m) 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.
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 US$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.
With the third, even taller Wolf Point South tower in the pipeline, Case hopes to bring its expertise to that and many other of the ambitious high-rise projects transforming Chicago's skyline.