Jutting into Lake Michigan from Chicago’s downtown waterfront, Navy Pier is Illinois’ most popular tourist destination.

Turning 100 in 2016, Navy Pier was renovated for its centennial celebrations.

Situated at the entrance to the pier, Polk Brothers Park was fitted with a brand new interactive cast stone water fountain, overlooked by a serpentine cast stone bench.

Polk Brothers Park would be the first major project I oversaw as the director of the CAD/CAM division at ACS.

The fountain was designed by James Corner Field Operations landscape architects, in conjunction with Fluidity Design Consultants. As is often the case in architectural projects, ACS received a partially-resolved Rhino CAD file as the starting point for our work.

After cleaning up the file to resolve some geometric continuity issues, I proceeded to section the model into manufacturable pieces. The size of the pieces is dictated by a number of factors, including the weight of the resulting sections, which can have impacts on handling and installation, and the size of the tooling and equipment which will be used in making forms for each piece.

My computer model of the fountain was thorough enough that the general contractor adopted it as the basis not only for the cast stone parts, but the foundation beneath the cast stone, as well as the electrical and plumbing components.

LEFT: Having modeled the foundation in computer space, I was able to determine certain sections of the foundation that could potentially interfere with the plumbing to the water nozzles.

BELOW: On a site visit to inspect the poured-in-place foundation, I was impressed that the concrete crew was able to precisely block out spaces to accommodate the plumbing in those tight areas, based on my CAD model.

Once the CAD model was sectioned and approved, I began creating forms. No two parts were alike. The fountain, more than 80 feet (24m) in diameter, called for more than 600 unique cast stone parts. I had a 5-axis CNC hotwire cutter and a 3-axis CNC panel router at my disposal, and I used a number of different strategies to create concrete formwork, depending on the size and shape of the required parts.

The fountain’s most intricate parts were removable cast stone inserts that housed the water nozzles and LED lighting. Each nozzle and light needed to be mounted within the insert at a very specific angle.

We sent a number of prototypes to the general contractor, working in tandem with the fountain designers, to develop and prove the mounting strategy for the water and lighting systems.

The undulating organic geometry of the fountain required that all 147 cast stone inserts housing the water nozzles and LED lighting be slightly different from each other.

With just a 3-axis CNC panel router, I had to devise a way to mill specific undercuts. The solution involved milling blanks from a number of directions and building up the components of the forms in a well-planned order.

From 147 unique fountain insert forms, I still have a spare that I keep on a shelf beside my desk. If I’m hiring for a spatial visualization dependent position, I’ll show it to potential candidates and ask them how I made it. The thought process behind their guesses tells me a great deal about whether they’re ideally suited to the task.

The mounting hardware for the lighting and water nozzles was cast directly into each piece. Mounting bezels and adjustment mechanisms needed to be in very specific positions. We needed to devise a way to accurately secure the hardware as the cast stone was poured into the forms.

I devised reuseable jigs made from foamed PVC that were attached to the forms right before concrete was poured.

For the official Polk Brothers Park opening ceremony, I secured permission to set my camera on a tripod overnight inside the Navy Pier administrative offices, overlooking the park, for a full 24-hour timelapse.

The mayor was in attendance at the opening ceremony; the sun was not.

The fountain was just one of two cast stone centerpieces in Polk Bros Park at the entrance to Navy Pier, the other being the Wave Bench that overlooks the fountain.

ACS’ work on Polk Bros Park won three Awards for Excellence from the Architectural Precast Association in 2017, in the categories of Craftsmanship, Trim and Landscape, and Green Building.

Comments from the jury included:

• “Nicely crafted, installation is seamless and connections are minimized.”

• “Another unique and well executed application of precast in a landscape setting.”

• “The water feature areas consist of well-fitting scallop textured precast panels each with smaller removal pieces to access the water jets below. A good example of form work fit and finish.”

https://www.archprecast.org/awards/