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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

New Park Brings a Spirit of Play to Chicago’s Lakefront

By T.R. Witcher

Ice skating loop and climbing wall in Maggie Daley Park provide active counterpart to Millennium Park.

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A large, 3.5-acre swath of Maggie Daley Park is given over to a series of playground environments for children. Michael Van Valkenburgh Associates, Inc.

March 3, 2015—Since opening in 2004, Chicago's Millennium Park, built atop a parking garage and active commuter rail lines, has transformed the image of the city. Wildly popular with tourists and locals alike, the park has burnished Chicago's credentials as an international destination, helped spur residential development nearby, and triggered other innovative park projects in the city. (Read " Chicago Turns Elevated Rail Line to Trail and Park" and " City Plans Walkway Along Chicago River" on Civil Engineering online.) Now, the city has opened a sequel of sorts—a new park immediately to the east, which is joined to Millennium Park by Frank Gehry's snakelike BP Bridge (read "Serpentine Span" in the February 2006 issue of Civil Engineering, pages 48-53 and 83).

The new park, Maggie Daley Park, includes the site of a former park space called Daley Bicentennial Plaza. The impetus for the $60-million project was the need to improve waterproofing of a garage beneath the greenspace. That gave the city the opportunity to radically rethink the staid park into something more adventurous.

"One of the biggest things we found at the beginning of the project was that Chicago was looking to make a place that would complement Millennium Park," says Matthew Bird, a senior associate with Michael Van Valkenburgh Associates, Inc., (MVVA), the landscape architecture firm based in Brooklyn, New York, and Cambridge, Massachusetts, that was hired to design the project.

If Millennium Park reads as an urbane showcase of cool outdoor art, sculpture, and performance spaces, Maggie Daley Park is its more activity-focused counterpart. Two of the standout features of the 26-acre park are a long ice skating loop referred to as a ribbon and a massive climbing wall system. Both are "very unlike anything that's been seen in Chicago or, on this scale, in the country," says Bird. And both are examples of the unique programming that the community wanted to see.

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A centerpiece of the new Maggie Daley Park is a quarter mile-long skating ribbon. Scott Shigley

The ice ribbon snakes through the heart of the park. It is generally about 20 ft wide, though it widens to nearly 40 ft at three critical access locations for skaters and equipment. For comparison, while an NHL rink covers about 17,000 sq ft, the ice ribbon comprises nearly 27,000 sq ft. And while the perimeter of a pro hockey rink is about 600 ft, the ribbon snakes through the park for nearly a quarter of a mile. The ribbon can accommodate roughly 700 skaters.

The quarter-mile of ice was broken into 11 zones of refrigerated slab. The zones are connected with large expansion joints specifically designed to transfer the cooling yet accommodate the large, seasonal, thermal movements of the long and narrow slabs. 

Jim Maland, the head of the recreational facilities group in Stantec's Saint Paul, Minnesota, office, explains that because the slabs undergo constant movement throughout the summer and winter seasons, making sure there was good refrigeration transfer across the joints while accommodating the nearly 1 in. of movement in a way that didn't unduly stress the reinforced-concrete slabs was a challenge. Stantec served as the "ice consultant" for the project.

Maland explained that numerous refrigeration supply and return mains had to be extended through geofoam and sections of fill that were located beneath the surface structures, but above the existing parking deck. The key was to align and construct the mains so that they would not interfere with other underground utilities and structures. The project required detailed coordination for the design and installation of footings, foundations, water and wastewater systems, and underground and surface drainage systems, as well as a "pretty significant" structural deck designed to support the refrigeration plant and climbing walls above. "It was a nightmare working through that," Maland says.

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A greensward dubbed the lawn valley slices diagonally through the site; soil placement and geofoam help create a dynamic sense of topography. Michael Van Valkenburgh Associates, Inc.

The geofoam beneath the soils and structures—71,000 cu yd of it supplied by Insulfoam's Mead, Nebraska plant—represents the largest installation of this polystyrene-based material ever used in a construction project, to the best knowledge of the engineering firm that designed and installed it, Tabitha Ventures, Inc., of Peoria, Illinois. Edward Taiwo, a project manager for Tabitha, explained in written responses to questions posed by Civil Engineering online that because the project was being constructed on top of a parking garage, weight was of primary importance. "Geofoam weighs in at an astonishing 1-2 lb/cu ft," Taiwo said. "That makes it 100 times lighter than soil and 29-30 times lighter than any other lightweight construction material you can imagine." If soil had been used for this purpose, he said, "The weight of the soil would have been enough to collapse the structural decking."

The need for contours to create the rising and falling slopes of the park also made geofoam a good choice. Although it can be installed in sections as large as 4 by 8 ft and as deep as 40 in., its depth can be shaved in multiples of 2 in. to create nearly any shape. "That met the needs of the site," Taiwo said. The site was leveled with a 4-in. layer of drainage material, and then the geofoam was assembled in layers, a 2 in. gap between them facilitating drainage from the surface. Gripper plates attached the layers while supporting the gaps. A layer of filter fabric was placed on top of the geofoam to enable water from the soil above it to flow into the gaps and through to the bottom drainage layer. "The gaps were an integral part of the design, the blockage of which might prevent drainage," Taiwo said. "This would imperil the serviceability of the whole structure."

Once the geofoam and soil were placed, soils of different types and depths—as well as the walkways, play equipment, and skating ribbon—were constructed. The skating ribbon includes 1 in. diameter tubing spaced every 3 in. apart on center. "It looks like a ribbon of pipe, so dense you hardly have space for concrete aggregate to pass through," Maland adds.

To form the ribbon, the concrete is chilled down to 10-12 °  F, and then water is sprayed on top of it to form thin ice laminates, between 1/16 and 1/18 in. at a time. Collectively the ice will be about 2 in. thick—dense enough and hard enough to show no oxygen bubbles, which restrict heat transfer and create soft ice, which can easily be abused by skates. The ice is painted white after the first quarter inch of ice is built to provide a highly reflective surface. This not only helps moderate radiant heat gain—by reflecting heat that might otherwise be absorbed by a darker surface—it also just looks good, especially at night when lights are shining on it and it casts a brilliant white glow.

The ribbon also has gentle hill grades of between 1.0 and 2.5 percent. In the summer, the ribbon will be a place for in-line skating, scootering, or just taking a stroll. It can also be used for small public events.

Stantec engineers wanted to put the ribbon's refrigeration plant in the middle of the ribbon loop to economize on transmission main lengths and simplify routing. Placing the plant in the middle of the ribbon required that a structural deck be built and supported by the existing parking-garage columns below. These would provide the necessary capacity to accommodate the heavy loads of the refrigeration equipment building and the new climbing structures that were also to be located in the middle of the ribbon. "The climbing walls were designed to completely enclose the refrigeration building where it could be neither seen nor heard," says Maland.

But the climbing walls encroached upon sight lines from the north end of the site across to Buckingham Fountain, the majestic centerpiece of Grant Park. This, Maland says, forced a critical redesign to compress the building to fit within minimum vertical clearances. Equipment sizes for the complex internal mechanical, electrical, and refrigeration systems had to be reconsidered to lower the building's roofline and give the climbing wall enough height to accommodate a good view. 

Ultimately the designers and engineers repositioned the plant a little to the west, then reshaped the climbing walls to preserve the views. The climbing walls peak at 40 ft and offer a variety of climbing opportunities for both beginners and experts. The wall system, one of the largest in the country, can easily accommodate between 70 and 80 climbers at a time. 

As designers began to assess the site, soliciting input from the community, they came to one key element they felt was missing from the surrounding parks: a place for children.

"There was not really a big play space in Grant Park until this came about," Bird says. Several years ago, the field house at the northern edge of Daley Bicentennial Park was proposed as a location for the city's children's museum, which was mulling over decamping from cramped digs at nearby Navy Pier. Even though plans for the largely underground museum were scrapped, the idea of the site as a kid-friendly space informed the programing. 

The southeast corner of the site features a 3.5-acre children's play area. "The park district had some great ideas for what they wanted to see," says Bird. "Something new, something they don't have anywhere else in the city. We've worked with a lot of different playground experts. We're able to come up with some really exciting features that aren't found in Chicago or a lot of places. They gave us a lot of latitude in how we could develop this area." 

The playground features four areas. The first is a natural "enchanted forest" without play equipment, where kids can walk around and find natural wood features, both plants growing now and trees reused from the old site to form sculptural features.

The second area, dubbed the sea, includes wavy topography that kids can run and up down on, a fisherman's-style ship, and a lighthouse for kids to climb. The third is a wavy lawn with steep slopes. 

The largest area is called the slide crater. It features a large tower bridge, a play pyramid, and a lot of slides that descend into a sunken zone in the playground. Kids can climb up 30 ft in the towers—one of the highest points in the project—to look out over the lake and city and then slide down into the crater. 

Martin Roura, ASLA, a senior associate of MVVA, says creating a sense of discovery was key. "That is something we really wanted to bring into this. We've all been kids. It's always great to keep discovering things, not knowing what's going to be around the corner."

The playground, ice ribbon, and climbing wall form a diagonal "active" axis line through the site; a more passive axis crosses from the other diagonal. This consists of a lawn valley and picnic grove. The entire site drops around 30 ft from north to south, and the design shapes the topography with a combination of soil and geofoam, in part to blunt some of the noise from Lake Shore Drive immediately to the east. The shaping also "allows us to create more closed spaces," Bird says, "and create some microclimates within the site that would be more enjoyable to visitors."

A hanging light catenary system creates consistent lighting along the length of the ribbon. Throughout the park, pedestrian-level light poles have all been reused from the original park. For the lawn valley, designers wanted to create "a place where people could be out at night but not feel under the glow of a parking lot," says Bird, yet also a place where there were no dark spots in the middle of the lawn, where pedestrians would not feel safe. The solution: a series of 13 50 ft tall light masts, which not only add sculptural punch to the park but also create a moonlight effect. Visitors can enjoy a nice ambient light across the entire lawn without feeling like they're under a spotlight.

The ice ribbon has already opened, and the few pieces still being wrapped up—portions of the playground as well as the climbing wall—should be open by spring. 

Before Maggie Daley Park, visitors used to come across the Gehry bridge from Millennium Park and turn back around. Now, says Roura, "It's not a place to visit and turn around. It's a place to enjoy, to be in."

 

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