DOWNTOWN — As Chicago gets its first taste of spring weather, Maggie Daley Park looks like it's covered in snow.
But that white stuff blanketing the northeast corner of Grant Park isn't precipitation — it's geofoam, and the fact that the eco-friendly filler already is being installed suggests the new park's development is right on track.
"The new park will feature a topographically varied landscape ... [that] creates opportunities for improved views to the lake and back to the city," said Nichole Sheehan, project manager for the Maggie Daley Park development. "To achieve this, large blocks of geofoam are being used to build the new undulating landforms that shape the future park."
Geofoam weighs less than 1 percent the weight of soil, Sheehan said. It's used to offset the weight of park features like large trees, a climbing wall and a skating ribbon piled on top of the underground parking structure.
It's being installed now, along with stormwater drainage pipes, electrical conduit and duct bank installation, Sheehan said.
When fully saturated, soil weighs 126 pounds per cubic foot, whereas geofoam will weigh less than 1¼ pounds per cubic foot after a heavy rainfall, Sheehan said.
Some geofoam was salvaged from the area before Maggie Daley Park construction began, but lots more has been bought to complete the park — about 75,000 cubic yards of the lightweight material in total, Grant Park Conservancy President Bob O'Neill said.
Also salvaged from the original site was 82,000 cubic yards of fill, or bulk soil, and 22,500 cubic yards of topsoil, O'Neill said. For two years, the soil has been stored in a massive mound at Peanut Park, a sunken, vaguely peanut-shaped area that will be absorbed by Maggie Daley Park.
This week, crews will start augmenting that soil, "mixing it with different types of natural, organic soils like peat moss and sand and all kinds of different things you add to soil to make it better, or change the acidity," O'Neill said.
Chemically altering the composition of the soil will let the park function "like one huge flower pot, and you get to decide what goes in it — a 28-acre planter," O'Neill said. "That will allow for a lot of different, nonindigenous plants, so we can plant trees and plants we never would have been able to support before."
More than 1,000 trees will be planted in Maggie Daley Park, including quaking aspens, shagbark hickory, Himalayan pine, blue Japanese white pine, witch hazel and bamboo, none of which would grow in Chicago's natural conditions. The park's sophisticated irrigation system, combined with custom soil additives, will help support these species through Midwestern climates.
O'Neill said that in addition to getting new varieties of trees, the park will get 40 percent more of them than the area had before its transformation into Maggie Daley Park.
"We're going from a few species to an incredible diversity," O'Neil said. "It's going to be like no other park in Chicago. It will become a real destination and an attraction with nature in mind. ... It'll be like going on vacation — such a respite from the hustle and bustle of everything in the city."
Mild weather could allow for planting to start as early as this fall, as crews work to assemble the park piecemeal, moving from north to south, O'Neill said.
The official plan calls for restoration and landscaping at the park's northeast end to be completed by spring 2015, and Sheehan said "despite challenging winter conditions this year, work is on track."
This week, demolition also started on the interior of the future Maggie Daley Park field house, which is being completely overhauled into a sleeker, eco-friendly design while retaining the basic structural components of the previous Richard J. Daley Bicentennial Plaza field house.
Looking forward, "water-piping work is slated to begin on site, and concrete formwork for the new park features will begin soon," Sheehan said.