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J.T. Magen resolves CoreSite’s new-build Chicago data center challenges

It took J.T. Magen two months of digging with massive drill bits to install the 219 caissons to support CoreSite Realty Corporation’s purpose-built Chicago data center. This was just the start of the construction hurdles to overcome on this complicated project. But with nationwide mission critical expertise, the J.T. Magen team was undaunted in taking on the challenges of the first-ever ground-up data center built in the city.

CoreSite CH2 is a four-story, 196,000 sq. ft. colocation facility specifically designed for the structural weight-bearing needs of large power, cooling, data and redundant systems. It’s located in Chicago’s South Loop business district on a brownfield site and was custom-designed by Corgan.

“All new buildings downtown need extensive deep foundations due to soft earth,” says Geoff Arend, J.T. Magen project executive. “Structural supports in some cases go all the way down to bedrock, depending on soil conditions and the building’s performance requirements.”

Photos: © J.T. Magan

Topping off is celebrated with a traditional evergreen tree afixed to the last steel beam installed atop the structure.

Deep foundation work

At the CH2 construction site, the 219 holes dug for the supporting top-of-rock and bell caissons averaged 55 feet deep. The painstaking process required special drill bits up to five feet in diameter biting into the dirt, coming back up to spin out the dirt, and going back down for more until the soil tests verified it was hard enough to weight bear, explains Arend.

Casings were pushed down into the drilled holes to keep them from collapsing, rebar cages were inserted and they were injected with concrete to establish the building footings. A total of 1,300 tons of rebar and 12,800 tons of concrete were used for the caissons and foundations.

The project then went vertical with grade beams and the steel structure, requiring more than 1,950 tons of structural steel. Two-thirds of the property footprint covering 1.54 acres is a metal structure; the buildout’s last third is concrete podium.

Site restrictions complicate logistics

Since this was tight lot-line-to-lot-line construction, there was no room for staging, laydown or storage of materials, Arend explains. This required an innovative strategy for equipment delivery – long-lead items were ordered early (even in bid phase), with constant vendor communication to keep sequencing on track.

Large equipment was fabricated and partially assembled off site, and then mounted on skids before coming to the jobsite for quick installation. Some construction materials were picked by a crane directly from the truck; others were staged on top of the pedestrian canopy.

Location impacts phasing

The site is in a congested urban area and there is a 24-hour UPS distribution facility across the street, so the project had to minimize impact on traffic and adjacent businesses, says Arend. This made phasing and deliveries a challenge – J.T. Magen had to close roads for the crane lifts, get permits and do work by night as a result. The project required close coordination with CDOT and other building department agencies.

To minimize street closures, J.T. Magen sequenced the building process so the crane could sit in the middle of the lot and build clockwise. With the middle section remaining to fill in, the crane eased out with the buildout, and was only on the street for a short period. “It was a unique approach,” says Arend.

Utility/equipment requirements

The challenge of getting the massive amount of power and other utilities needed for the data center required engineering, specification and logistical work with Commonwealth Edison Company, as well as other utilities providers, according to Wael Skaik, J.T. Magen MEPS project manager. To accommodate the increased power needs, J.T. Magen built a dedicated onsite vault for ComEd utilities to their specifications.

Once the structure was completed, J.T. Magen installed more than 1.4 million lbs. of equipment, including generators, chillers, enclosures, cooling towers, electrical switch gear, UPS systems, and redundant power and cooling systems, Skaik says. Some equipment was lifted to the roof, and others to specific floors. The generators were installed through an opening in the wall, put on rollers and pushed into place to be anchored.

Considering the complex logistical, foundation and MEPS requirements for CoreSite CH2, the completion schedule was aggressive, says Skaik. “I love how complicated this project was – all the challenges made it interesting.”

Photo: © McShane Fleming Studios