Northern Virginia Sterling II Data Center
Lead Design Firm: Corgan Associates
General Contractor: HITT Contracting Inc.
Civil Engineer: Bowman Consulting Group Ltd.
Structural Engineer: Cardno Limited
MEP Engineer: kW Mission Critical Engineering
Subcontractors: The Shockey Precast Group; Rosendin Electric Inc.
The project team was able to deliver in just 180 days this two-story, 22.5-MW, 225,000-sq-ft greenfield data center, including the fit-out and commissioning of 160,000 sq ft of data hall space and MEP galleries.
Design and construction occurred concurrently, requiring extensive coordination and communication among team members. The aggressive schedule was fast-tracked using double shifts for the shell construction. To accomplish the fit-out schedule, crews worked 24 hours a day, seven days a week.
The building features a precast structural concrete exterior atop concrete foundations, with a slab-on-grade first floor and a second floor consisting of a topping slab above precast double tees.
The team excavated and hauled away 35,000 cu yd of extra fill dirt in the first days on the job. To stay on schedule, trucks operated 16 hours each day. A January 2016 snowstorm dropped about 3 ft of snow on the jobsite. While some of HITT’s other sites were closed for five days following the storm, the data center team had crews back on site in 48 hours.
During building-pad preparation, the project team uncovered extensive unsuitable soils. The team worked with the designers to make a last-minute change from caissons and spread footings to adding more than 300 geopiles to the foundation design. The slab-on-grade design was modified to a thickened structural slab-on-grade instead of traditional ground-bearing slab-on-grade.
After building erection was complete, the upstairs data halls were built-out before the downstairs halls due to weather and unsuitable soils. Team members installed more than 200 pieces of equipment, including modular power and cooling units built off site simultaneously during project construction.
A prefabricated electrical distribution container arrived unannounced, 10 days past its original scheduled delivery. The team remobilized a 550-ton crawler crane and had the container rigged, set and terminated within five days to maintain the original start-up schedule.
Commissioning was expedited using temporary power before receiving permitted power from the electric utility. Another challenge arose when a failed electrical switchboard was discovered during commissioning. Along with the electrician and equipment vendor, team members worked together to correct the issue. Working 72 hours, they had a new board delivered from Dallas, installed and ready to resume testing without affecting to the commissioning timeline.
Site restrictions limited staging space on site because of the existing operational data center on the campus. An apartment complex and business parks surrounding the campus forced the project team to use offsite drop lots for materials and equipment.
After winter snowstorms, the team also had to contend with more than 23 days of rain in May. The project team overcame the project’s numerous obstacles to deliver it on schedule and within budget.
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