Swinerton broke ground on the project in June 2016. It was designed by Open Stuido Architecture. Unico Properties is the owner and co-developer while Confluent Development serves as the development partner, managing the project’s entitlement and construction management.
Located at 1615 Platte St., the infill development includes 80,000 sf of office space on the top three levels, 10,000 sf of Class A retail and restaurant space on the ground level, and three levels of underground parking. Online accounting software provider Xero will lease 30,000 sf and occupy the entire top level of the building.
With several thousand pedestrians and bicyclists passing the site each day, the re-emerging Platte Street area is a tough job site to negotiate.
“The zero-lot-line site is likely one of the most challenging locations in Denver’s Central Platte Valley,” said Adam Lulay, Swinerton senior project manager. The 29,000-sf site is adjacent to northbound Interstate 25 and fronts Platte Street. It is also bound to the south by the heavily used 16th Street Highland Pedestrian Bridge and the pedestrian plaza.
The Circa Building marks Confluent Development’s second project on Platte Street, following its award-winning office development, the Lab.
“The Circa Building is the product of expertise and collaboration from great industry leaders,” said Marshall Burton, president and CEO at Confluent Development.
“Our firm is invested in the success of the re-emerging Platte Street neighborhood and thrilled to once again be contributing to its thriving revitalization.”
The project includes flexible, 30,000-sf floor plates for office tenants, 191 stalls of underground parking (six of which are equipped with charging stations) and 16 heated bicycle stations. Additional project features include an auditorium with a 50-occupant capacity, solar capabilities, a community conference room, an outdoor gathering area, collaboration space, a workout studio and locker rooms. The project has achieved LEED Platinum certification. Some 20,000 sf of solar array tops the building, according to Lulay.
As for construction challenges, the team was prepared.
Early in preconstruction, the team determined that the original drilled pier foundation system was too costly, given the site’s geotechnical conditions.
“Instead of drilling caissons through hard bedrock, combined with the likelihood of encountering water due to the river’s proximity, we proposed a ring beam foundation not typically used in Denver,” Lulay said. “The ring beam foundation system is effective in areas where hard rock and shallow water tables coexist. This solution minimized the amount of equipment hauled in and out of the 35-foot-deep excavation, increased our schedule efficiency and created a safer working environment for our people,” he said.
“It’s always challenging, and fun, to build on a high-profile urban site,” he said. “Excavating to the bottom of the 35-foot-deep hole was a very challenging aspect as we encountered hard rock not found in many places in Denver. We surgically removed 18,000 cubic yards of hard bedrock with a 100,000-pound excavator, plus another 10,000 cubic yards of dirt, ash and rubble. It was an arduous task that drove the schedule for on-time completion.”
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