How it's drawn — and how it gets built.

Onni 606 is designed by IBI Group, the Toronto-based architecture and engineering firm. Midway through the project's permitting, IBI changed hands: the Dutch firm Arcadis agreed to acquire it in July 2022 and completed the deal on September 27, 2022.

Post-acquisition, IBI's buildings and placemaking teams were folded together with CallisonRTKL to form Arcadis' Architecture & Urbanism practice — so the firm credited on the drawings is now branded Arcadis IBI Group.

The development is registered with the U.S. Green Building Council and is targeting a LEED Gold rating, split across two rating systems for its different uses — the office component under LEED v4 BD+C: Core & Shell and the residential portion under LEED for Homes (Multifamily).

Per the project's environmental file, all building systems are to meet the current Bellevue Energy Code, with electricity and natural gas as the primary energy sources for heating, cooling, hot water, cooking and lighting.

The Vancouver landscape architect LOCI designed roughly 48,000 square feet of outdoor plazas across several levels, anchored by a public plaza of about 17,000 square feet at the southwest corner featuring a splash park and public art. LOCI describes the open space as “destined to become the City's social heart.”

Restaurants, a juice bar, bars, the childcare center, the two pools and a dog-walking area face the plaza network. LOCI coordinated its work with Balmori Associates, the lead designer of Bellevue's citywide Grand Connection greenway, so the master plan's design intent carries down to the block.

The approved design also keeps a piece of the block's heritage: the existing “Bell Gate” public-art piece is to be relocated to the north, and an on-site red oak is retained.

Design-review-era documentation itemized the commercial space as roughly 34,000 square feet of retail, a 22,000-square-foot food court and a 7,500-square-foot restaurant. The office-tower food court is intended to serve the general public via a new east–west midblock pedestrian connector along the north edge of the site. Later reporting cites about 38,000 square feet of retail/commercial overall, suggesting the program was consolidated during refinement.

The city treats Onni 606 as a single phased, three-tower project rather than discrete phases: the towers rise in an overlapping sequence off a shared podium, topping out years apart. At design-review approval the schedule had staggered tower completions of roughly October 2027, February 2029 and April 2030.

Onni builds its projects itself — through its in-house Onni Contracting arm rather than a third-party general contractor; no outside GC has been announced for 606.

The hard part is the hole. The project's environmental file puts total excavation at about 356,853 cubic yards for the below-grade garage (originally designed as six levels, later refined to five). Groundwater sits 65–87 feet below grade, and the state warned that the dig will most likely reach the regional Advance outwash aquifer — so dewatering relies on sumps and pumps, complicated by PCE-contaminated groundwater that must be managed, with vapor-intrusion mitigation built into the towers. The geotechnical work, by Geopacific (2017), found pre-glacial outwash and glacial till with low liquefaction hazard.