Seattle-based Mithun peaked this year at 70 architects on its payroll. As the economy works through its down cycle, the firm may shrink slightly by not replacing those who leave until the economy perks up.

The firm flourished with the recently ended development boom and comes out of it with an increased specialty in large, urban, mixed-use commercial projects.

Its largest current project, Lincoln Square, is a $360 million colossus immediately east of Bellevue Square in downtown Bellevue.

Lincoln Square will consist of two towers above 330,000 square feet of restaurants, retail, movie screens and a health club. One tower will total 530,000 square feet of offices. The other, to become Bellevue’s tallest at 42 stories, will house a 303-room Westin Hotel and 148 luxury condominiums above the hotel. All of that will stand atop a 4.5-acre underground parking garage providing more than 2,000 spaces.

Construction of the parking garage is nearly finished and the lead developer, Lend Lease Real Estate Investments, pegs completion of the entire project for spring 2003. James K. Cheng of Vancouver, B.C., who drew the initial designs, is an architect on the project with Mithun.

Another mixed-use proposal on Mithun’s plate is the Don Milliken-Vulcan Northwest plan for offices and condos over a grocery and other retail at the Quinton Instruments site in the Denny Triangle.

Also, developer Tom Lee’s apartments-over-grocery on the Planned Parenthood site in the Central District and apartments atop offices for the Hearing, Speech and Deafness Center near the Planned Parenthood site.

The firm recently landed a large mixed-use job in Portland, said spokeswoman Kipepeo Brown.

Construction finished this year on a 25-story assisted-living facility on First Hill called The Summit, which Mithun designed. The firm is now designing another assisted-living tower blocks from The Summit, called The Perry at Cabrini.

The firm’s project list also includes designing the new Pacific Northwest Aquarium on a downtown pier, teamed with Terry Farrell Partners of London.

Mithun has also pushed into sustainable design.

The firm designed the 200-plus-acre Puget Sound Environmental Learning Center, which is under construction on Bainbridge Island. The Brainerd Foundation, set up by former software executive Paul Brainerd, funded the center, where fourth- and fifth-graders and university graduate students will study environmental education. Mithun moved its offices last year onto the renovated Pier 56 on the downtown Seattle waterfront, a space that emphasizes sustainable design.

The economic slowdown, amplified by the Sept. 11 attack on the World Trade Center, drove more architecture firms to compete for municipal projects, many of which weren’t derailed like private projects were. Brown said Mithun feels at an advantage because it was already in municipal projects.

“We’ve gone to five or six municipal projects (bidding sessions) lately and seen some 30 proposals at each,” Brown said.