Some big changes are coming to the plaza at 200 Mill, home of the former City Hall building.

The city council on Nov. 21 selected Winson Investment of Bellevue to negotiate the possible re-development of the 3.79-acre site located along the Cedar River near the library.

Winson was one of two proposals that were submitted as part of a request for proposal process aimed at taking the building off of the city books, as well as re-developing a property the city sees as under-utilized.

“The former city hall sits right in the middle of several recognizable Renton landmarks,” Mayor Denis Law said in a press release. “It’s a valuable property with enormous potential and we want it to become a destination that enhances the city.”

Under Winson’s proposal, the new, completed site would contain an international school, senior housing, outdoor civic plaza, and a riverfront public park with an amphitheater in three new buildings.

Earlier this year, the city issued a request for proposals to solicit development options for the site after determining the former city hall building would require significant maintenance and structural upgrades. Studies have estimated these costs at more than $10 million, in addition to the costs of on-going annual building operations. The city has already made $1.8 million in improvements over the past four years.

“Given the high costs of upgrading the building and ongoing maintenance, it was important to eliminate the operating losses and find a better use for the site that would also include public benefits,” Law said. “This proposal does that and allows us to create better public access to the river.”

According to a presentation given during the Nov. 21 Committee of the Whole meeting by Community Development Project Manager John Collum, Winson proposes to tear down the current building, built in 1969, and construct three new buildings, including the school and an 11-story dormitory, as well as a 10-story senior housing facility.

Also included in the plans are a public meeting space, a gymnasium/theater, retail shops, a parking garage and a restaurant with river views.

The school would initially house up to 500 students in grades 6-12.

In return for the property, Winson would pay the city approximately $7 million, slightly more than the projected value. The total includes $4 million cash, plus the value of public improvements at cost, estimated at approximately $3 million.

Its development timeline for a three-phase project includes two alternative schedules over the next 4-5 years, dependent upon the status of existing tenant leases.

The Winson project was recommended by the city after it received the higher score according to a rubric used to judge the two proposals. The other proposal the city looked at came from Cosmos Development and was a smaller, mostly residential plan that required a public/private partnership in which the city would retain ownership of the current building, but agree to make improvements to both the interior and exterior.

In all, the Winson proposal scored higher in five of the seven review categories, including “proposed development concept,” which was worth the most points.

“Winson provided us with a very strong proposal and scored strongly in all of the selection criteria,” said City Council President Randy Corman, who served on the review committee. “We are excited to continue our negotiations with them.”

According to Collum, the current building is 75 percent occupied with leases extending through 2022. There are currently six tenants in the building, including the city attorney’s office. There are also two telecommunications tower leases for equipment on the building’s roof.

Collum said the developers were required to review the leases and that Winson will uphold all current obligations or work to re-negotiate the terms of the leases. However, demolition of the current building is slated for Phase 3 of the project, which should allow the current leases to run their course.

Despite its recommendation, the city does have some concerns about the Winson proposal, including the financial feasibility of the international school at the heart of the project and a need for a better understanding of the market for senior independent living in the city.

City officials also expressed concern that the public amenities portion of the proposal is significant and may require financial assurance of completion.

The city hopes to have a signed negotiating agreement with Winson Investment by the end of the year.