The group, called Seaholm Power Development, wants to restore the 1950s art deco facility and turn it into a mixed-use property. The developer agreed to make five percent of the units affordable housing for 40 years, which is 15 years longer than originally agreed.

"The fact that he would just step forward and increase the term of affordability significantly is really a terrific thing on their part,” Council Member Laura Morrison said.

Seaholm Power Plant shut down in the 1980s after about 35 years of use. Since then, it's been used for concerts and special events, but otherwise sat vacant. The city's worked with a developer for the last eight years to restore the plant.

Seaholm Power Development also agreed to keep the main floor of the original building open to the public. It will include a restaurant, an area to promote sustainable design and a permanent public art display.

"You have to figure out how you work the mechanics of making sure the public can come in, but making sure the business has security and the ability to carry on their business uninterrupted," developer John Rosato said.

Rosato says the main tenant of the power plant has not been finalized. The City Council will have priority for that space at the end of the tenant's lease.

Trader Joe's grocery will move into a new section of Seaholm by January 2014.