The Seattle City Council on Monday voted to approve a memorandum of understanding with the Los Angeles-based firm Oak View Group to redevelop Key Arena, the most significant step yet toward implementing a $660 million project that officials hope will attract NBA and NHL teams to the city.

Seattle's former male pro hoops team, the Sonics, left for Oklahoma City after Starbucks CEO Howard Schultz sold the team a decade ago.

Council members voted 7-to-1 in favor of the memorandum of understanding to renovate the Lower Queen Anne arena, which is owned by the city. Council member Lorena González was absent.

"I think it’s one of the strongest arena agreements in the country," said City Council president Bruce Harrell before the vote.

Council member Mike O' Brien, the no vote, said he would have abstained if council rules allowed him. He cited a lack of specificity in the agreement.

Today’s vote is bad news for supporters of a separate proposal to construct a sports and entertainment venue in SoDo, which is lead by investor Chris Hansen. Before the vote, council members rejected an amendment 6-to-2 from Mike O'Brien that would have struck an exclusivity clause in the agreement preventing the city from making similar deals with other developers to construct arenas with more than 15,000 seats, such as the SoDo project.

"What concerns me more is the reality we’re facing with this agreement is a potential monopoly of large venues by LiveNation," O'Brien said, referring to the live music company that partners with Oak View Group.

The deal between the city and Oak View Group calls for the firm to begin work on the project next year. It also sets a target completion date of September 2020, just weeks before the first puck drop of that year’s professional hockey season.

The plan, which is privately-funded, includes a provision allowing the city to keep its current level of revenue from the arena. For ten years, KeyArena would take 75 percent of any revenue on top of that. After ten years, the additional revenue would be split 50-50. In other words, the agreement ostensibly makes good on a goal for the city not to "go backwards" financially.

Under the agreement, Oak View Group will lease the arena from the city for 39 years. The firm will become eligible for an eight-year lease extension if it draws and maintains either a NHL or NBA team and contributes an additional $50 million in renovations. Oak View Group could get another eight-year extension after that period if the group fulfills those same terms again. Alternatively, the plan also allows Oak View Group to obtain both extensions at once if to brings on a team while putting $250 million toward capital improvements.

Neither a NHL nor NBA team is guaranteed under the plan, but reports suggest Seattle is one of the leading choices for a pro hockey expansion. Oak View Group CEO Tim Leiweke has been vocal about his aggressive push to land a NHL team, alongside partners David Bonderman, the investor and minority owner of the Boston Celtics, and Hollywood producer Jerry Bruckheimer. Bringing a pro basketball team back to Seattle would be a longer-term aspiration, as the NBA does not have any immediate plans to expand.

Even if no new pro sports team comes to Seattle, the arena could function as an entertainment venue, though projected revenue from such a situation is much smaller.

Oak View Group also agreed to contribute $40 million over its 39-year lease to a transportation fund to mitigate traffic impacts in surrounding neighborhoods, including Lower Queen Anne, downtown and South Lake Union.

Additional impacts of such a huge construction project are myriad. Hundreds of intermittent employees (ushers, sound technicians and the like) will see a source of income disappear. Tenants including Seattle Storm, Seattle University and Pottery Northwest will need a new home. Even skaters who frequent the skatepark at Seattle Center will need to find a new place to practice tricks until the city. The plan includes provisions to lessen the blow on all those impacts, asking Oak View Group to hire current employees, help relocate tenants and put money in for a new skatepark.

Approval of the memorandum of understanding does not mean Oak View Group will get a permit to begin building immediately. The council must still approve transaction documents, including votes on development and lease agreement. Oak View Group's proposal must also complete an environmental impact statement, community benefits agreement, and an agreement to integrate with other organizations housed at Seattle Center.