SEATTLE -- Christopher Hansen is making a $290 million proposal to his hometown that could be the impetus for a new sports arena that could bring the NBA and NHL to Seattle.

All he needs to make it a reality is city and county approval equaling $200 million and the two franchises.

Hansen, a hedge-fund manager based in San Francisco and a Seattle native, submitted a proposal to the city Thursday that calls for $290 million in private investment toward the construction of a new arena that would cost between $450 million and $500 million.

Hansen and his investment group also would be responsible for the purchase of an NBA franchise and finding a partner interested in bringing an NHL franchise to Seattle as well.

The proposal represents the first significant step toward solving the arena problem that was at the root of the SuperSonics' move from Seattle to Oklahoma City following the 2007-08 NBA season, leaving behind 41 years of history.

The proposal will now go before a review board -- a group of community leaders that includes one-time SuperSonics player and coach Lenny Wilkens -- with King County executive Dow Constantine hoping the review can be completed within a month.

According to a letter submitted by the Hansen, the remaining construction and development costs would be financed by the city and King County using taxes and revenues generated by the new facility and rent charged to the teams playing in the arena -- money that will not exist if the arena isn't built.

City officials are adamant there will be no new public taxes needed for the building and the city's portion of the investment will be capped at $200 million with any additional cost overruns paid by the private investors.

From there, Hansen's proposal would need city and county approval. City Councilman Tim Burgess believes the council could complete its arena review as early as June. But even with ultimate approval, no shovels will be going into the land just south of Safeco Field until an anchor tenant is in hand with a 30-year lease agreement that includes a no-relocation clause.

City officials say their projections for how the financing plan would work are based off having both an NHL and NBA team.