SEATTLE (AP) -- The hopes of bringing the NBA back to Seattle and adding an NHL team passed a significant milestone Thursday when a final environmental impact statement found no major issues to block a projected new multipurpose arena in Seattle's stadium district. But the toughest challenge might still be ahead for arena investor Chris Hansen and his partners: Rewriting the original language on the arena proposal for hockey to become the first tenant of a new building. ''I believe based on the conversations I've had with the NBA that without hockey first we're probably not going to get to an arena in Seattle,'' Seattle Mayor Ed Murray said. ''I've encouraged the investors interested in a hockey team in Seattle and those interested in a basketball team in Seattle to see if they can negotiate a better arrangement and come to the city with it and I would take it to council. What the details of those look like, I'm not going to start dictating those.'' The FEIS on the proposed arena near Safeco Field and CenturyLink Field was released by the city after nearly two years of work and comes with a competing suburban arena proposal gaining momentum after becoming public recently. It could become a race of arena proposals with the ultimate goal of getting both NBA and NHL franchises to call Seattle home in the near future. The original language under the memorandum of understanding among Hansen, the city of Seattle and King County was based around the acquisition of a basketball franchise first before arena construction could begin. The NBA has said it does not see expansion in the future, while the NHL has shown plenty of interest in Seattle as an expansion market with the lack of a suitable facility being the roadblock in moving forward. Hansen's group issued a statement after the FEIS was released Thursday saying he remains open to the idea of an NHL franchise being the first franchise to arrive. ''In light of recent speculation, we would just like to clarify that we have sought to be as accommodating as possible in our negotiations with potential NHL partners, with our only major requirements being that such a deal does not jeopardize the process or put the city, county, taxpayers or us in a worse financial position,'' Hansen's investor group wrote in a statement on its website. Seattle was close to landing a basketball franchise when Hansen's group attempted to purchase the Sacramento Kings in 2013 and move them north. The Kings ultimately remained in Sacramento and one of Hansen's biggest investors - Steve Ballmer - left the group to purchase the Los Angeles Clippers. While the NBA chatter has quieted, the talk of the NHL calling Seattle home has increased dramatically. Murray said he spoke with NHL Commissioner Gary Bettman Thursday morning and said the league would work with Seattle if investors come forward. But a hockey-first scenario would require the MOU to be rewritten and approved by city and county councils. Murray indicated there would need to be significant changes before he would support a revised proposal. ''If they want to open up the current MOU, which I think they need to do if we want to get an arena because basketball is a longer term proposition, then I think that they have to come up with a different financial arrangement,'' Murray said. ''I'm not going to dictate what that financial arrangement is.'' The project still needs approval of a street being vacated - likely to be reviewed later this year - and has faced opposition from the Port of Seattle and the Mariners regarding the location. A final master permit for the project could be issued in early 2016 with a target completion date of 2018, around the time many transit projects in the Seattle area are slated to be ready. The FEIS also said the arena would be an economic generator with an estimated positive economic benefit to King County of $230-$286 million each year. The release of the FEIS comes as Seattle faces mounting pressure from the suburb of Tukwila on a potential privately funded arena about 12 miles south of downtown. RLB Holdings Sports and Entertainment LLC filed an environmental application with Tukwila late last week for the ''Northwest Arena.'' The proposal calls for the arena and parking structure to be used for about 230 events each year. The arena would have capacity for 19,500 depending on the event and would have a capacity of 17,500 and 18,500 for NBA and NHL games.