The Seattle Department of Construction and Inspections has published the final environmental impact statement for the $700 million KeyArena renovation project that could start construction this fall.

The major renovation would meet NBA and NHL standards to possibly bring professional men’s basketball and hockey teams, while remaining home to the WNBA’s Seattle Storm.

KeyArena, formerly the Seattle Center Coliseum, was the longtime home of the Sonics and several minor-league hockey franchises (most recently the WHL’s Thunderbirds, now in their own facility in Kent). The Sonics used the venue from 1967 until the team moved to Oklahoma City ahead of the 2008-2009 season, citing a lack of public funding to renovate the Key or construct a new arena to meet NBA standards.

The Seattle City Council commissioned a study of the KeyArena in 2015, finding it in good condition, but too small and lacking in modern standards to accommodate either an NHL or NBA team. The study also concluded that the potential revenue from other entertainment was “largely offset by the additional costs of basic operations and maintenance of the KeyArena facility.”

Oak View Group was tapped to be the private developer leading the $700 million renovation project in June 2017, and a joint venture of Skanska and AECOM Hunt was named as the general contractor in late July 2018.

Seating capacity would increase from 10,442 unobstructed for hockey to 17,300 and 18,600 for basketball, up from 17,072. Concert seating would increase from 17,459 to 18,800, according to the FEIS.

The city council is expected to sign off on a number of actions for the renovation, including constructing a vehicular tunnel beneath Thomas Street, allowing for nighttime construction and amending Seattle’s sign code for more and brighter signage.

There would also need to be approved lease, development and Seattle Center Integration agreements, and the council could hold a public meeting on these actions this month, according to the FEIS. Oak View Group would need to provide a number of community benefits in the project and following construction, according to a memorandum of understanding.

Any appeals of the FEIS to the Seattle Hearing Examiner are due by Thursday, Sept. 13. If one is filed, construction — which is expected to take two years and begin in October — could be delayed by several months, and impact the timeline to bring an NHL franchise to town.

The plans also require approvals by the Seattle Landmarks Preservation Board, which landmarked the KeyArena and Bressi Garage in August 2017.

Meanwhile, the Storm have already announced Alaska Airlines Arena on the University of Washington campus as their “primary venue” in 2019. The Seattle University’s men’s basketball team will use their on-campus Connolly Center, and the annual Pac-12 Women’s Basketball Tournament will relocate to Las Vegas during construction.

Both the Oak View Group’s proposal and an alternative proposal would result in significant impacts to the KeyArena, Bressi Garage and the Northwest Rooms, including the International Fountain Pavilion and International Plaza, which would require building stabilization, dust and exhaust mitigation, restoring the garage exterior as needed and improving the HVAC system for MoPOP, among other measures during construction, according to the FEIS.

The project would require demolishing some existing structures and surface parking, and relocating the skatepark under the Oak View Group proposal — there is still no site selected for that — while the other alternative is fairly similar in terms of land use impacts but would not include nighttime construction or allowing video display signs facing First Avenue North. As with any major construction project, there would also be traffic impacts that include street closures, the loss of bicycle facilities, sidewalk access and bus stops. Alternative 2 would extend construction impacts by at least six months, according to the FEIS.

There would likely be short-term disruptions to all utilities during construction, as well as an increase in the rodent population, particularly during construction, which would also require mediation.

Up to 13 exceptional, legacy and street trees could be lost under Oak View’s proposal, while the modified proposal would cut that loss to up to 10. The FEIS states an executive order would require replacing trees by at least a 2:1 ratio.

Once the KeyArena renovation project is completed, the number of days when there are highly attended events could more than double, according to the FEIS, which “may be a quality of life consideration for some residents,” including increased congestion in an already congested part of the city.

Mitigating those impacts include more traffic control officers, improved traffic signal timing, increasing bus, light rail and monorail service, making bus stop improvements, adding more bicycle parking and a plan for ride-hailing pick-ups and drop-offs.

Greenhouse gas emissions would exceed 28,000 metric tons per pe year in the renovated KeyArena’s first year of operation (fall 2020/2021) if NBA and NHL events were held there, according to the FEIS, with 95 percent of those emissions coming from vehicles. The FEIS assumes state clean air requirements for motor vehicles will reduce emissions 16 percent by 2035.

A modernized KeyArena would provide an increased environmental performance under the city’s Leadership in Energy and Environmental Design (LEED) incentive program. Any new city construction or major renovation would need to be at least LEED Gold.

The FEIS incorporates input provided during a 45-day public comment period that followed the release of a draft environmental impact statement on April 23. There were more than 440 comments provided by 80 individuals, organizations and agencies.

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