Steve Mattson, director of operations for Oak View Group, said Monday that the goal remains to have approval to take control of the arena at Seattle Center by late fall and begin the construction process before the end of 2018.

"Every day we move them along a little bit and we feel really good about where we're at right now," Mattson said.

Oak View Group released new renderings of the remodeled arena on Monday, beginning a busy week for the group that is looking to bring the NHL to Seattle for the 2020 season. The group has formally filed for an expansion franchise with the NHL and is kicking off its season-ticket campaign on Thursday.

The new renderings focus largely on the south side of the current building where a new glass-enclosed atrium will serve as the main entrance for the building. The new atrium will be the biggest addition to the arena, but the facility will be gutted and rebuilt seemingly from the top down. It's all part of a $660 million project that if completed will finally solve Seattle's longtime arena problem.

Redeveloping the building isn't easy because of the historical landmark status of the arena's roofline. That limited what Oak View and architectural design firm Populous could do in creating a big enough footprint for a modern facility without being able to expand outward on three of the four sides of the building.

That's why the atrium addition is so important to the design. It will be the primary entrance for the building and bring spectators in at the top of the arena. The arena will feature four levels and Populous associate principle Geoff Cheong said the design attempts to embrace the history of the building.

"We've talked about the arena maintaining its cherished, humble character within the neighborhood, within Seattle Center ... but this is a remarkable, new identity, this south atrium. Its contemporary nature is very transparent and very inviting and a great first impression for residents and visitors to Seattle Center to embrace."