The Portland Timbers will begin construction on Providence Park this fall following the conclusion of their 2017 MLS season and plan to complete their more than $50 million stadium expansion project by April 2019.

The club was originally unsure whether their proposal would be finalized in time to start construction in 2017, but were able to start targeting this offseason as their start date after gaining approval for the project from both the City of Portland's Design Commission and the Portland City Council.

"We are absolutely starting in the offseason," Timbers President of Business Mike Golub said. "The project is progressing really well. Everything has gone really smoothly."

The stadium expansion project, which is expected to add 4,000 new seats to Providence Park, will include the construction of three new levels and a larger roof on the east side of the stadium, as well as the widening of the sidewalk and the addition of a covered arcade on SW 18th Ave.

The City Council took an important step last week when they unanimously voted to support the major encroachment on SW 18th Ave necessary for the project.

"The City gets a lot of credit," Golub said. "They've been great partners throughout this process."

Due to the construction schedule, the Timbers are expecting to play their first five to six games on the road in both 2018 and 2019. The construction will not impact the number of home games that the Timbers play at Providence Park in either season. Instead, the club's home games will simply be back-loaded on the schedule in both years.

The Timbers will also not be hosting their annual preseason tournament during construction.

The first phase of construction this fall will focus primarily on foundational and utility work.

The Timbers will continue construction during the 2018 season as they build the first of three new levels on the east side of Providence Park. Golub said the club is working to mitigate the impact of the in-season construction on fans. While no current seats or sight lines will be impacted by the ongoing construction, certain walkways may be closed during the season. The Timbers also plan to temporarily close the existing team store and build a new team store in the SW 20th Ave plaza.

"We're going to hopefully mitigate the disruption," Golub said. "The stadium is going to be open, but people in some sections are going to have to navigate some of the work that's ongoing. We want to make it as fan friendly as possible."

After the conclusion of the 2018 season, the Timbers will remove the current roof on the east side of the stadium, finish building the three new levels and install a new roof, along with finishing other key aspects of the project. The club plans to install new turf on the field at Providence Park before both the 2018 and 2019 seasons as well.

While the Timbers have gained the majority of major approvals needed to move forward with the proposal, they still have a few steps left before the project is finalized.

The club has agreed to terms with the City, but the City Council has yet to approve an amended operating agreement. That final approval is not expected to happen until October or November, but Golub said that the club is approaching the City about finalizing aspects of the term sheet earlier so that the club can begin construction on schedule.

The Timbers also need to gain final approval of an updated good neighbor agreement and complete a certified traffic mitigation plan.

But despite the final hurdles, Golub said that everything has gone smoothly in the process so far and he is excited about the current timeline for the project.

"A year ago, we didn't think it was possible to start this project in 2017 and be done by 2019," Golub said. "Things came together remarkably well and are continuing to move forward remarkably well."

-- Jamie Goldberg | jgoldberg@oregonian.com

503-853-3761 | @jamiebgoldberg