PORTLAND, Ore. (AP) — The Portland Timbers have unveiled plans for a privately funded addition to Providence Park that would add 4,000 seats.

The estimated cost of the expansion project is $50 million, paid for by the Timbers and National Women's Soccer League's Portland Thorns. It would add four levels to the east side of Providence Park.

The Timbers are popular in Portland with 112 straight sellouts of their downtown stadium that seats 21,144. There are some 13,000 fans on the waiting list for season tickets.

The MLS club will have its first meeting with the city's Design Commission on May 11. The commission must approve the plan before it can move forward.

The team's operating agreement will also have to be amended to reflect the expansion, which must be approved by the City Council.