OAKLAND -- The A's announced Thursday they will remove the tarps from the west side of third deck of O.co Coliseum if the team advances to the American League Championship Series.

Based on increasing ticket sales and projections for the ALCS, the A's will open up 11,698 new seats for sale, priced at $55 each and the tickets went on sale at 3 p.m. Thursday. Total capacity for the ALCS and World Series will now be 47,505.

"This has been a sensational year for the Athletics and for our fans," said Lew Wolff, owner and managing partner of the team. "We are thrilled with the tremendous outpouring of fan support."

A's president Mike Crowley said it was an easy call, based on the staggering demand for tickets in recent days. The club sold out the remaining 4,000 tickets for Thursday's Game 5 of the AL Division Series on Wednesday morning, and tickets for untarped sections have been moving swiftly.

As of Tuesday, there were about 38,000 seats available for the untarped sections, but Crowley said that total has been reduced to 15,000.

"And a vast majority of those tickets would be for a Game 7 here," Crowley said. "That only gets played here if we play the (Baltimore) Orioles."

The A's resisted calls and an online petition with more than 10,000 email signees to take down the tarps for the ALDS, citing inadequate advance ticket sales to warrant the cumbersome process to remove them.

"We had always taken the position that if we got to the ALCS and there was demand and excitement, we would remove them," Crowley said. "The crowds have been great. And all 37,000 of them have been A's fans. That was one of our concerns opening up the third deck, where the crowds can be more 50-50 between our fans and other teams' fans."

"It's gonna be louder," manager Bob Melvin said. "We certainly need to get there first. But boy, it's loud to begin with. I was having a hard time communicating with my coaches last night in the ninth inning it was so loud. You put another 12,000 people, it'll be deafening."