When PPL Park was being built, Philadelphia Union fans imagined what it could become: a grand soccer locus that routinely hosted large crowds.

That came to be.

Now fans may need to envision the year-old stadium in a new way: bigger.

Union officials are developing long-term plans to expand the arena, contemplating a three-phase process, the first to increase seating from 18,500 to 20,000.

If all goes well, that construction could start in 2014, according to team chief executive officer Nick Sakiewicz.

The second phase, dependent on numerous factors, including the economy, would bring seating to 27,000, and the third to about 30,000.

That would represent an overall 62 percent increase in capacity. New decks would rise over the sideline stands and above the east sections collectively known as the River End.

In its second Major League Soccer season, the Union are drawing sellout or near-sellout crowds to the Chester City waterfront, where PPL Park stands just south of the Commodore Barry Bridge. Last week, the team sold the remainder of the 13,000 season tickets allocated for this season and started a waiting list.

That list, and the deposits noted on it, would be part of a package of financial information the team would present to lenders to finance construction of a bigger stadium. The first phase would be built during the next three to five years, the future phases added according to demand.

"We are being strategic and trying to be smart about how and when to expand the building," Sakiewicz said.

Overall, expanded seating would make the stadium more closely resemble the rectangular designs of many European arenas. It also would block fans' gorgeous views of the Delaware River, where ships cruise past during games.

The team estimates the total cost of expansion, in today's dollars, at $25 million.

Jeff L'Hote, who runs LFC International, a world soccer consultancy in New York, said finance and growth trends make it wise for the Union to think now about future stadium expansion.

"If the Union in their second season [are] at 90 percent-plus capacity," he said, "what happens when they bring in their Beckham equivalent? . . . All the signs for the sport in general, and MLS in particular, are continuing growth."

For pro soccer teams here and around the world, L'Hote said, game-day income from ticket sales, parking, and concessions constitutes major revenue. Smart business models focus on increasing that match-day money, which means getting more people to the games. That, in turn, helps drive TV viewership and sponsorships.

"If I'm the Union," he said, "I don't want to be backpedaling five years from now: 'Why didn't I start this process of expansion three years ago?' "

The team plays 17 regular-season home games, and estimates the average per-game cost for a family of four at $217, including tickets, parking, concessions, and merchandise.

Last season, the then-first-year Union ranked fourth in league attendance, averaging 19,254 fans - the first two games having been played at much larger Lincoln Financial Field. This year, through May 25, the Union ranked sixth in an expanded 18-team league, drawing an average of 18,101.

The Union rank third in attendance as a percentage of capacity, selling 97.8 percent of their seats. The league average is 75.4 percent.

Attendance has been driven by a base of devoted fans, led by the Sons of Ben Supporters club - and by a team marketing effort aimed at people who love soccer.

This year, fans at the games say, it seems more hard-core supporters are persuading less-zealous friends to check out the game-day energy at PPL Park.

"They walk away saying, 'Wow, what an experience.' That's been huge for us," said Cara Joftis, Union vice president of marketing.

Big international exhibition games also create interest. A Union alliance with the Eagles brought Manchester United here last year and will deliver Real Madrid to Lincoln Financial Field on July 23.

Last year, the Union also played exhibitions against Celtic FC from Scotland and Chivas de Guadalajara from Mexico. The team takes on English Premier League club Everton FC at PPL Park three days before playing Real Madrid.

TV ratings for Union games have doubled, to about 60,000 viewers per match, in the first year of a three-year growth plan. The four-year, roughly $12 million sponsorship deal with Bimbo Bakeries USA made big news because it stamped the company name on the team jersey, but smaller agreements have helped, too.

The number of sponsors has grown from 20 to about 35, and sponsorship revenue has doubled to about $7 million, according to the Union.

In March, the team added Comcast SportsNet and the Comcast Network as broadcast partners, which put more games on TV along with a weekly show about the team, State of the Union.

Early on, team research found that 1.5 million people in the region identified themselves as avid soccer fans. That's whom the Union has gone after, forgoing ads on traditional sports programs such as Monday Night Football, and booking space on The Daily Show With Jon Stewart and on Discovery Channel programs like Deadliest Catch.

"The Union and PPL Park have been a resounding success. Having said that, we never rest on our laurels," Sakiewicz said. "I'm not naive to think it's all cherry pie now. There are challenges ahead of us."

The big one has been there from the start: The Philadelphia sports market is dominated by the Eagles, Phillies, Flyers, and 76ers. Union TV ratings, while up, are a fraction of those drawn by NFL teams like the Eagles.

Another is the economy. Will it ever recover?

A third can be reduced to two words: Euro snobs. Some fans believe the quality of MLS play is second-rate, and would rather watch English or Italian leagues on TV. It's uncertain how many soccer fans avoid MLS, but plainly, 1.5 million avid fans aren't buying Union tickets.

Still, the Union fan base has been growing. Last year, the team offered 12,000 season tickets - and sold them all. This year, it offered and sold 13,000. That helps explain the thinking behind an expanded stadium.

Along with those 13,000 season tickets, 2,500 seats go to group sales, 1,500 to corporate sponsors, and 500 to league sponsors each game.

That's 17,500 seats, meaning only about 1,000 a game are available for walk-up sales and for sales to fans who may want to see several, but not all, of the games. The Union want to create room particularly for young people - the season-ticket holders of tomorrow.

"We need to have the kids in the building," Sakiewicz said. "A 15-year-old today, in 10 years he's a season-ticket holder. But he's only a season-ticket holder if he gets into the games today."

Contact staff writer Jeff Gammage at 215-854-2415 or jgammage@phillynews.com.