By BO EMERSON

The Atlanta Journal-Constitution

Aliens seem to have dropped a black plastic-wrapped apartment building into the middle of Piedmont Park this week, where a 78-foot tall stage has been rising steadily since Monday in preparation for the landing of a Beatle.

Paul McCartney’s concert Saturday night, benefitting the Piedmont Park Conservancy, has turned the green space into an industrial hive of activity, though Conservancy Chief Operating Officer Chris Nelson assures that the concert will be kind to living things.

“The turf was in excellent shape to start with,” said Nelson, surveying the circus-like scene Friday, wearing wraparound shades and a safety-orange shirt. “When the event is over, we will immediately aerate the grass, we’ll water it, apply fertilizer ... our experience is that within a week or two, you’re not going to be able to tell that there was an event there.”

The care and feeding of the green stuff in preparation for this “Green Concert” does not come without great effort, however, and some frayed tempers.

“Aaaah!!” said an obviously agitated David Helberg, watching a truck pull onto the carefully groomed verdure and grabbing his radio to intervene. “Five days and 32 trucks and now somebody parks on my grass,” said the fuming Helberg, who handles operations at the site for concert promoter LiveNation.

Sheets of Rhino Mat and Dura Deck protected the turf from forklifts and cranes, as operators assembled 460,000 pounds of steel into the eight-story stage. Chain-link fences and security guards sealed off the 20-acre performance area — the Meadow can hold 50,000 but fewer are expected — from the rest of the park. On the curving roads surrounding the meadow, vendors unloaded 8-foot drifts of T-shirts and warehouse-sized stacks of cases of soft drinks and beer.

Lake Clara Meer looked clear. The dead fish killed by an algae bloom during the week were gone.

The forecast for Saturday: warm temperatures and a 10 percent chance of rain.

Watching from a nearby bench was Audrey McCombs of Arcada, Calif., who has seen McCartney on the current tour in Halifax, Canada, and at the Coachella, Calif., festival — which makes her one of the more fanatical 19-year-old followers of Sir Paul.

Other evidence of her zeal: She was pulled up on stage in Halifax, where the former Beatle autographed her arm; she promptly flew home to have the autograph turned into a tattoo. A YouTube video of McCombs getting the autograph turned her into a Web sensation.

“I went over and gave him a hug, then I sort of started to squeeze him and he said, ‘OK, OK,’ ” said the Humboldt State University student, showing off the black permanent signature on her left arm.

Her father, Mark McCombs, 48, a building contractor, stood close by and smiled at the tale.

“I’m not that into tattoos,” said the dad. “I told her, ‘OK,’ but in my heart I thought, ‘Yeah, right, like that’s going to happen.’ ” Yet, it did.

“If you see the video, you don’t have to be her dad to be heartwarmed by it. I think it’s the coolest thing ever.”

The young fan’s excitement also drew smiles from Lyn Talley, 58, and Barb Tyler, 56, friends from Cincinnati who came down for the Atlanta concert with memories of Beatlemania the first time it happened.

“We still scream,” Talley said. “We love it when we hear girls like [Audrey] who are really into the Beatles, because they keep the music alive.”

Said Tyler, “I’ve seen Paul over 50 times in concert, and I’m not done yet.”

Elsewhere in town visitors began arriving, checking into hotels and preparing for a weekend of entertainment that also includes Saturday shows by 1970s art rockers Steely Dan and 1980s pop metalists Def Leppard, a Braves-Phillies game and the Bronner Brothers hair show.

At the W Hotel in Midtown, Rhonda and Curtis Key of Lula dropped off their bags and anticipated a pleasant amble to the show at the nearby park. Curtis was eager to introduce his wife to her first McCartney performance. He saw Wings play in 1976 at The Omni and said, “It was the best show I’ve seen. Ever.”