The 2009 Post Yule Pyre. Photo: Flickr user Orin Zebest.

As far as annual events go, it’s one of the hottest on Ocean Beach: The Post Yule Pyre brings people from all over San Francisco and other parts of the Bay Area to throw old Christmas trees onto massive impromptu beach bonfires.

Participants in this year’s Pyre plan on meeting at the old Doggie Diner head at Sloat Boulevard and 45th Avenue at 7:30 p.m. Sunday. From there they will head down to Ocean Beach to start their fires.

Last year’s event was a festive affair, with a feel not unlike a school field trip to an exciting destination — though with the grown-up addition of flasks passed around out of sight of the police cars and park rangers that shadowed the group.

But in spite of the fun atmosphere and the cheerful flames, the Christmas-tree fires could be straining the compromise under which federal parks officials have officially sanctioned bonfires in fire pits on the north end of Ocean Beach.

Golden Gate National Recreation Area spokesman George Durgerian said that fires burning green wood send smoke and fumes into the residential areas east of the Great Highway, particularly in the Parkside and Sunset districts where many homes are close to the beach.

“We’ve asked people as of 2009 to stop burning Christmas trees bceause they’re just so dirty,” Durgerian said. “We’re trying to minimize the disturbance to the neighborhoods and the environment.”

While he wouldn’t say that anyone burning a tree on the beach would be cited or arrested, Durgerian said U.S. Park Police and National Park Service rangers would be on hand Sunday night.

Durgerian acknowledged that some Post Yule Pyre participants may clean up the debris and ashes from the burn. But he said that many others simply leave behind nails, plastic, ashes and charred trees.

The fire pits where fires are permitted in the Kelly’s Cove area of Ocean Beach are the result of negotiations between the GGNRA, which sought to eliminate bonfires altogether about a decade ago, and groups such as Burners Without Borders, which wanted to preserve the bonfire tradition. Burners, a group consisting largely of longtime Burning Man participants, built several of the fire pits now in place.

“Burners Without Borders has been extraodinarily generous,” Durgerian said.

But he noted that not everyone is happy that the fires continue.

“There are ongoing discussions within the park regarding the future of fires on the beach.”