They came. They smoked. They left more than 11 tons of trash.

After more than 8,000 people flocked Golden Gate Park on Wednesday, or 4/20, as the San Francisco’s marijuana-loving community call it, countless bottles of Shasta soda, beer cans, Fruit Loops boxes and butts were left scattered across the grassy, green lawn.

"We think we will end up with over 15,000 pounds of trash," San Francisco Recreation and Park General Manager Phil Ginsburg said Thursday morning. "Yes, it's impactful to our park." But when all was said and done, the total garbage tally? 22,000 pounds - 5,000 more than last year's 17,000, park officials noted.

The overall cost to taxpayers totaled about $50,000. Officials said total clean up effort cost $25,000 and likely another $25,000 will be needed in staff and city services for Wednesday and Thursday.

Images of the Annual 4/20 Smokeout in San Francisco

Police said the event was mostly peaceful. Police arrested eight of the 8,000 guests, including a robbery by a 19-year-old who threatened two 15-year-old boys with brass knuckles. Three other people were arrested for outstanding warrants, one was arrested for being drunk in public, one was arrested for assault and two were arrested for resisting arrest, police said.

Officers also removed four parents who brought small children to the smoky party, San Francisco police said.

The unsanctioned event has no permit and no event organizer, but even so, the city sends park crews out to clean up the mess at the taxpayer's expense.

"I really don't like it," said a 4/20 attendee named "Kourtney," who didn't look like he was cleaning up much trash himself.

Ginsburg said his employees would probably rather doing something else on a Thursday morning. But he noted it was Earth Day and that his crews were doing important work. The cleanup began at 6 a.m., he said, and would likely take a few hours.

More than 15,000 lbs of trash and cost of $50,000 for #420 cleanup at #GoldenGatePark per #SF Rec+Park GM. pic.twitter.com/PacGQqPdOA — Stephanie Chuang (@StephChuang) April 21, 2016

NBC Bay Area’s Terry McSweeney and Bay City News contributed to this report.