A park worker taped warning signs and caution tape around the sand play area of the playground. Someone drinking here late Thursday night smashed beer bottles along the retaining wall.
Park officials said the shards can't simply be sifted out, and now as many as 20 tons of sand must be replaced.
"This is just beyond the pale at this point," said San Francisco Recreation and Park Department spokeswoman Sarah Ballard. "Somebody just trashes it without regard for safety."
The cost of the vandalism is unclear, but the sandbox will be shut down for at least a week because the Recreation and Park Department needs to order a clean supply of sand.
Families wistfully steered their young children away from the sandbox Friday afternoon.
"That's sad because my daughter, this is her favorite place to play at the park," said Elizabeth Herrick. "It's sad that the city gets anything like this when it's being made so much more kid-friendly than it used to be."
It is the latest in a long list of acts of vandalism at Dolores Park. Just last week, vandals broke into and tagged a construction site, hotwired a vehicle and damaged new turf and an irrigation system. It's delayed the reopening of the park's north side by a month.
"We're going to have a coordinated response with the park rangers to see what we can do to figure out the best time to be here to try to catch people in the act," said San Francisco Police Department Capt. Dan Perea. "What makes me angry is all of these kids are here today and they're impacted by this, not the adults who did this damage."
The playground was closed early Friday afternoon as crews began shifting the sand ahead of a backhoe brought in to cart it away.
Disappointed kids watched the work. Park officials said the "anything goes" atmosphere in the park needs to come to an end.
"The truth is, if people can't do the right thing, we're going to end up with a very different feel here," said Ballard. "Much more enforcement; much more police presence."