"It's crazy! Gross!" said Kim Avalos, who frequents the trail. "What is that?!"
The San Francisco Bay Trail in South San Francisco curves around the mouth of the Colma Creek marsh. It's a popular walking and running trail, but local residents are starting to notice something in the water.
"Now that I'm looking at... wow...there's actually so many shopping carts out here," said Avalos. "There's an extreme amount."
Avalos works for a nearby garbage company. She says she walks the trail every day but has never seen anything like this.
"It's actually kind of insane to think about how they even got there," Avalos said.
It's the same story for others who frequent the trail. At first glance, mistaking the debris for rocks until they actually stare at it.
"It kind of blends in," said Hondres when we approached him on the trail. "I've never seen grocery carts out in the Bay like this... I don't know, it's kind of weird."
"Have you noticed it before?" 7 On Your Side's Stephanie Sierra asked another passer-by.
"Uh... no. This is kind of new," he said. "Someone is being very stupid... I've seen them over the years. I don't remember there being this many. There's quite a few."
Many people who frequent the trail said when it's high tide it's hard to notice anything.
"It does look like shopping carts, do you know if that's what it is?"
It's hard to say for sure. But at low tide, it certainly looks that way.
"It does look like shopping carts, amongst other things," Save the Bay representative Josh Quigley said.
And there's not just one or two, but there's what appears to be dozens of them spanning the Colma Creek marsh adjacent to the bay.
"Have you ever seen this many shopping carts along the bay?" Stephanie Sierra asked.
"I have not, no," Quigley said. "This is certainly the greater concentration that I've ever seen in one place."
Quigley is the Senior Policy Manager for Save the Bay, an environmental nonprofit founded in 1961 to stop excessive filling of the San Francisco Bay.
"I think it's really unfortunate... the bay is treated not as the jewel and resource that it should be, but as a dumping ground," Quigley said.
So, where is it all coming from? That seems to be up for debate.
"It could be a big prank, if anything, but at this rate I have no idea," said Alvin Lau, who visits the trail regularly.
"There's often homeless people in the mobile RV vehicles," said another. "There's always a lot of trash here, not going to lie."
"I don't know, maybe Costco. They are our neighbors," Kim Avalos said. "Could be because they do look bigger."
A Costco Business Center is about a mile from Colma Marsh. 7 On Your Side reached out to Costco's corporate office, and the South San Francisco Costco General Manager said: "We walk and clean the trail multiple times a week, in addition to checking for any carts that might end up in the bay."
The goal now is to clean it out -- and ensure it stays that way.
"Stop being dumb. There's only one planet we got, so take care of it," said Lau.
"It hurts me as an animal lover to see all these shopping carts in their place of habitat," Avalos said.
"Save the Bay" says overall pollution is decreasing across the bay shoreline, but there are instances--like this one--where smaller pockets need to be addressed.
Locally, there are regulations in place to prevent this type of pollution.
7 On Your Side contacted the San Francisco Bay Regional Water Quality Control Board to further investigate and clean up the area.
Take a look at more stories and videos by 7 On Your Side.
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