SAN DIEGO (CBS 8) -  From cars to garbage, you name it and it flowed down the San Diego River during the floods in December. But it's not what the river took with it that concerns one San Diego Metropolitan Transit System rider, it's what the river left behind.

"It's not that it's a catastrophe waiting to happen, it needs to be checked out," says Jon Dubard.

Jon is an avid trolley rider and captured some of the worst floodwaters on video as they rushed through the Fashion Valley Mall parking lot and right under the very trolley he was riding.  Once waters receded he captured more video; this time of the sinkholes left behind.

"You have sinkholes right near three supports," he points out.

The sinkholes are significantly large spanning the entire distance between three different concrete columns that support the Fashion Valley Transit Station.  The sinkholes range in depth, appearing to be several feet deep in some spots.

"It's not a problem where it needs to be checked out, like ok this needs to be filled in," Dubard explains. "It needs to be checked out by engineers.

News 8 contacted MTS, who sent a representative out to take a look, but it wasn't deemed something they needed to deal with after hours.

According to the Porter Concrete Association many of the columns here along the North side of the San Diego River are more than 100 feet below ground.

But it's what's taking place below ground that has Jon Dubard worried.

"You have sinkholes around those columns, but you don't have sinkholes around the other areas which also flooded," he told News 8.  His concerns over the sinkholes prompted an email, he says, to MTS CEO Paul Jablonski, who according to Dubard didn't respond to him at the time of this story. 

The MTS representative we spoke to said they believe it to be superficial surface settling and that those who ride the trolley should feel safe in doing so.  She also said that MTS engineers would come out and assess the situation on Friday.

News 8 plans on being out with the engineers and will bring you the latest on the situation on News 8 at 5 and 6:30.