One of the biggest problems for rescue workers to get the victims in Thursday night's drowning at Falls Park is the piles and piles of foam on the water.
It's a phenomenon common to the Falls, but it's especially bad this time of year.
Mountains of foam billowing from the falls may be light weight, but it played a heavy role in the trouble rescue workers faced in trying to get divers into the water.
"In some cases the foam was so think that it was four to six feet deep, so you would lose your own people putting them into the water,” Jim Sideras of Sioux Falls Fire & Rescue said.
All that foam comes from phosphorus runoff into the river. It can occur naturally, but you see so much of it because of agricultural products and the fertilizer we use on our lawns.
"It doesn't cause a problem until it hits the falls and then the big Sioux Falls agitates the water, allow the air to be entrapped in the water and it creates the foam," City Environmental Manager Bob Kappel said.
The way the river turns doesn't help matters either.
"The nature of the falls and the way the river turns there, it kind of entraps the foam in that area; there's the issue of the falls being the agitator; there's an entrapment area that doesn't allow the foam to move out. Also this time of year which probably made it worse is there is ice on the river. There's still ice and the ice blocks that foam from naturally washing down stream," Kappel said.
Firefighters tried hosing down the foam because dumping defoaming chemicals into the river isn't allowed. It's a Falls phenomenon that goes uncontrolled.
"Unfortunately in the spring time they do become the largest washing machine in the state of SD which creates that foam," Kappel said.
There is no regulation about the amount of phosphorus discharge that can go into rivers in South Dakota.