The flow of wastewater spilling into a St. Petersburg creek since the weekend has been stopped.

Late Monday, Pinellas County crews installed a 20-inch valve on the sewer pipe and tied that into a temporary sewer line. By early Tuesday afternoon, a bypass was complete, stopping the spillage flow in the sewer line at 7780 62nd Avenue North.

With a second valve is in place and the flow stemmed, repairs on the broken pipe can begin, Pinellas officials said.

The line ruptured Saturday at 11:30 p.m., likely from excessive rain putting pressure on the system, according to Pinellas County officials. The roadway is partially closed.

Since late Saturday, an estimated two million gallons of raw sewage has leaked from the broken pipe. Crews have been routing the spill down a drainage ditch into Joe's Creek, out into Boca Ciega Bay and eventually out into the Gulf of Mexico.

Officials said the health risks are low but the creek waters have been tested for environmental concerns.

"When there's not a sufficient level of dissolved oxygen in water, it could kill organisms,” said Nancy Smith, a marine science professor at Eckerd College. “From microscopic organisms all the way up through the food web to large fish."

In the world of marine biology it's called "trophic cascade." In layman's terms, it's a domino effect.

Smith said all the sewage needs to do is throw off one part of the ecosystem to cause a chain reaction. And at this point, there's not much that can be done.

"Once sewage is out in the open water way, it's very difficult to clean up,” Smith said.

The best hope is for containment at the source, which is what the county achieved Tuesday afternoon by fixing the leak.