Authorities are investigating to find out how raw sewage wound up being dumped into Storm Lake. Barb Lynch of the Iowa Department of Natural Resources says the sewage came from a storm sewer, and was discovered Saturday.Lynch says a man was walking his dog and noticed the sewage. She says the community’s done a lot to encourage folks to report such incidents. Lynch says every storm drain has a sign with a phone number which asks residents to call local law enforcement if something bad is coming out.Lynch says they haven’t determined where the sewage came from yet. A video scope has been put down the storm drain to try to identify the problem. She says the incident is definitely not normal. She says it should just be groundwater and run-off from the streets going through the storm sewers. She says the presence of sewage seemed to stop Saturday night, but it’s still be checked. Lynch believes just a small amount of sewage made it into Storm Lake, and it should have a “minimal” impact on the lake.