MILWAUKEE (CBS 58) -- It's been a dry Tuesday but Monday's heavy rain led to an overflow of combined sewage into local waterways.

CBS 58 News spoke with a spokesman for the Milwaukee Metropolitan Sewerage District who wasn't sure whether that overflow had ended yet.

MMSD tries to avoid overflows but they're done to protect homes.

"Preventing basement backups is our number one priority during a storm. We want to protect property, we want to protect public health. When sewage gets into a basement, there can be issues with cleanup if not done properly. And it's a bigger health threat than the sewage and rain and storm water getting into the rivers untreated," said Bill Graffin with MMSD.

It's been a rainy year and this was the sixth overflow of 2018 for MMSD. That's all they're legally allowed without possible penalties from regulators.