2019 CSO Notification Report

Preventing sewage from backing up into your basement is our highest priority when too much rain gets into the sanitary sewer system. Unfortunately, our only weapon in that battle is a relief valve that sends excess water to the nearest river or lake, an overflow pipe. As a region, we've invested more than $4 billion to reduce sewer overflows, a massive effort that is paying off. Our current financial forecast through 2025 calls for investing $1.5 billion in clean water infrastructure, flood management, and debt financing to help protect public health and Lake Michigan.

Prior to the Deep Tunnel, this region used to pollute Lake Michigan with an average of 8 billion to 9 billion gallons of sewage every year. Here's the record since 1994, the first full year of operation for the Deep Tunnel system:

mmsd sewer overflow graphic