Monitoring Bacteria in Stormwater
In Milwaukee, like many cities around the country, centuries-old sewer infrastructure is failing and leaking, and sewage is entering the waterways through broken pipes, cross connections with the stormwater system, and other routes. To better understand the flow of bacteria from stormwater systems to local rivers, Milwaukee Riverkeeper and other partners have monitored bacteria levels entering rivers from the storm sewer system for several decades. Bacteria, along with associated viruses and pathogens, are threatening public health and keeping local waterways from meeting the “swimmable, fishable” goals of the Clean Water Act.
Data shows that bacteria loads in local streams greatly exceed expected amounts from stormwater runoff alone, and these loads have increased over the past two decades. This signifies that a lot of bacteria is entering rivers through failing sanitary sewage infrastructure, either directly or via the storm sewer system. As part of a monitoring study with Dr. Sandra McLellan at UWM-School of Freshwater Sciences from 2008 to 2016, we found that well over 50% of stormwater outfalls in the lower Menomonee and Kinnickinnic Rivers was contaminated by human bacteria. Almost every portion of the Menomonee and Kinnickinnic River within the Milwaukee Estuary is listed as impaired or proposed to be listed for bacteria in recent Impaired Waters lists approved by US EPA. In recent years, Milwaukee Riverkeeper has helped Wauwatosa and Milwaukee test for bacteria in the storm sewer system, as part of their work to meet state stormwater regulations.
Our volunteers also monitor surface water for bacteria in areas outside of Milwaukee Metropolitan Sewerage District’s service area.
Let’s Dive in a Little Deeper
Why Do We Monitor Stormwater?
By studying bacteria levels, Milwaukee Riverkeeper and partners help map sources of bacteria contamination for municipalities. This helps to prioritize addressing the source of pollution (i.e. repairing leaky infrastructure, illicit connections, etc.), and also helps protect public health. Bacteria is used as a surrogate for viruses and pathogens that can make people sick. Where bacteria levels are high, there can be potential threats to human health.
What is a TMDL?
A TMDL (Total Maximum Daily Load) is a pollutant reduction plan that is required in the U.S. under the Clean Water Act for every impaired water body. The TMDL refers to the maximum amount of a pollutant or “load” that a water body can receive while still meeting water quality standards. It serves as a “pollution budget” designed to ensure that impaired water bodies (those not meeting quality standards) are restored to health by ratcheting down pollution in a similar way that financial budgeting involves reducing spending and making smarter decisions!
