The Milwaukee Metropolitan Sewerage District’s campaign to end all sewer overflows into Lake Michigan by 2035 has encountered a daunting obstacle: Climate change.
Milwaukee is one of many Great Lakes cities that rely on combined sewer systems, which collect and treat stormwater and wastewater in combined pipes. Heavy rains can overwhelm those systems, causing combined sewer overflows that send untreated sewage into the Great Lakes.
Scientists have said climate change is producing more extreme weather events, including more torrential downpours in the Great Lakes region.
“Climate change affects everything we do … we’re seeing more intense storms, more regularly,” said Kevin Shafer, executive director of the Milwaukee Metropolitan Sewerage District during a speech at the Ninth Annual Great Lakes Restoration Conference in Milwaukee. “If climate change comes about the way (experts) are talking about, we will have more overflows unless we do something about it.”
Milwaukee has spent more than $4 billion over the past two decades to reduce sewer overflows, which included building a massive underground tunnel that can hold 521-million gallons of stormwater.
The MMSD is now spending another $1.3 billion on green infrastructure — wetlands, green roofs, rain gardens and rain barrels — than can handle another 740 million gallons of stormwater runoff.
Those efforts have decreased the size and frequency of Milwaukee’s sewer overflows, but the problem persists. Heavy rains in April 2013 forced Milwaukee to discharge 1.1 billion gallons of untreated sewage mixed with stormwater into Lake Michigan.
The storms caused similarly large sewer overflows in several other Great Lakes cities. Past studies have shown that Great Lakes cities discharge more than 30 billion gallons of raw and partially treated sewage into the lakes each year.
Milwaukee’s use of green infrastructure to reduce sewer overflows has made Wisconsin’s largest city a poster child for how other Great Lakes communities can adapt to climate change.
Conservation leaders at the Great Lakes Restoration Conference said government agencies, cities, farmers and urban dwellers must take up the cause of reducing stormwater runoff — one of the worst sources of pollution entering the Great Lakes and its tributaries.
Melinda Koslow, regional program manager for a National Wildlife Federation climate adaptation program called SafeGuards, said the Great Lakes Restoration Initiative could help blunt the effects of climate change in the region. The GLRI has provided $1.3 billion over the past four years to clean up toxic hot spots in the lakes, reduce polluted runoff, keep invasive species out of the lakes, and restore wetlands and wildlife habitat.
“We need restoration to help us combat climate change,” Koslow said. “Climate change adaptation and (ecological) restoration is something we can model for the rest of the world.”
The panelists said there are many ways to adapt to climate change and reduce polluted stormwater runoff: Restore wetlands and create other green spaces; conserve water; install rain gardens; use fewer lawn and agricultural chemicals; and place vegetated roofs on commercial and industrial buildings.
Al Douglas, director of Ontario’s Center for Climate Change Impacts and Adaptation Resources, said sinking Great Lakes water levels in recent years has forced climate change into the public’s consciousness.
“Talk of water levels is in the newspaper every week,” Douglas said. “People are feeling the changes and we need to respond to them.”