Fixing the problem isn't cheap, as other cities throughout the region have found.
Grand Rapids, 150 miles west of Detroit, spent two decades and roughly $240 million separating and upgrading its sewage and stormwater drains. The city relied on combined sewers built in the 1800s, until they started separating them in the 1990s.
The city's sewer system, which serves 272,000 people, is almost entirely separated now, said Mike Lunn, the manager of Grand Rapids' Environmental Services Department. The city used state loans and taxpayer money to pay for the projects.
"You have to dig up the street. You have to go right through people's neighborhoods," Lunn said. It's a daunting task.
But it's paid off: the city used to discharge anywhere from 6 billion to 12 billion gallons into the Grand River before the upgrades. That number decreased to 49 million gallons in 2011.
On the western shore of Lake Michigan, Milwaukee has a combined sewer system and has historically had overflow problems similar to Detroit. Since the mid-90s, however, discharges into Lake Michigan have dropped by 80 percent – largely due to a 405 million gallon underground tunnel to capture overflow, according to the Milwaukee Metropolitan Sewerage District.
The city added another 100 million gallons of underground storage capacity with two tunnels completed in 2006 and 2010, respectively. The price tag over two decades? $4 billion.
Heavy storms still tax Milwaukee's combined system – the city sent 2.8 billion gallons of untreated sewage and stormwater into Lake Michigan in 2010. Milwaukee has set a goal to completely eliminate discharges by 2035 and is turning to green projects – such as trees, rain barrels, porous pavement, planted rooftops – to bolster the recent tunnel additions.
Atlanta also spent $4 billion over the past decade separating its sewer and stormwater systems, improvements forced on the city by the federal government. "We had to inspect every linear foot of our system – 1,600 miles," said Jo Ann Macrina, commissioner of DeKalb County's Department of Watershed Management.
More immediate concerns
But Detroit has set aside only $57 million for system improvements this year. And the department is not looking at climate change projections as it plans upgrades, Schechter said.
"Population, population density, and economic growth/contraction are a more immediate concern," he said in an email.
Ken Kunkel, a National Oceanic and Atmospheric Administration scientist and North Carolina State University professor thinks that's a mistake – one not unique to Detroit. Few U.S. water and sewer utilities have reached out to NOAA about using climate data in planning sewer upgrades. Most rely on historic data.
"All models point to bigger storm events in the Midwest," Kunkel said. Utilities, he added, "should worry about it and be planning for it."
And some have. The Water Utility Climate Alliance formed in 2007 as a way for water and sewage service providers to incorporate climate data into future infrastructure plans. There are 10 utility members now. None are from the Midwest.
However, Milwaukee's recent long-term sewage district plan – aimed to completely eliminate discharges by 2035 – incorporated climate modeling, which prompted the heavy investment in porous concrete, as well as ponds, lakes and more natural areas instead of tunnels and more basins.
"Climate change has had an effect on recent precipitation patterns, and precipitation has a direct effect on the region's sewer systems," the city concluded in a recent report. "Green infrastructure is a safe 'no regrets" strategy."