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Myths and Facts About the July Flood

And what you can do to prevent more overflows

Aug. 18, 2010
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We’re still feeling the effects of the intense storm of July 22-23, when many neighborhoods and homes were flooded by up to 9 inches of rain in a very short span of time.

Since the storm, many myths have circulated about what happened, what should have happened to prevent basement backups and sewage overflow into local waterways, and what can be done in the future to prevent flooding and water damage.

Here are some of the most prominent myths—and facts—about the flood, the role of the Milwaukee Metropolitan Sewerage District (MMSD) and how local governments, businesses and individuals can improve the area’s water management.

Myth: The basement backups and sewage overflows are all MMSD’s fault.

Fact: MMSD is only one part of a carefully integrated system of public and private infrastructure. While MMSD owns 300 miles of pipes and the Deep Tunnel, the 28 municipalities in MMSD’s region own 3,000 miles of pipes, and individual property owners also own another 3,000 miles leading from their properties to the local sewer line.

Before figuring out what happened during the July storm, it’s best to look at how the system works during a regular rainfall. During an average rainstorm, water goes into a catch basin or storm drain and then flows into the municipally owned sewer system (either a storm sewer or a combined sewer containing both storm water and sanitary sewer water). If it’s in a separated sewer area, the untreated storm water goes directly into a local waterway. If it’s in a combined sewer area, it goes to the metropolitan interceptor sewer, owned by MMSD, which leads to the Jones Island or South Shore water treatment facilities, where both the storm water and sanitary sewer water are treated before being discharged. During heavier rainstorms, that water goes to the Deep Tunnel, where it’s held until it can be treated.

On the night of the big July storm, a lot of that rainwater didn’t even make it to the MMSD pipelines.

Here’s what happened during that storm: A lot of water was trying to enter the local sewer system during a short period of time—for example, through the grates in the street. But the rainfall was so intense it couldn’t filter into the sewer grates fast enough, so it seeped into people’s homes—though the window wells or through leaky or cracked walls and floors. This water then drained through the basement floor drain. When it did, it flowed to the sanitary sewer system, as if it was sewage. That storm water overloaded the sanitary sewer pipes that are owned by the individual and the local municipalities, and then backed up into basements.

“There were probably a lot of instances in the last storm where there was so much flow so fast on the local system that it never had a chance to get to our pipes because the local system couldn’t keep up and it backed up into people’s homes,” said Bill Graffin, MMSD’s public information manager.

Not only that, but an overloaded pipe in one home can start a chain reaction and flood other homes on the block.

That’s why many municipalities need to address the size and condition of their storm sewers to ensure that they can handle an intense storm. Because if heavy rainfall can get into the system in a decent amount of time, the water won’t back up into basements.

Myth: The Deep Tunnel failed on the storm of July 22-23.

Fact: The Deep Tunnel did not prevent an overflow during this very heavy rainfall, but the Deep Tunnel prevented a bad situation from becoming much worse. During the big storm, which was so exceptional that it made national and international news, an estimated 30 billion to 80 billion gallons fell on the region. MMSD can treat and store 1.1 billion gallons per day, which is more than adequate for an average heavy rainstorm.

The Deep Tunnel holds 521 million gallons of water in reserve, until it can be treated. In doing the math, the Deep Tunnel could never have held the amount of water that fell on the region in just a few hours.

So why do we need the tunnel? Because without it, that half a billion gallons of untreated water would have flowed directly into Lake Michigan or flooded basements and streets—and we would have between 50 and 60 overflows per year, as we had before the Deep Tunnel was built.

“If the Deep Tunnel had not been built, you would have had a massive overflow and the same number of—if not more—basement backups,” said MMSD Executive Director Kevin Shafer.

Myth: We could eliminate overflows if we separated the combined sewers that exist in parts of Milwaukee and Shorewood.

Fact: Unfortunately, even sewer separation would not have prevented overflows from the July storm. The mechanics of separation is complex and cannot be done on 11% of the combined sewers because they are located in Downtown Milwaukee and cannot be disturbed due to that location. Second, it would cost an exorbitant amount—about $4.5 billion to $5.8 billion—to separate the sewers and upgrade other features in the system, according to MMSD’s calculations. That estimate includes the cost to add 230 million gallons of capacity to the Deep Tunnel, add 300 million more gallons to the treatment facilities, add another 100 million gallons to tunnel pumping to relieve the tunnel, and then spend at the very least $2.7 billion to separate the sewers. That is a very conservative estimate, and even those additions may not prevent overflows and backups during intense storms. Finally, where sewers are separated, all of the storm water that contains the oil, rubber from tires and animal waste drains untreated into the waterways.

So the combination of combined sewers and the Deep Tunnel reduces pollution.

“The pollution would have been worse getting to the rivers than what we had, because we were able to capture it [in the Deep Tunnel] and treat part of that flow,” MMSD’s Shafer said.

Myth: MMSD pumped untreated sewage into Lake Michigan.

Fact: MMSD has 150 points where untreated overflows are released. Only two of those 150 points go directly into the lake. The rest of them flow into the region’s three rivers—the Milwaukee, Menomonee and Kinnickinnic rivers—which then flow into Lake Michigan. By the time it gets into the lake it’s sort of milky white, MMSD’s Graffin said, not some sort of a brown plume that looks like untreated, raw sewage. According to the state Department of Natural Resources (DNR), MMSD reported releasing 171 million gallons of untreated water from the sanitary sewer system into local waterways and 1.9 billion gallons of combined sewer overflows (a mix of storm water and sanitary sewer water, which is about 90% storm water and 10% sanitary sewer water). MMSD is allowed to have six combined sewer overflows per year and averages about 2.6 overflows annually.

But MMSD wasn’t the only entity to have overflows. According to the DNR, 12 local municipalities in MMSD’s region reported sanitary sewer overflows as a result of the July storm. Those municipalities are Milwaukee, Mequon, Brookfield, Cudahy, Wauwautosa, Muskego, Fox Point, Menomonee Falls, Shorewood, Brown Deer, Elm Grove and Whitefish Bay. South Milwaukee, which has its own treatment facility, also reported a sanitary sewer overflow.

Although the state does not allow any of these municipalities to release sanitary sewer overflows into local waterways, Jim Fratrick, a watershed specialist at the DNR, said that none of these municipalities would be punished because all are in compliance with a 2005 order to upgrade their systems. None of their actions was negligent, Fratrick said, which would be a reason for some sort of punitive DNR action.

Myth: That bad smell along the lakeshore is sewage that was released directly into the waterways.

Fact: That bad smell doesn’t seem to have anything to do with the overflows. Actually, it’s a problem with algae called cladophora, said Fratrick of the DNR, a recurring problem along the lakeshore.

Myth: Milwaukee Mayor Tom Barrett promised that he’d shake up MMSD so that there would be no overflows and he hasn’t done anything.

Fact: Barrett commissioned an independent audit, which found that MMSD’s management of the system could not be faulted for overflows that resulted from a 19-day window of heavy rain in 2004. However, that audit did turn up problems with infiltration and inflow in all of the communities in MMSD. Infiltration and inflow problems include leaky pipes, downspouts that are connected to the sewer system, foundation drains in homes, and illegally hooked-up sump pumps.

MMSD has identified weak spots in the region and has allocated $1 million to the municipalities so they can begin to repair those problems, and it is aiming to allocate $30 million over the next five years for further work.

Myth: There’s nothing I can do as a concerned citizen about protecting the region from flooding and overflows.

Fact: While these intense storms have been rare in the past, they’re going to be regular occurrences in the future, experts say, the result of climate change. These are going to be especially difficult to deal with in a highly developed urban area like Milwaukee, since pavement, large-scale development and aging infrastructure make high volumes of water difficult to absorb.

Fortunately, there are many strategies that individuals, businesses and local governments can implement to improve the region’s water management. But there’s an added benefit, too: These solutions consume far less energy than traditional sewage systems use to pump and treat wastewater and storm water.

  • Homeowners can disconnect their downspouts from the sewer lines and run them away from their homes and into their gardens or lawns. They can add rain barrels, which hold up to 55 gallons of water that can be used for gardens and lawns when it isn’t raining. They can plant rain gardens or native plants, which improve water absorption. Owners of older homes with foundation drains can add a sump pump, which would remove water from their home.

  • Businesses and some homeowners can add green roofs, which reduce storm-water runoff, decrease a building’s energy consumption and improve air quality.

  • Governments or large property owners can add more greenspace to their developments in the form of greenways, wetlands or bioswales. Porous pavement would allow water to drain into the ground below the pavement, instead of running into the sewer system. And more trees and plants located along roadways will enhance absorption of storm water.


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