Tuesday, January 19, 2010

2009 Metro Detroit Sewage Numbers

Last year was a bad year for combined sewage overflows in Metro Detroit. Over 37 billion gallons of sewage overflowed into Metro Detroit waterways in 2009. This total was an 11 billion gallon increase from 2008.

Combined sewer overflows (CSOs) occur when it rains. Older sewer systems receive municipal waste along with storm water. During heavy rains the sewers fill up and rather than having sewage back up into streets and basements, the sewage is then released into the local waterways.

The main way that Metro Detroit is dealing with sewage treatment is by building retention treatment basins. These basins hold the excess storm water and sewage and are supposed to hold and treat the wastewater. What often happens is that the sewage only gets partially treated. This means that the sewage is treated with chlorine and the solids are allowed to settle. This is better than just releasing raw sewage but it does not get rid of all of the dangerous pathogens.

All sewage categories were unusually high in 2009. One category that was higher than normal was diluted raw sewage. In 2008 there were 1.2 billion gallons of diluted raw sewage released into metro Detroit waterways while 2009 brought over 5 billion gallons of diluted raw sewage. This is significant because this is untreated sewage. To put it in perspective how high this number is consider that in 2007 the rest of the entire state of Michigan excluding Wayne County only had 3 billion gallons of CSOs.

The annual rainfall for Detroit was nearly the same. The total rainfall for 2008 was 33.98 inches while 2009 brought a little bit more rain for a total of 34.12 inches. It is hard to blame the rain for this large increase in CSOs.

The majority of these high sewage numbers occurred during nine wet weather events where each time at least a billion gallons of partially treated sewage and diluted raw sewage were released into the waterways. The biggest CSO of the year occurred between March 7 and March 16. A total of over 8.6 billion gallons of sewage overflowed into the Detroit and Rouge Rivers. 6.9 billion gallons were partially treated sewage while the other 1.7 billion gallons was diluted raw sewage.

The nine biggest Wayne County CSO events yielded 75 percent of the total Wayne County CSO releases. Over 90 percent of the diluted raw sewage releases for Wayne County also occurred during these nine events.

Despite the recent problems much progress has been made. Consider that in 1988 there were 613 CSO outfalls throughout Michigan. As of 2008 that number has been reduced to 154 CSO outfalls. Recently though, progress has stalled.

The biggest problem that municipalities are facing comes down to money. It is really expensive to overhaul the sewer systems. The Upper Rouge Tunnel Project would have greatly reduced CSOs for Metro Detroit but it had to be abandoned last April because of the $1.2 billion cost. The Detroit Water and Sewerage Department (DWSD) would have had to hike water rates 16 percent and that was seen as unreasonable in today’s economy.

The Upper Rouge Tunnel Project was part of a court mandate to reduce CSOs into the Rouge River. This was part of the conditions of 2008 litigation brought by the EPA. The city has until 2015 to comply with the court order. Now that the project has been canceled the DWSD is drafting new plans. Two possible outcomes are a smaller tunnel, though that has already been rejected once, partly because Michigan has stricter wastewater standards than the EPA. The other possible outcome could be getting more time to comply.

There are other less expensive methods to curbing CSO overflows. One is green infrastructure. There are things that anyone can do such as using rain barrels to collect rainwater rather than directing rainwater to sewers. You can use the collected water to irrigate your flowers or garden.

Other green infrastructure solutions include green roofs. Where gardens are planted on roofs to reduce rainwater, these roofs also last longer than your conventional roof though the initial installation cost is higher.

Any time you can avoid directing rainwater to the sewers you are helping to combat CSOs. A lot of this can be achieved through rethinking how we design structures such as buildings or parking lots. A simple green oasis can help reduce the burden of CSOs on waterways and is aesthetically pleasing.

These are important issues since global warming is expected to change precipitation patterns in the Great Lakes. It will rain less often, but when it does rain it will be intense storms. This will wreak havoc on the local waterways if our infrastructure is not updated.

These are how the numbers shake out for 2009:

Macomb County
Partailly Treated Sewage: 2,092
Diluted Raw sewage: None
Raw Sewage: 3

Oakland County
Raw sewage: 12 million gallons
Diluted Raw Sewage: None
Partially Treated Sewage: 139 million gallons

St. Clair County
Raw sewage: 13 million gallons
Diluted Raw Sewage: 57 million gallons
Partially Treated Sewage: 156 million gallons

Wayne County
Raw sewage: 156 million gallons
Diluted Raw Sewage: 4.95 Billion gallons
Partially Treated Sewage: 29.2 Billion gallons
Blended Effluent: 574 million gallons

Raw sewage: 184 million gallons
Diluted Raw Sewage: 5 billion gallons
Partially Treated Sewage: 31.4 billion gallons
Blended Effluent: 574 million gallons
Total: 37.2 billion gallons

These are my 2009 totals in excel format available for download HERE.

It has every individual release along with where and when it happened along with which waterways were affected. I also summarized the ten biggest CSO events of the year.

All of this data came from the MDEQ website.

(Important note)
There are gaps in data for Dearborn. Of 54 total combined sewer overflow events for Dearborn, 28 event dates had a volume total for the amount of partially treated sewage released into the waterways. The other 26 CSO events had incomplete data. Between the beginning of 2009 and July 11, there were 968 gallons of partially treated sewage released into the waterways from Dearborn. After July 11, Dearborn quit reporting the total volume of sewage that was released into the environment.

More Resources

Steve Neavling wrote a great story in the Free Press on the sewers today:
Aging sewage systems breed record bacteria in our waters

This is a great story about the sewage overflow issue from The Windsor Star:
Windsor cleans up act as Detroit spews sewage into river

Anybody that wants to see the Rouge River up close and personal should check out the book Up the Rouge! by Joel Thurtell.

Toxic Waters New York Times Series

EPA Report on Climate Change and CSO Mitigation on the Great Lakes

Green Cities, Great Lakes: The Green Infrastructure Report

by Jason Tafilowski

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