BLUE NOTES W/ KEVIN SHAFER

01/14/19 02:50:pm

e-Newsletter | January 14, 2019

What does the average six-year-old, the mailbox at your house, and the rain gauge at Mitchell International Airport have in common? Don’t overthink it. The answer is 45 inches. That’s the average height for the first two and the total rainfall measured in 2018 for the third. This is nearly a foot above our average of 33.5 inches. 

If every mailbox in our region had water up to its 45-inch height, that would equate to approximately 320 billion gallons of water entering rivers and urban infrastructure. Can’t picture that much water? To put that into perspective, the MMSD deep tunnels hold 521 million gallons. It would take 614 tunnels to capture all that water, which is economically implausible.

To simplify the discussion, think of this large volume of rainwater as a budget – a water budget. As this rainfall hits the ground, it flows either into a municipal separated sewer system, which is meant to only receive sewage, or a combined sewer which receives both stormwater and sewage. The separate sewer area would have received approximately 302 billion gallons of water and the combined sewers 18 billion gallons.

These municipal sewer systems deliver flow to the MMSD regional system either by illegal connections, leaky pipes, old foundation drains (separated sewer system), or by direct connections (combined sewer system). MMSD must take steps to manage these sources by either cleaning the water and releasing it to Lake Michigan or overflowing excess water (stormwater and sewage) to the rivers and Lake Michigan.

In 2018, the MMSD system of pipes and tunnels captured approximately 76 billion gallons or 24% of the 320 billion gallons. While MMSD had six combined sewer overflows totaling 1.2 billion gallons, MMSD still captured and cleaned 98.37% of the 76 billion gallons. 

Our distribution of the 320-billion-gallon budget would have resulted in three paths for the sewage and rainwater to reach Lake Michigan: 1) 1.2 billion gallons through overflows from MMSD’s system; 2) 74.8 billion gallons of cleaned water from MMSD water reclamation facilities; and 3) 244 billion gallons that entered the municipal storm sewer systems through stormwater runoff. 

As we make investments to reduce pollution sources into Lake Michigan and adapt to climate change, these numbers help us to understand where those investments need to be made. MMSD must continue to clean as much sewage and stormwater as possible, while reducing overflows. Our goal is to increase the 98.37% value to 100%, but this region also needs to make investments on the land surface to reduce the 244 billion gallons of polluted stormwater runoff. We need to manage water where it falls by implementing green or natural infrastructure improvements at our homes, businesses, and public lands. Each of us can also take simple steps, like picking up litter and dog waste. 

Everything we do matters. We can get ahead of our some of changing climate concerns if we take these steps now. I’d like to think our steps now will help our 45-inch-tall, six-year-old residents to have safe drinking water, less flooding, and a cleaner place to live throughout their lives.