| 4 min read | by Doug Marrin, |

Dexter’s storm conveyance system directly impacts waterways such as Mill Creek

If you haven’t been thinking about Dexter’s stormwater drainage system lately, it might be because it’s doing its job, and you can thank the city’s Department of Public Works (DPW) for keeping it that way.

I know. It sounds like a real yawner to talk about but after sitting down with Eric Hartman, Lead Utility Operator for the City of Dexter, who talked me through the community’s Storm Conveyance System (aka storm drains), I admit I found it all pleasantly fascinating.

According to Eric, Dexter is in good shape. “When it comes to funding stormwater maintenance, Dexter is a very good community with stable funding mechanisms in place,” he explains. “Not all communities are as fortunate as us. They don’t have people in place who understand these systems and make an effort to maintain them.”


It sounds easier enough – water trickling through hidden pipes to parts unknown, out of sight, out of mind – but storm drainage is actually a fairly complex system. To get us started, here are a few numbers reported by the City in their Stormwater Management Plan that you can toss out when the regular conversation dies:

  • 22: miles of stormwater pipeline in the City of Dexter.
  • 11: miles of road in the City.
  • 2: area of the City in square miles
  • 31: percent of City area that has impervious surfaces
  • 4,067: population as of 2010 Census
  • 48: detention ponds
  • 358: manholes
  • 24: outfalls into the watershed
Eric Hartman

Eric explains stormwater runoff as simply as he can to me: “Say, for example, a business has an acre property and they put up a three-quarter acre building with an impermeable surface for the roof and parking lot. When it rains, that water can no longer soak into the ground. It sheets off into the road and has to now be managed.”

That doesn’t sound too bad but hang on a minute.

The U.S. Geological Survey tells us that “One inch of rain falling on 1 acre of ground is equal to about 27,154 gallons and weighs about 113 tons.” That’s a lot of water!

Dexter has almost 400 acres of impermeable surface. If a storm drops an inch of rain, that’s 10,861,154 gallons of water (1,680,016 cubic feet). The permeable ground is already saturated and all this water has to go somewhere.

If you’re like me, a visual helps in understanding how much water we’re talking about here.

The USGS also tells us last August 10, 2019, the flow rate of Mill Creek was 28 cubic feet a second. Imagine how exciting Dexter Daze would suddenly have become if Mill Creek was suddenly diverted and emptied out into the town square (or triangle) for 16 hours and 45 minutes. Or, setting Paul Bunyan mythology aside, imagine dumping Wylie swimming pool out on the streets … 220 times.

Here’s another conversation tidbit: The January 11, 2020 storm dropped 2-3 inches of rain in 24 hours. It would have been hellacious if our drains didn’t work. We’d be all Hans Brinker, Or the Silver Skates until the new ice age melted.

One of Dexter’s 48 detention ponds

OK, you get it. We’re talking a lot of water. But it’s more than a deluge of Biblical proportions filling our gutters, floating our little paper boats, with some clown whispering ‘we all float down here Georgie.’ There are scarier things going on down there.

 “It’s not just figuring out where to channel the water,” says Eric. “There is grime and chemical build-up that gets washed into the system and that has to be dealt with before you put it back into the watershed.”

Eric is in his element here. He has a degree in Environmental Technology which basically looks at how humans impact the environment, and how it can be minimized. He has been in the water industry since 2008 and with Dexter since 2012. Environmental stewardship is his passion.

People don’t give much thought to silt build-up. We don’t have to. Eric and the other silent heroes at the DPW do that for us. Left unchecked, silt would build up and clog our pipes like a brick of cheese. To keep from happening, DPW goes around and sucks it out of special traps (Elmer Fudd voice: “I got you now you rascuey sludge“). But instead of a shotgun, they use something that looks like a big vacuum cleaner, similar to removing the solids from a septic tank.

That’s the easy part. There’s another more dangerous monster lurking beneath the streets of our fair town – chemicals and toxins.

“Vehicles drip a lot of fluids on the roads that are very toxic,” says Eric. “It takes very little oil to contaminate a whole lot of water. That has to be managed before putting the water back into the rivers.”

To prevent these toxins from polluting the environment, Dexter has installed separators. Separators work the opposite of the silt traps where the heavier materials sink and the water runs over the top. Chemical separators collect the chemicals, like engine oil, floating on top of the water while the clean water runs through underneath. The chemicals can then be taken off the top.

Sitting in Dexter City Council meetings, coal tar sealants for the roads came repeatedly came up for discussion on the agenda as the council worked out an ordinance prohibiting their use. This was always my signal to start daydreaming or yawn loudly. Is there anything that could be more boring? ‘Coal tar,’ it sounds like we’re back in the 1800s. But actually, if I would have paid attention there was a cool little story unfolding right in front of my drooping eyes.

Eric explains: “Most communities have adopted a coal tar epoxy/sealer ban. Coal tar epoxies were a common ingredient in driveway sealers and present a hazard to the environment as they are a carcinogen. It has been found that when a coal tar sealer is applied to an asphalt driveway that the carcinogens wash out into the storm/water ways during rain events. Dexter now prohibits their use.”

And here I thought the City Council was banning coal tar because it stinks or had the word ‘coal’ in it. It turns out the Council was being environmentally conscious and preventing the toxins from being washed out into our much-cherished environment where it can affect aquatic life among other things. Who wants to eat a trout that tastes like a driveway patch?

System outlet

Storm drains don’t just keep our roads from turning into cement ponds every time it rains, they serve our backyards as well. This makes yard maintenance kind of a big deal.

“When a yard is heavily fertilized, the rain or irrigation carries those chemicals off the property with the runoff and it goes right into the river where the phosphorous feeds all the harmful algae and bacteria,” explains Eric. “It’s ironic, but the yard that looks most environmentally friendly by being green and healthy is actually the most harmful.”

“The same can be said for pet waste,” continues Eric. “There are nutrients in there that also provide the necessary components for bacteria and algae to take over the waterways.”

You can look at it this way: We wouldn’t let people poop in the river or dump their sewage there. That’s why we built wastewater systems. Granted, it’s hard to imagine that little pile of doggie doo in the weeds as doing anyone any much harm unless they step in it, but think of the big picture. There are a lot of dogs in Dexter that, when considered collectively, download a prodigious amount of (you know what) daily. It’s encouraging individuals to embrace their responsibility in the collective picture. Scoop the poop, even in your own yard.

Dan Hoey detention pond

One more thing: I would never forgive myself if I thought you were losing sleep and binging on Jacked Doritos fretting over the amount of water that can fall in a storm and how it might stress the storm conveyance system. Be at peace. Those 48 detention ponds act as buffers to prevent the system from being overwhelmed.

So we don’t have to think much about our storm conveyance systems and thank God for that. We’ve got other things to do. A big thanks to Eric and everyone at the DPW working behind the scenes, thinking, and worrying over these things so that we don’t have to. We appreciate it immensely.