Indubitably impervious and impenetrable

Alliteration, onomatopoeia and other big words provide me with great joy. I discover a new word, love the meaning of it, and then begin to use it so frequently that I forget it is not really a “normal” word. I learned about plethora sometime during grade school and have used it ever since whenever there are seemingly endless possibilities. “What should we eat for dinner, honey?” “Well, Gary, there are a plethora of options to choose from here in Stillwater.” Ennui is a delicious word that I picked up while working at a local museum. Meaning extreme boredom, listlessness and dissatisfaction from a lack of interest, there are a plethora of circumstances in life in which ennui is just the right way to describe one’s mood.

In the world of water resources management, strange words proliferate. There are riparian areas along rivers and streams, lakes suffer from eutrophication, and bioretention cells are built to mitigate the impacts of impervious surfaces. Translated, I mean to say healthy rivers and streams are bordered by plants and trees, our lakes sometimes turn green, and people can plant raingardens to make up for the fact that water doesn’t soak into concrete or asphalt.

In one community in Connecticut, researchers have been struggling with the question of how to fix a stream that runs through a college campus. It is obvious that the stream is suffering, and monitoring has shown that the fish and bugs that should live in the water don’t. However, when researchers tried to pinpoint what pollutant in particular was causing the problem in the stream, they couldn’t. Nutrients like nitrogen and phosphorus are a tiny bit of the problem. Oil, sand, and salt washing off of the roads on campus are a tiny bit of the problem. Also problematic is the slightly higher temperature of rainwater entering the creek through storm sewers after it washes off of the hot rooftops on campus and flows across hot asphalt parking lots. Eventually, however, the folks in Connecticut decided that they could fix a plethora of problems impacting their creek by reducing the amount of impervious surface on campus.

A homeowner in Mahtomedi shows off a driveway that lets rainwater soak through into the ground.

Impervious surfaces include rooftops, sidewalks, driveways, roads and other surfaces that water can’t soak into. In many newer neighborhoods, where clay soils get compacted during construction, even lawns are mostly impervious, leading to the nickname “green concrete.” As it turns out, we can almost always predict the health of a lake or stream purely based on how much of the land draining to that lake or stream is covered in impervious surfaces. The higher the percentage of impervious surfaces in the surrounding watershed, the worse the water will be.

Local communities and watershed organizations spend a lot of time and money cleaning up dirty lakes and streams. Because most of the pollutants that wind up in the water originate on the land, oftentimes miles from our lakes and streams, resource managers also spend considerable time retrofitting existing roads, parking lots and neighborhoods with pervious pavement, raingardens and other practices that create opportunities for rainwater running off of impervious surfaces to soak into the ground instead of flowing untreated to nearby water bodies. It is worth noting, however, that we can also reduce water pollution simply by limiting the amount of impervious surface within a watershed, and this is true whether you are dealing with developed communities like Oakdale, Stillwater and Woodbury or relatively rural areas like Scandia and West Lakeland Township. It is also worth noting that the cumulative impact of increasing impervious surface on numerous disconnected lots within a watershed is pretty much the same as if all those impervious surfaces were connected together into one big blob.

What does this mean for the typical homeowner? Should you avoid adding on an addition to your lakefront home or building that three car garage that you’ve always wanted? Yes, that would be better for water quality, but for most of us, those kinds of sacrifices go a little too far. A more realistic compromise is to make the majority of the driveway for your new garage only one car wide, or even to build an old-style driveway with two strips of concrete instead of a ten-foot wide swath of pavement. In the case of one couple I know, they realized that they could shrink the length of their driveway, thereby reducing impervious surface, simply by building their new garage on the other side of the house, closer to the road.

So now, before my dear readers lapse into ennui, I will close with the following summary. Indubitably, impervious surfaces impact our local water resources, but happily a plethora of options exist for addressing this conundrum.