Woodbury rain gardens are a success. Right?

The two-year rain garden project in Woodbury, which I wrote about in July, ends the construction phase this week when the last batch of plants is delivered to the homeowners who volunteered to turn their property over to an idea to clean up the waterways.

Now the really ugly part begins. Rain gardens take awhile to get going and, I learned via comments to the original post, neighbors tend not to like the looks of them. And why should they? They look like a gangly pre-teen.

That’s why a post today on the streets.mn blog by Samuel Geer, a landscape designer, is well worth checking out.

What do these things look like 10 or so years from now? Geer found out by visiting Burnsville, where the rain garden project is “the poster child for rain gardens and stormwater retrofits,” he writes.

Aside from the fact that they all seemed pretty well maintained, you could tell that there had been some professional refurbishment as well. The grassed inlets had been replaced somewhat recently error to prevent sedimentation of the garden basins and landscape edging or pavers served as an additional sediment trap and energy dissipation system.

Without this kind of protection, the fine particles carried in the runoff will rapidly plug up the basin, killing the plants and preventing infiltration. In addition, you could see that for the newer gardens, the curb cut inlet had been replaced with a sump catch basin that could be cleaned out by a Vactor Truck.

This move results in a more reliable maintenance regime than expecting the homeowner to regularly rake sediment out of the turf strip as it accumulates.

Well, swell. When the Woodbury garden construction was finished a couple of weeks ago, they rolled the sod near the inlets, apparently ignoring Burnsville’s teaching.

The Burnsville rain gardens are still thriving after almost a decade because they are functionally designed and we can intuitively recognize them as infrastructure. This visibility and care in engineering is the key to earning green infrastructure a real seat at the infrastructure table.

The water captured by these rain gardens is a drop in the bucket compared to the ecological services performed by say, an intact wetland or an agricultural buffer strip. However, they present a compelling vision for a green street with layered functions that people can appreciate and wrap their minds around.

So if the neighbors can be patient, maybe something like this in Woodbury…

… will end up looking like this in Burnsville:

streets.mn

But it’ll be a challenge. Samuel says the Burnsville rain gardens thrived because 80 percent of the residents built them. Otherwise, he says, they’ll be overburdened by sediment — sand, for example. In my neighborhood, very few rain gardens were built.

I’ll let you know in 10 years.

  • BReynolds33

    The first block quote makes it all seem like an ongoing project. Is the city funding the upkeep, or is that for homeowners?

  • MrE85

    When you get away from the MPR booth at the Fair, check out the rain gardens near the Eco Experience building (the one with the big wind turbine blade mounted out front). They have some RGs that have been there a few years, complete with flowers and plants. You might even find an expert on the things inside.

  • Tyler

    How do rain gardens handle all the road salt the city is so kind to put down? Burnsville pictures look healthy, but I wonder all the same..

  • Josh D.

    Rain gardens typically do just fine with salt because there’s usually a frozen chunk of ice blocking them from the road during winter. I have not seen any instances of salt damages to plants so far.

    As far as sedimentation, a sod strip is not the worst thing in the world. Its purpose is pre-treatment, that is, it gathers the larger sediment so that it does not clog the rain garden as your post alludes to. But it quickly builds with sediment, making it too high which keeps water from entering the garden if it is not cleaned often. The “rain guardian” is likely the pre-treatment that Burnsville is using, it catches the sediment in a neat box that is easy to vacuum out. The issue is money of course, if I remember right they run around $700, and they require a concrete pad beneath them which costs a few more hundreds. Add that on to a 20 rain garden project and its a decent chunk of change. Some think its worth it, other not.

    In my experience, I have not seen fine sediment “rapidly” killing off plants and preventing infiltration (clogged inlets are far more common), but it will happen at some point, some sooner than others. If it does, the rain garden did it’s job, it prevented the sediment from entering streams/lakes/ect. but now the cost of removing it is likely greater then the up front cost of the rain guardian.

    There are many, many mature rain gardens throughout the metro that look great. A little maintenance goes a long way, and most people are pleasantly surprised how fast they fill in the season after they are planted.