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From Dirty Streets to Clean BMPs – Maintaining rain gardens along roadways

by Mary Travaglini


Children playing in gutters is mostly a thing of the past.

When my dad was a child growing up five miles from downtown Philadelphia, he and his friends would lie in the roadway gutter pans during rain storms to let the water wash over them. It was the 1930s version of a water park. When I tell people this, they think it’s pretty gross and unsafe. To be sure, there probably was some sewage in the water, but up and down the street it was substantially contained in the courtyard outhouse. Otherwise, there were few pollutants we now associate with cities. In the 1930s, the roads were made of hard packed dirt perhaps coated in edible oils; there were few cars and those cars moved slowly. The cars were maintained to perfection and didn’t leak, the tires were real rubber, and the cars and the roads didn’t wear down from use by high-speed vehicles. No one used fertilizers and pesticides on their lawns, a lot of rooftop water was collected in cisterns for home use, and well, the list goes on.


A slew of contaminants enter raingardens and bio-retention cells along with the rush of urban stormwater runoff.

Fast forward to today, where the water coming off our properties and roads is full of petrochemicals, heavy metals from brakes, pesticides, roadway millings and spallings, fly ash, binders and sealers, oils and grease, bacteria from dumpster leaks and dog waste, and more. In the 21st century, I probably wouldn’t want to stand barefoot in a gutter pan during a storm, let alone lie in it. But every day, my job is to maintain rain gardens and bio-retention areas that get the first flush after every storm complete with all of those pollutants. The soils and plants can’t move out of the way of stormwater that, in addition to being polluted, is hot and moving fast. And polluted water is just the main threat that roadside rain gardens face. People step in them, cars drive in them, trash blows into them, leaves accumulate in them, and dogs poop in them. It’s hard to name something that doesn’t cause an impact.

Can Best Management Practices Help?

So where do we even start with maintenance of roadway Best Management Practices (BMPs)? What are we learning and how fast are we adapting?

Normally we’d start with the question of how to keep pollutants out of and off of our streets, and then address whether roadway BMPs are the right way to handle street runoff.  But that is another article with another set of questions. So I’ll limit the commentary on this to the following: good siting and design of roadway BMPs cannot be understated. Planners, landscape architects, and engineers should spend some time outside in the rain, and then dedicate more time and creative thinking to this kind of non-traditional, micro-scale design. Input should always be solicited from those who maintain them, to create the most sustainable practices possible.

After a storm, sediment and debris fill a roadside rain garden.

After a storm, sediment and debris fill a roadside rain garden.

Once a rain garden or bio-retention cell is built and stormwater is flowing into it, we start to see just how tough a BMP has to be to handle the conditions. Sediment builds up quickly, water causes erosion or slope destabilization, plants are saturated and flooded for short periods of time, then drought-stricken between storms, mulch breaks down quickly or floats away, soil biology goes on a roller coaster ride. Neighbors start to complain, as they now see in plain sight what used to be invisible to them in a storm drain. It’s a new paradigm, and we are learning each day what it takes to maintain these gardens.

What’s Necessary for Maintenance Success?

What I can tell you is this – I haven’t found it easy. I need a well-trained crew who understands how stormwater works, who knows plant identification and care, who knows the difference between roadway sediment and bio-retention media, and who provides dedicated manual labor. I need to figure out the nuances of each garden to know how to maintain or recover function or aesthetics, how to prevent erosion, how to boost the survival of plants, and I need my crew to know the same. I need to see plants as structural components and not future meadows or forests. I need to fix damages from cars and trampling while trying to satisfy all the neighbors with their varied perspectives, likes, and dislikes. I need to educate our neighbors so they understand and accept the rain gardens in their neighborhoods. I need to answer to the permitting agencies that these are functioning as designed. I need to keep them working four seasons a year, for decades on end. I need an ongoing budget, and I need folks to understand why a continuous funding source is necessary, which requires a lot of explaining and teaching.

During the peak growing season, a well-cared-for roadside rain garden is functional and aesthetically pleasing.

During the peak growing season, a well-cared-for roadside rain garden is functional and aesthetically pleasing.

Every day I learn something new. I don’t do the same things today that I did three years ago to maintain roadside raingardens. Looking ahead another three years, I may question how I do things today.

Join me for the ELA webinar Dirty Streets to Dirty BMPs: Maintaining Clean Stormwater BMPs along Roadways on November 4th. During this webinar, I’ll share some lessons learned from my work maintain roadway raingardens in Montgomery County Maryland.

About the Author

Mary Travaglini provides direction and oversight for the inspection, maintenance, and repair of green stormwater infrastructure for Montgomery County, Maryland, including green roofs, pervious pavement, bio-retention, and raingardens. She sees firsthand the impacts of stormwater and human use of our built environment on stormwater facilities, and uses field observations to inform better design, construction, and maintenance of these practices. Mary has degrees in natural resources and landscape architecture, and has previous experience with invasive plant management, trail construction, and landscape design, all of which she applies to her work in stormwater management. She still drinks local tap water, despite knowing where it came from.


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