Maintaining Permanent Stormwater Control Measures

Each spring and summer for the past three years, I have done annual “long-term operations and maintenance inspections” of permanent stormwater control measures. In other words, an inspection of detention and retention basins, bioretention basins, underground detention systems, green roofs, and permeable pavers, to ensure they are being maintained and are properly functioning. While there are a few I come across that are in excellent condition, most of these stormwater control measures need some sort of routine maintenance, and then there are ones that need major maintenance.

What do permanent stormwater control measures do?

Permanent stormwater control measures capture stormwater (caused by rain or snowmelt) from impervious surfaces like pavement and roofs. While each of these stormwater control measures functions differently, their collective purpose is to help reduce problems like downstream flooding, streambank erosion, pollutants getting into streams, rivers, and Lake Erie. Additionally, in areas where applicable, they help reduce combined sewer overflows. With the numerous benefits that stormwater control measures can provide, maintaining them to function properly is crucial.

What are maintenance items for stormwater control measures?

Routine maintenance such as mowing within a detention basin, removing areas where phragmites or cattails are beginning to grow within a detention or retention basin, removing sediment accumulation observed within the mulch of bioretention basins, monitoring and having underground detention systems jetted out when needed, are examples of what needs to be done to ensure proper function of these stormwater control measures. Just like other infrastructures need routine maintenance, performing these routine maintenance items is beneficial not only for the downstream areas of these stormwater control measures, but also is necessary to prevent these measures from becoming inadequate.

What happens when these stormwater control measures are not maintained?

When stormwater control measures are not maintained, they begin to not function to the ability that they were designed to function. Detention basins could become overrun with phragmites and cattails. Bioretention basins, specifically the specialized soil within bioretention basins, may become clogged and not allow stormwater to infiltrate as much, which in turn would also reduce their ability to remove stormwater pollutants. Underground detention systems could become clogged with sediment, debris, and litter. Green roofs could have erosion issues, especially if the plantings within the green roof are not properly cared for. Permeable pavers could clog if the surface where they are located has leaf debris, sediment, or nearby mulch beds. Basically, anything that can become clogged within the gaps of the permeable pavers reduces the function of the permeable pavers.

Why do people think detention basins are wetlands?

A real-world example that I (and all my colleagues in the stormwater division) come across, are properties with detention basins which have become overrun with cattails, phragmites, purple loosestrife, curly dock, and common burdock. Oftentimes when we alert the property owner or manager about the issue, we get a response something along the lines of “well that’s basically a wetland… if anything I’m creating wetland habitat”. While people who say this mean well and have good intentions, however, a detention basin is not – and should not be a wetland. Aside from the fact that all the species of plants I mentioned are invasive, they take up stormwater volume capacity within the detention basin. Additionally, when I have been told this (on more than one occasion) I feel there is more than enough mowed grass lawns at these properties, which could be turned into a native meadow or woods. What should be done is, the detention basin should be mowed and maintained, and some of the mowed grass areas on other parts of the property should be more natural. Also, a stormwater control measure that does exist -- however is very rarely designed, is extended detention constructed wetland. While I feel this would make a great stormwater control measure, I also fear that no maintenance would be done because people would just think they are actual wetlands, which, like detention basins, they are a first and foremost a stormwater control measure infrastructure.

In any case, if people think of stormwater control measures more as “infrastructure” rather than something that’s "just there," would that help with bringing some of the non-maintained or rarely maintained basins out of their inadequate state? I ponder this question when I am doing inspections of neglected and poorly maintained stormwater control measures. With climate change we can expect to see more frequent and more intense rain events in northeast Ohio. Additionally, the winter will likely come with more snowmelt events. All this added stormwater, coupled with less trees and forested lands around headwater streams, one thing is for certain, and that is to better protect downstream environments, we need to have more stormwater infrastructure and we need more of this infrastructure to be better maintained.

Blog Author: Chris Vasco, Stormwater Specialist

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