Like All Municipal Utility Assets, Green Infrastructure Must Be Maintained
Green infrastructure (GI) practices are a form of stormwater management designed to help mimic the natural runoff cycle, often by infiltrating stormwater runoff into the soil and re-charging groundwater. GI, when properly designed and applied, reduces the volume and rate of stormwater runoff from sites while also reducing the pollutants that are often found in urban stormwater discharges. Some of the more commonly used urban green infrastructure practices include bio-retention areas, tree pits, rain gardens, and green roofs – to be effective, these features must be kept alive and healthy. Similarly, infiltration practices such as basins, drywells and trenches, porous pavement and paver systems must be kept free of sediment and other materials that may reduce their ability to infiltrate. This summer’s drought conditions in the northeast have severely impacted the health, appearance, and functionality of our communities’ “living” green infrastructure systems. In contrast, the recent areal flooding and torrential downpours have overwhelmed the pervious surface areas that were designed to mitigate surface runoff and localized flooding. Could some of this have been prevented?
Like all infrastructure assets, proactive and regular maintenance of GI practices is paramount to sustaining the long-term capital investment, function and benefits of GI. More often than not, recipients of State or local grants for constructing GI facilities must develop and commit to implementing a long-term maintenance program to sustain the life of the asset. These O&M plans are often stipulated within a facility maintenance agreement, or similar legal instrument, and reference State GI maintenance guidance for best management practices (see links below). This obligates the GI facility owner to maintain, clean, repair, replace and operate the GI stormwater control measures to consistently achieve the litany of benefits associated with GI, such as:
Maintaining the GI’s ability to treat stormwater for water quality and volume attenuation to improve surface and groundwater quality and mitigate localized nuisance flooding;
Improving natural habitats and urban forests with native species to increase pollinator opportunities, mitigate invasive species and heat island effects, and improve nutrient uptake to restore a better ecologic balance involving all aspects of the hydrologic cycle; and
Reducing flooding and the impacts to storm sewer and possibly sanitary sewer infrastructure in areas of combined sewers that can result in overflows to sensitive waterbodies and aquatic life.
Unlike buried conveyance assets, green infrastructure is highly visible and becomes part of a neighborhood’s identity, improving aesthetics, quality of life, and attractiveness for continued economic investment and development. GI practices that are not properly maintained will not only lose some of their functionality, but their poor appearance may also negatively influence the public’s perception of the owner’s level of care and effectiveness of these practices. This could result in complaints and possible backlash from residents who may not support new GI initiatives in their communities in the future, not to mention a potential “breach of contract” with a funding agency.
Maintaining GI vegetation consisting of grasses, perennials, trees or shrubs requires care, knowledge, and the ability to identify beneficial plants from invasive and performance reducing species. Many well-intended smaller communities look to their Public Works Department to maintain their GI practices, adding to an already full spring and summer workload. Training of municipal staff is essential to the long-term successful integration of GI into a municipal stormwater management system; it should be considered part of the investment. Alternatively, relief from this maintenance burden could be accomplished through public outreach and education under a community’s MS4 program, wherein volunteer organizations, citizen’s groups, or benefitting businesses could be enlisted for assisting with annual GI maintenance tasks.
The importance for consistent and scheduled GI maintenance cannot be minimized. It will help avoid the large expense of reconstructing a failed stormwater management asset and negative community perceptions that could result from a lack of attention. For more information, please see the links below for operations and maintenance techniques pertinent to New York, Maryland, Connecticut, and Maine.
- Connecticut Stormwater and Green Infrastructure Maintenance Guidance Document
- Maine Stormwater and Green Infrastructure Maintenance Guidance Document
- Maryland Stormwater and Green Infrastructure Maintenance Guidance Document
- New York State Stormwater and Green Infrastructure Maintenance Guidance Document Links
Special thank you to Brad Grant, Ken Knutsen, P.E., Sean Sweeney, P.E., Rachel Schnabel, P.E., Amy Parrish, P.G. LEHS, Jason Gillespie, Steve Lezinski, BCES, Ashlyn Maurer, P.E., Nicole Cleary, P.L.A., Tom Baird, P.E., Bill Bray, P.E., and Holly Lauzon for your contributions to this blog.