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Stormwater O&M: When construction ends, the work begins

Stormwater O&M: When construction ends, the work begins Barr’s design of this constructed wetland at Carleton College in Minnesota provides stormwater treatment for the college’s 800-acre arboretum. The wetland's design treats water before it reaches the Cannon River and fits into the arboretum’s natural landscape.

Over the last two decades, innovative stormwater management practices have been implemented by cities, watershed organizations, and developers throughout the country. These practices include rain gardens, infiltration and filtration basins, detention basins, bioretention cells, proprietary underground treatment systems, and more. But, over time, these systems have been strained by aging infrastructure, deferred maintenance, and climate change and may no longer be performing as designed.

The fact is a lot of money goes into stormwater best management practices (BMPs) that reduce runoff volumes, improve water quality, and mitigate flood risk. Whether you’re using capital-improvement money, grants, or cost-share funds, it’s important to remember that the work—and the costs—don’t end when construction is finished. Proper maintenance is critical to the long-term performance of stormwater management systems; without it, you’ll be risking your investment. The potential costs to fully repair or reconstruct a system can far exceed routine maintenance.

Incorporating maintenance into project design

Ideally, maintenance should begin with project design. Planning access for inspection and maintenance is critical. Private development projects often rely heavily on below-ground systems to maximize the developable space. Underground systems are also used for retrofit projects in fully developed watersheds where space is limited. The downside of underground systems is that they can be more challenging to inspect and maintain than surface systems due to lack of visibility and limited access.

Designing practices without involving the staff who will be responsible for their long-term function can also result in systems that cannot be properly maintained. If possible, we recommend involving maintenance staff early in the design process—not only those staff members responsible for structural cleanouts but also vegetation maintenance and even forestry staff.

Ongoing maintenance considerations

Beyond upfront preparations for maintenance during the design process, there are a number of approaches to keep stormwater management systems working as intended. Here are a few:

Underground filtration/infiltration system inspections

Underground stormwater treatment systems can be effective at protecting water quality and mitigating flood risk, but only when maintained properly. Unfortunately, these underground systems are too often out of sight, out of mind. These systems should be inspected at least a couple of times a year, including after rain events, to confirm that they are functioning as the manufacturer intended. Barr’s NASSCO-certified (the industry standard in underground inspection) staff regularly inspect underground filtration/infiltration systems, as well as storm sewers and tunnels, to confirm they’re operating correctly and to catch any problems early.

Green stormwater infrastructure inspections

Green stormwater infrastructure practices (rainwater gardens, tree trenches, swales, filter strips) capture and treat stormwater at its source. The benefits of these practices include enhancing biodiversity in urban areas, managing stormwater flows, treating stormwater before it permeates groundwater, reducing urban temperatures, and improving air quality. To provide these benefits, on top of water quality performance, a well-thought-out inspection, operations, and maintenance program is critical. This helps to ensure the practices function as designed and remain beautiful and evolving spaces that offer habitat. We also assist clients in hiring contractors to maintain green infrastructure features and make necessary repairs to preserve their function.

Barr helped an existing retail property—Maplewood Mall in Maplewood, Minnesota—redesign its parking areas and pedestrian plazas to both improve stormwater quality and enhance the user experience. The design includes 375 trenched trees that clean rainwater (as shown above), a rainwater cistern to collect and store rainwater for future use, and a rainwater garden, among other unique features.

Pond cleanouts and dredging

Stormwater ponds are designed to capture runoff from impervious surfaces. They not only decrease downstream flooding but also prevent polluted runoff (runoff that contains sediment, oil, salt, and nutrients from plant materials) from contaminating lakes and rivers. The pond works by allowing sediment and associated pollutants to settle and remain until they can be removed and properly disposed of. Like other stormwater practices, stormwater ponds must be inspected and maintained to work effectively. Ponds also need to be dredged periodically (usually once every 10–20 years).

Stormwater operation and maintenance plans

Stormwater management systems that function effectively protect water quality, offer environmental benefits, and protect public safety. Operation and maintenance (O&M) plans for those systems not only help yield those benefits but also protect your infrastructure investment. Stormwater management systems should be inspected every year (often a few times a year) to look for sediment and debris accumulation, clogging, weeds, and damage. We recommend that clients take advantage of technology to make their O&M plans “living” documents.

Barr developed custom tools for the City of Edina, including an iPad checklist for use during inspections and an online GIS database and tracking tool to manage inspection progress and maintenance recommendations. The tool is optimized for MS4 tracking and reporting, streamlining the annual reporting process.

Barr staff inspect an underground stormwater treatment system in Edina, Minnesota.

Prioritizing stormwater infrastructure for maintenance

You establish priorities when you set your family’s budget. The same should be true when you consider maintenance for stormwater infrastructure. In either case, you need good data to make informed decisions.

Working with the Hennepin County Regional Railroad Authority (HCRRA), Barr developed a risk-based program to help manage its stormwater infrastructure. The risk assessment used spatial data of HCRRA’s stormwater infrastructure and other parameters such as topography, hydrology, soils, and information about county and public infrastructure (roads, trails, railroads, structures, etc.). Stormwater infrastructure condition and inspection data were used to evaluate the likelihood and possible consequences of infrastructure failure. A risk matrix was then created using the failure likelihood and failure consequence rankings to identify and prioritize actions related to ongoing inspection, maintenance, and replacement of HCRRA stormwater infrastructure.

Barr also helped the city of Calgary on a low-impact development assessment and monitoring and maintenance prioritization project to help evaluate the performance of their existing stormwater infrastructure and target efforts to improve and restore function.

Learn more

Well-maintained stormwater infrastructure is critical to our communities—preventing flooding and protecting water quality. A thoughtful inspection and maintenance protocol keeps it functioning and helps avoid unexpected, expensive repair or replacement costs. Whatever your operations and maintenance needs, Barr can help. Contact our team for help getting your stormwater management system on the road to better health.

Interested in learning more about watershed management? Join us at the 2023 Minnesota Watersheds Annual Conference and Trade Show in Alexandria, Minnesota, on November 28–December 1. Visit us at Booth #40 and attend the “Developing Strategies for Ecosystem Protection and Enhancement within Riley Purgatory Bluff Creek Watershed District (RPBCWD)” session on November 30, presented by Landscape Architect and Ecologist Fred Rozumalski and RPBCWD’s Terry Jeffery.

About the author

Nathan Campeau, vice president, senior water resources engineer, has two decades of experience in hydrologic and hydraulic analysis, flood-risk management, green infrastructure, and GIS. Nathan is a NASSCO-certified professional engineer (CO, MI, MN, WI) and an ENVISION-accredited professional. He works closely with watershed districts and cities on projects involving stormwater management, flood analysis and mitigation, and low-impact site design. Nathan has helped plan, implement, and maintain hundreds of green infrastructure practices.


Nathan Campeau, Vice President, Senior Water Resources Engineer
Nathan Campeau
Vice President, Senior Water Resources Engineer
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