Practices for managing stormwater runoff have evolved over the years. Changes to regulations, land use and weather patterns impact how transportation agencies integrate stormwater control options into road and waterway networks. Local agencies have used a stormwater maintenance guide produced by the Local Road Research Board (LRRB) in 2009. Over a decade of new research and the development of new tools for stormwater control necessitated revisions to the guidance document. The updated Stormwater BMP Inspection and Maintenance Resource Guide provides recommendations for enhancing traditional stormwater practices and presents new, innovative strategies and guidance on stormwater best management practices (BMPs).
As weather patterns shift and the severity of storms increases, managing stormwater runoff is important to prevent flooding and associated safety risks, environmental impacts; and damage to property, roads and bridges. Providing an interface between natural and built environments, stormwater control is governed by regulation and must be tailored to accommodate land use and management objectives. The 2009 Stormwater Maintenance BMP Resource Guide, produced by LRRB, provided guidance for local governments to implement and maintain stormwater BMPs.
Stormwater ponds used to be the primary proactive practice for managing runoff. But technologies for stormwater management have evolved to enable more effective removable of soluble pollutants, as is required by federal regulations. New technologies include infiltration, bioretention and various filter materials. LRRB and MnDOT have also sponsored research projects that further inform stormwater BMPs.
LRRB was interested in revising the 2009 guide to focus on inspection and maintenance of stormwater BMPs with updated approaches to commonly used and new, innovative BMPs.
What Did We Do?
While the 2009 Stormwater Maintenance BMP Resource Guide provided a comprehensive resource for installing, operating and maintaining stormwater BMPs, several revisions were needed. Investigators first reviewed the stormwater literature as well as the Minnesota Stormwater Manual, a comprehensive living document managed by the Minnesota Pollution Control Agency that covers numerous general stormwater concepts and issues, regulatory concerns, pollutants and modeling.
“The range of best management strategies detailed in the new manual will support county engineers in choosing the right stormwater practices for their projects,” said Brian Giese, county engineer, Pope County.
Other literature informing the revisions included research on stormwater management issues, such as a recent LRRB-sponsored study that found runoff from rural roads contains less of some pollutants than high-volume urban roads and provided recommendations for stormwater treatments for low-volume roads. Another recent LRRB study analyzed the numerous factors that affect how well stormwater ponds retain phosphorus. In that study, researchers produced a pond assessment tool and suggested guidance updates.
To update the 2009 guide, investigators sought to produce an accessible document that explained the reasoning for using various stormwater BMPs to support organizations and agencies of all sizes, capacities and levels of experience in managing stormwater.
What Was the Result?
The revised Stormwater BMP Inspection and Maintenance Resource Guide recognizes that stormwater BMPs “require a substantial commitment to maintenance, including regular inspections and assessments.” The guide informs users of benefits, limitations, field inspection resources and maintenance recommendations for various stormwater BMPs such as stormwater ponds, wetlands, bioretention, sedimentation chambers and infiltration.
Among the new BMPs in the guide are floating treatment wetlands—vegetated islands within stormwater ponds that can increase pollutant retention—and stormwater harvesting, which involves collecting, treating and potentially reusing runoff to reduce demand on current water supply systems. Additionally, a new chapter covers how to best meet stormwater management objectives with respect to specific pollutants, including solid particles, phosphorus, nitrogen, metals, chloride, pathogens and organic chemicals.
What’s Next?
The revised Stormwater BMP Inspection and Maintenance Resource Guide is available online. Its availability will be announced at conferences, in various publications, and through educational training, where the guide will be a resource for professional development and certification courses and programs. Regular updates would keep the guide current as stormwater management strategies evolve and climate and infrastructure needs continue to change.
Crossroads 