Multipurpose Benefits of Regional Stormwater Treatment Facilities

Preserving the watershed regime via a “treatment train” approach

As public and private entities continue to embrace low-impact development (LID) and associated micro-scale onsite facilities such as porous landscape detention, parking lot swales, rain gardens, and others, it is important to recognize that larger, “regional” stormwater management facilities are valuable as well. Indeed, the multipurpose benefits of regional facilities such as wet ponds, extended detention basins, full-spectrum detention, aboveground sand filter basins, wetlands, and wide major drainageways that are natural in appearance and that integrate water-quality and channel stability features are numerous. When combined, LID and regional facilities accomplish the ultimate goal of preservation of the watershed regime via a “treatment train” approach.

Photographs 1 though 4 illustrate representative regional BMPs. Regional facilities can:

• Provide much-needed open space in urban areas and integrate nicely into a network of undeveloped major drainageways that feature parks, trails, ponds, wetlands, and ample “green space.”
• Provide active and passive public recreational opportunities, in a safe manner.
• Create wildlife and aquatic life habitat.
• Increase residential and commercial property values and neighborhood appeal.
• Attenuate peak discharges from new and existing development for a wide range of storms.
• Play an important role in maintaining downstream channel stability.
• Facilitate maintenance and reduce maintenance costs, by storing/treating a comparatively large runoff volume for larger tributary areas into few locations.
• Be utilized by land planners and landscape architects as strategic features in overall community development plans.
• Be integrated into major drainageway master plans, site drainage plans, watershed plans, and hydrologic models, due to their relatively large, discrete nature (by contrast, it is typically not practical to integrate large numbers of small LID features into large-scale hydrologic models).

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The authors acknowledge that there are many regional facilities in the United States that are unsightly, unsafe, poorly maintained, and ineffective from the standpoints of hydrologic and/or water-quality function, and in general, are community liabilities rather than community assets. Nevertheless, experience also shows that with proper planning, design, construction, and assured long-term monitoring and maintenance, the benefits of regional facilities listed above are attainable, and that such facilities can be vital components in public and private stormwater management programs and offer the advantages listed earlier. At the same time, there are few, if any, programs/communities in United States that inspect and assure continued maintenance and design function of multiple LID facilities where they are used, and their long-term fates will only be determined over the coming years.
We hope that stormwater planners and designers will embrace the philosophy of utilizing LID as source stormwater runoff controls, along with larger facilities at the regional level. We look forward to receiving observations from other readers of Stormwater on this subject.

Author's Bio: Jonathan Jones, P.E., is chief executive officer, with Wright Water Engineers Inc. in Denver, CO.

Author's Bio: Jane Clary, is a senior water resources scientist, with Wright Water Engineers Inc. in Denver, CO.

Author's Bio: Andrew Earles, Ph.D., P.E., is with Wright Water Engineer Inc. in Denver, CO.

Author's Bio: Ben Urbonas, P.E., is manager of the Master Planning Program for the Urban Drainage & Flood Control District in Denver.

Author's Bio: James Guo, Ph.D., P.E., is a professor in the University of Colorado's Civil Engineering Department.