National Academies Press: OpenBook

A Watershed Approach to Mitigating Stormwater Impacts (2017)

Chapter: Chapter 8 - Conclusions

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Page 94
Suggested Citation:"Chapter 8 - Conclusions." National Academies of Sciences, Engineering, and Medicine. 2017. A Watershed Approach to Mitigating Stormwater Impacts. Washington, DC: The National Academies Press. doi: 10.17226/24753.
Page 94

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94 C H A P T E R 8 Conclusions Meeting the requirements of stormwater regulations and water resources protection are emerging as two of the most critical environmental requirements DOTs must manage for the delivery and maintenance of roadway projects and facilities. Addressing stormwater issues in a project-by-project fashion, however, can be very inefficient and much less effective in actually addressing important watershed water quality and habitat issues. By taking a watershed-based approach to mitigation for stormwater impacts, DOTs can often realize more cost-effective and environmentally superior alternatives for compliance with existing and emerging regulations. By allowing off-site mitigation using a watershed approach, whether in-kind or out-of-kind, a more efficient and cost-effective mitigation solution, that truly provides water quality and habitat improvements that are beyond what can be achieved on-site, can be attained. The WBSMT was developed to aid in identifying mitigation opportunities and to provide a quantified approach for accounting for on-site mitigation and for equivalency when selecting off-site mitigation options. Tools such as this must be developed to support cost-effective watershed-based storm- water mitigation options that are acceptable to the regulatory community. Additional research is needed to better understand the relationship between watershed processes, receiving water health, and ecosystem services before more robust linkages between out-of-kind mitigation and stormwater impacts can be made. Given the complexities of these relationships and the limited availability of mitigation performance data, it may be several decades or longer before the state of the science can support the development of a tool that can reliably quantify the ecosystem benefits of alternative stormwater mitigation measures. Until such time, it will be necessary to rely upon qualitative metrics or professional consensus-based factors, such as those currently used in the WBSMT.

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TRB's National Cooperative Highway Research Program (NCHRP) Research Report 840: A Watershed Approach to Mitigating Stormwater Impacts provides a practical decision-making framework that will enable state departments of transportation (DOTs) to identify and implement offsite cost-effective and environmentally beneficial water quality solutions for stormwater impacts when onsite treatment and/or mitigation is not possible within the right-of-way.

The report is accompanied by the Watershed-Based Stormwater Mitigation Toolbox, a Microsoft Excel-based program to facilitate the characterization of the project watershed and the identification of mitigation options at the planning level.

Disclaimer - This tool is offered as is, without warranty or promise of support of any kind either expressed or implied. Under no circumstance will the National Academy of Sciences, Engineering, and Medicine or the Transportation Research Board (collectively "TRB") be liable for any loss or damage caused by the installation or operation of this product. TRB makes no representation or warranty of any kind, expressed or implied, in fact or in law, including without limitation, the warranty of merchantability or the warranty of fitness for a particular purpose, and shall not in any case be liable for any consequential or special damages.

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