Volume Reduction of Highway Runoff in Urban Areas: Final Report and NCHRP Report 802 Appendices C through F (2015) / Chapter Skim
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Pages 7-19
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C H A P T E R 2 Research Approach To meet the objectives of the project, the research approach was divided into five tasks as introduced below. • Task 1 included characterizing the urban highway environment relative to runoff volume reduction.
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• Characterize the key types of urban highway projects and conditions that the Guidance Manual must support, • Identify the key physical parameters that are most influential in volume reduction effectiveness and feasibility, and • Identify site and watershed information and assessment needs for project planners and designers seeking to apply VRAs. Subtask 1.1: Summarize the Regulatory Context Stormwater quality regulations were identified as the main motivations for the use of stormwater VRAs.
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In addition, this task identified the key constraints for volume reduction that are expected to be encountered in the types of urban highway projects that the Guidance Manual supports. The research team reviewed and summarized the challenges for implementing volume reduction, including, but not limited to: • Physical Limitations: Constrained urban highway settings by definition have limited surface area within the right-of-way (ROW)
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The purpose of this subtask was to develop information to educate users on basic principles of volume reduction and what levels of reduction are potentially reasonable and not. Additionally, the identification of key parameters was used to identify site and watershed assessment needs, as well as to formulate and communicate the key research needs to be addressed in subsequent detailed analyses (Task 4)
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Subtask 2.2: Develop a Preliminary Menu of Volume Reduction Approaches and Evaluation Methods The research team compiled a preliminary inventory of conventional and innovative VRAs based on results of Subtask 2.1. From this inventory, the team worked with the Project Panel to select the most promising nine (9)
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This guidance was also intended to provide technical basis for where VRAs may not be feasible or appropriate. The selection and evaluation matrices, flowcharts, and worksheets include considerations related to the following: Feasibility criteria - The research team investigated volume reduction implementation feasibility and provided guidance for considering the following factors in determining the applicability, feasibility, and desirability of a VRA for a given site: • Climate and local hydrology • Availability of space and elevation differential • Site soil infiltrative capacity limitations • Potential for utility conflicts and impacts to existing infrastructure • Potential impacts to ground water and • Various other potential feasibility criteria.
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Subtask 3.2: Summarize Feasibility-related Research Gaps and Identify Focused Analysis Topics As an outcome of the previous tasks, the research team identified areas that were considered to be significant research gaps and/or opportunities to consolidate available research to be applicable to the urban highway environment. Such research gaps and/or opportunities were documented and recommended for further study when encountered.
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relevance to users of the Guidance Manual. These findings were incorporated in the main body of the Guidance Manual, as appropriate, and the more detailed supporting documentation was incorporated into the Guidance Manual as White Papers.
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References to Final Work Products The results of this task are presented in their entirety as White Papers #1 through 4 (Appendices C through F, respectively)
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• VRA design adaptations to improve volume reduction performance and/or applicability to the urban highway environment (Section 4.2; Appendix A)
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goals of these parts of the Guidance Manual as it applies to their situation. However, they also recognized that other DOTs would potentially benefit from these parts of the Guidance Manual.
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quality calculations, the resulting guidance and tools from NCHRP Project 25-40 provide more information and water quality calculations. • The Tool currently accepts inputs in the form of the design volume, flowrate, or tributary area ratio and translates this input (with the user-defined geometric assumptions specific to a VRA)
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• Preliminary Draft Final Report documenting the entire research approach that includes an executive summary of the research results. • Revised Final Guidance following one round of Panel comments; including response to comments.
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