Research Idea Details

 

"Green" or "Low Impact Development" design features and management practices, such as rain gardens, vegetated swales, and permeable paving systems, can be important elements of storm water management systems for highway corridors. These design features and management practices may have considerable advantages as compared with conventional storm water management practices, as discussed further below, but presently these practices are used sparingly. The lack of compiled, analyzed, and easily-accessible information on the performance of green design features and management practices is a barrier to their implementation. Without accurate, reliable, and quantified information on the performance and benefits of green design features and management practices, engineers working on highway projects cannot account for the performance of the management practices, and may end up designing redundant systems or may avoid these features entirely. In addition, budget decision-makers need quantified information on the performance and benefits of these management practices so they can ensure transportation project dollars are being well-spent. 

 

A National Cooperative Highway Research Program project, number 25-20(01), was undertaken beginning in 2002 to address the need for accurate, reliable information on the performance of Best Management Practices for highway runoff control. This proposed research project would complement and supplement the Project 25-20(01) work.

 

 

The objective this research is to directly address the need for accurate, reliable information on the performance of green design features and management practices for management of storm water in highway corridors, with specific focus on runoff volumes. Project 25-20(01) research will provide valuable information on BMP pollutant removal performance, as well as an assessment of the potential effectiveness and suitability of LID design strategies for addressing storm water impacts from highways. This proposed research would build on the 25-20(01) work by providing quantified information on the performance of BMPs in controlling run-off volumes. Once compiled and analyzed, quantified information on the performance and benefits of green design features and management practices can be made available to highway engineers and project planners for use in decision-making on specific projects. The results of the research can potentially be provided to users in the form of reference tables/databases and run-off curves. 

 

 

Run-off from impervious surfaces, including streets and highways, is a stressor for many streams, rivers, and lakes. While conventional storm water management measures, such as enclosed sewers and detention ponds, efficiently remove excess rain water from highway corridors and can cap peak flow amounts, these practices do not completely solve the run-off problem. The total volume of water being released to surface water bodies is significantly higher as compared to the predevelopment condition. Impervious surfaces can also adversely impact streams in dry weather conditions — shallow aquifers which would normally contribute flow to streams and wetlands in low flow conditions are less able to perform this function because the impervious surfaces reduce groundwater recharge. 

 

Green design features and management practices, such as rain gardens, vegetated swales, and permeable paving systems, are intended to address these environmental impacts by managing some or all of the storm water on a site through infiltration, retention and evapotranspiration. In some cases using green design features and management practices may be more cost-effective than conventional storm water management practices.

 

 

1. Research Plan. The first step for the contractor engaged to do this work will be to develop a plan for compiling, analyzing, and presenting data on the performance of green design features and management practices in controlling run-off volumes. The research should be done following rigorous protocols so the results can be used by engineers working on highway projects. The focus will be on green design features and management practices in and near highway corridors, for example vegetated swales in center medians or adjacent to roadways, permeable pavement sections of highway shoulder. In developing the research plan the contractor should review methodologies for assessing the performance of storm water BMPs, such as the Technology Acceptance Reciprocity Partnership (TARP) protocol for storm water best management practice demonstrations, and consult with University researchers working on BMP performance projects (University of Illinois, University of New Hampshire, University of Vermont, University of Wisconsin). Existing research and reports should be reviewed (e.g.,

25-20(01) work, Performance of Grassed Swales Along East Coast Highways, Center for Watershed Protection, 2003), and Federal and State highway design guidelines should be examined.

 

2. Survey of Existing Data and Studies. The second step will most likely be a survey of existing data and studies on the performance of green design features and management practices. Data and studies will be screened and classified. Data/studies that do not meet acceptance criteria will not be utilized.  

 

3. Analysis of Existing Data and Studies. The third step will likely be intensive analysis of the data on the performance of the green design features and BMPs, with a focus on effectiveness in reducing runoff volumes. Additional considerations may be limitations on use of the design features/management practices.  

 

4. Presentation of Findings. Findings will be compiled, and conclusions and recommendations will be presented, as appropriate, based on the data analysis. The deliverables will be a compilation of existing information (e.g., a reference table or database providing information on the performance of the BMPs) and a research agenda detailing the key data gaps and research needs. The data elements provided in the reference table/data should include data elements necessary for the development of run-off curves that could potentially be used in a possible enhancement to the NRCS run-off model TR-55.