Hydraulic Modifications To Achieve Watershed Total Maximum Daily Loads

Focus Area

Water Quality/Wetlands


Natural Resources







Research Idea Scope

TERI Administrator Note (2007): Funded as NCHRP Project 25-31 Hydraulic Modifications to Existing Drainage Infrastructure in Ultra-Urban Areas to Achieve Watershed Total Maximum Daily Loads

The transportation community is faced with a need to mitigate pollutant loadings from existing facilities to achieve watershed TMDLs. The mitigation need is made more acute as the land use around transportation facilities competes for a finite amount of allowable pollutant load. Existing transportation infrastructure includes extensive hydraulic facilities, which may be suitable for retrofit to provide such water quality benefits. Examples would include catch basin/inlet modifications, detention pond retrofit to embankments and/or outlet works, riser structures added to culvert/embankment systems, and the fostering of pipe storage in storm drains. The project is oriented to these and other possibilities.

Transportation administrators are under pressure to address water quality concerns, some of which are driven by TMDL litigation. Reactive solutions can be expensive and unwarranted even though they can relieve short-term pressure. There are no coordinated programs to address how the existing infrastructure can be modified to benefit water quality. This problem is critical as the TMDL process moves forward, and agencies are spending money for TMDL implementation but do not have focused direction with respect to exploiting existing infrastructure or meaningful partnering. The mitigation of the adverse water quality of highway runoff is a modern need. Existing infrastructure addresses getting rid of water and minimizing the spread of water in the gutters. This infrastructure offers several possibilities for retrofits to enable water quality mitigation. Focusing on what can be done with what we have is an immediate need that can address TMDL implementation in a cost-effective manner.

The proposed research includes the following activities:

1. Identify any of the elements of existing hydraulic facilities that may be modified or enhanced to provide water quality benefits;
2. Review operation and design principles that can enable feasible and cost-effective modifications-hard design and/or management change;
3. Find and evaluate existing retrofits;
4. Install promising prototypes for evaluation through an annual monitoring cycle;
5. Generate implementation guidance for the retrofit of hydraulic facilities; and
6. Identify watershed partners that will share investment in modifications.

Suggested By

Transportation Research Board 2002 Environmental Research Needs Conference Notes

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