Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff
State DOTs are increasingly subject to Total Maximum Daily Load (TMDL) requirements for water quality improvement
that are implemented through National Pollutant Discharge Elimination System (NPDES) permits.
As a result, state
DOTs may incur significant costs to construct, operate, maintain, and monitor performance
of best management practices and other stormwater treatment facilities that treat
stormwater from sources outside the right-of-way, as well as stormwater from roadway
sources.
TRB’s National Cooperative Highway Research Program
(NCHRP) Research Report 918: Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff describes how to evaluate TMDLs and develop a plan
to comply with the requirements of a TMDL. The methods provide a robust approach
to determining the pollutants of concern and how to assess the contribution of the roadway
while understanding other important factors that affect overall pollutant loads, including
adjacent land uses and watershed conditions and characteristics.
A set of
presentation slides summarizing the project that developed the report is available for download.
This Summary Last Modified On: 10/18/2019