Nutrient (Nitrogen/Phosphorus) Management and Source Control

Focus Area

Water Quality/Wetlands


Natural Resources







Research Idea Scope

EPA has reported recently that the amount of nitrogen and phosphorus pollution entering our waters has escalated dramatically over the last 50 years, and that this trend will continue with US
population growth (EPA 2011). In addition, EPA has developed numeric nutrient criteria in Florida and has suggested numeric requirements be incorporated into NPDES Permits for TMDLs (EPA 2010). EPA has also begun dialogue to work in partnership with states to address phosphorus and nitrogen pollution using a framework for state nutrient reductions (EPA 2011). EPA acknowledges that nutrient pollution has the potential to become one of the costliest and most challenging environmental problems.

Many state DOTs have spent millions of dollars and are planning to spend billions of dollars collectively to comply with nutrient related regulations over the next several decades. DOTs
have invested considerable research dollars in how to best control nutrient sourcing in the highway environment and have engaged in regulation development to better represent DOT contribution to nutrient loading. While significant progress has been made in understanding nitrogen and phosphorous cycling and nutrient management approaches in the highway environment, there is a need to document what has been learned, and develop equitable approaches to nutrient management in the linear environment on a watershed scale.

Therefore, it is recommended that additional nutrient research be performed to facilitate effective nutrient management and provide tools for DOTs:

  • Quantify and develop concepts of nutrient sourcing in the highway environment. This would include providing a clear definition of nutrient sources and discuss variations in load due to geographic location.
  • Develop and identify a summary of nutrient contributing mechanisms in the highway environment and identify loading rates, cost of removal, and comparison to other nutrient sources in the watershed.
  • Develop a nutrient adaptive management framework for DOTs to implement that could be included in NPDES permits and address EPA’s current framework for nutrient management.

Urgency and Payoff

This research is intended to provide a common ground between the highway and regulatory communities, targeting environmentally responsible nutrient management that employs feasible, economically prudent strategies for the highway environment. To increase the probability of success, the regulatory community, highway drainage community, and the environmental water chemistry community should participate in both the development and review of the research results, with members of these communities included in the research team and review panel.

To highway agencies, nutrients are an essential element to maintaining the roadway turf and landscaping, an essential part of erosion control and pollution abatement. Thus, our focus must
be to manage, not just eliminate nutrients. Given the limitations of a public, linear facility, and the scarcity of public highway funding, we need highway specific, cost effective treatment methods to satisfy our need to remove excess nutrients. These tools are expected to include both source controls and nutrient removal methodology.

Urgency – Nutrient management for DOTs has taken on a high priority with the proliferation of nutrient TMLDs in many states.  There are few viable methods for nutrient reduction in highway runoff and a concise accounting of the sources as well as a framework for reduction is needed.

Suggested By

AASHTO Stormwater Community of Practice - State of the Practice Report, May 2011