Identification of Constituents of Concern for Highways

Focus Area

Water Quality/Wetlands


Natural Resources






1-2 years

Research Idea Scope


Many NPDES Permits require DOTs to identify constituents of concern
from highway and support facilities. Constituent of concern are known or
emerging potential pollutants that are generated within the right of way. The
source of some constituents may not be completely understood, or the relative
load of the constituent from various sources within and external to the right
of way may not be known. It is also important to understand the mobility of the
pollutant within the environment, changes, if any, it may undergo when mixing
with the receiving water, and the potential beneficial use impairments. These
questions are especially important for emerging pollutants for which there may
be limited information or data.

Research Objective:

The purpose of the research is to develop a standardized approach for
determining constituents of concern for DOTs. The framework will allow for a
universal application, but will be developed considering DOT facilities and
land uses. The research will also document the mobility of the constituent, and
its fate in the environment. A procedure will be developed to assess the
relative contribution of the constituent from various sources in the
environment, and to determine the potential impact on receiving water
beneficial uses.

Specific Tasks:

Task 1 – Literature Review,
Compilation of Data and Survey of State Practices and Experience

The literature review and the data compilation will focus on the
following areas

Highway characterization data, selected from a
broad range of geographic conditions and traffic levels;

Source studies for known pollutants, in highway

Emerging constituents of concern in highway

Methods to assess impact to beneficial uses.

Task 2 – Method to
Determine Highway Runoff Constituents of Concern

A framework will be developed that can be applied by the DOT to
determine a “suite” of constituents of concern the will be the focus of the
DOT’s stormwater program. The framework will provide a stepwise procedure for
DOTs to assess their characterization data, as well as emerging constituents of
concern to develop a final “list” for the stormwater program.

Task 3 – Evaluation of
Sources, Fate and Transport of Constituents of Concern

This task will develop as standardized procedure to assess the
relative sources of the identified constituent. This will allow DOTs to develop
effective BMPs that target the source and allow a basis to establish a target
effluent concentration using MEP technology. A method to determine the fate of
the constituent in the environment will also be developed, potential
transformations and ultimately, impact of the constituent on the beneficial
uses in the receiving water. 

Suggested By

Center for Environmental Excellence by AASHTO Stormwater Management Community of Practice