Environmental Review Toolkit

Stormwater Management and Water Quality

When precipitation occurs over highways and other impervious surfaces, the resulting stormwater can carry debris, sediment, and chemicals into water sources, diminishing their quality. In addition to the stormwater runoff that carries sediment and pollutants into water sources, highway construction and maintenance activities have potential to affect nearby bodies of water.

The FHWA provides the following reports and guidance for controlling stormwater runoff along highways and minimizing the effects of transportation projects on water quality:

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  • Determining the State of the Practice in Data Collection and Performance Measurement of Stormwater Best Management Practices, 2014 - The objective of this research project is to assess the state of practice of data collection and performance measurement in stormwater management programs at state Departments of Transportation (DOTs). Specifically, this study evaluates if it is feasible to develop performance measures for stormwater that state DOTs can use in performance-based planning and programming. The study focused on both construction-phase as well as post-construction application of BMPs to protect water quality.
  • Evaluation of Best Management Practices for Highway Runoff Control, 2006 - This report focuses on improving the scientific and technical knowledge base for the selection of best management practices (BMPs) through a better understanding of BMP performance and application. This report documents an extensive program of research on the characterization of BMPs and stormwater, and the influence of factors such as land use practice, hydraulic characteristics, regional factors, and performance evaluation. The report includes a CD containing a spreadsheet model and three additional volumes: User's Guide for BMP/LID Selection, Appendices to the User's Guide, and Low Impact Development Design Manual for Highway Runoff Control.
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  • Remotely Monitoring Water Quality Near Highways - A Sustainable Solution, 2015 - Collecting water quality data on streams located near highways can be challenging in remote and difficult-to-reach locations. Obtaining and transporting water samples is time-consuming, expensive, and sometimes dangerous. Another key challenge is that transportation agencies can miss the release of toxins and pollutants that occur in a short time period or the first flush of stormwater runoff from highways. Collecting water quality data is crucial, however, to State departments of transportation in their effort to meet U.S. Environmental Protection Agency National Pollutant Discharge Elimination System permit requirements, particularly during the first flushes of spring stormwater runoff.

    Placing sensors directly in the water to collect data is an appealing solution, but these in situ sensors typically rely on batteries that have to be replaced as often as every 3 weeks. Designing a renewable and self-sustaining onsite system is the goal of the Exploratory Advanced Research (EAR) Program project, "A Remote, Self-Sustained System for Monitoring Water Quality Near Highways." Montana State University conducted this research, which was funded by the Federal Highway Administration (FHWA).
  • Quantifying the Components of Impervious Surfaces, 2007 - The objectives of this study are to (1) determine the makeup of total area and the relative contribution of individual components; and (2) assess the accuracy of various techniques in use for determining total impervious area. Six urban and suburban watersheds were selected for study that represent a wide geographic distribution across the country. High-resolution orthoimagery (1meter or better) was obtained for each watershed. Six classes of impervious cover were manually digitized as polygon features in a geographic information systems (GIS) environment. Relevant GIS data were obtained from County or City GIS departments. The six classes of cover were roads, buildings, parking lots, driveways, sidewalks, and other (such as sport courts). Quality control was provided by independent validation and mapping spot checks. The total area for each impervious surface class was totaled for the six watersheds and the percentage of each class was calculated against the total area of impervious cover. The largest area class of impervious cover was buildings at 29.1percent, followed by roads (28.3 percent), and parking lots (24.8 percent); with the remaining three totaling 14-percent - driveways, sidewalks, and other, where other were any other features that were not contained within the first five.
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  • Stochastic Empirical Loading Dilution Model (SELDM), 2013 - The USGS, in cooperation with the FHWA, developed the Stochastic Empirical Loading and Dilution Model (SELDM) to replace the FHWA runoff-quality model developed in the 1980's and published in 1990. That model was limited to a few water-quality constituents, was based on the assumption that upstream concentrations are equal to zero, was based on water-quality standards from the 1980's, was not compatible with newer operating systems, and there was no mechanism for continuing model support. SELDM is designed as a tool that can be used to transform disparate and complex scientific data into meaningful information about the risk for adverse effects of runoff on receiving waters, the potential need for mitigation measures, and the potential effectiveness of such management measures for reducing these risks. SELDM is designed to help develop planning-level estimates of event mean concentrations, flows and loads from a highway site and an upstream or lake basin. The model has been tested by the FHWA, many State DOTs, the EPA, and several other regulatory agencies. This resulted in a robust model that will be acceptable to DOTs, regulators, and resource-management agencies.
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