A probabalistic methodology for estimating water quality effects from highway stormwater runoff

To assess the significance of pollutant loads from highways, in terms of the extent to which they may cause adverse impacts on a beneficial use, the cumulative frequency distribution of pollutant concentrations downstream of the highway discharge is computed and may be compared with concentration levels at which a particular adverse effect will be produced. The model described can be used to compute the frequency or recurrence of storm runoff events that result in violations of water quality criteria or other effects levels. Data collected at highway sites throughout the US are used to evaluate the statistical properties of highway runoff flows and concentrations; regional values for precipitation and streamflow from standard monitoring programs are used to provide the other necessary input parameters.