Characteristics of the event mean concentration (EMC) from rainfall runoff on an urban highway

The purpose of this study was to investigate the characterization of the event mean concentration (EMC) of runoff during heavy precipitation events on highways. Highway runoff quality data were collected from the 7th highway, in South Korea during 2007–2009. The samples were analyzed for runoff quantity and quality parameters such as CODcr, TSS, TPHs, TKN, NO3, TP, PO4 and six heavy metals, e.g., As, Cu, Cd, Ni, Pb and Zn. Analysis of resulting hydrographs and pollutant graphs indicates that the peak of the pollutant concentrations in runoff occurs 20 min after the first rainfall runoff occurrence. The first flush effect depends on the preceding dry period and the rainfall intensity. The results of this study can be used as a reference for water quality management of urban highways.

Research highlights
► Field test on urban highway were performed to 50 of 100 storm events for 3 years.
► The peak pollutant concentrations occurs 20 min after the first runoff.
► The first flush effect depends on the preceding dry period and rainfall intensity.
► Relationship between runoff and event mean concentration for SS and COD.
► A crest of the EMC by 70–80 m3/event and decreasing EMC after 70–80 m3/event.