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Characteristics of run-off quality and pollution loading from a highway toll-gate

The Ministry of Environment of the Republic of Korea has been seriously considering implementing a TMDL (Total Maximum Daily Load) as a mandatory requirement on watersheds because of the potential water pollution from highway toll-gates. The purpose of this study was to investigate the characteristics of run-off quality and pollution loading during rainfall events at a highway toll-gate. Samples were analysed for run-off quantity and quality parameters such as CODcr, TSS, total petroleum hydrocarbons, nutrients (TKN, NO3, TP and PO4) and several heavy metals (As, Cu, Cd, Ni, Pb and Zn). Based on a hydrograph and pollutant graph analysis, the pollutant concentration peak occurred in the run-off 10 minutes after the onset of rainfall. The typical first flush effect on the concentration depended on the rainfall intensity and the number of antecedent dry days. The relationships between the run-off and the event mean concentrations of the pollutants (e.g. TSS and COD) were described by general nonlinear equations. For governmental implementation of TMDL policies, the estimation of the cumulative TSS load was 1032 kg/(ha·yr) in 2007, 963.44 kg/(ha·yr) in 2008 and 847.21 kg/(ha·yr) in 2009. This information can lead to improved practical water quality management practices and reduced costs of improving water quality.