![]() ![]() Among the contaminants, suspended solids are the most abundant contaminant in highway runoffs (Torres 2010). On every highway segment, these contaminants need to be controlled and quantified for the sustainability of water and land resources. A diversified nature of organic and inorganic contaminants can be found in highway stormwater runoffs (Dang et al. The highways add a large amount of water and, if contaminated, can completely alter the environment of receiving streams (Kriech and Osborn 2022 Calabro 2010). ![]() ![]() Highways are one of the primary sources of contaminants to the receiving water environment in an urban environment (Flint and Davis 2007). The first flush portion (initial 25% of runoff) of highway runoff poses a higher threat to the receiving environment than the later runoff volumes. The study concluded that the risk from contaminants in highway stormwater depends particularly on the specific highway sections’ properties. Total suspended solids are the most threatening contaminant in highway runoffs. The analysis showed that the highway characteristics significantly affect contaminant concentrations, but storm characteristics on contaminant concentrations are not found to be significant. The risk assessment was conducted by the analysis of variance. The event mean concentrations of dissolved organic carbon (50–145 mg/L), total suspended solids (1500–3900 mg/L), chromium (0.25–0.45 mg/L), and lead (0.1–0.8 mg/L) are found to be higher than the environmental quality standards. The highway stormwater was monitored for organics, metals, solids, and macro-nutrients at three highway sections. These values are also correlated with highway characteristics (area, slope, and traffic count) and storm characteristics (storm depth, cumulative runoff volume, antecedent dry days, and cumulative flow). Event mean concentrations have been used as baseline numeric values for calculating the risk of discharging highway stormwater directly into the water bodies. For this study, three highway segments were selected in the city of Rawalpindi, Pakistan. Therefore, a numeric and straightforward risk assessment protocol has been developed in this study that minimizes the errors. The conventional risk analysis protocols for directly discharging highway runoff are prone to systematic and judgmental errors. Highway stormwater runoff pollution has become a severe risk factor for water bodies nowadays. ![]()
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