A co-financing model for the mitigation of highway runoff pollution

Highway runoff impacts urban and natural ecosystems negatively. A financing model, that is economically feasible and accepted by all stakeholders, has been a limitation for the implementation of pollution control measures. A case-study on a 279-km Portuguese Highway is presented as a basis for a co-financing model. Runoff pollution load was estimated for quality indicators (TSS, COD, Zn, Cu, Pb), and the total cost of infiltration trenches, sand filters, bioretention filters, wet basins, dry basins and constructed wetlands systems was computed for four catchment scenarios. The effect of the equivalent catchment size and system type on the total cost was evaluated. The users 'Willingness to Pay' (defined as pay-per-user and availability to participate actively and financially) was assessed through a survey (1192 responses). A proposed co-financing model suggests that citizens will participate up to 36.8% of the constructed wetlands cost. This multidisciplinary approach results in potential outcomes that include a legal framework, proven technical solutions, and users' environmental responsibility.