In this paper it is argued that roadways change the quantity and quality of natural runoff; that these changes can significantly impair aquatic habitat; that flow variations, obstructions, destruction of riparian habitat, temperature, turbidity/suspended solids (SS), salt, and trace chemicals from roadways are key factors whose effects can be readily reduced, but that temperature and silt loads are two of the primary culprits; and that roadways designed to infiltrate runoff within the right-of-way are environmentally better than those designed to carry runoff quickly and directly to outlet. Roadway stormwater that (a) shows high wet-weather flow rates, (b) is hot, (c) is turbid with a high concentration of particulates, and (d) may be salty, - is likely to also comprise a broth of many other toxins. Removal of the primary stressors (flow variations, temperature, and suspended sediments) will substantially reduce other toxins as well. Such removal may not be sufficient, because the synergistic, additive or antagonistic effects (of all constituents in the broth) on fish and invertebrates is poorly known, and deserve long-term and detailed study. It is not suggested that there is a single Ontario solution: what may work in southern Ontario may not work in northern Ontario, because of different traffic densities, average temperatures, geomorphology, geochemistry, hydrology, road salt applications, different stages of the evolving impacted ecosystem, and so on. (A)
Abstract