Assessment of existing roadside swales with engineered filter soil: I. Characterization and lifetime expectancy.

Roadside infiltration swales with well-defined soil mixtures (filter soil) for the enhancement of both infiltration and treatment of stormwater runoff from roads and parking areas have been common practice in Germany for approximately two decades. Although the systems have proven hydraulically effective, their treatment efficiency and thus lifetime expectancies are not sufficiently documented. The lack of documentation restricts the implementation of new such systems in Germany as well as other countries.