The attenuation and treatment of runoff using sand tanks

This paper describes how the runoff from roads and other paved surfaces can be attenuated and treated by a sand/gravel filter tank. It proposes a design for such a tank and gives details of tests carried out on a two-dimensional (2D) section of the tank. These tests showed that significant reductions were achieved in suspended solids, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and concentrations of road salt, although there was little effect on the levels of metals. This work also shows how the hydraulic performance of such a tank can be represented by a double-reservoir model using both design storm events and historic rainfall data. A 2D finite difference model of the tank is also described.