Multi-cell water detention pond for improved storm water quality

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Stormwater retention ponds are used extensively in both small and large municipalities. The ponds collect storm runoff from surrounding areas and, after the water is retained within a pond for some period, its discharge is released into the environment (e.g. a river). The ponds are used to help prevent flooding and to improve water quality. The ponds are designed according to best management practices, however these practices were not developed with due consideration to the flow patterns within the pond. It is known that the way the flow moves through the pond significantly influences how much sediment and pollutants are removed. This proposal is to test a new design for a multi-cell stormwater retention pond that was developed based on computational fluid dynamics modeling of the pond. The design is such that it is expected to increase sediment and pollutant removal in the ponds over current standards while lessening maintenance costs. It is designed so that most sediment should drop out in the first cell of the pond and so that all of the fluid within the cell will be moving continuously. The ponds use a vortex motion within the circular cells that is created by installing an outlet of each cell at the centre of each cell. Further, the piping of the ponds have been designed in such a way that a cell can easily be taking offline for maintenance. To test the design, first a hydraulic model of the multi-cell design will be created to assess the flow conditions in the cells. Then, sediment will be added to the flow to assess the deposition patterns. This will then be modelled using computational fluid dynamics (CFD) software. Measurements of flow, water quality, and sediment deposition from an existing pond will then be used to test the accuracy of the CFD for field conditions. These will then be applied to assess the water quality improvements that would be seen in the multi-cell pond over that seen at the existing pond.