Efficiency and flow regime of a highway stormwater detention pond in Washington, USA

Wet detention ponds are a preferable alternative in treating stormwater runoff. Literature suggests that a detention pond's efficiency in removing principal pollutants of concern, TSS and metals, is highly variable and is affected by a complex array of factors including its geographic location. The objective of this paper was to investigate the TSS and metal removal efficiency of a highway stormwater detention pond in Spokane, Washington along with its flow regime. Pond influent and effluent data for TSS and metal were collected for approximately two years. TSS removal by the pond was found to be 68.1-99.4% with an average of 83.9%. Average metal removal efficiency was 54.7-64.6% which is 72.5-86.9% of the TSS removal. The pond's flow regime was found to vary with its changing surface topography, a result of sedimentation of suspended solids.