Suspended Solids Size Distribution Determined with the Winged Arm Sampler

Key to pollution prevention efforts in urban areas are the installation and maintenance of stormwater best management practices (BMPs). Improving the design of stormwater BMPs requires more accurate information about stormwater particles. For stormwater BMPs which treat particles through settling, particle size is the primary variable to determine settling velocity. For stormwater BMPs which remove particles via filtration or infiltration, knowledge of particle size and composition is also important. As always, better knowledge of what is coming down the pipe enables a better distribution of resources to meet water quality goals. Monitoring is one means of obtaining suspended solids concentration and particle data. Automated sampling has evolved to be the preferred method of stormwater runoff monitoring efforts due to several factors. Chief among these is the ability of automated equipment to operate in standby mode and to be ready to collect samples when a storm event occurs. Automated equipment is also capable of collecting multiple samples during a single storm event. This is especially important given the large variation in pollutant concentrations that have been found within single storm events (Li et al., 2005). It is now standard practice to sample at intervals along the hydrograph, with the sampling intervals determined by cumulative flow volume.