AbstractAlthough biofilters and bioretention controls have been extensively studied and are encouraged as effective stormwater controls, there is remaining uncertainty concerning their long-term performance and required maintenance. Most full-scale monitoring efforts have been of short duration, with no clogging or breakthrough observed. This paper describes the long-term monitoring results of media-based stormwater controls located at the Santa Susana Field Laboratory (SSFL) in Ventura County, California, an industrial site with historic aerospace and energy research. The 10 stormwater controls examined in this paper were grouped into four types (referred to as culvert modifications, which are media filters installed at drainage road crossings, detention bioswales having large subsurface storage, a large sedimentation pond/biofilter treatment train, and a sedimentation tank/media filter treatment train). Data were available for about 6–9 years of monitoring. This paper examines the trends in performance and usage until major maintenance is required. In almost all cases, the effluent concentrations tracked the influent concentrations, with no significant performance or effluent concentration differences with time. Silt clogging at one facility occurred as predicted based on initial laboratory tests, and the media in that control was replaced on schedule.