This system was designed for a 16-acre scrap metal transportation, storage and sorting facility on the Duwamish River in Seattle.Several years after installation, the facility began transitioning from a general industrial stormwater permit to an individual permit. The treatment system was upgraded with triplex adsorptive multi-media vessels in 2017 in anticipation of the new permit.A small-scale pilot treatment system was installed and operated during the 2019-2020 wet season. The pilot system demonstrated that the addition of co-precipitation and adsorptive media blend to the existing system can achieve all proposed low-level individual permit parameters.