Abstract: A stormwater inlet near an upper edge of a layered filter media vessel is equipped with a distribution header that ensures effective use of the surface area of the filter media by providing plural spaced streams of stormwater thereat, each at a point of impact having its energy dissipated by a layer of material that covers the upper layered filter media surface. The stormwater inflow is metered to control the stormwater pollutant removal process kinetics, thereby slowing the mean free path of the stormwater therethrough and optimizing pollutant capture. The water level within the vessel is height adjustable manually by a pivot arm in the form of a standing column of water coupled to the water within the container. Weep conduits are provided to slowly drain down the standing water in the system between storm events, simplifying maintenance and promoting best removal of pollutants from first-flush storm events. Stormwater pretreatment, e.g. by use of an oleophilic agent or a pH-buffering agent, is provided.