Abstract: In combination, a flow control bypass basin for receiving rainfall runoff water from a surface, an immiscible liquids separator downstream of the bypass basin, and a drain. The bypass basin passes the initial, dirty and oily, portion of the rainfall runoff to the separator and bypasses subsequent runoff water instead to the drain. The bypass basin includes a tank, an inlet in communication with the tank's interior, a primary outlet from the bypass basin to the separator, and a bypass outlet from the bypass basin to the drain, with the bypass outlet being located a substantial height above the primary outlet. Interposed between the bypass outlet and the interior of the tank is a riser tube having a mouth disposed in the lower portion of the tank and an upper end closed to the interior of the tank but open to the bypass outlet.

Abstract: An apparatus and method for removing articles of a first liquid from a second liquid using law, the first liquid, such as oil, having a greater buoyancy than the second, such as water, with both liquids being immiscibly combined into a flowing fluid mixture. Surges in the mixture's flow are dampened, and the mixture is constrained to have a limited horizontal flow velocity through the tank of the apparatus. A separator chamber with a plurality of parallel subchannels formed by spaced vertical plates has a geometry that reduces and controls the Reynolds number of the subchannels and controls the velocity through the subchannels, causing the flow therethrough to be substantially non-turbulent. A first gate inhibits the flow of sediment into the separator chamber. The flow path length through the separator chamber is such that the particles will have sufficient time to rise above a downstream exit, near the bottom of the separator chamber, and into a holding chamber.