Abstract: A particle separator apparatus includes a pond and a separation vault, which receive a runoff stream. The vault includes an entrance for the runoff stream, the entrance having a primary skimmer thereabout for removing floating objects from the stream. A holding chamber is provided for catching and holding particulate matter as the particulate matter drops out of the runoff stream. The holding chamber includes a plate module, having plural corrugated plates spaced apart from one another therein, for providing the aerobic and anaerobic treatment to stabilize the runoff stream. A final skimmer is located at the rear of the vault, and includes a final skimmer plate which directs floating objects to a floating hose, which removes any remaining floating objects from the runoff stream.