(last updated August 12, 2013)
Clarifiers are designed to be installed below grade to allow the storm water to flow via gravity and are designed to reduce heavy solids and O&G. Gravity flow is important as the free oils need to be kept separate from the storm water so separation may take place in the clarifier. If the storm water is pumped into the clarifier, the free oils may become emulsified and not separate inside the clarifier. Also, it is important to have an “Off Line” clarifier to keep a large storm event from scouring the clarifier and washing out all of the contaminants previously trapped inside. The clarifier can also be used as a pump basin if downstream treatment is needed.