This paper proposes an integrated approach to storm water management and storm water treatment. Today's requirements for capturing and treating the first-flush of storm water can be met with a new device that also controls peak flows over a wide range of storms and uses a net storage volume that is substantially lower than the storage computed by traditional reservoir routing methods.The extention basin debuts here as the most efficient method of reducing peak storm water flows--being far more effective than the retention or detention basins in common use today.