(A) Detention shall be required for all proposed developments where the runoff rate from the proposed post-developed conditions shall increase when compared to the pre-developed conditions. In addition, detention may be required for any development in areas where downstream flooding has been identified by the stormwater office. The pre- and post-developed runoff rates shall be determined using methodologies specified in the town’s Stormwater Design Manual.
(B) The following requirements shall be fulfilled for all detention facilities.
(1) The runoff from the developed condition peak storm with a 100-year return period storm shall be limited to the runoff rate from the pre-developed condition peak storm with a ten-year return period storm.
(2) The runoff from the developed condition peak storm with a ten-year return period storm shall be limited to the runoff rate from the pre-developed condition peak storm with a two-year return period storm.
(3) There shall be no increase in the runoff rate from the pre-developed conditions to the post-developed conditions for all storms at all discharge points along the property line.
(4) An adequate downstream receiving facility shall be identified on the plans. There shall be no increase in erosion potential on the adjoining properties.
(5) Earthen embankments, dams and/or berms designed and constructed to detain or impound stormwater shall be designed using criteria specified in the town’s Stormwater Design Manual.
(Ord. 3, 2012, passed 1- -2012)