6400 MERRILL CREEK PKY 2018-01-01 MF Import

volume of runoff from the 6 month, 24-hour storm. The followinq two methods are acceptable for determininq the wet pond dasign volume; either 1) multiply the area of impervious surface in the contributing basin by the precipitation associated with tha desiqn storm or 2) determine the total ��olume of stormwater runoff using the Santa Barbara Urban Hydrograph method or comparable method. At least 50t of the wetpond design volume is required to be permanent storage in the pond. City standards require the maximum storage in the wetpond (dead storage + live storage) during the desiqn atorm to be equal. to or greater than the calculated required wetpond volume. The design storm must be routed through the pond to demonstrate that this requirement is beinq met, unless the entire required wetpond volume is provided as dead storaqe. The minimum allowable orifice size for a restrictor device associated with a wetpond is 1 inch. If a 1 inch orifice doesn't result in the required storage in the pond, then the percentage of the required wetpond volume provided as dead storage must be increased until the requirement is satisfied. The standards require a minimum of 30$ of the required permanent storage volume to be associated with the wetland treatment cell. A maximum of 70� is tu be associated with the open water cell. ` / As an alternative to the open water cell of the pond, a -�--wetvault may be provided. With the deep portion of the �� wetpond provided underground, fencing can often be avoided. In addition, vehicle access can be provided to the top of the vault instead of the to the bottom of the pond, and a 72 �,� inch manhole is not required upstream of the pond for grit �,e"F removal. /�nd -Ftu pv,�� w.�� }ai� �a iees s�� l ace c�n.le . ,��,�.� °�i� �o��• �� If the wetvault option is chosen, a minimum volume equal to ,� „� a 15 minute detention time for the peak rate of daveloped G�en c�'. flow from the 6 month, 24-hour storm must be provided. Flow �9y l �� should enter one end of the vault and leave the other, and ;�U�� i5 the depth of permanent storage should be between 3 and 6 r�� {J��k 4 feet. ��,a `�� k -�� The following information is needed for City review and ��I� �r�l approval of wetponds: v+�K'es�,)r 1) wetpond sizing calculations, including the wetpond � 1��yJ� • design volume, wetpond permanent storage volume, Ja and wetpond treatment cell volume 2) orifice sizinq calculations 3) stage-storage relationship of the pond 4) results of routing the design storm through the pond