10315 19TH AVE SE SITE DEVELOPMENT 2016-01-01 MF Import

b) a wetpond or constructed wetland in series with a SMI StormFilter (see the addition criteria for SMI StormFilters) 20. All storm water facilities shall be designed in accordance with City standards, and shouid be designed and initially constructed to meet the requirements of all planned future expansion on the site. If the storm water facilities are not designed and constructed initial!•y for all phases of this project, the runoff control requirements for future phases of the project shall be those standards in effect at the time of application for each building permit. 21. SMI StormFilter: The City will allow the use of a Stormwater Management, Inc. (SMI) StormFilter to help meet the City's storm water treatment standards, provided the design and construction of the SMI StormFilter meet the following criteria: i. The StormFilter must be preceded by a pretreatment wetvault/tank containing at least 30% of the 6-month, 24-hour storm runo�volume from the contributing developed drainage area. ii. The StormFilter must treat at least the 6-month, 24-hour storm. iii. The StormFilter shall be designed using a maximum flow rate of 7.6 gpm per cartridge. Flows exceeding the design flow shall be bypassed around the system, but should generally pass through the pretreatment wetvault/tank. iv. The StormFilter media shall target dissolved pollutants and nutrients as well as total suspended solids. As more effective med�a become available in the future, the StormFilter shall be upgraded, during routine cartridge replacement, to utilize these improved media. v. The StormFilter shall be designed with a minimum of 2.3 feet of head differential between the inverts of the inlet and outlet of the filter. Downstream hydraulic calculations will be performed to demonstrate that downstream conditions will not reduce the hydraulic potential across the filter due to backwater effects. vi. Routine maintenance of the StormFilter is required. A detailed operation and maintenance plan for the system must be prepared for approval by the City. A certificate of system maintenance must be submitted to the City annually. vii. Maintenance and operation of the StormFilter on this site shall be adapted, in the future, to reflect the current knowledge regarding this emerging technology. viii. All other applicable, and non-conflicting, criteria in the current edition of SMI's Product Design Manual shall be followed in the design, construction and maintenance of the SMI StormFilter on this site. ix. For StormFilter located downstream of detention systems, the SMI mass loading design procedure shall be utilized, with the following assumptions: 1. TSS removal required = 80% 2. Vb = the volume of dead storage plus the 7-day average live storage volume from the routing of the 6-month, 24-hour storm through the !��