1505 112TH ST SW 2018-01-02 MF Import

vegetated awaleaI Current City standards call for vegetated "ales to be designed for the 2-year, 24-hour storm peak discharge, with higher flows diverted around the swale. In this case, all flows up to the point that the secondary orifice comes into play should be routed to the swale. All flows through the secondary orifice and through the overflow should be routed directly to the wetland outfall system. The following criteria apply for the design flow in the swale: ..n.. = 0.12 max velocity = 1.5 feet per second 12ii Max. depth = 0.5 feet 4�r 1A� ed ✓ Calculations must be submitted showing that the , the designed biofiltration swale meets City stanlength of dards. r(WO 011/watat ea s ator/grit removal vaults City standards call for the vault to have an inlet capacity determined by using the rational formula with a rainfall e,� intensity of o.5 inches per hour over the contributing area. PTyf In addition, bypass piping is required for the vault per Por a0 r City standards. Normally, the vault inlet capacity should /1" �„e be reached at the point that the water elevation in the rol ,p bypaaa pipe is at Its peak for the 10 year storm. However, 1/if tha oil/water separator is located after the detention system and before the swale, the separator can be designed for the maximum flow entering the Swale before direct overflow to the wetland from the detention vault occurs. N2 bypass ping for the separator would be�gquiLed_fpr Shia configure off ---- The separator must be sized to provide a 15 minute detention time for the design flow. The entire contributing area must be used in calculating the size of the oil/water separator vault although only the Paved surface is required to be routed through the separator. The following information regarding the oil/water separator must be submitted for review and approval: ^ ' 1) design inlet capacity calculations 2) oil/water separator sizing calculations f..3) bypass sizing calculations