1001 SHUKSAN WAY 2016-01-01 MF Import

� . I Detention Pond Design Criteria � Water Qualitv/Water Quantitv Svstems The following stormwater detention design criteria will apply to this project: I � • Release rate of half of the 2-yeaz pre-existing 24-hour dasiga storm with detention for the balance of a 2-year developed 24hour design storm � . Release rate of a ]0-yeaz pre-existing 24hour design sterm with detention for the balance of a I 10-year developed 24-hour design storm . Release rate of a 100-year pre-existing 24-hour design s�orm with detention for the ba'ance of � a 100-yeaz developed 24-hour design storm The proposed project site will be 90 percent impervious(pavement, ioof, sidewalk,etc.); I therefore, a volume correction factor of 0.46 is applied to the detention pond according to the City of Everett Stormwater Management Manual. I Design Summary ( Preciaitation Data I The following is a table of rainfall depths for the 6-month, 2-year, 10-year, and 100-year, 24-hour Istormc from the City of Everett Stormwater Management Manual: Desi¢n Storm Rainfall Denth (inches) I6-month, 24-hour 0.99 2-year, 24-hour 1.55 I 10-year, 24-hour 2.25 100-yeaz, 24-hour 3.25 i � Computations for Stormwater Detention IThe Santa Barbara Urban Hydrograph (SBUH) method with type lA stomu was used with the WaterWorks HMS computer program to calculate the peai:flows and volumes of tt�e various I storrtu, the detention pond outlet orifice sizes in the control structure, and the requved detention pond volumes. The new convol discharge orifice structure was sized to pass the pre-developed conditions discharge rates of one-half the 2-year, 24-how stottn, as well as the 10-year and 100- i year, 24-hour storm events. IFood Suviccs o(Amcrica Stamwatcr Sitc Plan and S�amwata Detentim Pand ��^°� t Hydraulic Rcport _5' �u�� (�t I tJ t