7Mins 76.022 89.922 108.405 157.047 8Mins 71.878 84.930 102.294 147.925 9Mins 68.292 80.615 97.016 140.061 10Mins 65.146 76.833 92.393 133.185 12Mins 62.355 73.480 84.638 127.103 20Mins 46.270 54.219 64.838 92.438 30Mins 36.992 43.165 51.431 72.796 1 Hour 24.439 28.295 33.487 46.768 Table 3 Rainfall intensities to be used within Maroondah – (Raw Data: 19.01, 4.32, 1.32, 37.95, 7.58, 2.41, skew=0.35, F2=4.28, F50=15) April 2013 8.1.3 (A) - Area of Catchment Area (hectares) to include total lot size, including all pervious and impervious areas. 8.2 Worked example: Rational method to determine PSD A typical 2 unit site of area 865m2 assuming 35% site coverage: Formula: Where: C = 0.51 I = 68.292 mm/hr A = 0.0865 hectares Q = (0.51 x 68.292 x 0.0865) / 360 = m3/s or 8.37 L/s 9. Onsite detention The planning permit conditions will generally detail if the development requires on site detention storage. A typical planning permit condition would require the following: Limit the Permissible Site Discharge (PSD) to the equivalent of a 35% impervious site coverage, or the pre-developed discharge rate, if it is less than 35% impervious site coverage, to the satisfaction of the Responsible Authority, and Provide appropriate stormwater detention storage to limit the maximum discharge rate to the PSD. 9.1 On site detention volume requirements All developments that require onsite detention must detain a minimum of 1 in 10 year storm event; however there may be cases where a property is required to store a 1 in 20 year or 1 in 100 year storm event. The following table outlines the detention requirements for various property situations:
7Mins 76.022 89.922 108.405 157.047 8Mins 71.878 84.930 102.294 147.925 9Mins 68.292 80.615 97.016 140.061 10Mins 65.146 76.833 92.393 133.185 12Mins 62.355 73.480 84.638 127.103 20Mins 46.270 54.219 64.838 92.438 30Mins 36.992 43.165 51.431 72.796 1 Hour 24.439 28.295 33.487 46.768 Table 3 – Rainfall intensities to be used within Maroondah (Raw Data: 19.01, 4.32, 1.32, 37.95, 7.58, 2.41, skew=0.35, F2=4.28, F50=15) April 2013 8.1.3 (A) - Area of Catchment Area (hectares) to include total lot size, including all pervious and impervious areas. 8.2 Worked example: Rational method to determine PSD A typical 2 unit site of area 865m2 assuming 35% site coverage: Formula: Where: C = 0.51 I = 68.292 mm/hr A = 0.0865 hectares Q = (0.51 x 68.292 x 0.0865) / 360 = m3/s or 8.37 L/s 9. Onsite detention The planning permit conditions will generally detail if the development requires on site detention storage. A typical planning permit condition would require the following: Limit the Permissible Site Discharge (PSD) to the equivalent of a 35% impervious site coverage, or the pre-developed discharge rate, if it is less than 35% impervious site coverage, to the satisfaction of the Responsible Authority, and Provide appropriate stormwater detention storage to limit the maximum discharge rate to the PSD. 9.1 On site detention volume requirements All developments that require onsite detention must detain a minimum of 1 in 10 year storm event; however there may be cases where a property is required to store a 1 in 20 year or 1 in 100 year storm event. The following table outlines the detention requirements for various property situations:
engineering-development-design-guidelines.docx