Laserfiche WebLink
4 ONSITE STORMWATER MANAGMENT <br /> The flow control and water quality requirements are controlled by the 2010 <br /> City of Everett Stormwater Management Manual. Per the requirements in the <br /> Manual, onsite drainage must be detained to match the pre-developed storm <br /> events between half the two-year event through the fifty-year event. Pre- <br /> developed storm conditions were considered to be forested with HSG C soils for <br /> both basins. <br /> Basin A <br /> In the developed state, Basin A will be comprised of the following coverage: <br /> Modeled Coverage Area <br /> C, Lawn, Flat 0.93 acres <br /> Roof, Tops, Flat 0.29 acres <br /> Roads, Flat 0.61 acres <br /> Total 1.83 acres <br /> NGPA Area 0.50 acres <br /> A detention vault per Chapter 3, Volume III of the Manual has been proposed to <br /> manage the drainage in this basin. After detention, outflow will be piped to <br /> the existing culvert under 19th Ave. SE where it will outfall into Silver Lake. <br /> The vault has been sized using WWHM4. Based on the system sizing, a <br /> detention vault providing 15,394 cf of detention will be required. The <br /> proposed vault will provide a total of 16,200 cf with 7.5' of live storage, which <br /> exceeds the required detention. <br /> Based on Chapter 13, Volume III of the City of Everett Stormwater Management <br /> Manual, any BMP which has a General Use Level Designation from the <br /> Washington State Department of Ecology may be used to meet water quality <br /> July 2014 4-1 LDC Job No. 13-144 <br />