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( <br /> ( <br /> t <br /> � <br /> ! V, rin;ilpsis �nd Design of Required Runoff'Control 13A1P's <br /> 1 <br /> � The parking arca and the wash pad ��rea havc bccn trcated as hvo drainage suU-basins fur <br /> � a joint storm ���atcr :malysis. Thc bas�n bowidarics and arca calculations arc provided in <br /> � Appcndix r1. <br /> � Storm�rater Coavevance <br /> i Design Criteria for Storm���ater Convcyance System <br /> � • All Gxisting and Proposed convep:mcc systcros shall be design to com�ey <br /> � runoff from thc 25-year storm. (Standards 4-1) <br /> i • Tight-lined convcyance systcros receiving nmoff from relativcly small and/or <br /> i highly impc�vious drainage arcas shall be sired using tlows dctermined using <br /> the rational melhod. (Standards d-I) <br /> � • A backwatcr analysis may bc required for a proposed or existing pipe syslem <br /> i if the ability uf thc pipe syslem to convey the pcak rate of runoff from the 25- <br /> i ycar design storm event may be affected by taihvater conditions anywhere in <br /> thc pipc systcm. <br /> I <br /> • Su�uctures such as catch basins and numholes for propuscd pipc systcros, must <br /> � providc a minimum of 0.5 fect of frceboard behveen the hcadwatcr surface <br /> � (hydraulic grade line) and the top of the structure for flow from the 25-�ear <br /> � storm. Howevcr, structures may o��crtop for Oow resultin� from a 100-ycar <br /> storm. <br /> i <br /> ( Cakulalions fur Slorm�valer Com�e��ance Syslem <br /> � <br /> • Rational mcthod and the local IDF ctu•vc for City of Cverett �aerc used as a <br /> ' basis fbr calculating thc 35-ycar design stonn flow. <br /> ' • Backwatcr analysis ���as run using thc `_'�-ycar dcsi�n storm Oow usina the <br /> � stormwatcr u•eaunent systems bypass overflow ele��ation as tail water conu�ol. <br /> i <br /> • A sunun�u�y of this infonnation is provided in Table l. Backup calculations <br /> � and dctailed backwatcr analysis are pro��idcd in r�ppcndix 13. <br /> ( Tablc 1- Convey:mcc System Sumroary <br /> � System Area (ac) Pcuk 2i.yr \linimum Treeboard <br /> I�lo�ti• (ft) <br /> � (cl's) <br /> � Total Draina e 1.42 3.86 .45 <br /> ( <br /> r _ � _ <br />