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'li <br />' <br />I � <br />� <br />I � <br />�_ <br />Hoglunds Top Shop <br />Drainage Study <br />June 23,2008 <br />SITE HYDRAULIC ANALYSIS <br />Total Site Development Area <br />EXISTING CONDITION <br />Ex. Buildings (4 EA) <br />Asphalt Pazking <br />Sidewalk <br />Gravel <br />Concrete <br />Existing Impervious Area <br />Existing Pervious <br />Ll = 125' asphalt (aJ 4.0% <br />L2 = 74' grass @ 1.4% <br />Assume Te = 7-minutes <br />DEVELOPED CONDITION <br />Existing & New Build.ing <br />Cona SW <br />Asphalt Pazk'.ng <br />Proposed Impervious Are1 <br />Proposed Pervious <br />= 26,592 SF G.610 Acres <br />3,974 SF <br />8,369 SF <br />590 SF <br />2,290 SF <br />1.808 SF <br />17,032 SF <br />9,539 SP <br />7,365 SF <br />590 SF <br />12.734 SF <br />20,689 SF <br />5,903 SF <br />0..391 Acres <br />0.219 Acres <br />U.4745 Acres <br />0.1355 Acres <br />NET IMP�RVIOUS = 20,689 —17,032 = 3,657SF «5,000 SF THRESHOLD <br />THEREFORE, DETENTION NOT REQUIRED <br />P2 = 1.5 <br />P 1 U = 2.2 <br />P100 = 3.2 <br />A. DESIGN CAITERIA <br />I The City of Everett Drainage Ordinance does not require that storm water from new <br />impervious surfaces crcated by development of less than 5,000 CF be detained. However, <br />since the downstream pip:ng drains not to the Combined Sewer System as previously <br />supposed but to Pigeon Creek #2, water quality treatment under the 1992 DOE manual <br />� , will be required. <br />� The project MDNS comments were written indicating that the new impervious <br />surfaces were now being defined as "hydraulically connected" pavements, which now <br />will rcquire treatment. <br />5 <br />