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6. STORMWATER CONTROL PLAN <br /> A. Detention Pipe An3lysis <br /> Pre-Developed Site Hydrology (Disturbed An�a Only) <br /> The existing site to be converted from grass the pavement and roof is located <br /> along the north side of the property. This area is currently used for vehicle <br /> storage and had contained a building that was demolished in the past. The <br /> existing area is currently covered in grasses and portions of t:�e R.O.W. to be <br /> paved also contain gravel surfacing. The on-site area mostly drains to the north <br /> and northwest toward the existing alley with a small portion draining toward the <br /> Paine Ave R.O.W. to the northeast. <br /> As per the interim Public Works Policy #7_-11 the existing site will not be modeled <br /> as forested land cover but rather the exi;�ting site conditions. <br /> Using VWVHM# software the basin was analyzEd for the existing flow conditions <br /> for the disturbed basin only. 7his data was then used as the matching criteria <br /> required in the sizing of the detention pipe. <br /> Detention Pipe <br /> Totai Site Area: 0.24 ac (Area Tributa.ry to Pipe Only) <br /> I-lydrologic Soils Group C (Till) <br /> Impervious Area: 0.03 ac (gravel) <br /> P� dious Area 0.21 ac Qawn) <br /> Existin Condition Eoant Out ut; WWMW3 <br /> Peak Flov� cfs Area (ac) <br /> 2-yr current 0.02 0.24 <br /> 1�r current 0.04 0.24 <br /> 100- r current 0.08 024 <br /> Developed Site Hydrology <br /> For ihe developed site hydrology, the site will be assumed to be fully paved since <br /> the detention system is beiny sized for the parking and roof areas only with the <br /> small area of bypass. The bypass area was input into ihe VWUAIH3 software <br /> separate from the impervious surfaces collected by the detention pipe. This <br /> allowed the software to ensure this project met the runoff requirements at the <br /> connection point to the sewer main in Paine Ave. <br /> -- 11-i15 <br /> Glacie�ProFeAies page 73 <br /> December 2011 <br />