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MAPLE ST <br /> Section 5 Onsite Storm Water Management <br /> 5,1 EXISTING CONDITIONS <br /> The existing site is located at 2405 Maple St and contains an existing single-family residence,driveway,walkways <br /> and patio, landscaping and a few trees. The site contains gentle to moderate slopes, draining to the east, and <br /> southeast edges of the property. According to the USDA information the site is underlain by "Alderwood-Urban <br /> land complex, 2 to 8%slopes".The report is included in the Appendix section of this report for reference. <br /> The total existing area for the house is 859 sf.This roof area is based on the projected horizontal area of the roof, <br /> not the actual surface area of the roof(including the angled surface areas). Other impervious surfaces include a, <br /> 300 sf detached garage, 1,000 sf gravel driveway, 11 sf of uncovered deck, and 54 sf walkway.The total existing <br /> impervious area is 2,224 sf.The remaining 2,699 sf of the site is landscaped with lawn.Totals were evaluated using <br /> best available resources such as site plan,aerial maps and survey. Please see survey of existing lot on the following <br /> pages. <br /> For the purpose of determining the flow control threshold, the Predeveloped condition is modeled as existing <br /> conditions per Section 1-3.4.7 of the 2019 DOE Manual. Per Section 6-10.1 of the City of Everett Drainage <br /> Specifications Stormwater discharges should match the developed discharge durations to the existing site <br /> durations for the range of existing discharge rates from the 10-year peak flow through the full 100-year peak flow. <br /> Peak runoff rates from the developed site should not exceed existing site runoff rates in the 25-year and 100-year <br /> using a 5-minute timestep. The corresponding areas and associated WWHM output are included below. A full <br /> WWHM report is located in the Appendix. <br /> PREDEVELOPED CONDITIONS <br /> Impervious <br /> House 859 sf <br /> Detached Garage 300 <br /> Gravel Driveway 1,000 sf <br /> Deck 11 sf <br /> Walkway 54 sf <br /> Total Impervious 2,224 sf <br /> Pervious <br /> Lawn 2,699 sf <br /> Total Pervious 2,699 sf <br /> TOTAL LOT AREA 4,923 sf <br /> 113 JOB#19-336 <br /> Storm Drainage Report 5.1 <br />