Laserfiche WebLink
INFILTRATION BMPS <br /> T5.15 Permeable Pavements <br /> Project submission requirements include submitting results of infiltration (Ksat) testing, groundwater <br /> elevation testing (or other documentation and justification for the rates and hydraulic restriction layer <br /> clearance) with the justification for the feasibility decision regarding permeable pavement, and as <br /> justification for assumptions made in the runoff modeling. <br /> BMP T5.14A- Rain Garden <br /> The top of the ponded surface area below the overflow shall be at least 5%of the total hard surface area <br /> draining to the rain garden. If lawn/landscaped areas will also be draining to the rain garden, it is <br /> recommended that the top of the ponded surface area below the overflow be increased by 2%of the <br /> lawn/landscaped area. The table below provides rain garden geometry based upon contributing area. Refer <br /> to the Rain Garden Handbook for Western Washington:A Guide for Design, Installation, and Maintenance <br /> (Hinman et.al. 2013)for construction guidance. Rain gardens shall be designed in accordance with the <br /> SWMMWW. <br /> Side Contributing Minimum Top of Minimum Bottom Minimum Top <br /> Slope Area Ponding Area of Ponding Area of Berm Area <br /> (ft2) (ft2) (ft2) (ft2) <br /> 2:1 800 or less 40 0.11 50 <br /> 2:1 1400 or less 70 0.13 110 <br /> 3:1 3000 or less 150 0.06 235 <br /> • Hard surface area requiring mitigation (ft 2): - <br /> ■ Lawn/landscape contributing area (ft 2):_ - <br /> • Total contributing area (ft2): <br /> Top of Ponded Surface Area (ft2)= 0.05*(total hard surface area (ft2))+0.02*(lawn/landscape area (ft2)) <br /> = 0.05*( -ft2)+0.02*( ft2) <br /> ft2 <br /> City of Everett Public Works <br /> Small Project Stormwater Site Plan Report-Dec 2019 41 <br />