Stormwater Surface Filtration/Infiltration Facility Sizing Spreadsheet <br />24 Hour Storm, NRCS Type 1A Rainfall Distribution <br />City of Eugene <br />Version 2.1 <br />3 <br />Project Name: Oakleigh Meadows Cohousfnq Date: 31J11201 <br />Project Address: Oaklelcih Lane, Permit Number: <br />Eugene, OR 97402 Catchment ID: Rain Garden 3 <br />Designer: Michael A Cox <br />Company: SSW EngineeeM Inc. <br />Instructions: <br />1. Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. <br />2. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate <br />calculations with the facility. <br />3. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) <br />4.For infiltration facilities in Class A or B soils where no infiltration testing has been perfromed use an infiltration rate of 0.5 in/hr: <br />For all facilities use a maximum soil infiltration rate of 2.5 in/hr for topsoil/growing medium. <br />"Yes" from the dropdown boxes below next to the design standards requirements for this facility. <br />I Pollution Reduction (PR) Yes <br />Flow Control (FC) Yes <br />Destination (DT) NO 'M infiltration facility must be chosen asthe facility type to meet destination requirements <br />Site Data-Post Development' <br />Total Square Footage Impervious Area= 1854 sgft Total Square Footage Pervious Area=~sgft <br />Impervious Area CN= 98 Pervious Area CN= 85 <br />Total Square Footage of Drainage Area= 1854 sft Time of Concentration Post Development= min <br />Weighted AverageCN= 98 <br />Site Data-Pre Development (Data in this section is only used if Flow Control is required) <br />Pre-Development CN= 85 Time of Concentration Pre- Devolopment= 10 min <br />Soil Data <br />Tested Soft Infiltration Rate= 2.5 in/hr (see Note4) <br />Design Soil Infiltration Rate= 2.5 in/hr <br />s Used For.Calculations <br />Requirement <br />Rainfall Depth <br />Design Storm <br />Pollution Reduction <br />1.41inches <br />Water Quality <br />Flow Control <br />3.61inches <br />Flood Control <br />Destination <br />3.61 inches <br />Flood Control <br />Destination Design= bibr <br />Soil Infiltration Rate. <br />Facility Type= Filtration Rain Garden Facility Surface Area= 180 sgft <br />Surface Width=1 61ft Facility Surface Perimeter=) 72 ft <br />Surface Length=s 301ft Facility Bottom Area=1 81 sgft <br />Facility Side Slopes={ 31to 1 Facility Bottom Perimeter=1 60 ft <br />Max. Ponding Depth <br />f in Stormwater Facility= I 61in Basin Volume=) 67.5 cf <br />Depth of Growing Medium (Soil)= 18 in Ratio of Facility Area to Impervious Area= ~ OA97 <br />31.11/2013-10:54 AM ' 1 - 583 <br />