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I I Worksheet for Calculating the Combination Flow and Volume Method Instructions:After completing Section 1,make a copy of this Excel file for each Drainage Management Area within the project. Enter information specific to the project and DMA in the cells shaded in yellow. Cells shaded in light blue contain formulas and values that will be automatically calculated. 1.0 Project Information 1 1-1 Project Name: 1717 Doolittle Drive The calculations presented here are based on the combination flow and volume 1-2 City application ID: G15-0006 hydraulic sizing method provided in the Clean Water Program Alameda County C.3 Technical Guidance,Version 4.0.The steps presented below are explained in Chapter 5, 1-3 Site Address or APN: 1717 Doolittle Drive Section 5.1 of the guidance manual,applicable portions of which are included in this file, 1-4 Tract or Parcel Map No: 3236(Bk.66 Pg.72) in the tab called"Guidance from Cha.ter 5". I/ 1-5 Site Mean Annual Precip.(MAP)' 17.0 Inches Refer to the Mean Annual Precipitation Map in Appendix D of the C.3 Technical Guidance to determine the MAP,in inches,for the site. Click here for map 1-6 Applicable Rain Gauge' Oakland Enter"Oakland Airport"if the site MAP is 16.4 inches or greater. Enter"San Jose"if the site MAP is less than 16.4 inches. I MAP adjustment factor is automatically calculated as: 0.93 (The"Site Mean Annual Precipitation(MAP)"is divided by the MAP for the applicable rain gauge,showin in Table 5.2,below.) . ,.(;)Calculate Percentage of Impervious Surface for Drainage Management Area(DMA) 2-1 Name of DMA: DMA 5 For items 2-2 and 2-3,enter the areas in square feet for each type of surface within the DMA. Area of surface type within DMA Adjust Pervious Effective Impervious Type of Surface (Sq.Ft) Surface Area ' 2-2 Impervious surface 78,610 1.0 $f 2-3 Pervious service 6,490 0.1 Total DMA Area(square feet). 85,100 2-4 Total Effective Impervious Area(EIA) 79,259 Square feet I3.0 Calculate Unit Basin Storage Volume in Inches Table 5-2: Unit Basin Storage Volumes(in inches)for 80 Percent Capture Using 48-Hour Drawdowns Unit Basin Storage Volume(in)for Applicable Runoff Coefficients I Applicable Rain Gauge Mean Annual Precipitation(in) Coefficient of 1.00 Oakland Airport 18.35 0.67 San lose 14.4 0.56 I3-1 Unit basin storage volume from Table 5.2: 0.67 Inches (The coefficient for this method is 1.00,due to the conversion of any landscaping to effective impervious area) 3-2 Adjusted unit basin storage volume: 0.62 Inches (The unit basin storage volume is adjusted by applying the MAP adjustment factor.) I 3-3 Required Capture Volume(in cubic feet): 4,100 Cubic feet (The adjusted unit basin sizing volume[inches)is multiplied by the size of the DMA and converted to feet) 4.0 Calculate the Duration of the Rain Event I 4-1 Rainfall intensity 0.2 Inches per hour 4-2 Divide Item 3-2 by Item 4-1 3.10 Hours of Rain Event Duration 5.0 Preliminary Estimate of Surface Area of Treatment Measure AIIIIIMIIIIIIIIIIMIIIIIIIIIIIIIIIIIIIMIIIIII 5-1 4%of DMA impervious surface 3,170 Square feet I 5-2 Area 25%smaller than item 5-1 2,378 Square feet 5-3 Volume of treated runoff for area in Item 5-2 3,075 Cubic feet(Item 5-2*5 inches per hour*1/12*Item 4-2) 6.0 Initial Adjustment of Depth of Surface Ponding Area ,,, 6-1 Subtract Item 5-3 from Item 3-3 1,025 Cubic feet(Amount of runoff to be stored in ponding area) 6-2 Divide Item 6-1 by Item 5-2 0.4 Feet(Depth of stored runoff in surface ponding area) 6-3 Convert Item 6-2 from ft to inches 5.2 Inches(Depth of stored runoff in surface ponding area) I 6-4 If ponding depth in Item 6-3 meets your target depth,skip to Item 8-1. If not,continue to Step 7-1. 7.0 Optimize Size of Treatment Measure 7-1 Enter an area larger or smaller than Item 5-2 2,610 Sq.ft.(enter larger area if you need less ponding depth;smaller for more depth.) I 7-2 Volume of treated runoff for area in Item 7-1 3,375 Cubic feet(Item 7-1*5 inches per hour*1/12*Item 4-2) 7-3 Subtract Item 7-2 from Item 3-3 725 Cubic feet(Amount of runoff to be stored in ponding area) 7-4 Divide Item 7-3 by Item 7-1 0.28 Feet(Depth of stored runoff in surface ponding area) 7-5 Convert Item 7-4 from feet to inches 3.33 Inches(Depth of stored runoff in surface ponding area) 7-6 If the ponding depth in Item 7-5 meets target,stop here. If not,repeat Steps 7-1 through 7-5 until you obtain target depth. 8.0 Surface Area of Treatment Measure for DMA MIIIIIIIIIINIIIIMIIIIIIIIIIMIIIIIIIIIIIIIIIM 8-1 Final surface area of treatment* 2,610 Square feet(Either Item 5-2 or final amount in Item 7-1) *Note:Check with the local jurisdiction as to its policy regarding the minimum biotreatment surface area allowed. I