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d.\mju\lts\decalc <br /> LOVELACE ROAD TRANSFER STATION <br /> STORM DRAINAGE DESIGN SUMMARY OF CALCULATIONS <br /> By: Mark Urquhart <br /> Date: August 17, 1993 <br /> Attached are drainage calculations according to County Standards as described in the <br /> drainage design criteria. This summary indicates, by topic, how the Lotus 123 <br /> spreadsheet calculations or other calculations used in the sheets were performed. <br /> I Sheet 1 of 2: <br /> A. Area Calculations and composite Coefficient <br /> Areas were calculated using polyline (dashed lines) area calculations from the CADD <br /> Drainage Design Map (RSI-7). The composite runoff coefficients are based on weighting <br /> of the coefficients and areas. For example Basin number 13 has <br /> ((.16/.5)x.75)+((.3 4/.5)x.95)_.89. <br /> B. Critical Time to Inlet <br /> The sheet indicates the length and slope of drainage travel from the furthest points of <br /> _ the subareas. County design criteria required the minimum 10 minute flow time was <br /> used for all basins. The flow times were estimated using either D-5 from the County <br /> manual and a check of the sources. <br /> C. Intensity <br /> Based on the 10 minute concentration time the IFD curve Attachment 1 4/4 indicated <br /> approximately 2.22 inches per hour for the 100 year storm. <br /> D. Peak Runoff <br /> By the rational formula, peak flow for each basin inlet area calculated by taking the total <br /> area x composite coefficient x intensity. As an example for basin 2: .09 x .88 x 2.22 = <br /> .18cfs. <br /> II. Sheet 2 of 2: <br /> Columns 1 and 2: <br /> Flow at inlet (DI) uses the flow (Q) from sheet 1/2 for each basin. The DI <br /> numbers shown are according to the attached drainage design map and are <br /> calculated working downstream to common inlets. branches are grouped in the <br />