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SHAK EY I S <br />FOR DETERMINING THE VOLUME OF STORM RUNOFF <br />THE RATIONAL METHOD WAS u5E0. DETENTION VOLUME <br />REQUIREMFN75 WERE CALCULATED USING THE °SIMPLIFIED <br />'RATIONAL' METHOD TEGHNIQU-" AS PRE5ENTED IN <br />ST9RMWATER MANAGEMENT PROCEOURES Ah1p METHODS <br />PREPARED Ev URS COMPANY OATEO 5c-PTernc36R 19-77 <br />FOR BOTH THE G HOUR STORM AND THF_ 20 MINUTE ZTORM <br />AND USING THE CITY OF EVERETT MINIMUM RECOMMENDED <br />ORIFICE 51ZE OF 2Yq.° 'TO ALLOW A DISCHARGE CAPACITY . <br />;OF 0.25 Gusic, FEET PER 5ECOND AT A 3%z FOOT HEAD. <br />Z. DETERMINATION OF PEAK FL -OW FROM EXISTING - <br />I CONDITION: <br />CEX15T1Nra- ` E.Xi5TIWG RUNOFF CAEPFIGIENT A5 <br />DETERMcNEp FROM ENCLO5E[) R. UIVOFF <br />COEFFICIENTS TABLE-, <br />C10 VEAR = RAINFALL INTEIJSITY FOR STORM OF 10 <br />YCAR FREQUENCY AS OFTERMINF_D FROM <br />ENCLOSED I50PLUVIAL <br />FOR X%a PAvEO, 709c UNPAVED WITH NO PLANT C-ROWTH <br />Cf=xm-riNc- = (0.30)(0.95)+ (a70)(0.75) - 0. 8 <br />QEXISTINC-= CEXISTIN(= X �IOYCPR X A <br />2 <br />'fin /hc�(0.5 acres� <br />= 0.08 cf> FOR GHR ssoRM <br />SING QEXI5fINJ& =0.08 < QAI-1-0.�.)A8LE. - 0.25 <br />Q,, = 0. 25 cfs <br />DF-7ERMINATION OF VOLUME OF STORM RUNOFF 5TORAGE, <br />RE-QUIRED TO LIMIT OUTFLOW TO ALLOWABLE VALUES: <br />n i <br />{ QFUTVRG- = CFUrURE_ X Lx5 VEAR x A <br />}Ii 1I <br />1 ` <br />I <br />7s - 117 <br />