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, Pacific Topsoils Riveraide site—Stortn Drainage Report <br /> GFK Consul�ng Inc. <br /> Checking for stability during a high flow event, I have chosen to use the more conservative <br /> runoff estimate from W1NHM3 for Q�oo hourly peak= 1.41 cfs, using the coRection factor of <br /> 1.6 to estimate a peak for a 15 minute flow step, Q�oo,c.m��r= 2•Zscfs for each swale. An <br /> assumed worst case grass cover yields an n value of 0.04; the resulting depth of flow is 5.16" <br /> with a velocity of 1.23fps. This falls below the 2.5 fps maximum for scouring and indicates <br /> that the design is ok for stability as well as water quality. <br /> ewswor <br /> n�w o�nvw <br /> q��r.� o.00 z.ze <br /> n a.ao o.ao <br /> B(11) 3.00 3.OU Trap. <br /> Ltflape 3.00 3.OU <br /> RSblope 3.00 3.00 <br /> y(11) 0.�3 OA3 <br /> 5(NI1) 0.005 0.005 <br /> LQ1) IDO.ODO 10D.000 <br /> t(�m) 0.000 1.352 <br /> A(tQ 1.831 <br /> p�(q 5.708 V(Ilh) 1.232 <br /> R(ly 0.321 <br /> Job: P�eific Topwib Fiuerside sih MsaM��: Bio S1We Of00 <br /> gy; (3F1( D�e: 8I5f2010 <br /> 5.2 Onsibe Conveyance Capacity <br /> The total predicted 100 year runoff rate for the asphalt cap is 4.49 cfs. Assuming that this <br /> flow is split evenly between the two asphalt gutters, the Q100 for the gutters is 2.25 cfs. The <br /> gutter geometry is half circular with an average width and depth of 3' and 1' respectively and <br /> a channel slope of 1%. Flow calculations indicate that the gutter flow would be 5" deep with a <br /> velocity of 4.62 fps. More than enough capaciry is avsilable. <br /> The 8" pipe conveying water"uphill" and back to the top of the bio swale has been set at a <br /> nearly flat slope in order to keep the bio swale construction as shallow as possible and <br /> prevent conflicts with the existing clay cap that is part of the containment structure. <br /> Calculation of the flow capacity for the 8" requires calculation of flow under pressure head. <br /> Evaluation of these pipes was done using DOT HY8 culvert sizing software with the following <br /> resa;:s. <br /> enoi2o�o 9 /� <br /> C:\Project data\Project files\PTopsoils Rlverside site\Reports\Riverside4.do � �,/� <br /> 1 , <br /> c <br /> \ <br />