2300 KASCH PARK RD 2018-01-01 MF Import

� � 'I I EXAfdPLE PROBLEM: lo illuslrate the use of the , I II I .1 . . .. �i').� �,p�J . i I.) � � nquo�ions and graphs derived in this report. .. i i ,..��_ �.�.. . � Designcriferia '� ,,„. �`��;��y � � A 50 ocre parcel of land is to be developed inb c resi• �; --i—�� •+��., � '� denfinl subdivision wilh a runoff coefficient of U.30. 3,;,�; «L;, �`t�---�' An upen ditch drain is avoilablo odjacent to this 50 aue ' yI�—'�—� pm c^I of lond,and can accept sform runof(al a rote of � � I I I nu�;y�nn�e: than 10 CFS from Ihe proposed subdi.ision. a !I� Su!lici_ri grade is available lo allow 6..`•fl.depth o(re- � o,,,� _ I I � feniiwi and a gravity (low orifice ou!IeL Determine (!) • � � �oq.' i 1 ths volume of retention required,and(2)Ihe size of oub � �� . '� flow pipe required. � i1 � w.� I � I I �� i ;I� . � � . . .. . �� .. . ,. Solulion I � Ouiv�Ow 10. 1 �� 1, from ihe design criterio, mlculate Qo � ��f I ' Qo _ A�lowable outflow ...� s�,,.o. �.�,..,� s�o.,a. ' acreage X runoff inef(icient .� �� i.e. c� o�un r�.,. i�„i ww.. tv�i ! F ' � h oo — iocFs = a.ea� cFs 1 o�^�•� ��sseze� �osoo+ 50 ac X 0.30 acre imperviousness � �. I 7._zs.Y o. �" T+Fe-.oai ' .nn M.� 2. Colculate the lime in min 1ha!the mazimum voiume •. � ,�..• r�.. s • io r 1 � of atorage will occur from ihe orifice oullet storage � • p To T•-»+� V� • �iy--cow* time equation. ' r. I � 'r a r ° ..:.,.., . �, /6562.5 i. i 1' _ — 25 + �I Qo � ; gravity cys!em has fo heaj up before it will reoch the - � � meximum rate. It is possiblr to hove a gravity system 6562.5 -. 1 thot will head up at a rcpid role at the beginning of the T = — 25 + 0.667 '� storm,and at a slower rote at the end of fhe sform,but it � is�nol_�o�ssible for a.gmvity system fo require less stor• T = 74.22 min � ogc�on�he comlant rate rystem for.a given size oullef. -- � �� .. Calculate the maximum volume of sloroge per ocre Relention basin design imperviousness irom the orifice c-�.�!:et srorage equotion. � ,i DESIGN MEfHOD 1050�T 1 1. Defermine the amountof acreoge(A)contribuling VS — T + ZS —40 OoT runoff to the reteMion basin ond its runoff coef8cient (C�. 10500�74.22) �� 2. Determine Ihe mazirnum al�owable outFlow in Vs = �4 22 �F 25 —40(0.667)(74.�2) '� CFS from the loml municipal government reaula- ' �� tions and/or the exisling ouiiet mnditions if there Vs = 5875.18 ft'/acre imperviousnass �, are no governmeN regulations. q, Ccdcula�r Ilie tofol volume of 5toroge rrquired (or � 3. �alculale Qo = I Allowa6le �ut0ow __ the enure sile. Acreoge X RunoR Coefficienf V1 = Vs X ti acres X runoff wefficient � ,' ' 4. Determine the type of outlet that will be used. (ori• Vt = 5875.18 (50)(0.30� � 1 fice or pump� �.�� 1 5. Calculate fhe maximum storage time(T� from Ihe Vt = 88,127.76 ff' � � � slorage time equa:,on corres�anding to !ne type of � K oullet selected in Step 4. 5. Because of s��ficienl grade available, Ihe design ' 6. Colculale ihe ma:imum storage(Vs)from the stor• depth of rcfenhon is 6.5 ft. Now selea o . oul(low � age equation correspc.�ding to the type of auflel se• ^� �, pipe from the orifice �ormula thal will yield the �I• � � IecteJ in Step 4. (Vs will be in 7`.��• , lowable outflow of 10 CFS unaer a head of 6.5 fl. fP ��(�� Acres X Runoff Coe?¢ient Q = 0.62a \ 2 gh � 7, Colculate Ihe total volume of stora e required for � the eMire'site (VI = Vs x C X�A Q _ 10 CFS 90. If fhe ouflel is to be on orifice o eratin Arca = . . P 9 �nder a 0.62 '�2 gh 0.62 \ 64.4� J � head, select a depih o, retention and a corre- • i � sponding oulflow pipe thal v�ill yield an out0ow in sec- 7 CFS equal to the maximum allowable as defen Area = 0.785 fr � mined in slep 2 operating under 1he head as dcler- . mined by Ihe depth of retention. Selecl a 12 in.-diameter outflow pipe Rb. If thvoutlet ii to be a pump,eeled a dep�h of reten- 6. Pbt ihe sfmage required per acre imper�ious:iess � tion and a pump that will yield an oulflow in CF$ (Vs) versus the oufflow per ocre imperviousness equal to Ihe maa�mum allowable as defermined in (Qo)on ihe orifice outlel �roph. One will see ihol step 2. it falls eaacfly on �he curve. 0 1 ' dT ,. � .� .. . ,