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S'CORIv1�VAT[R SITE PI.AN <br />:1UGUSTA NOODS COND01vfINlUMS <br />It�TENTION/D�TENTION SYST�`I <br />,b1AY 20, 2003 <br />PAG[ 21 <br />n��sty i <br />The stonn drainage systcm used in Basin I consists of collection and conveyance of <br />runoff to a sedimentation vault. The release from this vault is discharged to an <br />infiltration/dispersion trcnch. The trench has bcen designcd to intiltrate thc two year <br />runoff and overflow larger events as sheet ilow, diercby helpine to maintain die <br />hydrology of the wedand. <br />BMP RU.IS WET VAULT/TANK <br />The scdimentation vault has been sized for the 6 month storm event per the mquirements <br />of the CEM Manual using the following equations: <br />Q� = 6 month volumc/36,400 <br />= 771 /36,400 = 0.0089 <br />V,,,,,, = 1676.5 Q� H usc FI = 3.d2' <br />= IC76.5(0.0089)(3.42) <br />=�1 cf <br />A Cuz concrcte CCP �77 GI, or equal, provides approximately 1 l8 cf of dead storage and <br />is proposcd for usc on this projcct. <br />BMP RI.iS ROO� RUNO�F INPILTRATION AND DISPERSION SYS"CEVIS <br />The intiltration/dispersion trench sized according to thc rcquirements ot the CEM <br />Manual. .iic undcrlyin, soil is a sancfy loam material �vidi an infiltration ratc of 1.02 <br />inciies per hour, see Tablc 3-2.1 of the CGM Ma��ual. Thc trench outtlow was then sized <br />using Darcy's Law of ground water movement: <br />Q=f iAs <br />=(1.02)(I)(30*6)/(12*6U*60)=0.011 cfs <br />StormShedT"' was then used to route the 2 year storm event through the trench and <br />detemiine thc rcyuired depth oFdrain rock. A 24" perforated pipe and drain rock �vith a <br />minimum 30% void ratio was used to c�ilculate the storage ��olume. 5ec attachec( <br />Stom�ShcdT"' output in Appcndix D ti�r stugrstoraec, stagc-discharge and Icvcl pool <br />routing printouts. The rcquired trench dimensions arc as follows: <br />Lcngth = SO fcet <br />Widdi = 6 fect <br />Depth = 3.7 fect, (4.67 feet requircii) <br />Z2 <br />���e:,�x:-�c��:��n�5�s�,., w�c; sn� w.�o oa-m�oo�:,m���,�ssroa-0n.00cDWHl;rm <br />