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Ci13NGRAL CONSIDf.iRA'fION <br />'�hc property in question is approximatch� 2.0 acres in size with a stream/wedand diat <br />bisccts the property in a north-south dircction. 'The proposal is to construct 23 single <br />I�amily units in thc R I a zonc to City Standards. <br />"l�he exisling vegetation consists of 7-8 ycar old Alder trecs and blackberry bushes. The <br />vcgetation docs not havc undcrlying mat of leavcs, etc. that would qualify thc site as even <br />a second growth iorest condition. Flowevcr, f'or purposes of this project we will use the <br />CN number corresponding to a sccond growth forest condition but usc thc actual <br />condiiion for runofT timc for conccntration. <br />Drainagc on thc sitc is towards thc strc.imhvciland; soil typcs are I lydrologic Soils C and <br />ior lillurc purposes under thc l:verett Storm�vater Managcmcnt Manual- wc have uscd <br />soils typcs at SmiJy Loam. <br />PLANNGD CONDI IIONS <br />'I�hc storm drainagc will bc handlcd in thc follo�ving �v:iys: <br />I. 'I'hcrc will bc a R/D vaull constructcd to handlc stonnwater from thc main <br />road and drivcways .md thc rootiop buildings for thc f'our castcrly �anits; it <br />will he sizcd to control thc runoff 1rom the 2 ycar developed storm to a ratc <br />calculated lor'h the existing ratc, 10 year developcd to ihe 10 year existing. <br />100 ��car devcloped to the 100 ycar cxisting �vith the City's cor�ection factor <br />addcd in. ft will be an open pond (with fencing) with water quality Fcawres <br />per thc Cily's rcquircmcnts. <br />2. Dispersion trcnches will be provided lo c<trry wuter Irom the downspouts from <br />all but thc 4 most castcrly lots (cach unit will have 7(0 s.f.) which will drain <br />into thc wctland/strcam to providc a sourcc of watcr for thc wetland/strcam. <br />fhcy �.vill bc sizcd similarly to thc projcct recently constructed two properties <br />(a thc north. l:ach of thc fimr trcnches will hc constructed parallel to thc <br />contours ancl will hcn�c dil�lcring dimcnsions. <br />CALCULA'I'IONS <br />Calculations li�llow lor thr ruol'top inliltration trcnchcs <br />Units 3-7 will havc 3800 s.0 tributar�• to it. ��t 4'W e ZS'D and 1.30'/IOOs.f. requirc 49 <br />I.0 of trcnch: 50 I.0 arc providcd: <br />Units S-I I n�ill li,nc 30d0 s.f tribumr� to it. �\t -�'1\' s 2.i'D and 1.3'/100 s.0 requirc 39 <br />Lf of u•ench: �0 I.0 are pru��ided: <br />Units 12-tG will ha�c i800 s.ftributary to it. At +.>�\1' x 2.i'D and 1.27'/100 s.f. <br />rcyuires 4S I.f. oftrench: �0 I.0 arc providcJ. <br />� <br />