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A Jitched, scasonal drainagc fhat yualifics :Gs a C:itcgory N strcam flows along the castcm property <br /> boundary from north to south. 'J'he drainage enters a 17G-foot long culvert that discharges into <br /> Silvcr Lakc, south of SR 527. The drainage convcys Ilows from a detention pond and wedand <br /> Ircatcd north of 110'�' SlreeL The drainagc also collects nmotf from roof drains and untreated <br /> su,�.Lc nmoff from an apariment complcx to the cast as well as from the Safeway slore in the <br /> north�vestem portion of the site wh�re the current drainage system docs not c•�ntain and collect a!I <br /> runoff: Vcgetation along the drainagc is dominated by mowcd lawn to the cast (off-sile) and weeds <br /> such as Himalayan blackbcrry along its westcm tlank(on-site). <br /> DEA identificd one small (4,2G8 square-foot) Catcgory 3 wetland (Wetland A) associated with the <br /> scasonal drainagc locatcd along lhe castcm property boundary. "Phc wcUand is dominated by reed <br /> c:u�arygrass identificd as an invasive wced by thc City of Everett. "Che wetland appears to have <br /> formed as a result of overtopping of lhc clitch during high Ilows. The wetland is located zdjacent to <br /> a 90-degree bend in �I�c ditch whcre evidencc of overiopping is demonstrated by erosion and <br /> sedimcnt deposils. <br /> General �yetlancl runetions. The existing fimctions provided by WeUand A are si„enircantly <br /> limitecl by thc currently dcgraded conditions. Watcr quality is likely compromiscd by the discharge <br /> of untreated runoff into thc on-sitc drainagc, the past degradation of vegetation along the drainage <br /> corridor and within the wedand, tlic ditching and other�;rading A�at has occurred over time, a��d the <br /> continuous dumping of trash in and around thc wcUand. Ditching, grading,soil compaction, culvert <br /> install:dion, and vcgetatiai alteration havc degraded hydrology, including groundwaler excliinge <br /> and tloochvatcr storagc. Wildlifc habilat fimctions havc been impacted by vegetation alteration, <br /> which has resulted iu decrcascd haUital divc!sity and the establishmcul of predominantly weeds on- <br /> sitc. The dumping of trash, pcist brading, and dominance of �viceds on-site has significantly <br /> compromisccl sitc acsthctics. <br /> Stormwatcr Storagc runclions. Un�lcr thc cxisting conditions, thc drainage ditch that flows <br /> tiirough Wclland A is lhc pri!nary source of wctland hydrology. WeQand A receives water that <br /> ovcrtops the ditch during high tlow evcnts. Groundwatcr derived from the ditch during the periods <br /> that it covcys watcr is also a likcly source of wetland hydrology. Based on topography survey data, <br /> approximatcly I,S00 squarc fect of d�e wctland occurs in a slight depression and traps surface <br /> �vater, whcrcas lhc remaindcr of thc �vedand is a flo�v-through system that does not retain surface <br /> «�ater. Thc �verigc dcpth of the depressional portion of Wetland A is less than 0.5 feet below the <br /> elevation of the Iop of tlie ctitch. Given lhis, the dead storage capacity of the weUand is less than <br /> 900 cubic fect. 13ecausc U�e llo�v-through portion of the wetland has no metered tlow (unrestricted <br /> outlet), no ef!ectivc live storagc is provided by Well:uid A. <br /> The hydraulic residence lime provideci by thc flow-through portion of Wedand A is considerably <br /> less thau onc d.ry. [3asc�1 on an estimated maxinmm ponding depth of 0.5 foot and usir.g an average <br /> cvapor.riion ratc for western �Vashington, the estimated l�ydraulic residence time }or thc <br /> appro�im,ilrly 900 cubic fect of pondcd n�ater would be about 19 months. This assumes tlrat tlie <br /> _ P Io10DN'B017J 011J45(U IkA4Re 'sN WMAmdRe�o�t Ju�y 1(pl doc <br /> Scnsilivc Arcas 1?v�lualion 12 July 2004 � <br /> Silvcr lakc Centcr Property �lj <br />