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'i �:..u.9. <br /> �,. , <br /> R <br /> � � �' , <br /> ,o � � <br /> Ga H <br /> t" y f/� <br /> H� H I <br /> K n <br />� y �y <br />� � H � V�I G4 'kiCi 14�lb UHVIU EVH('IS S, RSSUC_'ATES BELLEVU P.7/17 . <br /> fn H <br /> [�JO � <br /> H t7 <br /> OH <br /> O <br /> �� � CONCEPTCTAI. PRO,�ECT biITIGATiON <br /> � y� � i <br /> f�i� y <br /> ge y Due to the presence of low value wetlands, filling them as proposed, is expected to cause ' <br /> �a� r on]y minlma! impacts to the site. A micigation plan to compensate for the ]oss of chese � <br /> � y � wetlands is nlso pro posed on the Phase 1T porlion of the project. This mitigadoa plan <br /> y o � e mmends a 1:1 rado of re lscin the existing wedands with the crzation o f ne w we t l a n d <br /> r co P S ,i <br /> c Y7rdvzrs <br /> habitat, and would be d'uectly associated with ihe recommendadon of a re ent ry <br /> of Waslungton study. <br /> A University of Washington, Department oE Civil En�neering smdy was conducted to <br /> analyze and make recommendatior�s for improving the water qualiry of Silver L,al:e,locatcd <br /> direcdy south of the subject development site. This s[udy (Silver Iake �Vater Quality, <br /> Nutrient Loading And Man<lgement, Water Resources Series Technica! Report No. 106- <br /> May, 1985) spacifically recommends watershed improvements to counteracc inereased rates <br /> of surface water runoff caused by clearing of native vegetation and larger areas of <br /> impervious surfaces as a result of increased developmenc. 1'lie same study refers to thc we <br /> and importance of vegetated clrainage courses and ponds for filcering pollutanu, dataining <br /> storm water,and thercfore, improvinE qualiry water that may enter Si1vCr La:e. The Pl�ase <br /> j �.► II portion of the Silver T2idge Apanment Project has been idenufied by the Silver Lakz <br /> o�.� water qualiry study as a desirable retention/decenuon ponding arza of sufticient size to <br /> � serve two sub-Uasin areas. <br /> , f"'� Wefland mitigauon is proposed for the dalineated wedand areas (Pigura 1) that exist on <br /> "�` the subject properry. Uue to their ce;neral property locution and consrquent atfects on the <br /> project si[e plan, thz exis[ing wedand valuns and funccions have been reviewad. Wedand <br /> creauon projects can be considered when exisdng wetlanJ values are low and desired I <br /> I 1��� miUgation resulW are feusible. An availabie water sourca combined with lar_d having little <br /> topograpluc relief are two cricical elamants for mitigation fexsibility. A source of water and <br /> appropriate land for mitigation appeur to be availabla for wetland davelopmenG This <br /> section discusses concepts related to development and creation of higlily valued wetland <br /> ��1 habitat. <br /> The impacts from proposed 611ing of the wetland areas can be easily compensated througli <br /> � '�� a mitigation plan that emphasizes mcreasing water quality and by incorporating a higher <br /> value wedund habitat. The nortl�ern poruon of ��e subjea property appears to have an <br /> � adequate source of water for wedand creation and, if intercepted aecording to the projeet's <br /> approved drainage plan, will be d'uected to an appropriute site for water qualiry <br /> �I(�d imprcvement and pocen:ial storm water sturage. �xcavacion for a wedand sice having a <br /> significant area of open watar would allow introduction of aquacic bed planc species such <br /> as water-lilies and common duckweed. The potential eusts for adding ocher vegetation <br /> zones of emergent marsh and scrub/shrub communitizs that create diversity and wildlife <br /> covar. These two zones offer more wcdand funccional v�ilues by incorporaiing plant species <br /> such as seJges, bulrushes, cattails,waterpluntain, and arrowhead (emerpent marsh zone) in , <br /> addition to willow, red-osier dogwood, western crabapple, and bearberry l�oneysuckle <br /> (scruU/shrub zona). I <br /> ', <br />