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I <br /> Figure 2: Terrestrial Attenuation for Hard Sites <br /> I <br /> Terrestrial Attenuation for Hard Sites <br /> 90 <br /> ��� „S <br /> 80 p <br /> • <br /> 70 <br /> 60 "Tali <br /> v <br /> b40 Background Noise <br /> 416.lit _ -- -,n Construction Noise <br /> 20 =_ _= — _--- <br /> + 134.86 <br /> 0 <br /> 50 500 5000 50000 — 8 6561nx <br /> )Distance(feet) <br /> I2.4.2 Turbidity <br /> I Onsite clearing, earthwork and landscaping activities could potentially temporarily suspend sediment <br /> materials. If runoff from construction and landscape activities entered the Snohomish River, <br /> suspended sediment in the runoff may cause a temporarily increased level of turbidity. While no in- <br /> I water work is proposed, some work may occur at the river's edge beyond the protection of a silt fence. <br /> The Washington Administrative Code (WAC) makes allowances for temporary turbidity due to <br /> construction activities in WAC 173-201A-200(1)(e). Temporary mixing is subject to constraints of <br /> I WAC 173-201A-400(4) and (6). For waters less than or equal to 10 cubic feet per second (cfs) flow at <br /> the time of construction,the point of compliance shall be 100 feet downstream of the action.If waters <br /> are between 10 cfs and 100 cfs during construction the point of compliance shall be two hundred <br /> I (200) feet downstream of the Action Area.Due to the stream's estimated flow rate,two hundred(200) <br /> feet downstream temporary plume limit is being included in the Action Area to account for possible <br /> increases in downstream turbidity associated with buffer restoration. Any turbidity impacts are <br /> I expected to be temporary and minimal due to the small scale of the activities, conservation measures <br /> and BMPs for the project. <br /> I In addition, new impervious areas may have an effect on local hydrologic and water quality function <br /> within the watershed. As there are currently no stormwater collection conveyances and treatment <br /> established to collect and treat runoff from these surfaces.The proposed project improvements which <br /> I include stormwater detention facilities,water quality treatment,and adequately sized infiltration should <br /> not only minimize downstream impacts to the floodplain, but improve the overall downstream <br /> condition of the Snohomish River. <br /> I <br /> Soundview Consultants LLC December 8,2016 <br /> 1413.0003 Riverside Business Park—FEMA ESA Habitat Assessment Report Page 6 <br />