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�l JACOBSON <br /> JCCONSULTING ERCIREERS <br /> Core Requirements: <br /> 1. Stormwater Discharge to the Natural Location — Drainage associated with the project <br /> will maintain its current drainage pattern. Stormwater runoff from the school will <br /> discharge into two different sub-basins and will connect to the City's combined sewer <br /> system. <br /> 2. Offsite Analysis: <br /> a. Direct Discharge to Combined Sewer Basin — The north and eastern portions of <br /> the school site discharge directly to the City of Everett combined sewer system, <br /> via piped connection, within Federal Avenue. The downstream flow path was <br /> observed (description provide below) and no areas of concern/flooding were <br /> apparent. <br /> Stormwater discharge from the site enters the municipal combined sewer system <br /> in Federal Avenue along the east edge of the project parcel. The combined sewer <br /> proceeds north in Federal Avenue via increasing pipe diameter, starting at 10-inch <br /> diameter pipe and increasing to 12" diameter pipe until reaching 33' Street at <br /> which time the combined sewer flows west for 2-blocks in 18" diameter pipe until <br /> changes direction again and flows north in Tulalip Avenue in 24" diameter pipe. <br /> No evidence of flooding or drainage issues were apparent along the downstream <br /> observations. <br /> b. Discharge to Wetland — Areas of the site that drain to the southeastern portion of <br /> the site drain through a depressional wetland located in the southeastern portion <br /> of the site was identified by the School District's wetland hydrologist. The wetland <br /> was identified as a category Ill wetland. Stormwater discharges to the wetland <br /> discharges under Federal Avenue in an 18" culvert. The culvert discharges to an <br /> open channel east of Federal Avenue and ultimately flows into a combined sewer <br /> system located in Friday Avenue. The combined sewer in Friday Avenue flows <br /> north and ultimately the combined sewer discharges to the same location as the <br /> other sub-basin on the Jackson Elementary School parcel. <br /> 3. Flow Control Facilities— Since the project is in the combined sewer basin and is not <br /> changing the net effective impervious surface (considering lawn areas with under <br /> drains are modeled in stormwater calculations as an impervious surface) no flow <br /> control facilities are being provided. <br /> 4. Construction stormwater pollution prevention — The project will pursue erosion and <br /> sediment controls to prevent, to the maximum extent practicable, the transport of <br /> sediment from the project site to downstream drainage facilities, water resources, and <br /> adjacent properties. <br /> 255 S.King Street,Suite 800,Seattle,WA 98104 I 206.426.2600 I JACOBSONENGINEERS.COM <br />