9929 EVERGREEN WAY HORIZON BANK 2018-01-01 MF Import

The siltation control devices will remain in place until all construction work is completed per the specifications and details on the construction plans and all areas are stabilized. All pipes and catch basins will be cleaned and flushed prior to being put into service. Once constructed, proper, regular maintenance of the treatment and conveyance system will allow the systein to function optimally. Downstream Analvsis: Runoff from the site will enter the public drainage system at two locations. The rooftop runoff will be tight-lined to an existing manhole near the southwest corner of the proposed building in 100T" Street. Runoff from the remainder of the site will be discharged tu the system in 4T" Avenue east of the site. Ttiese two systems converge at the intersection of 100T" Street and 4T" Avenue southeast of the site. Both systems consist of 24" concre:e pipes and manholes. The drainage continues south along the west side of 4T" Avenue to Everett Mall Way. At this point the drainage flows northeast along Everett Mall Way in 18" and 15" pipes. The pipe siopes appear to be greater than those found in the 24" pipes, therefore providing su�cient capacity. Conclusions: The proposed development will decrease stormwater runoff, due to the required landscaping and the existing site being impervious. It is proposed to treat all of the runoff frorn pollution generating surfaces prior to discharging from the site. There are no anticipated adverse impacts on the downstream conveyance system due to this develapment. M:\Sdg�2004�259-SDG-04 - FSI - Horizon Bank in Everett\DRAIN\Drainage Analysis•259.doc �