2000 TOWER ST INDEX HALL 2023-12-29

METHODOLOGY Drainage design for the project is based on City of Everett Municipal Code (EMC) 14.28, Surface and Storm Drainage. EMC 14.28 refers to the 2019 version of the Washington State Department of Ecology's (DOE) Stormwater Management Manual for Western Washington (Stormwater Manual) for the city's stormwater technical manual. This project is located within a Combined Sewer Collection Area and subject to different stormwater requirements, detailed in Section 6-10, Combined Sewer System, of the 2020 CS'ty of Everett Design and Construction Standards and Specifcations (DCSS). The project is categorized as a redevelopment project, but falls below the threshold for flow control BMPS. On -site storrawater management design requirements will be used for this project to achieve the Flow Control Performance Standard. The following sections address the requirements from Section 6.10 of the DCSS. STORMWATER NARRATIVE Existing Conditions The project site is currently an open grass lawn area with pedestrian sidewalks. The site is bounded to the north by a campus pedestrian plaza near Glacier Hall, to the west by the Gray Wolf Hall building, to the east by the Shuksan Hall building, and to the South by a paved campus parking lot. Access to the project site is from the parking lot for vehicles and sidewalks for pedestrians. The site is generally flat, with slight sloping from south to north. The site is composed mostly of grass lawn, with two pedestrian sidewalks running north -south through the site. A portion of the site was occupied by the Index Hall building (13,320 SF), which was demolished in the summer of 2019. The majority of the stormwater from the site infiltrates the underlying soil. Some stonnwater is collected in area drains that discharge to the existing private combined sewer system, which discharges to the City's combined sewer system that extends to the northeast. Downstream Analysis Stonsevater from the project site discharges to an existing private combined sewer system that extends approximately 130 feet to the north edge of the Index Field Quad before turning and continuing east. The pipe system continues east for approximately 650 feet to an 18-inch pipe system along Tower Street. The private 18-inch combined sewer continues east along Tower Street for approximately 700 feet before turning and extending north along Waverly Avenue. Stormwater Site Plan 2 Oh = Index Lawn Project