10330 4TH AVE W 2016-01-01 MF Import

SUMMARY OF STORM DRAINAGE ANALYSIS FOR THE SOUTH POINTE ASSISTED LIVING FACILITY SECTION 24, TOWNSHIP 28, RANGE 4 EVERETT, WASHINGTON December 12, 1995 GENERAL This portion of the analysis is included as an addition to the storm water hydraulic calculations to give an overall description of the storm drainage system on and off the site. For this analysis one site visit was made to note the condition of the existing drainage system. PROPOSED SITE The project site is located on the west side of Emander Road (4th Ave W) just north of 104th Street SW in Everett, Washington ( See enclosed vicinity map ). The applicant is proposing to construct a single level assisted living facility with a total area of approximately 10,000 square feet. The site is about 0.55 acres and consists of a single drainage sub-basin that has been labeled SB-1. The existing site was previously used as a single family residence and cc+nsists of three b��ildings with associated sidewalks, lawns, and gardens. The site topography is generally flat with some sloping in the southwest corner at about a 2% grade. The drainage pattem is basically a sheet flow and the surtace flow appears to infiltrate prior to leaving the site. There is no off-site upstream tributary drainage basin contributing to the project site. METHOD OF ANALYSIS Drainage calculations were pertormed in accordance with methods described in the 'Stormwater Management Manual for the Puget Sound Basin' . Proposed storm drainage conveyance and detention facilities were analyzed using the Soils Conservation Services (SCS) hydrograph method. The 'Water Works' Hydrology program was used to generate, add, and route hydrographs.