12728 19TH AVE SE BASE FILE 2025-07-29

4. DEVELOPED CONDITIONS The proposed project Everett Office Building is located at Bothell Everett Highway in the City of Everett, Washington. More generally, the site is located in Section 30, Township 28 North, and Range 5 East of the Willamette Meridian in Snohomish County, Washington. The project contains approximately 1.44 acres. There are no critical areas located within the site. The proposal is to construct a three-story commercial office building, approximately 0.95 acres of parking area, and associated utilities. The access to the site will be from 19th Ave. SE(SR527). An 88'x 24.25' x 7.7' vault is proposed to meet the detention requirements conforming to the City of Everett standards. The vault is sized to accommodate a volume of 8,406 CF which includes a factor of safety of 42-percent. SBUH methodology using "Stormshed 2G" software by Engenious Inc. is used for detention/water quality calculations. The detention system is designed to release at %2 of the existing 2-year, 10- year, and 100-year frequency storm event rates with detention sizing for the 100-year storm. The 2-year, 10-year, and 100-year(24-Hour) storm volume calculations assumed the existing site to be second growth forest with a CN= 81. Pre-treatment in the form of 3' of dead storage has been provided within the vault per city of Everett standards. The outflow from the vault will be discharged to the existing storm on the west side of 19th Ave SE via a closed pipe system. Water quality would be obtained by the use of a 5- cartridge stormfilter downstream of the detention vault per City of Everett standards. The soils were found to be of low permeability as per the Geotech report. We will not use any Low Impact Development(LID)practices for this project.