2611 ROCKEFELLER AVE ROCKEFELLER SQUARE 2 2024-08-12

SECTION IV: CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN ' This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the Construction stormwater permit requirements for the project Rockefeller Square at ' 2611, 2613, & 2617 Rockefeller Ave. Everett, WA 98201. It is located in Section 20, Township 29 North, and Range 5 East of the Willamette Meridian in the City of Everett, ' Washington. The site is currently developed with four residential homes. The site contains one ' drainage that slopes to the slightly to the east. There are no critical areas located within the site. Per NRCS survey of Snohomish County, the project site contains Alderwood soils that have a hydrologic classification of Type"C". ' The proposal is to construct a three-story residential building with an underground parking garage. The total proposed impervious surfaces will be 9,875 SF. The access to the parking garage will be from the alley in between Rockefeller Ave and Oakes Ave. The project site is legally served by a combined storm and sanitary sewer system, in which case the stormwater standards shall be as determined by Public Works Department ' policy. The existing basin was modeled as existing conditions per section 6-10 of the City Design and Construction Standards and Specifications. Flow control requirements will be ' met by a 19LF 4-foot diameter detention pipe on the south side of the building. The project is exempt from water quality as the project discharges to the combined sewer and any new PGHS will be minimal. ' Per Vol I figure 2.4.2 of the SWMMWW, Minimum requirements #1 through #9 shall apply for this project. Refer to section 1.2 for Minimum Requirements Summary. ' For onsite stormwater management (MR#5) list # 2 was used per Vol 1 section 2.5.5 of the SWMMWW. Full dispersion was considered first however it was deemed infeasible due to ' the lack of native vegetation. Downspout full infiltration and bioretention was deemed infeasible as the site lacks the necessary area to accommodate infiltration facilities within ' Insight Engineering Co. -Stormwater Site Plan 12/30/20 - I