3523 BROADWAY 2025-07-24 - Laserfiche WebLink

Stormwater Site Plan Report CG Project#13017.20 Chapter III — Site Development Plan with On-Site Stormwater Management Chapter 111 Summary: Narrative The proposed area of work is to be collected in catch basins,tying into the site's existing storm system. The proposed work adds approximately 4,357 square feet of new/replaced impervious area, but is below thresholds for flow control and water quality. Several design strategies will be used to assist in on-site stormwater management and are listed in the following paragraphs.The most common design strategies that involve more infiltration and dispersion type techniques were not incorporated due to limitations of the site. Space limitations remove the possibility of dispersion, and the soil is not well suited to s` infiltration. It is not recommended that a rain garden be placed in the landscaping due to the area being within 100' of both deep soil contamination and the distribution system for 32,000 gallons worth of petroleum. Proposed improvements discussed below are recommended by the City of Everett Storm water Management Manual in Volume I,Section 3.2.4. To the maximum extent possible,the duff layer, native topsoil and natural vegetation on the site will be left undisturbed. Stormwater runoff from proposed impervious surfaces will be kept as close to existing conveyance systems as possible to minimize site impact.The runoff will be collected in site catch basins and routed into the existing conveyance lines. Lastly,the proposed site grading is designed in an attempt to limit the cut and fill quantities as much as practicable. Catch basins will be installed with floatable material separator/gas trap tees on their outlets, in order to provide a degree of water quality to site runoff. 250 4th Ave South,Suite 200 Edmonds, WA 98020 ENGINEERING