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Thomson Residence <br />Stormwater Site Plan Report <br />March 5, 2021 <br />Section I, Page 4 <br />Minimum Requirements <br />The project must meet the requirements of the Combined Sewer Requirements of the Everett Manual per <br />Section 6.10. These requirements take precedence over the requirements of the SWMMWW; however, <br />the project must consider the Minimum Requirements for stormwater management per Section 2.4 of <br />the SWMMWW. The project is classified as New Development and will consider Minimum Requirements <br />#1-5 because the amount of new plus replaced hard surfaces is less than 5,000 sf. <br />6-10.1(1) Flow Control: Per the requirements of the Combined Sewer section of the Everett Manual, <br />projects which add over 200 sf of net new impervious surface or convert Y acres of native vegetation to <br />lawn or landscape must comply with the flow control performance standard of section 6-10.1 of the <br />Everett Manual. The project adds more than 200 sf of net new impervious area, and flow control is <br />required. A description of the Flow Control Measures on the proposed project is in Section IV. <br />6-10.1(2) Design Documentation: Projects in the combined sewer area shall provide documentation of <br />compliance with the stormwater standards. Proper documentation and calculations have been provided <br />and are shown in this report and the civil plans. <br />6-10.2 Conveyance Sizing: Stormwater conveyance systems shall be designed and implemented according <br />to Section 4-2.2 of the Everett Manual. Section 4-2.2 specifies that conveyance systems be sized for the <br />25-year recurrence interval peak flow rate. See Section IV for conveyance pipe calculations. <br />Minimum Requirement #1: Preparation of Stormwater Site Plans: The stormwater site plan consists of <br />this report and the civil drawings and is prepared in accordance with Chapter 3 of Volume I of the DOE <br />Manual and the 2016 Ordinance. <br />Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (SWPPP): The SWPPP <br />shall include a narrative and drawings. The SWPPP narrative shall include documentation that addresses <br />the 13 elements of Construction Stormwater Pollution Prevention. See Section V and the civil drawings. <br />Minimum Requirement #3: Source Control of Pollution: All known, available and reasonable source <br />control BMPs are required for all projects approved by the City. BMPs for Landscaping and <br />Lawn/Vegetation Management (S411 from Section 2.2 of Volume IV of the DOE Manual) should be used <br />for lawn/vegetation management on this site. The Operation & Maintenance Manual found in Section VIII <br />addresses Lawn/Vegetation management. <br />Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls: Natural drainage <br />patterns shall be maintained, and discharges from the project site shall occur at the natural location, to <br />the maximum extent practicable. The manner by which runoff is discharged from the project site must <br />not cause a significant adverse impact to downstream receiving waters and down -gradient properties. A <br />qualitative analysis of the upstream and downstream system entering the site is presented in Section III. <br />250 4th Avenue South, Suite 200 <br />Edmonds, WA 98020 <br />ENGINEERING ph. 425.778.8500 1 C 425.778.5536 <br />www.cgengineering.com <br />