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2023 Docket Enabling Ordinance December 19, 2023 <br />Page 101 <br /> <br /> <br />developer, owner and/or designer of liability for errors or omissions in the design of <br />storm drainage facilities. <br />B. Core Element No. 2: Construction Stormwater Pollution Prevention. Prepare and maintain <br />a construction stormwater pollution prevention plan on site during the entire project and <br />amend as necessary. <br />C. Core Element No. 3: Source Control of Pollution. Apply all known, available and <br />reasonable source control BMPs. Operational and structural source control BMPs shall be <br />selected, designed and maintained according to the SWMMEW. <br />D. Core Element No. 4: Preservation of Natural Drainage Systems. Preserve natural drainage <br />systems to the extent possible at the site. <br />E. Core Element No. 5: Runoff Treatment. Projects that result in five thousand square feet or <br />more of new pollutant-generating impervious surfaces shall design, size, construct, <br />operate and maintain runoff treatment at the site. Development proposing a volume- <br />based treatment facility shall design to the SCS Type IA storm with a 6-month return <br />frequency. Development proposing a flow-rate-based treatment BMP shall design <br />facilities using Method 1 or Method 2 as described in Section 2.7.6 of the Storm Water <br />Management Manual for Eastern Washington when treatment occurs before detention. <br />When treatment will occur downstream of a detention BMP, designers shall use the 2- <br />year release rate of the detention BMP. <br /> <br />F. Core Element No. 6: Flow Control. Projects that result in ten thousand square feet or <br />more of new impervious surfaces shall design, size, construct, operate and maintain <br />stormwater flow control facilities at the site. <br />G. Core Element No. 7: Operation and Maintenance. Projects that utilize structural BMPs <br />shall prepare an operation and maintenance plan that is prepared in accordance with the <br />SWMMEW. <br />H. Core Element No. 8: Local Requirements. Projects that meet the requirements of Kittitas <br />County Road Standards will meet any optional requirements that are adopted as a part <br />of this chapter or required by Kittitas County Public Works. <br />I. Conveyance Systems. All new conveyance systems, and existing conveyance systems <br />receiving increased flow rates as a result of a project, shall be analyzed and designed to