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1.5 PREPARING A STORMWATER MANAGEMENT PLAN The intent of this section is to assist with an applicantis stormwater facility planning efforts. These steps are not required for design, permit, or construction approvals, yet are useful to consider when preparing stormwater management plans. - Step 1- Layout Your Proposed Footprint Prepare a site plan that shows all existing development, proposed development and the grading details of the site. Step Z - Identify Your Stormwater Management Needs Flood Control: All stormwater runoff from impervious surfaces must discharge to approved discharge points (Eugene Code 9.6791, Appendix A). Identify existing impervious surfaces, the existing stormwater discharge points for those existing impervious surfaces, and the available existing stormwater systems. For more information on " Stormwater Flood Control° see SCWM 1.6 of this manual. Stormwater Quality: Generally, all development and redevelopment land use applications and building permits that propose 1 square feet or more of new or replaced impervious surface must treat the stormwater runoff from that impervious area on -site before discharging to ' the public stormwater system (for exemption review, see Eugene Code 9.679, Appendix A). For more information on " Stormwater Quality" see Section 1.7 of this manual Oil Control: Eugene Code 9.6794 (Appendix A) Flow Control: Stormwater runoff from non - residential development sites that will be conveyed by an open drainage way located in a Headwaters Stream (see map, Appendix n, may require retention or detention (see Eugene Code 9.6793 for specific code requirements). For more information on "Flow Control" see Section L9. If the site is at or above elevation 500 feet, and using a vicinity map, trace the stormwater runoff How pattern from the development site to an elevation below 500 feet If the stormwater runoff does not enter a Headwater Stream, no How control standards are needed. Source Controls: Site uses and characteristic such as, fuel dispensing, above ground storage of liquids and bulk storage, material transfer areas, loading docks, solid waste storage, vehicle and equipment washing areas, and parking areas may trigger additional water quality measures. For specific code requirements on what uses and characteristics will require additional measures, see Eugene Code 9.6795. Typical source control measures include covering potential pollutant areas, paving the areas to protect the underlying soils, hydraulically Isolating drainage patterns, and containing potential pollutants. Chapter 3 of this manual will provide details on which measures to implement Step 3 - Evaluate Your Development Site and Development Plan Identify the types of soils and infiltration rates of the soils. Identify the ultimate discharge point(s) of the stormwater runoff from the site. Calculate your new /replaced impervious surface area(s). Stmmnvater Management Manual 1 -13 Eugene 2014