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climate data. For the stormwater retrofits, the water quality design storm is based on the 6 -month, <br />3 -hour in accordance with the SWMMEW (Ecology, 2019). <br />3.3. Stormwater Features <br />The existing storm sewer mapping was developed with the Plan. It includes a storm sewer <br />network of clay and PVC pipe, catch basins, manholes, and a ditch. The majority of the urbanized <br />developed area within the City drains to a main storm sewer trunk line discharging to a <br />200 -foot -long ditch south of East California Avenue. This ditch flows into Crystal Creek east of <br />East Hoffmanville Avenue. The area south of California Avenue lacks storm sewer infrastructure. <br />4. Core Element Analysis <br />Ecology expects a Core Element analysis for all projects, even if the project is a retrofit. Ecology <br />uses this analysis to determine project eligibility for funding. This site is considered <br />redevelopment in accordance with Section 2.6 of the SWMMEW (Ecology, 2019). The project <br />does not include any changes to land use or additional impervious areas. Furthermore, the <br />project does not propose replaced impervious surfaces. Therefore, according to the flow chart in <br />Figure 2,2 of the SWMMEW (Ecology, 2019), the Core Elements #2 and #3 apply to the land <br />disturbed. The project does not require Preparation of a Stormwater Site Plan (Core Element #1), <br />Preservation of Natural Drainage Systems (Core Element #4), Runoff Treatment (Core Element <br />#5), or Flow Control (Core Element #6). <br />Ecology has established a procedure to quantify the water quality benefit for retrofit projects. A <br />baseline is determined based on what would be required if the project was to meet <br />new/redevelopment standards. The project does not require Runoff Treatment (Core Element #5) <br />or Flow Control (Core Element #6) being this a retrofit project. The water quality benefit expected <br />under this retrofit project is described later under Section 7. <br />5. Alternatives Considered <br />The study identifies Best Management Practices (BMPs) to provide stormwater runoff treatment <br />for Total Suspended Solids (TSS) and provide for reduction in other pollutants within the <br />urbanized areas of the City. The alternatives considered for this study are intended to meet these <br />design objectives. Priority is given to Low Impact Development (LID) BMPs that accomplish both <br />flow control and runoff treatment, although runoff treatment is the focus of the retrofits. Table 1 <br />provides a summary of the considered altematives along with descriptions, benefits, limitations, <br />and recommendations regarding preferred alternatives. <br />4 <br />