Res-2022-046 - Laserfiche WebLink

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climate data, For the stormwater retrofits, the water quality design storm is based on the 6-month, 3-hour in accordance with the S\ /MMEW (Ecology, 2019r. 3.3. Stormwater Features The existing storm sewer mapping was developed with the Plan. lt includes a storm sewer nefwork of clay and PVC pipe, catch basins, manholes, and a ditch. The majority of the urbanized developed area within the City drains to a main storm sewer trunk line discharging to a 200-foot-long ditch south of East California Avenue. This ditch flows into Crystal Creek east of East Hoffmanville Avenue. The area south of California Avenue lacks storm sewer infrastructure. 4. Core Element Analysis Ecology expects a Core Element analysis for all projects, even if the project is a retrofit. Ecology uses this analysis to determine project eligibility for funding, This site is considered redevelopment in accordance with Section 2,6 of the S\ AIMEW (Ecology, 2019). The project does not include any changes to land use or additional impervious areas. Furthermore, the project does not propose replaced impervious surfaces. Therefore, according to the flow chart in Figure 2.2 of lhe SWMMEW (Ecology, 2019), the Core Elements #2 and#3 apply to the tand disturbed. The project does not require Preparation of a Stormwater Site Plan (Core Element #1), Preservation of Natural Drainage Systems (Core Element #4), Runoff Treatment (Core Element #5), or Flow Control (Core Element #6). Ecology has established a procedure to quantify the water quality benefit for retrofit projects. A baseline is determined based on what would be required if the project was to meet nedredevelopment standards. The project does not require Runoff Treatment (Core Element #5) or Flow Control (Core Element #6) being this a retrofit project. The water quality benefit expected under this retrofit project is described later under Section 7. 5. Alternatives Considered The study identifies Best Management Practices (BMPs) to provide stormwater runoff treatment for Total Suspended Solids (TSS) and provide for reduction in other pollutants within the urbanized areas of the City. The alternatives considered for this study are intended to meet these design objectives. Priority is given to Low lmpact Development (LlD) BMPs that accomplish both flow control and runoff treatment, although runoff treatment is the focus of the retrofils. Table I provides a summary of the considered alternatives along with descriptions, benefits, limitations, and recommendations regarding preferred alternatives. 4