Resolution_City of Roslyn_PF Funding Award Agmt

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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 SWMMEW (Ecology, 2019). 3.3. Stormwater Features The existing storm sewer mapping was developed with the Plan. It includes a storm sewer network 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 SWMMEW (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 the SWMMEW (Ecology, 2019), the Core Elements #2 and #3 apply to the land 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 new/redevelopment standards. The project does not require Runoff Treatment (Core Element #5) or Flow Control (Core Element 46) 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 Impact Development (LID) BMPs that accomplish both flow control and runoff treatment, although runoff treatment is the focus of the retrofits. Table 1 provides a summary of the considered alternatives along with descriptions, benefits, limitations, and recommendations regarding preferred alternatives.