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Sullivan Park Fire Station Conversion Draft Environmental Assessment 4.7 Floodplains and Hydrologic Assessment The Flood Insurance Rate Map (FIRM) prepared by the Federal Emergency Management Agency(FEMA)for the area of the proposed project-FIRM Map Panel 2160, dated September 16,2005-shows that neither the Conversion Site nor the Replacement Site is located within any Special Flood Hazard Areas that would be subject to inundation by the 100-year storm event(Appendix A,Figure 4.7-1) (FEMA 2005). The waters of Silver Lake are mapped as Zone A 100-year floodplain. The stormwater management facilities on the Conversion Site discharge runoff into Silver Lake. The additional runoff that results from site development is not of sufficient quantity to increase flood hazards on the lake. Development being considered on the Replacement Site,primarily trail improvements, should not affect the timing or quantity of stream flow in the on- site stream,which also drains to Silver Lake via a pipe system under I-5. Runoff from any impervious trails would infiltrate into adjacent forested soils. Wetland hydrology would also be unaffected. Therefore,there are no floodplain or hydrological impacts associated with the Proposed Action. 4.8 Water Quality 4.8.1 Surface Water Conversion Site The Conversion Site does not contain any surface waters, other than a drainage swale installed to collect stormwater runoff from the fire station roof, fire station parking lot (serves visitors and employee vehicles), and roadway. An oil-water separator in the fire station parking lot captures potential fuels which may be discharged in runoff. The fire engine bays and the fire engine washing area drain into the City's sewer system. Stormwater runoff from the roof and main parking lot is discharged from the swale into adjacent Silver Lake via the City's stormwater pipe system. Replacement Site The Replacement Site contains a Category I wetland along the eastern boundary,with a ditched, untyped stream flowing through it. Observations of the stream in both summer and winter suggest that it has perennial flow. As indicated above, development being considered on the Replacement Site, primarily trail improvements, should not affect the timing or quantity of stream flow in the on-site stream, and would thus not degrade water quality through increased erosion of stream banks. Stormwater from the trails,which would be Page 24