As with most of the region, the City of Fremont utilizes a municipal separate stormwater sewer system (MS4), simply referred to as the storm drain system. The MS4 refers to a conveyance or system of conveyances, including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drain. Stormwater and sanitary sewage are managed in separate systems. The MS4 discharges directly to nearby water bodies such as creeks, rivers, and eventually out to the San Francisco Bay without any treatment.

Green stormwater infrastructure (GSI) uses plants, soil, and natural processes to manage rainwater throughout Fremont. By mimicking how natural landscapes absorb and filter water, features like rain gardens, planted areas, and permeable pavement let rain soak into the ground instead of running off streets and sidewalks. This helps reduce flooding, improves water quality, and keeps pollution out of local creeks, wetlands, and the Bay.