ABSTRACT
A 20-ha fallow agricultural field in Fremont (Alameda County), California was converted into a seasonal freshwater wetlands. Impetus for constructing this system was multiobjective, but driven by recognition that urban stormwater runoff is a significant pollution source to San Francisco Bay. Developing wetlands to treat urban stormwater runoff presents a different set of problems than developing a system to treat wastewater. This chapter addresses these differences and creation of a particular wetlands. Wetlands enhance water quality through a variety of physical, chemical, and biological processes that trap and degrade pollutants. The physical processes of sedimentation, adsorption, and filtration are key in capturing pollutants. Once in the system, pollutants may be degraded, stored indefinitely, or removed periodically (usually through dredging). Clearly, urban stormwater wetlands systems provide an outstanding opportunity to meet water quality objectives and provide a multitude of other benefits to society.
