CHALLENGES IN THE DEVELOPMENT AND IMPLEMENTATION OF A BACTERIAL TMDL IN AN ARID ENVIRONMENT

The City of Los Angeles will be subject to more than 60 TMDLs over the next decade. Los Angeles is situated in an arid environment, receiving on average less than 20 inches of precipitation per year. Most of this precipitation comes during the “rainy season”. The City's major river, the Los Angeles River, is highly modified and effluent dependent. Most of the year flows in rivers and streams in the Los Angeles area are modest, and the water is of anthropogenic origin. During rain events, flow can increase by orders of magnitude for a short period. This makes Total Maximum Daily Loads (TMDLs) especially challenging because compliance must address these extreme flows during rain events, yielding in some cases separate wet- and dry-weather compliance strategies. These challenges, which are financial as well as technical, are discussed here for the Santa Monica Bay Beaches Bacterial TMDL (SMBBB TMDL).