The Clean Water Act was enacted in the United States in 1978, representing one of the most significant pieces of environmental protection legislation in the nation’s history. Amended several times since, the Act gives the United States Environmental Protection Agency and State regulatory agencies far-reaching authority over facilities that discharge pollutants to waterbodies, including municipal stormwater systems. Within the past five years, particularly in southern California, pollutant discharge permits for municipal stormwater systems have begun to include strict limits for pollutants in discharges to impaired waterbodies. As a “compliance pathway”, the stormwater permits in the Los Angeles region have adopted an innovative watershed planning approach based around peer-reviewed, public domain water quality and BMP models. Development of these plans, known as Watershed Management Plans, has provided, for the first time, detailed estimates of the extent and location of stormwater infrastructure required to achieve water quality standards and the associated capital and operation and maintenance costs.
This paper will present an overview and outcome of five (5) major Watershed Management Programs in the Los Angeles area. Each plan covers numerous cities and waterbodies with an “infrastructure recipe” that has reasonable assurance of achieving the water quality standards for those waterbodies. The recipe includes the location and extent of low impact development (LID) projects, green streets, and regional projects that intercept runoff from large drainage areas. The modeling approach is based around two public-domain models – a watershed model known as LSPC and a BMP model known as SUSTAIN – both supported by USEPA. Detailed engineering efforts were used to develop the inputs and assumptions of the BMP model and also to develop cost estimates. By electing to pursue the optional compliance pathway in their Permits, the municipalities have facilitated a robust, integrated approach to stormwater management for their watersheds to address the priority water quality conditions.