Tainted runoff from urban areas in the 101 Freeway corridor in the northern part of the watershed have overloaded the waterways with nutrients and sediment, hurting aquatic life.
The U.S. Environmental Protection Agency is proposing new pollution standards for the creek and lagoon to reduce sedimentation and levels of nitrogen and phosphorus that stoke harmful algae growth.
Surveys have shown that bottom dwelling aquatic life – the clams, crustaceans and worms eaten by birds and other wildlife – are in poor shape, affecting the greater ecosystem.
Ultimately communities in the upper watershed such as Agoura Hills and Calabasas, along with the Los Angeles County Flood Control District, would be required to take steps to reduce polluted runoff.
If successful, the controls would mean cleaner water flowing into the lagoon, a coastal wetland that the state is dredging and reshaping as part of a controversial restoration project.
The proposed standards, which also include new pollution limits for parts of the Ventura River, are the final ones developed under a 1999 legal settlement between the EPA and local environmental groups. The agency is expected to adopt the standards after a 40-day public comment period.