What on earth are TMDLs?
by Michael Weber
The water flowing down Mono Basin streams is as pure as one could want. This high quality makes these streams especially attractive to cities in Southern California, which need clean water to dilute the high concentrations of salt found in water diverted from the Colorado River. Indeed, water quality will only become more important in meeting the needs of more people in the future. A recent agreement between Los Angeles-based environmental organizations and the U.S. Environmental Protection Agency (EPA) will help meet these needs by improving water quality outside of the Mono Basin. It all has to do with TMDLs.The Clean Water Act of 1972 required a clean-up of the nation’s waters, which led to reductions in pollution from sewage treatment plants and industrial sources. (By promoting the use of low-flow toilets, the Mono Lake Committee helped sewage treatment plants in Los Angeles reduce the volume of sewage to be treated.) However, the government did little to stem the tide of pollution flowing from farm fields, city streets, and parking lots.
This will change under the recent consent decree between EPA and environmental groups. Under the decree, the EPA must start addressing these other sources of water pollution by setting Total Maximum Daily Loads or TMDLs for pollutants entering specific streams, lakes, and coastal waters.
Once set by the government, TMDLs will be divided among those groups or individuals polluting the water. For instance, the government will set a limit on the amount of nitrogen that can enter LA County’s Malibu Creek. This amount will be divided up among all of the polluters associated with Malibu Creek water.
Setting TMDLs for bodies of water in Los Angeles and Ventura counties alone will take many years partly because there are so many and such diverse sources of pollutants. Sources of pollution can range from farm fields to residential developments.
The payoff from the implementation of TMDLs will be waters that people can swim and fish in or use as sources for drinking water. And that is a good thing for Mono Basin streams.
Michael Weber is an environmental writer based in Southern California. He volunteered his time to gather this update for the Committee.
Return to Spring 1999 Newsletter
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