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Valley Briefing

Keeping Our Water Clean

April 21, 1996

What's in our water, and who makes sure it's safe to drink?

Water must be monitored regularly so that it meets state and federal quality standards. The Los Angeles city Department of Water and Power is responsible for safety and secondary standards-smell, taste and clarity. The DWP also tests levels of calcium and magnesium-nontoxic minerals that contribute to "hard" water.

In 1992, the microorganism cryptosporidium tainted drinking water in Milwaukee, causing thousands of cases of intestinal illness and more than 100 deaths. Although Los Angeles County hasn't suffered a waterborne illness outbreak in this century, the EPA has determined that the risk of contamination from the droppings of birds, deer and coyotes that make their home surrounding the city's open reservoirs is too great to be ignored. So by 2003, four of the city's open reservoirs-Encino, Hollywood and Upper and Lower Stone Canyon-must be either covered or have on- site filtration plants.

To keep track of contaminants, water is collected from 150 sites throughout the city, including reservoirs, wells and distribution mains in residential neighborhoods. About 50 of those sites are in San Fernando Valley neighborhoods. Teams of chemists, microbiologists and engineers at a lab in Arleta analyze the samples, monitoring and recording minute levels of contaminants.


Water Contaminants

The DWP classifies water contaminants three ways: organic, inorganic and microbiological. Organic chemicals include herbicides and pesticides; inorganics such as arsenic and zinc naturally seep into water as it courses down from the Sierra Nevada; microbiological organisms such as coliform bacteria come from birds and animals that dwell along reservoir shorelines. Dozens of chemicals are tested, such as those shown below, which were tested at the Los Angeles Aqueduct Filtration Plant, before treatment, in 1995.


How Water is Contaminated

The water in Los Angeles' open reservoirs is vulnerable to contamination from a number of sources. Algae, crustaceans and wildlife droppings can pollute the water. Chemicals get into water from industrial and agricultural runoff.


1. Agricultural: Herbicide and pesticide runoff.

2. Wildlife

* Algae blooms in standing reservoir water

* Bird and animal waste runs into open reservoirs

* Crustacea (crab and shrimp) in reservoir water

3. Industrial Chemical solvents runoff

4. Cholorination Treated aqueduct water stored in reservoirs is disinfected again, using chlorine. This process can produce potentially dangerous byproducts known as trihalomethanes.


Water Quality Questions?: Call the DWP at (800) 342- 5397.



Agent Class Cause Max.amt.allowed Amt.detected Benzene Organic Industrial: 1 ppb None detected solvent Styrene Organic Industrial: 100 ppb None detected solvent Chlordane Organic Agricultural: 0.1 ppb None detected pesticide PCBs Organic Agricultural: 0.5 ppb None detected pesticide Arsenic Inorganic Natural 0.05 ppm 0.014 ppm mineral Cyanide Inorganic Natural 0.2 ppm None detected mineral Fluoride Inorganic Natural 1.6 ppm 0.6 ppm mineral Coliform Microbiological Animal: 5%* 0.5% bacteria


Note: ppb- parts per billion (micrograms per liter); ppm-parts per million (milligrams per liter) * Maximum percentage of positive samples allowed.

Sources: Los Angeles Department of Water and Power; staff reports.

Researched by JULIE SHEER / Los Angeles Times

Testing Water

The DWP performed about 141,000 tests on Los Angeles drinking water in fiscal 1994-95. A breakdown of the types of contaminants tested:

Microbiological: 42%

Organic: 33%

Inorganic: 25%

Note: Inorganic contaminants include minerals that occur naturally; organics are chemicals resulting from agriculture or other industry; microbiologicals include parasites from animal droppings.

Source: Los Angeles Dept. of Water and Power

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