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Rating Your Drinking Water

March 10, 1988

The Los Angeles Department of Water and Power is beginning distribution of brochures summaries the quality of the drinking water it sells. Summaries will be included with bills by service area; the sample report below reflects service area A in West Los Angeles and in the San Fernando Valley. The DWP tests for numerous substances on a periodic schedule; state and federal regulations control the amount of chemicals allowed in drinking water. In the brochure, the DWP states that all of its water meets such regulations; that statement is disputed by some environmentalists who say that, on some days, contaminants exceed safe limits. The City Council approved the brochure, agreeing with the DWP that yearly averages show that the water is safe.


1. The DWP lists the sources of drinking water, as figured by the average percentage of supply over six months.

2. The Maximum Allowable Level is set at the Federal Maximum Contaminant Level or at the State Action Level. The federal level reflects not only the goals set as a result of health concerns, but cost and feasibility as well. The goal is set at levels where no known or anticipated adverse health effect may occur, including a margin of safety. The state guilding is set by the Department of Health Services.

3. Citywide average for number of indicator organism colonies per 100 milligrams.

4. Milligrams per liter. This is approximately equivalent to parts per million.

5. Based on Total Trihalomethane (TTHM) levels from water samples taken from the distribution system. TTHMs are compounds formed when naturally occurring organic matter combines with chlorine.

6. The TCE level exceeded 0.005 mg/liter for one day in 1987 and for 3 days in 1986. However, since the federal standard is based on an annual average of four quarterly samples, the water met the standard.

7. The maximum level for PCE is established by a State Action Level. POCE, like TCE, is an industrual solvent used in metal degreasing and dry cleaning.

8. Turbidity Unit is a measure of the suspended material in water.

9. Picocuries per liter are units of measurement for radioactivity.

10. Unregulated substances advisory levels are set for substances that affect the physical characteristics of water, but do not have health effects at the levels found in water.

11. There are no advisory levels for total hardness and sodium.

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