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Additional Information About Tap Water


The availability of clean, safe, healthy drinking water is something most of us take for granted. The water that flows from your tap is more than just a convenience; it contributes to the quality of life that we all enjoy. A well maintained water system is critical to public health, fire protection, and comes at a value that can’t be beat when compared to bottled water.

Some EMWD Drinking Water is Fluoridated

EMWD purchases water from The Metropolitan Water District of Southern California that is already fluoridated. For more information, please refer to the following links:

Emerging Constituents Report

For several years, water and wastewater agencies in Los Angeles, Orange, Riverside and San Bernardino counties have been using our expertise in water sampling and analysis to help state and federal agencies expedite and focus their research efforts on traces of various unregulated chemicals detected in local water supplies. These chemicals are collectively referred to as “emerging constituents” (or “ECs”), and include pharmaceuticals, ingredients in personal care products and industrial compounds. The proactive and voluntary EC sampling and monitoring efforts of local agencies have been coordinated on a regional basis through the Santa Ana Water Project Authority’s (SAWPA) Emerging Constituents Program Task Force.

Additional Resources: 

Wondering about Perchlorate?

Note: Maximum contaminant levels (MCLs) are measured in parts per billion (ppb). One part per billion is roughly equivalent to one drop of water in an Olympic-sized swimming pool.

What is EMWD doing to reduce levels of perchlorate in the local water supply?

EMWD strives to remain an industry leader in environmental consciousness by using blending treatment techniques that result in water that complies with all state and federal environmental, health and safety regulations.

EMWD is closely monitoring the blended water from affected well systems to ensure that perchlorate is not entering the water system above the current MCL of 6 ppb.

EMWD’s desalter wells are treated by reverse osmosis to less than 4 ppb.

Is there perchlorate contamination in the EMWD service area?

EMWD has some water wells that contain perchlorate. Three of these wells are blended with State Water Project water from the Mills Filtration Plant until the perchlorate level is below the detection limit of 4 parts per billion (ppb). All blending is done at each of the well sites and before the first customer service. At no time has EMWD served undiluted well water containing perchlorate to customers.


(parts per billion)



5.2 – 7.0

< 4


11 – 12 

< 4


<4 – 4.3

< 4

These wells represent approximately 1.7 % of the total water served by EMWD.

What is the State of California doing to remedy this problem?

The California Department of Public Health has adopted an MCL and public health goal of 6 ppb for drinking water. A well that exceeds the current perchlorate MCL (6 ppb) can be treated by blending to dilute down to legal levels.

What are the sources of perchlorate contamination?

The Colorado River has been a main source of perchlorate contamination in Southern California. This is a serious problem since roughly a third of Southern California’s drinking water comes from the Colorado River. Experts point to a former ammonium perchlorate manufacturing facility in Nevada as the origin of the contamination.

Most of the perchlorate contamination appears to be the result of past activities in the aerospace industry. Kerr-McGee Chemical LLC, currently Tronox LLC, has been a significant manufacturer of perchlorate and began a clean-up effort in 1999. Clean-up efforts have significantly reduced the amount of perchlorate that enters the Colorado River.

The perchlorate detected in the EMWD wells is coming from the groundwater basins. The source of contamination has not been determined. Potential sources include Colorado River Water as it has been used in the valley for many years or use of fertilizers containing perchlorate as the area is primarily agricultural.

How does perchlorate impact public health?

The California Office of Environmental Health Hazard Assessment (OEHHA) links perchlorate consumption to impairing thyroid function. At some level, EPA advises perchlorate interferes with the ability of the thyroid to utilize iodine to produce thyroid hormones. It is important to note that perchlorate was used as a medicine for years to tame hyperactive thyroids.

The California Department of Public Health (CDPH) does not believe any health effects would result from a perchlorate level of 6 ppb. OEHHA has set California’s current perchlorate Public Health Goal (PHG) at 6 ppb. One part per billion is roughly equivalent to one drop of water in an Olympic-sized swimming pool.

CDPH has set the MCL for perchlorate at 6 ppb to be in line with OEHHA’s PHG.

When was perchlorate contamination discovered in California?

Perchlorate water contamination first gained statewide attention as a drinking-water concern in 1985 after the Environmental Protection Agency (EPA) detected perchlorate in wells servicing households in the San Gabriel Valley (Aerojet’s original facility, near Los Angeles).

Since then, perchlorate has been found throughout Northern and Southern California.

Perchlorate is a salt used in rocket fuel, munitions, fireworks and explosives. It is also a component of air bag inflators, an additive in lubricating oils, tanning and finishing leather, fabrics and dyes, electroplating, aluminum refining, fertilizers and in production of paints and enamels.

Perchlorate helped build Cold War-era weapons. It was used in rockets that put people on the moon and space shuttles in orbit. It also was used for more mundane uses such as in making fireworks in San Bernardino County.

Concerned about copper and lead?

Lead and Copper Fact Sheet

Do you have spots on your dishes from the dishwasher?

We have more information on the the new phosphate-free detergents on the market.