Perchlorate FAQs

EMWD strives to remain an industry leader in environmental consciousness by using blending treatment techniques that result in water that complies with all 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.

Eastern Municipal Water District has some water wells that contain perchlorate. Three of these wells are blended with State Project water from the Mills Filtration Plant until the perchlorate level is below the detection limit of 4 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.

SOURCE	AVERAGE RANGE (parts per billion)	AFTER BLENDING WITH MILLS WATER (IN DISTRIBUTION SYSTEM)
WELL 44	5.2 - 7.0	< 4
WELL 49	11 - 12	< 4
WELL 57	<4 - 4.3	< 4

These wells represent approximately 1.7 % of the total water served by Eastern Municipal Water District.

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.

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.

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 parts per billion (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 Maximum Contaminant Level (MCL) for perchlorate at 6 ppb to be in line with OEHHA's PHG.

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.