Monrovia Water Department

The sources of tap water (both municipal and bottled) include rivers, lakes, streams, ponds, reservoirs, springs, and groundwater wells. As water travels over land or through the ground, it dissolves naturally-occurring minerals and, in some instances, radioactive materials, and can pick up substances from animal or human activity.

The City of Monrovia's water supply consists entirely of groundwater drawn from wells in the main San Gabriel Basin. Potential contaminants in source water include:

• Microbial contaminants such as viruses and bacteria from sewage treatment plants, septic systems, agricultural operations, and wildlife
• Inorganic contaminants including salts and metals that occur naturally or result from urban stormwater runoff, industrial/domestic wastewater discharges, oil/gas production, mining, or farming
• Pesticides and herbicides from agriculture, urban runoff, and residential uses
• Organic chemical contaminants, including synthetic and volatile organic compounds from industrial processes, petroleum production, gas stations, stormwater runoff, and septic systems
• Radioactive contaminants that can be naturally-occurring or result from oil/gas production and mining

To ensure safe municipal water, the USEPA and the state Department of Health Services establish regulations limiting contaminant levels in public water systems. Department regulations also set limits for bottled water contaminants to provide equal public health protection.

Tables 1 and 2 in our annual report list all water contaminants detected during our most recent sampling. The presence of these substances doesn't necessarily indicate a health risk. The Department allows monitoring for certain contaminants less than annually because their concentrations typically don't change significantly year to year.

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